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mariadb/mysys/mf_keycache.c
Vasilii Lakhin 5f7c2a617f Fix typos in C comments in miscellaneous files
2025-03-24 13:36:28 +11:00

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/* Copyright (c) 2000, 2013, Oracle and/or its affiliates.
Copyright (c) 2017, 2022, MariaDB Corporation.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */
/**
@file
The file contains the following modules:
Simple Key Cache Module
Partitioned Key Cache Module
Key Cache Interface Module
*/
#include "mysys_priv.h"
#include "mysys_err.h"
#include <keycache.h>
#include "my_static.h"
#include <m_string.h>
#include <my_bit.h>
#include <errno.h>
#include <stdarg.h>
#include "probes_mysql.h"
/******************************************************************************
Simple Key Cache Module
The module contains implementations of all key cache interface functions
employed by partitioned key caches.
******************************************************************************/
/*
These functions handle keyblock cacheing for ISAM and MyISAM tables.
One cache can handle many files.
It must contain buffers of the same blocksize.
init_key_cache() should be used to init cache handler.
The free list (free_block_list) is a stack like structure.
When a block is freed by free_block(), it is pushed onto the stack.
When a new block is required it is first tried to pop one from the stack.
If the stack is empty, it is tried to get a never-used block from the pool.
If this is empty too, then a block is taken from the LRU ring, flushing it
to disk, if necessary. This is handled in find_key_block().
With the new free list, the blocks can have three temperatures:
hot, warm and cold (which is free). This is remembered in the block header
by the enum BLOCK_TEMPERATURE temperature variable. Remembering the
temperature is necessary to correctly count the number of warm blocks,
which is required to decide when blocks are allowed to become hot. Whenever
a block is inserted to another (sub-)chain, we take the old and new
temperature into account to decide if we got one more or less warm block.
blocks_unused is the sum of never used blocks in the pool and of currently
free blocks. blocks_used is the number of blocks fetched from the pool and
as such gives the maximum number of in-use blocks at any time.
Key Cache Locking
=================
All key cache locking is done with a single mutex per key cache:
keycache->cache_lock. This mutex is locked almost all the time
when executing code in this file (mf_keycache.c).
However it is released for I/O and some copy operations.
The cache_lock is also released when waiting for some event. Waiting
and signalling is done via condition variables. In most cases the
thread waits on its thread->suspend condition variable. Every thread
has a my_thread_var structure, which contains this variable and a
'*next' and '**prev' pointer. These pointers are used to insert the
thread into a wait queue.
A thread can wait for one block and thus be in one wait queue at a
time only.
Before starting to wait on its condition variable with
mysql_cond_wait(), the thread enters itself to a specific wait queue
with link_into_queue() (double linked with '*next' + '**prev') or
wait_on_queue() (single linked with '*next').
Another thread, when releasing a resource, looks up the waiting thread
in the related wait queue. It sends a signal with
mysql_cond_signal() to the waiting thread.
NOTE: Depending on the particular wait situation, either the sending
thread removes the waiting thread from the wait queue with
unlink_from_queue() or release_whole_queue() respectively, or the waiting
thread removes itself.
There is one exception from this locking scheme when one thread wants
to reuse a block for some other address. This works by first marking
the block reserved (status= BLOCK_IN_SWITCH) and then waiting for all
threads that are reading the block to finish. Each block has a
reference to a condition variable (condvar). It holds a reference to
the thread->suspend condition variable for the waiting thread (if such
a thread exists). When that thread is signaled, the reference is
cleared. The number of readers of a block is registered in
block->hash_link->requests. See wait_for_readers() / remove_reader()
for details. This is similar to the above, but it clearly means that
only one thread can wait for a particular block. There is no queue in
this case. Strangely enough block->convar is used for waiting for the
assigned hash_link only. More precisely it is used to wait for all
requests to be unregistered from the assigned hash_link.
The resize_queue serves two purposes:
1. Threads that want to do a resize wait there if in_resize is set.
This is not used in the server. The server refuses a second resize
request if one is already active. keycache->in_init is used for the
synchronization. See set_var.cc.
2. Threads that want to access blocks during resize wait here during
the re-initialization phase.
When the resize is done, all threads on the queue are signalled.
Hypothetical resizers can compete for resizing, and read/write
requests will restart to request blocks from the freshly resized
cache. If the cache has been resized too small, it is disabled and
'can_be_used' is false. In this case read/write requests bypass the
cache. Since they increment and decrement 'cnt_for_resize_op', the
next resizer can wait on the queue 'waiting_for_resize_cnt' until all
I/O finished.
*/
/* declare structures that is used by st_key_cache */
struct st_block_link;
typedef struct st_block_link BLOCK_LINK;
struct st_keycache_page;
typedef struct st_keycache_page KEYCACHE_PAGE;
struct st_hash_link;
typedef struct st_hash_link HASH_LINK;
/* info about requests in a waiting queue */
typedef struct st_keycache_wqueue
{
struct st_my_thread_var *last_thread; /* circular list of waiting threads */
} KEYCACHE_WQUEUE;
/* Default size of hash for changed files */
#define MIN_CHANGED_BLOCKS_HASH_SIZE 128
/* Control block for a simple (non-partitioned) key cache */
typedef struct st_simple_key_cache_cb
{
my_bool key_cache_inited; /* <=> control block is allocated */
my_bool in_resize; /* true during resize operation */
my_bool resize_in_flush; /* true during flush of resize operation */
my_bool can_be_used; /* usage of cache for read/write is allowed */
size_t key_cache_mem_size; /* specified size of the cache memory */
size_t allocated_mem_size; /* size of the memory actually allocated */
uint key_cache_block_size; /* size of the page buffer of a cache block */
size_t min_warm_blocks; /* min number of warm blocks; */
size_t age_threshold; /* age threshold for hot blocks */
ulonglong keycache_time; /* total number of block link operations */
uint hash_entries; /* max number of entries in the hash table */
uint changed_blocks_hash_size; /* Number of hash buckets for file blocks */
int hash_links; /* max number of hash links */
int hash_links_used; /* number of hash links currently used */
int disk_blocks; /* max number of blocks in the cache */
size_t blocks_used; /* maximum number of concurrently used blocks */
size_t blocks_unused; /* number of currently unused blocks */
size_t blocks_changed; /* number of currently dirty blocks */
size_t warm_blocks; /* number of blocks in warm sub-chain */
ulong cnt_for_resize_op; /* counter to block resize operation */
long blocks_available; /* number of blocks available in the LRU chain */
HASH_LINK **hash_root; /* arr. of entries into hash table buckets */
HASH_LINK *hash_link_root; /* memory for hash table links */
HASH_LINK *free_hash_list; /* list of free hash links */
BLOCK_LINK *free_block_list; /* list of free blocks */
BLOCK_LINK *block_root; /* memory for block links */
uchar *block_mem; /* memory for block buffers */
BLOCK_LINK *used_last; /* ptr to the last block of the LRU chain */
BLOCK_LINK *used_ins; /* ptr to the insertion block in LRU chain */
mysql_mutex_t cache_lock; /* to lock access to the cache structure */
KEYCACHE_WQUEUE resize_queue; /* threads waiting during resize operation */
/*
Waiting for a zero resize count. Using a queue for symmetry though
only one thread can wait here.
*/
KEYCACHE_WQUEUE waiting_for_resize_cnt;
KEYCACHE_WQUEUE waiting_for_hash_link; /* waiting for a free hash link */
KEYCACHE_WQUEUE waiting_for_block; /* requests waiting for a free block */
BLOCK_LINK **changed_blocks; /* hash for dirty file bl.*/
BLOCK_LINK **file_blocks; /* hash for other file bl.*/
/* Statistics variables. These are reset in reset_key_cache_counters(). */
ulong global_blocks_changed; /* number of currently dirty blocks */
ulonglong global_cache_w_requests;/* number of write requests (write hits) */
ulonglong global_cache_write; /* number of writes from cache to files */
ulonglong global_cache_r_requests;/* number of read requests (read hits) */
ulonglong global_cache_read; /* number of reads from files to cache */
int blocks; /* max number of blocks in the cache */
uint hash_factor; /* factor used to calculate hash function */
my_bool in_init; /* Set to 1 in MySQL during init/resize */
} SIMPLE_KEY_CACHE_CB;
/*
Some compilation flags have been added specifically for this module
to control the following:
- not to let a thread to yield the control when reading directly
from key cache, which might improve performance in many cases;
to enable this add:
#define SERIALIZED_READ_FROM_CACHE
- to set an upper bound for number of threads simultaneously
using the key cache; this setting helps to determine an optimal
size for hash table and improve performance when the number of
blocks in the key cache much less than the number of threads
accessing it;
to set this number equal to <N> add
#define MAX_THREADS <N>
- to substitute calls of mysql_cond_wait for calls of
mysql_cond_timedwait (wait with timeout set up);
this setting should be used only when you want to trap a deadlock
situation, which theoretically should not happen;
to set timeout equal to <T> seconds add
#define KEYCACHE_TIMEOUT <T>
- to enable the module traps and to send debug information from
key cache module to a special debug log add:
#define KEYCACHE_DEBUG
the name of this debug log file <LOG NAME> can be set through:
#define KEYCACHE_DEBUG_LOG <LOG NAME>
if the name is not defined, it's set by default;
if the KEYCACHE_DEBUG flag is not set up and we are in a debug
mode, i.e. when ! defined(DBUG_OFF), the debug information from the
module is sent to the regular debug log.
Example of the settings:
#define SERIALIZED_READ_FROM_CACHE
#define MAX_THREADS 100
#define KEYCACHE_TIMEOUT 1
#define KEYCACHE_DEBUG
#define KEYCACHE_DEBUG_LOG "my_key_cache_debug.log"
*/
#define STRUCT_PTR(TYPE, MEMBER, a) \
(TYPE *) ((char *) (a) - offsetof(TYPE, MEMBER))
/* types of condition variables */
#define COND_FOR_REQUESTED 0
#define COND_FOR_SAVED 1
#define COND_FOR_READERS 2
typedef mysql_cond_t KEYCACHE_CONDVAR;
/* descriptor of the page in the key cache block buffer */
struct st_keycache_page
{
int file; /* file to which the page belongs to */
my_off_t filepos; /* position of the page in the file */
};
/* element in the chain of a hash table bucket */
struct st_hash_link
{
struct st_hash_link *next, **prev; /* to connect links in the same bucket */
struct st_block_link *block; /* reference to the block for the page: */
File file; /* from such a file */
my_off_t diskpos; /* with such an offset */
uint requests; /* number of requests for the page */
};
/* simple states of a block */
#define BLOCK_ERROR 1U/* an error occurred when performing file i/o */
#define BLOCK_READ 2U/* file block is in the block buffer */
#define BLOCK_IN_SWITCH 4U/* block is preparing to read new page */
#define BLOCK_REASSIGNED 8U/* blk does not accept requests for old page */
#define BLOCK_IN_FLUSH 16U/* block is selected for flush */
#define BLOCK_CHANGED 32U/* block buffer contains a dirty page */
#define BLOCK_IN_USE 64U/* block is not free */
#define BLOCK_IN_EVICTION 128U/* block is selected for eviction */
#define BLOCK_IN_FLUSHWRITE 256U/* block is in write to file */
#define BLOCK_FOR_UPDATE 512U/* block is selected for buffer modification */
/* page status, returned by find_key_block */
#define PAGE_READ 0
#define PAGE_TO_BE_READ 1
#define PAGE_WAIT_TO_BE_READ 2
/* block temperature determines in which (sub-)chain the block currently is */
enum BLOCK_TEMPERATURE { BLOCK_COLD /*free*/ , BLOCK_WARM , BLOCK_HOT };
/* key cache block */
struct st_block_link
{
struct st_block_link
*next_used, **prev_used; /* to connect links in the LRU chain (ring) */
struct st_block_link
*next_changed, **prev_changed; /* for lists of file dirty/clean blocks */
struct st_hash_link *hash_link; /* backward ptr to referring hash_link */
KEYCACHE_WQUEUE wqueue[2]; /* queues on waiting requests for new/old pages */
uint requests; /* number of requests for the block */
uchar *buffer; /* buffer for the block page */
uint offset; /* beginning of modified data in the buffer */
uint length; /* end of data in the buffer */
uint status; /* state of the block */
enum BLOCK_TEMPERATURE temperature; /* block temperature: cold, warm, hot */
uint hits_left; /* number of hits left until promotion */
ulonglong last_hit_time; /* timestamp of the last hit */
KEYCACHE_CONDVAR *condvar; /* condition variable for 'no readers' event */
};
KEY_CACHE dflt_key_cache_var;
KEY_CACHE *dflt_key_cache= &dflt_key_cache_var;
#define FLUSH_CACHE 2000 /* sort this many blocks at once */
static int flush_all_key_blocks(SIMPLE_KEY_CACHE_CB *keycache);
static void end_simple_key_cache(void *keycache_, my_bool cleanup);
static void wait_on_queue(KEYCACHE_WQUEUE *wqueue,
mysql_mutex_t *mutex);
static void release_whole_queue(KEYCACHE_WQUEUE *wqueue);
static void free_block(SIMPLE_KEY_CACHE_CB *keycache, BLOCK_LINK *block);
#ifndef DBUG_OFF
static void test_key_cache(SIMPLE_KEY_CACHE_CB *keycache,
const char *where, my_bool lock);
#endif
#define KEYCACHE_BASE_EXPR(f, pos) \
((ulong) ((pos) / keycache->key_cache_block_size) + (ulong) (f))
#define KEYCACHE_HASH(f, pos) \
((KEYCACHE_BASE_EXPR(f, pos) / keycache->hash_factor) & \
(keycache->hash_entries-1))
#define FILE_HASH(f, cache) ((uint) (f) & (cache->changed_blocks_hash_size-1))
#define DEFAULT_KEYCACHE_DEBUG_LOG "keycache_debug.log"
#if defined(KEYCACHE_DEBUG) && ! defined(KEYCACHE_DEBUG_LOG)
#define KEYCACHE_DEBUG_LOG DEFAULT_KEYCACHE_DEBUG_LOG
#endif
#if defined(KEYCACHE_DEBUG_LOG)
static FILE *keycache_debug_log=NULL;
static void keycache_debug_print(const char *fmt,...);
#define KEYCACHE_DEBUG_OPEN \
if (!keycache_debug_log) \
{ \
keycache_debug_log= fopen(KEYCACHE_DEBUG_LOG, "w"); \
(void) setvbuf(keycache_debug_log, NULL, _IOLBF, BUFSIZ); \
}
#define KEYCACHE_DEBUG_CLOSE \
if (keycache_debug_log) \
{ \
fclose(keycache_debug_log); \
keycache_debug_log= 0; \
}
#else
#define KEYCACHE_DEBUG_OPEN
#define KEYCACHE_DEBUG_CLOSE
#endif /* defined(KEYCACHE_DEBUG_LOG) */
#if defined(KEYCACHE_DEBUG_LOG) && defined(KEYCACHE_DEBUG)
#define KEYCACHE_DBUG_PRINT(l, m) \
{ if (keycache_debug_log) fprintf(keycache_debug_log, "%s: ", l); \
keycache_debug_print m; }
#define KEYCACHE_DBUG_ASSERT(a) \
{ if (! (a) && keycache_debug_log) fclose(keycache_debug_log); \
assert(a); }
#else
#define KEYCACHE_DBUG_PRINT(l, m) DBUG_PRINT(l, m)
#define KEYCACHE_DBUG_ASSERT(a) DBUG_ASSERT(a)
#endif /* defined(KEYCACHE_DEBUG_LOG) && defined(KEYCACHE_DEBUG) */
#if defined(KEYCACHE_DEBUG) || defined(DBUG_TRACE)
static long keycache_thread_id;
#define KEYCACHE_THREAD_TRACE(l) \
KEYCACHE_DBUG_PRINT(l,("|thread %ld",keycache_thread_id))
#define KEYCACHE_THREAD_TRACE_BEGIN(l) \
{ struct st_my_thread_var *thread_var= my_thread_var; \
keycache_thread_id= thread_var->id; \
KEYCACHE_DBUG_PRINT(l,("[thread %ld",keycache_thread_id)) }
#define KEYCACHE_THREAD_TRACE_END(l) \
KEYCACHE_DBUG_PRINT(l,("]thread %ld",keycache_thread_id))
#else
#define KEYCACHE_THREAD_TRACE_BEGIN(l)
#define KEYCACHE_THREAD_TRACE_END(l)
#define KEYCACHE_THREAD_TRACE(l)
#endif /* defined(KEYCACHE_DEBUG) || defined(DBUG_TRACE) */
#define BLOCK_NUMBER(b) \
((uint) (((char*)(b)-(char *) keycache->block_root)/sizeof(BLOCK_LINK)))
#define HASH_LINK_NUMBER(h) \
((uint) (((char*)(h)-(char *) keycache->hash_link_root)/sizeof(HASH_LINK)))
#if (defined(KEYCACHE_TIMEOUT) && !defined(_WIN32)) || defined(KEYCACHE_DEBUG)
static int keycache_pthread_cond_wait(mysql_cond_t *cond,
mysql_mutex_t *mutex);
#else
#define keycache_pthread_cond_wait(C, M) mysql_cond_wait(C, M)
#endif
#if defined(KEYCACHE_DEBUG)
static int keycache_pthread_mutex_lock(mysql_mutex_t *mutex);
static void keycache_pthread_mutex_unlock(mysql_mutex_t *mutex);
static int keycache_pthread_cond_signal(mysql_cond_t *cond);
#else
#define keycache_pthread_mutex_lock(M) mysql_mutex_lock(M)
#define keycache_pthread_mutex_unlock(M) mysql_mutex_unlock(M)
#define keycache_pthread_cond_signal(C) mysql_cond_signal(C)
#endif /* defined(KEYCACHE_DEBUG) */
#if !defined(DBUG_OFF)
#if defined(inline)
#undef inline
#endif
#define inline /* disabled inline for easier debugging */
static int fail_hlink(HASH_LINK *hlink);
static int cache_empty(SIMPLE_KEY_CACHE_CB *keycache);
#endif
#ifdef DBUG_ASSERT_EXISTS
static int fail_block(BLOCK_LINK *block);
#endif
static inline uint next_power(uint value)
{
return (uint) my_round_up_to_next_power((uint32) value) << 1;
}
/*
Initialize a simple key cache
SYNOPSIS
init_simple_key_cache()
keycache pointer to the control block of a simple key cache
key_cache_block_size size of blocks to keep cached data
use_mem memory to use for the key cache buffers/structures
division_limit division limit (may be zero)
age_threshold age threshold (may be zero)
DESCRIPTION
This function is the implementation of the init_key_cache interface
function that is employed by simple (non-partitioned) key caches.
The function builds a simple key cache and initializes the control block
structure of the type SIMPLE_KEY_CACHE_CB that is used for this key cache.
The parameter keycache is supposed to point to this structure.
The parameter key_cache_block_size specifies the size of the blocks in
the key cache to be built. The parameters division_limit and age_threshold
determine the initial values of those characteristics of the key cache
that are used for midpoint insertion strategy. The parameter use_mem
specifies the total amount of memory to be allocated for key cache blocks
and auxiliary structures.
RETURN VALUE
number of blocks in the key cache, if successful,
<= 0 - otherwise.
NOTES.
if keycache->key_cache_inited != 0 we assume that the key cache
is already initialized. This is for now used by myisamchk, but shouldn't
be something that a program should rely on!
It's assumed that no two threads call this function simultaneously
referring to the same key cache handle.
*/
static
int init_simple_key_cache(void *keycache_,
uint key_cache_block_size,
size_t use_mem, uint division_limit,
uint age_threshold, uint changed_blocks_hash_size)
{
SIMPLE_KEY_CACHE_CB *keycache= keycache_;
size_t blocks, hash_links;
size_t length;
int error;
DBUG_ENTER("init_simple_key_cache");
DBUG_ASSERT(key_cache_block_size >= 512);
KEYCACHE_DEBUG_OPEN;
if (keycache->key_cache_inited && keycache->disk_blocks > 0)
{
DBUG_PRINT("warning",("key cache already in use"));
DBUG_RETURN(0);
}
keycache->blocks_used= keycache->blocks_unused= 0;
keycache->global_blocks_changed= 0;
keycache->global_cache_w_requests= keycache->global_cache_r_requests= 0;
keycache->global_cache_read= keycache->global_cache_write= 0;
keycache->disk_blocks= -1;
if (! keycache->key_cache_inited)
{
keycache->key_cache_inited= 1;
keycache->hash_factor= 1;
/*
Initialize these variables once only.
Their value must survive re-initialization during resizing.
*/
keycache->in_resize= 0;
keycache->resize_in_flush= 0;
keycache->cnt_for_resize_op= 0;
keycache->waiting_for_resize_cnt.last_thread= NULL;
keycache->in_init= 0;
mysql_mutex_init(key_KEY_CACHE_cache_lock,
&keycache->cache_lock, MY_MUTEX_INIT_FAST);
keycache->resize_queue.last_thread= NULL;
}
keycache->key_cache_mem_size= use_mem;
keycache->key_cache_block_size= key_cache_block_size;
DBUG_PRINT("info", ("key_cache_block_size: %u",
key_cache_block_size));
blocks= use_mem / (sizeof(BLOCK_LINK) + 2 * sizeof(HASH_LINK) +
sizeof(HASH_LINK*) * 5/4 + key_cache_block_size);
/* Changed blocks hash needs to be a power of 2 */
changed_blocks_hash_size= my_round_up_to_next_power(MY_MAX(changed_blocks_hash_size,
MIN_CHANGED_BLOCKS_HASH_SIZE));
/* It doesn't make sense to have too few blocks (less than 8) */
if (blocks >= 8)
{
for ( ; ; )
{
/* Set my_hash_entries to the next bigger 2 power */
if ((keycache->hash_entries= next_power((uint)blocks)) < blocks * 5/4)
keycache->hash_entries<<= 1;
hash_links= 2 * blocks;
#if defined(MAX_THREADS)
if (hash_links < MAX_THREADS + blocks - 1)
hash_links= MAX_THREADS + blocks - 1;
#endif
while ((length= (ALIGN_SIZE(blocks * sizeof(BLOCK_LINK)) +
ALIGN_SIZE(hash_links * sizeof(HASH_LINK)) +
ALIGN_SIZE(sizeof(HASH_LINK*) *
keycache->hash_entries) +
sizeof(BLOCK_LINK*)* ((size_t)changed_blocks_hash_size*2))) +
(blocks * keycache->key_cache_block_size) > use_mem && blocks > 8)
blocks--;
keycache->allocated_mem_size= blocks * keycache->key_cache_block_size;
if ((keycache->block_mem= my_large_malloc(&keycache->allocated_mem_size,
MYF(0))))
{
/*
Allocate memory for blocks, hash_links and hash entries;
For each block 2 hash links are allocated
*/
if (my_multi_malloc_large(key_memory_KEY_CACHE, MYF(MY_ZEROFILL),
&keycache->block_root,
(ulonglong) (blocks * sizeof(BLOCK_LINK)),
&keycache->hash_root,
(ulonglong) (sizeof(HASH_LINK*) *
keycache->hash_entries),
&keycache->hash_link_root,
(ulonglong) (hash_links * sizeof(HASH_LINK)),
&keycache->changed_blocks,
(ulonglong) (sizeof(BLOCK_LINK*) *
changed_blocks_hash_size),
&keycache->file_blocks,
(ulonglong) (sizeof(BLOCK_LINK*) *
changed_blocks_hash_size),
NullS))
break;
my_large_free(keycache->block_mem, keycache->allocated_mem_size);
keycache->block_mem= 0;
}
if (blocks < 8)
{
my_errno= ENOMEM;
my_error(EE_OUTOFMEMORY, MYF(ME_FATAL),
blocks * keycache->key_cache_block_size);
goto err;
}
blocks= blocks / 4*3;
}
keycache->blocks_unused= blocks;
keycache->disk_blocks= (int) blocks;
keycache->hash_links= (int)hash_links;
keycache->hash_links_used= 0;
keycache->free_hash_list= NULL;
keycache->blocks_used= keycache->blocks_changed= 0;
keycache->global_blocks_changed= 0;
keycache->blocks_available=0; /* For debugging */
/* The LRU chain is empty after initialization */
keycache->used_last= NULL;
keycache->used_ins= NULL;
keycache->free_block_list= NULL;
keycache->keycache_time= 0;
keycache->warm_blocks= 0;
keycache->min_warm_blocks= (division_limit ?
blocks * division_limit / 100 + 1 :
blocks);
keycache->age_threshold= (age_threshold ?
blocks * age_threshold / 100 :
blocks);
keycache->changed_blocks_hash_size= changed_blocks_hash_size;
keycache->can_be_used= 1;
keycache->waiting_for_hash_link.last_thread= NULL;
keycache->waiting_for_block.last_thread= NULL;
DBUG_PRINT("exit",
("disk_blocks: %d block_root: %p hash_entries: %d\
hash_root: %p hash_links: %d hash_link_root: %p",
keycache->disk_blocks, keycache->block_root,
keycache->hash_entries, keycache->hash_root,
keycache->hash_links, keycache->hash_link_root));
}
else
{
/* key_buffer_size is specified too small. Disable the cache. */
keycache->can_be_used= 0;
}
keycache->blocks= keycache->disk_blocks > 0 ? keycache->disk_blocks : 0;
DBUG_RETURN((int) keycache->disk_blocks);
err:
error= my_errno;
keycache->disk_blocks= 0;
keycache->blocks= 0;
if (keycache->block_mem)
{
my_large_free((uchar*) keycache->block_mem, keycache->allocated_mem_size);
keycache->block_mem= NULL;
}
if (keycache->block_root)
{
my_free(keycache->block_root);
keycache->block_root= NULL;
}
my_errno= error;
keycache->can_be_used= 0;
DBUG_RETURN(0);
}
/*
Prepare for resizing a simple key cache
SYNOPSIS
prepare_resize_simple_key_cache()
keycache pointer to the control block of a simple key cache
release_lock <=> release the key cache lock before return
DESCRIPTION
This function flushes all dirty pages from a simple key cache and after
this it destroys the key cache calling end_simple_key_cache. The function
takes the parameter keycache as a pointer to the control block
structure of the type SIMPLE_KEY_CACHE_CB for this key cache.
The parameter release_lock says whether the key cache lock must be
released before return from the function.
RETURN VALUE
0 - on success,
1 - otherwise.
NOTES
This function is the called by resize_simple_key_cache and
resize_partitioned_key_cache that resize simple and partitioned key caches
respectively.
*/
static
int prepare_resize_simple_key_cache(SIMPLE_KEY_CACHE_CB *keycache,
my_bool release_lock)
{
int res= 0;
DBUG_ENTER("prepare_resize_simple_key_cache");
keycache_pthread_mutex_lock(&keycache->cache_lock);
/*
We may need to wait for another thread which is doing a resize
already. This cannot happen in the MySQL server though. It allows
one resizer only. In set_var.cc keycache->in_init is used to block
multiple attempts.
*/
while (keycache->in_resize)
{
/* purecov: begin inspected */
wait_on_queue(&keycache->resize_queue, &keycache->cache_lock);
/* purecov: end */
}
/*
Mark the operation in progress. This blocks other threads from doing
a resize in parallel. It prohibits new blocks to enter the cache.
Read/write requests can bypass the cache during the flush phase.
*/
keycache->in_resize= 1;
/* Need to flush only if keycache is enabled. */
if (keycache->can_be_used && keycache->disk_blocks != -1)
{
/* Start the flush phase. */
keycache->resize_in_flush= 1;
if (flush_all_key_blocks(keycache))
{
/* TODO: if this happens, we should write a warning in the log file ! */
keycache->resize_in_flush= 0;
keycache->can_be_used= 0;
res= 1;
goto finish;
}
DBUG_SLOW_ASSERT(cache_empty(keycache));
/* End the flush phase. */
keycache->resize_in_flush= 0;
}
/*
Some direct read/write operations (bypassing the cache) may still be
unfinished. Wait until they are done. If the key cache can be used,
direct I/O is done in increments of key_cache_block_size. That is,
every block is checked if it is in the cache. We need to wait for
pending I/O before re-initializing the cache, because we may change
the block size. Otherwise they could check for blocks at file
positions where the new block division has none. We do also want to
wait for I/O done when (if) the cache was disabled. It must not
run in parallel with normal cache operation.
*/
while (keycache->cnt_for_resize_op)
wait_on_queue(&keycache->waiting_for_resize_cnt, &keycache->cache_lock);
end_simple_key_cache(keycache, 0);
finish:
if (release_lock)
keycache_pthread_mutex_unlock(&keycache->cache_lock);
DBUG_RETURN(res);
}
/*
Finalize resizing a simple key cache
SYNOPSIS
finish_resize_simple_key_cache()
keycache pointer to the control block of a simple key cache
DESCRIPTION
This function performs finalizing actions for the operation of
resizing a simple key cache. The function takes the parameter
keycache as a pointer to the control block structure of the type
SIMPLE_KEY_CACHE_CB for this key cache. The function sets the flag
in_resize in this structure to FALSE.
RETURN VALUE
none
NOTES
This function is the called by resize_simple_key_cache and
resize_partitioned_key_cache that resize simple and partitioned key caches
respectively.
*/
static
void finish_resize_simple_key_cache(SIMPLE_KEY_CACHE_CB *keycache)
{
DBUG_ENTER("finish_resize_simple_key_cache");
mysql_mutex_assert_owner(&keycache->cache_lock);
/*
Mark the resize finished. This allows other threads to start a
resize or to request new cache blocks.
*/
keycache->in_resize= 0;
/* Signal waiting threads. */
release_whole_queue(&keycache->resize_queue);
keycache_pthread_mutex_unlock(&keycache->cache_lock);
DBUG_VOID_RETURN;
}
/*
Resize a simple key cache
SYNOPSIS
resize_simple_key_cache()
keycache pointer to the control block of a simple key cache
key_cache_block_size size of blocks to keep cached data
use_mem memory to use for the key cache buffers/structures
division_limit new division limit (if not zero)
age_threshold new age threshold (if not zero)
DESCRIPTION
This function is the implementation of the resize_key_cache interface
function that is employed by simple (non-partitioned) key caches.
The function takes the parameter keycache as a pointer to the
control block structure of the type SIMPLE_KEY_CACHE_CB for the simple key
cache to be resized.
The parameter key_cache_block_size specifies the new size of the blocks in
the key cache. The parameters division_limit and age_threshold
determine the new initial values of those characteristics of the key cache
that are used for midpoint insertion strategy. The parameter use_mem
specifies the total amount of memory to be allocated for key cache blocks
and auxiliary structures in the new key cache.
RETURN VALUE
number of blocks in the key cache, if successful,
0 - otherwise.
NOTES.
The function first calls the function prepare_resize_simple_key_cache
to flush all dirty blocks from key cache, to free memory used
for key cache blocks and auxiliary structures. After this the
function builds a new key cache with new parameters.
This implementation doesn't block the calls and executions of other
functions from the key cache interface. However it assumes that the
calls of resize_simple_key_cache itself are serialized.
The function starts the operation only when all other threads
performing operations with the key cache let her to proceed
(when cnt_for_resize=0).
*/
static
int resize_simple_key_cache(void *keycache_,
uint key_cache_block_size,
size_t use_mem, uint division_limit,
uint age_threshold, uint changed_blocks_hash_size)
{
SIMPLE_KEY_CACHE_CB *keycache= keycache_;
int blocks= 0;
DBUG_ENTER("resize_simple_key_cache");
DBUG_ASSERT(keycache->key_cache_inited);
/*
Note that the cache_lock mutex and the resize_queue are left untouched.
We do not lose the cache_lock and will release it only at the end of
this function.
*/
if (prepare_resize_simple_key_cache(keycache, 0))
goto finish;
/* The following will work even if use_mem is 0 */
blocks= init_simple_key_cache(keycache, key_cache_block_size, use_mem,
division_limit, age_threshold,
changed_blocks_hash_size);
finish:
finish_resize_simple_key_cache(keycache);
DBUG_RETURN(blocks);
}
/*
Increment counter blocking resize key cache operation
*/
static inline void inc_counter_for_resize_op(SIMPLE_KEY_CACHE_CB *keycache)
{
keycache->cnt_for_resize_op++;
}
/*
Decrement counter blocking resize key cache operation;
Signal the operation to proceed when counter becomes equal zero
*/
static inline void dec_counter_for_resize_op(SIMPLE_KEY_CACHE_CB *keycache)
{
if (!--keycache->cnt_for_resize_op)
release_whole_queue(&keycache->waiting_for_resize_cnt);
}
/*
Change key cache parameters of a simple key cache
SYNOPSIS
change_simple_key_cache_param()
keycache pointer to the control block of a simple key cache
division_limit new division limit (if not zero)
age_threshold new age threshold (if not zero)
DESCRIPTION
This function is the implementation of the change_key_cache_param interface
function that is employed by simple (non-partitioned) key caches.
The function takes the parameter keycache as a pointer to the
control block structure of the type SIMPLE_KEY_CACHE_CB for the simple key
cache where new values of the division limit and the age threshold used
for midpoint insertion strategy are to be set. The parameters
division_limit and age_threshold provide these new values.
RETURN VALUE
none
NOTES.
Presently the function resets the key cache parameters concerning
midpoint insertion strategy - division_limit and age_threshold.
This function changes some parameters of a given key cache without
reformatting it. The function does not touch the contents the key
cache blocks.
*/
static
void change_simple_key_cache_param(void *keycache_, uint division_limit,
uint age_threshold)
{
SIMPLE_KEY_CACHE_CB *keycache= keycache_;
DBUG_ENTER("change_simple_key_cache_param");
keycache_pthread_mutex_lock(&keycache->cache_lock);
if (division_limit)
keycache->min_warm_blocks= (keycache->disk_blocks *
division_limit / 100 + 1);
if (age_threshold)
keycache->age_threshold= (keycache->disk_blocks *
age_threshold / 100);
keycache_pthread_mutex_unlock(&keycache->cache_lock);
DBUG_VOID_RETURN;
}
/*
Destroy a simple key cache
SYNOPSIS
end_simple_key_cache()
keycache pointer to the control block of a simple key cache
cleanup <=> complete free (free also mutex for key cache)
DESCRIPTION
This function is the implementation of the end_key_cache interface
function that is employed by simple (non-partitioned) key caches.
The function takes the parameter keycache as a pointer to the
control block structure of the type SIMPLE_KEY_CACHE_CB for the simple key
cache to be destroyed.
The function frees the memory allocated for the key cache blocks and
auxiliary structures. If the value of the parameter cleanup is TRUE
then even the key cache mutex is freed.
RETURN VALUE
none
*/
static
void end_simple_key_cache(void *keycache_, my_bool cleanup)
{
SIMPLE_KEY_CACHE_CB *keycache= keycache_;
DBUG_ENTER("end_simple_key_cache");
DBUG_PRINT("enter", ("key_cache: %p", keycache));
if (!keycache->key_cache_inited)
DBUG_VOID_RETURN;
if (keycache->disk_blocks > 0)
{
if (keycache->block_mem)
{
my_large_free((uchar*) keycache->block_mem, keycache->allocated_mem_size);
keycache->block_mem= NULL;
my_free(keycache->block_root);
keycache->block_root= NULL;
}
keycache->disk_blocks= -1;
/* Reset blocks_changed to be safe if flush_all_key_blocks is called */
keycache->blocks_changed= 0;
}
DBUG_PRINT("status", ("used: %lu changed: %lu w_requests: %lu "
"writes: %lu r_requests: %lu reads: %lu",
keycache->blocks_used, keycache->global_blocks_changed,
(ulong) keycache->global_cache_w_requests,
(ulong) keycache->global_cache_write,
(ulong) keycache->global_cache_r_requests,
(ulong) keycache->global_cache_read));
/*
Reset these values to be able to detect a disabled key cache.
See Bug#44068 (RESTORE can disable the MyISAM Key Cache).
*/
keycache->blocks_used= 0;
keycache->blocks_unused= 0;
if (cleanup)
{
mysql_mutex_destroy(&keycache->cache_lock);
keycache->key_cache_inited= keycache->can_be_used= 0;
KEYCACHE_DEBUG_CLOSE;
}
DBUG_VOID_RETURN;
} /* end_key_cache */
/*
Link a thread into double-linked queue of waiting threads.
SYNOPSIS
link_into_queue()
wqueue pointer to the queue structure
thread pointer to the thread to be added to the queue
RETURN VALUE
none
NOTES.
Queue is represented by a circular list of the thread structures
The list is double-linked of the type (**prev,*next), accessed by
a pointer to the last element.
*/
static void link_into_queue(KEYCACHE_WQUEUE *wqueue,
struct st_my_thread_var *thread)
{
struct st_my_thread_var *last;
DBUG_ASSERT(!thread->next && !thread->prev);
if (! (last= wqueue->last_thread))
{
/* Queue is empty */
thread->next= thread;
thread->prev= &thread->next;
}
else
{
DBUG_ASSERT(last->next->prev == &last->next);
/* Add backlink to previous element */
thread->prev= last->next->prev;
/* Fix first in list to point backwords to current */
last->next->prev= &thread->next;
/* Next should point to the first element in list */
thread->next= last->next;
/* Fix old element to point to new one */
last->next= thread;
}
wqueue->last_thread= thread;
}
/*
Unlink a thread from double-linked queue of waiting threads
SYNOPSIS
unlink_from_queue()
wqueue pointer to the queue structure
thread pointer to the thread to be removed from the queue
RETURN VALUE
none
NOTES.
See NOTES for link_into_queue
*/
static void unlink_from_queue(KEYCACHE_WQUEUE *wqueue,
struct st_my_thread_var *thread)
{
KEYCACHE_DBUG_PRINT("unlink_from_queue", ("thread %ld", (ulong) thread->id));
DBUG_ASSERT(thread->next && thread->prev);
if (thread->next == thread)
{
/* The queue contains only one member */
wqueue->last_thread= NULL;
}
else
{
/* Remove current element from list */
thread->next->prev= thread->prev;
*thread->prev= thread->next;
/* If first element, change list pointer to point to previous element */
if (wqueue->last_thread == thread)
wqueue->last_thread= STRUCT_PTR(struct st_my_thread_var, next,
thread->prev);
}
thread->next= NULL;
#ifdef DBUG_ASSERT_EXISTS
/*
This makes it easier to see it's not in a chain during debugging.
And some DBUG_ASSERT() rely on it.
*/
thread->prev= NULL;
#endif
}
/*
Add a thread to single-linked queue of waiting threads
SYNOPSIS
wait_on_queue()
wqueue Pointer to the queue structure.
mutex Cache_lock to acquire after awake.
RETURN VALUE
none
NOTES.
Queue is represented by a circular list of the thread structures
The list is single-linked of the type (*next), accessed by a pointer
to the last element.
The function protects against stray signals by verifying that the
current thread is unlinked from the queue when awaking. However,
since several threads can wait for the same event, it might be
necessary for the caller of the function to check again if the
condition for awake is indeed matched.
*/
static void wait_on_queue(KEYCACHE_WQUEUE *wqueue,
mysql_mutex_t *mutex)
{
struct st_my_thread_var *last;
struct st_my_thread_var *thread= my_thread_var;
DBUG_ASSERT(!thread->next);
DBUG_ASSERT(!thread->prev); /* Not required, but must be true anyway. */
mysql_mutex_assert_owner(mutex);
/* Add to queue. */
if (! (last= wqueue->last_thread))
thread->next= thread;
else
{
thread->next= last->next;
last->next= thread;
}
wqueue->last_thread= thread;
/*
Wait until thread is removed from queue by the signaling thread.
The loop protects against stray signals.
*/
do
{
KEYCACHE_DBUG_PRINT("wait", ("suspend thread %ld", (ulong) thread->id));
keycache_pthread_cond_wait(&thread->suspend, mutex);
}
while (thread->next);
}
/*
Remove all threads from queue signaling them to proceed
SYNOPSIS
release_whole_queue()
wqueue pointer to the queue structure
RETURN VALUE
none
NOTES.
See notes for wait_on_queue().
When removed from the queue each thread is signaled via condition
variable thread->suspend.
*/
static void release_whole_queue(KEYCACHE_WQUEUE *wqueue)
{
struct st_my_thread_var *last;
struct st_my_thread_var *next;
struct st_my_thread_var *thread;
/* Queue may be empty. */
if (!(last= wqueue->last_thread))
return;
next= last->next; /* First (oldest) element */
do
{
thread=next;
DBUG_ASSERT(thread && thread->init == 1);
KEYCACHE_DBUG_PRINT("release_whole_queue: signal",
("thread %ld", (ulong) thread->id));
/* Take thread from queue. */
next= thread->next;
thread->next= NULL;
/* Signal the thread. */
keycache_pthread_cond_signal(&thread->suspend);
}
while (thread != last);
/* Now queue is definitely empty. */
wqueue->last_thread= NULL;
}
/*
Unlink a block from the chain of dirty/clean blocks
*/
static inline void unlink_changed(BLOCK_LINK *block)
{
DBUG_ASSERT(block->prev_changed && *block->prev_changed == block);
if (block->next_changed)
block->next_changed->prev_changed= block->prev_changed;
*block->prev_changed= block->next_changed;
#ifdef DBUG_ASSERT_EXISTS
/*
This makes it easier to see it's not in a chain during debugging.
And some DBUG_ASSERT() rely on it.
*/
block->next_changed= NULL;
block->prev_changed= NULL;
#endif
}
/*
Link a block into the chain of dirty/clean blocks
*/
static inline void link_changed(BLOCK_LINK *block, BLOCK_LINK **phead)
{
DBUG_ASSERT(!block->next_changed);
DBUG_ASSERT(!block->prev_changed);
block->prev_changed= phead;
if ((block->next_changed= *phead))
(*phead)->prev_changed= &block->next_changed;
*phead= block;
}
/*
Link a block in a chain of clean blocks of a file.
SYNOPSIS
link_to_file_list()
keycache Key cache handle
block Block to relink
file File to be linked to
unlink If to unlink first
DESCRIPTION
Unlink a block from whichever chain it is linked in, if it's
asked for, and link it to the chain of clean blocks of the
specified file.
NOTE
Please do never set/clear BLOCK_CHANGED outside of
link_to_file_list() or link_to_changed_list().
You would risk to damage correct counting of changed blocks
and to find blocks in the wrong hash.
RETURN
void
*/
static void link_to_file_list(SIMPLE_KEY_CACHE_CB *keycache,
BLOCK_LINK *block, int file,
my_bool unlink_block)
{
DBUG_ASSERT(block->status & BLOCK_IN_USE);
DBUG_ASSERT(block->hash_link && block->hash_link->block == block);
DBUG_ASSERT(block->hash_link->file == file);
if (unlink_block)
unlink_changed(block);
link_changed(block, &keycache->file_blocks[FILE_HASH(file, keycache)]);
if (block->status & BLOCK_CHANGED)
{
block->status&= ~BLOCK_CHANGED;
keycache->blocks_changed--;
keycache->global_blocks_changed--;
}
}
/*
Re-link a block from the clean chain to the dirty chain of a file.
SYNOPSIS
link_to_changed_list()
keycache key cache handle
block block to relink
DESCRIPTION
Unlink a block from the chain of clean blocks of a file
and link it to the chain of dirty blocks of the same file.
NOTE
Please do never set/clear BLOCK_CHANGED outside of
link_to_file_list() or link_to_changed_list().
You would risk to damage correct counting of changed blocks
and to find blocks in the wrong hash.
RETURN
void
*/
static void link_to_changed_list(SIMPLE_KEY_CACHE_CB *keycache,
BLOCK_LINK *block)
{
DBUG_ASSERT(block->status & BLOCK_IN_USE);
DBUG_ASSERT(!(block->status & BLOCK_CHANGED));
DBUG_ASSERT(block->hash_link && block->hash_link->block == block);
unlink_changed(block);
link_changed(block,
&keycache->changed_blocks[FILE_HASH(block->hash_link->file, keycache)]);
block->status|=BLOCK_CHANGED;
keycache->blocks_changed++;
keycache->global_blocks_changed++;
}
/*
Link a block to the LRU chain at the beginning or at the end of
one of two parts.
SYNOPSIS
link_block()
keycache pointer to a key cache data structure
block pointer to the block to link to the LRU chain
hot <-> to link the block into the hot subchain
at_end <-> to link the block at the end of the subchain
RETURN VALUE
none
NOTES.
The LRU ring is represented by a circular list of block structures.
The list is double-linked of the type (**prev,*next) type.
The LRU ring is divided into two parts - hot and warm.
There are two pointers to access the last blocks of these two
parts. The beginning of the warm part follows right after the
end of the hot part.
Only blocks of the warm part can be used for eviction.
The first block from the beginning of this subchain is always
taken for eviction (keycache->last_used->next)
LRU chain: +------+ H O T +------+
+----| end |----...<----| beg |----+
| +------+last +------+ |
v<-link in latest hot (new end) |
| link in latest warm (new end)->^
| +------+ W A R M +------+ |
+----| beg |---->...----| end |----+
+------+ +------+ins
first for eviction
It is also possible that the block is selected for eviction and thus
not linked in the LRU ring.
*/
static void link_block(SIMPLE_KEY_CACHE_CB *keycache, BLOCK_LINK *block,
my_bool hot, my_bool at_end)
{
BLOCK_LINK *ins;
BLOCK_LINK **pins;
DBUG_ASSERT((block->status & ~BLOCK_CHANGED) == (BLOCK_READ | BLOCK_IN_USE));
DBUG_ASSERT(block->hash_link); /*backptr to block NULL from free_block()*/
DBUG_ASSERT(!block->requests);
DBUG_ASSERT(block->prev_changed && *block->prev_changed == block);
DBUG_ASSERT(!block->next_used);
DBUG_ASSERT(!block->prev_used);
if (!hot && keycache->waiting_for_block.last_thread)
{
/* Signal that in the LRU warm sub-chain an available block has appeared */
struct st_my_thread_var *last_thread=
keycache->waiting_for_block.last_thread;
struct st_my_thread_var *first_thread= last_thread->next;
struct st_my_thread_var *next_thread= first_thread;
HASH_LINK *hash_link= (HASH_LINK *) first_thread->keycache_link;
struct st_my_thread_var *thread;
do
{
thread= next_thread;
next_thread= thread->next;
/*
We notify about the event all threads that ask
for the same page as the first thread in the queue
*/
if ((HASH_LINK *) thread->keycache_link == hash_link)
{
KEYCACHE_DBUG_PRINT("link_block: signal",
("thread %ld", (ulong) thread->id));
keycache_pthread_cond_signal(&thread->suspend);
unlink_from_queue(&keycache->waiting_for_block, thread);
block->requests++;
}
}
while (thread != last_thread);
hash_link->block= block;
/*
NOTE: We assigned the block to the hash_link and signalled the
requesting thread(s). But it is possible that other threads runs
first. These threads see the hash_link assigned to a block which
is assigned to another hash_link and not marked BLOCK_IN_SWITCH.
This can be a problem for functions that do not select the block
via its hash_link: flush and free. They do only see a block which
is in a "normal" state and don't know that it will be evicted soon.
We cannot set BLOCK_IN_SWITCH here because only one of the
requesting threads must handle the eviction. All others must wait
for it to complete. If we set the flag here, the threads would not
know who is in charge of the eviction. Without the flag, the first
thread takes the stick and sets the flag.
But we need to note in the block that is has been selected for
eviction. It must not be freed. The evicting thread will not
expect the block in the free list. Before freeing we could also
check if block->requests > 1. But I think including another flag
in the check of block->status is slightly more efficient and
probably easier to read.
*/
block->status|= BLOCK_IN_EVICTION;
KEYCACHE_THREAD_TRACE("link_block: after signaling");
#if defined(KEYCACHE_DEBUG)
KEYCACHE_DBUG_PRINT("link_block",
("linked,unlinked block %u status=%x #requests=%u #available=%u",
BLOCK_NUMBER(block), block->status,
block->requests, keycache->blocks_available));
#endif
return;
}
pins= hot ? &keycache->used_ins : &keycache->used_last;
ins= *pins;
if (ins)
{
ins->next_used->prev_used= &block->next_used;
block->next_used= ins->next_used;
block->prev_used= &ins->next_used;
ins->next_used= block;
if (at_end)
*pins= block;
}
else
{
/* The LRU ring is empty. Let the block point to itself. */
keycache->used_last= keycache->used_ins= block->next_used= block;
block->prev_used= &block->next_used;
}
KEYCACHE_THREAD_TRACE("link_block");
#if defined(KEYCACHE_DEBUG)
keycache->blocks_available++;
KEYCACHE_DBUG_PRINT("link_block",
("linked block %u:%1u status=%x #requests=%u #available=%u",
BLOCK_NUMBER(block), at_end, block->status,
block->requests, keycache->blocks_available));
KEYCACHE_DBUG_ASSERT((ulong) keycache->blocks_available <=
keycache->blocks_used);
#endif
}
/*
Unlink a block from the LRU chain
SYNOPSIS
unlink_block()
keycache pointer to a key cache data structure
block pointer to the block to unlink from the LRU chain
RETURN VALUE
none
NOTES.
See NOTES for link_block
*/
static void unlink_block(SIMPLE_KEY_CACHE_CB *keycache, BLOCK_LINK *block)
{
DBUG_ASSERT((block->status & ~BLOCK_CHANGED) == (BLOCK_READ | BLOCK_IN_USE));
DBUG_ASSERT(block->hash_link); /*backptr to block NULL from free_block()*/
DBUG_ASSERT(!block->requests);
DBUG_ASSERT(block->prev_changed && *block->prev_changed == block);
DBUG_ASSERT(block->next_used && block->prev_used &&
(block->next_used->prev_used == &block->next_used) &&
(*block->prev_used == block));
if (block->next_used == block)
/* The list contains only one member */
keycache->used_last= keycache->used_ins= NULL;
else
{
block->next_used->prev_used= block->prev_used;
*block->prev_used= block->next_used;
if (keycache->used_last == block)
keycache->used_last= STRUCT_PTR(BLOCK_LINK, next_used, block->prev_used);
if (keycache->used_ins == block)
keycache->used_ins=STRUCT_PTR(BLOCK_LINK, next_used, block->prev_used);
}
block->next_used= NULL;
#ifdef DBUG_ASSERT_EXISTS
/*
This makes it easier to see it's not in a chain during debugging.
And some DBUG_ASSERT() rely on it.
*/
block->prev_used= NULL;
#endif
KEYCACHE_THREAD_TRACE("unlink_block");
#if defined(KEYCACHE_DEBUG)
KEYCACHE_DBUG_ASSERT(keycache->blocks_available != 0);
keycache->blocks_available--;
KEYCACHE_DBUG_PRINT("unlink_block",
("unlinked block %u status=%x #requests=%u #available=%u",
BLOCK_NUMBER(block), block->status,
block->requests, keycache->blocks_available));
#endif
}
/*
Register requests for a block.
SYNOPSIS
reg_requests()
keycache Pointer to a key cache data structure.
block Pointer to the block to register a request on.
count Number of requests. Always 1.
NOTE
The first request unlinks the block from the LRU ring. This means
that it is protected against eviction.
RETURN
void
*/
static void reg_requests(SIMPLE_KEY_CACHE_CB *keycache,
BLOCK_LINK *block, int count)
{
DBUG_ASSERT(block->status & BLOCK_IN_USE);
DBUG_ASSERT(block->hash_link);
if (!block->requests)
unlink_block(keycache, block);
block->requests+=count;
}
/*
Unregister request for a block
linking it to the LRU chain if it's the last request
SYNOPSIS
unreg_request()
keycache pointer to a key cache data structure
block pointer to the block to link to the LRU chain
at_end <-> to link the block at the end of the LRU chain
RETURN VALUE
none
NOTES.
Every linking to the LRU ring decrements by one a special block
counter (if it's positive). If the at_end parameter is TRUE the block is
added either at the end of warm sub-chain or at the end of hot sub-chain.
It is added to the hot subchain if its counter is zero and number of
blocks in warm sub-chain is not less than some low limit (determined by
the division_limit parameter). Otherwise the block is added to the warm
sub-chain. If the at_end parameter is FALSE the block is always added
at beginning of the warm sub-chain.
Thus a warm block can be promoted to the hot sub-chain when its counter
becomes zero for the first time.
At the same time the block at the very beginning of the hot subchain
might be moved to the beginning of the warm subchain if it stays untouched
for a too long time (this time is determined by parameter age_threshold).
It is also possible that the block is selected for eviction and thus
not linked in the LRU ring.
*/
static void unreg_request(SIMPLE_KEY_CACHE_CB *keycache,
BLOCK_LINK *block, int at_end)
{
DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
DBUG_ASSERT(block->hash_link); /*backptr to block NULL from free_block()*/
DBUG_ASSERT(block->requests);
DBUG_ASSERT(block->prev_changed && *block->prev_changed == block);
DBUG_ASSERT(!block->next_used);
DBUG_ASSERT(!block->prev_used);
/*
Unregister the request, but do not link erroneous blocks into the
LRU ring.
*/
if (!--block->requests && !(block->status & BLOCK_ERROR))
{
my_bool hot;
if (block->hits_left)
block->hits_left--;
hot= !block->hits_left && at_end &&
keycache->warm_blocks > keycache->min_warm_blocks;
if (hot)
{
if (block->temperature == BLOCK_WARM)
keycache->warm_blocks--;
block->temperature= BLOCK_HOT;
KEYCACHE_DBUG_PRINT("unreg_request", ("#warm_blocks: %lu",
keycache->warm_blocks));
}
link_block(keycache, block, hot, (my_bool)at_end);
block->last_hit_time= keycache->keycache_time;
keycache->keycache_time++;
/*
At this place, the block might be in the LRU ring or not. If an
evicter was waiting for a block, it was selected for eviction and
not linked in the LRU ring.
*/
/*
Check if we should link a hot block to the warm block sub-chain.
It is possible that we select the same block as above. But it can
also be another block. In any case a block from the LRU ring is
selected. In other words it works even if the above block was
selected for eviction and not linked in the LRU ring. Since this
happens only if the LRU ring is empty, the block selected below
would be NULL and the rest of the function skipped.
*/
block= keycache->used_ins;
if (block && keycache->keycache_time - block->last_hit_time >
keycache->age_threshold)
{
unlink_block(keycache, block);
link_block(keycache, block, 0, 0);
if (block->temperature != BLOCK_WARM)
{
keycache->warm_blocks++;
block->temperature= BLOCK_WARM;
}
KEYCACHE_DBUG_PRINT("unreg_request", ("#warm_blocks: %lu",
keycache->warm_blocks));
}
}
}
/*
Remove a reader of the page in block
*/
static void remove_reader(BLOCK_LINK *block)
{
DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
DBUG_ASSERT(block->hash_link && block->hash_link->block == block);
DBUG_ASSERT(block->prev_changed && *block->prev_changed == block);
DBUG_ASSERT(!block->next_used);
DBUG_ASSERT(!block->prev_used);
DBUG_ASSERT(block->hash_link->requests);
if (! --block->hash_link->requests && block->condvar)
keycache_pthread_cond_signal(block->condvar);
}
/*
Wait until the last reader of the page in block
signals on its termination
*/
static void wait_for_readers(SIMPLE_KEY_CACHE_CB *keycache,
BLOCK_LINK *block)
{
struct st_my_thread_var *thread= my_thread_var;
DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
DBUG_ASSERT(!(block->status & (BLOCK_IN_FLUSH | BLOCK_CHANGED)));
DBUG_ASSERT(block->hash_link);
DBUG_ASSERT(block->hash_link->block == block);
/* Linked in file_blocks or changed_blocks hash. */
DBUG_ASSERT(block->prev_changed && *block->prev_changed == block);
/* Not linked in LRU ring. */
DBUG_ASSERT(!block->next_used);
DBUG_ASSERT(!block->prev_used);
while (block->hash_link->requests)
{
KEYCACHE_DBUG_PRINT("wait_for_readers: wait",
("suspend thread %ld block %u",
(ulong) thread->id, BLOCK_NUMBER(block)));
/* There must be no other waiter. We have no queue here. */
DBUG_ASSERT(!block->condvar);
block->condvar= &thread->suspend;
keycache_pthread_cond_wait(&thread->suspend, &keycache->cache_lock);
block->condvar= NULL;
}
}
/*
Add a hash link to a bucket in the hash_table
*/
static inline void link_hash(HASH_LINK **start, HASH_LINK *hash_link)
{
if (*start)
(*start)->prev= &hash_link->next;
hash_link->next= *start;
hash_link->prev= start;
*start= hash_link;
}
/*
Remove a hash link from the hash table
*/
static void unlink_hash(SIMPLE_KEY_CACHE_CB *keycache, HASH_LINK *hash_link)
{
KEYCACHE_DBUG_PRINT("unlink_hash", ("fd: %u pos_ %lu #requests=%u",
(uint) hash_link->file,(ulong) hash_link->diskpos, hash_link->requests));
KEYCACHE_DBUG_ASSERT(hash_link->requests == 0);
if ((*hash_link->prev= hash_link->next))
hash_link->next->prev= hash_link->prev;
hash_link->block= NULL;
if (keycache->waiting_for_hash_link.last_thread)
{
/* Signal that a free hash link has appeared */
struct st_my_thread_var *last_thread=
keycache->waiting_for_hash_link.last_thread;
struct st_my_thread_var *first_thread= last_thread->next;
struct st_my_thread_var *next_thread= first_thread;
KEYCACHE_PAGE *first_page= (KEYCACHE_PAGE *) (first_thread->keycache_link);
struct st_my_thread_var *thread;
hash_link->file= first_page->file;
hash_link->diskpos= first_page->filepos;
do
{
KEYCACHE_PAGE *page;
thread= next_thread;
page= (KEYCACHE_PAGE *) thread->keycache_link;
next_thread= thread->next;
/*
We notify about the event all threads that ask
for the same page as the first thread in the queue
*/
if (page->file == hash_link->file && page->filepos == hash_link->diskpos)
{
KEYCACHE_DBUG_PRINT("unlink_hash: signal",
("thread %ld", (ulong) thread->id));
keycache_pthread_cond_signal(&thread->suspend);
unlink_from_queue(&keycache->waiting_for_hash_link, thread);
}
}
while (thread != last_thread);
link_hash(&keycache->hash_root[KEYCACHE_HASH(hash_link->file,
hash_link->diskpos)],
hash_link);
return;
}
hash_link->next= keycache->free_hash_list;
keycache->free_hash_list= hash_link;
}
/*
Get the hash link for a page
*/
static HASH_LINK *get_hash_link(SIMPLE_KEY_CACHE_CB *keycache,
int file, my_off_t filepos)
{
reg1 HASH_LINK *hash_link, **start;
#if defined(KEYCACHE_DEBUG)
int cnt;
#endif
KEYCACHE_DBUG_PRINT("get_hash_link", ("fd: %u pos: %lu",
(uint) file,(ulong) filepos));
restart:
/*
Find the bucket in the hash table for the pair (file, filepos);
start contains the head of the bucket list,
hash_link points to the first member of the list
*/
hash_link= *(start= &keycache->hash_root[KEYCACHE_HASH(file, filepos)]);
#if defined(KEYCACHE_DEBUG)
cnt= 0;
#endif
/* Look for an element for the pair (file, filepos) in the bucket chain */
while (hash_link &&
(hash_link->diskpos != filepos || hash_link->file != file))
{
hash_link= hash_link->next;
#if defined(KEYCACHE_DEBUG)
cnt++;
if (! (cnt <= keycache->hash_links_used))
{
int i;
for (i=0, hash_link= *start ;
i < cnt ; i++, hash_link= hash_link->next)
{
KEYCACHE_DBUG_PRINT("get_hash_link", ("fd: %u pos: %lu",
(uint) hash_link->file,(ulong) hash_link->diskpos));
}
}
KEYCACHE_DBUG_ASSERT(cnt <= keycache->hash_links_used);
#endif
}
if (! hash_link)
{
/* There is no hash link in the hash table for the pair (file, filepos) */
if (keycache->free_hash_list)
{
hash_link= keycache->free_hash_list;
keycache->free_hash_list= hash_link->next;
}
else if (keycache->hash_links_used < keycache->hash_links)
{
hash_link= &keycache->hash_link_root[keycache->hash_links_used++];
}
else
{
/* Wait for a free hash link */
struct st_my_thread_var *thread= my_thread_var;
KEYCACHE_PAGE page;
KEYCACHE_DBUG_PRINT("get_hash_link", ("waiting"));
page.file= file;
page.filepos= filepos;
thread->keycache_link= (void *) &page;
link_into_queue(&keycache->waiting_for_hash_link, thread);
KEYCACHE_DBUG_PRINT("get_hash_link: wait",
("suspend thread %ld", (ulong) thread->id));
keycache_pthread_cond_wait(&thread->suspend,
&keycache->cache_lock);
thread->keycache_link= NULL;
goto restart;
}
hash_link->file= file;
hash_link->diskpos= filepos;
link_hash(start, hash_link);
}
/* Register the request for the page */
hash_link->requests++;
return hash_link;
}
/*
Get a block for the file page requested by a keycache read/write operation;
If the page is not in the cache return a free block, if there is none
return the lru block after saving its buffer if the page is dirty.
SYNOPSIS
find_key_block()
keycache pointer to a key cache data structure
file handler for the file to read page from
filepos position of the page in the file
init_hits_left how initialize the block counter for the page
wrmode <-> get for writing
page_st out {PAGE_READ,PAGE_TO_BE_READ,PAGE_WAIT_TO_BE_READ}
RETURN VALUE
Pointer to the found block if successful, 0 - otherwise
NOTES.
For the page from file positioned at filepos the function checks whether
the page is in the key cache specified by the first parameter.
If this is the case it immediately returns the block.
If not, the function first chooses a block for this page. If there is
no not used blocks in the key cache yet, the function takes the block
at the very beginning of the warm sub-chain. It saves the page in that
block if it's dirty before returning the pointer to it.
The function returns in the page_st parameter the following values:
PAGE_READ - if page already in the block,
PAGE_TO_BE_READ - if it is to be read yet by the current thread
WAIT_TO_BE_READ - if it is to be read by another thread
If an error occurs THE BLOCK_ERROR bit is set in the block status.
It might happen that there are no blocks in LRU chain (in warm part) -
all blocks are unlinked for some read/write operations. Then the function
waits until first of this operations links any block back.
*/
static BLOCK_LINK *find_key_block(SIMPLE_KEY_CACHE_CB *keycache,
File file, my_off_t filepos,
int init_hits_left,
int wrmode, int *page_st)
{
HASH_LINK *hash_link;
BLOCK_LINK *block;
int error= 0;
int page_status;
DBUG_ENTER("find_key_block");
KEYCACHE_THREAD_TRACE("find_key_block:begin");
DBUG_PRINT("enter", ("fd: %d pos: %lu wrmode: %d",
file, (ulong) filepos, wrmode));
KEYCACHE_DBUG_PRINT("find_key_block", ("fd: %d pos: %lu wrmode: %d",
file, (ulong) filepos,
wrmode));
#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG)
DBUG_EXECUTE("check_keycache2",
test_key_cache(keycache, "start of find_key_block", 0););
#endif
restart:
/*
If the flush phase of a resize operation fails, the cache is left
unusable. This will be detected only after "goto restart".
*/
if (!keycache->can_be_used)
DBUG_RETURN(0);
/*
Find the hash_link for the requested file block (file, filepos). We
do always get a hash_link here. It has registered our request so
that no other thread can use it for another file block until we
release the request (which is done by remove_reader() usually). The
hash_link can have a block assigned to it or not. If there is a
block, it may be assigned to this hash_link or not. In cases where a
block is evicted from the cache, it is taken from the LRU ring and
referenced by the new hash_link. But the block can still be assigned
to its old hash_link for some time if it needs to be flushed first,
or if there are other threads still reading it.
Summary:
hash_link is always returned.
hash_link->block can be:
- NULL or
- not assigned to this hash_link or
- assigned to this hash_link. If assigned, the block can have
- invalid data (when freshly assigned) or
- valid data. Valid data can be
- changed over the file contents (dirty) or
- not changed (clean).
*/
hash_link= get_hash_link(keycache, file, filepos);
DBUG_ASSERT((hash_link->file == file) && (hash_link->diskpos == filepos));
page_status= -1;
if ((block= hash_link->block) &&
block->hash_link == hash_link && (block->status & BLOCK_READ))
{
/* Assigned block with valid (changed or unchanged) contents. */
page_status= PAGE_READ;
}
/*
else (page_status == -1)
- block == NULL or
- block not assigned to this hash_link or
- block assigned but not yet read from file (invalid data).
*/
if (keycache->in_resize)
{
/* This is a request during a resize operation */
if (!block)
{
struct st_my_thread_var *thread;
/*
The file block is not in the cache. We don't need it in the
cache: we are going to read or write directly to file. Cancel
the request. We can simply decrement hash_link->requests because
we did not release cache_lock since increasing it. So no other
thread can wait for our request to become released.
*/
if (hash_link->requests == 1)
{
/*
We are the only one to request this hash_link (this file/pos).
Free the hash_link.
*/
hash_link->requests--;
unlink_hash(keycache, hash_link);
DBUG_RETURN(0);
}
/*
More requests on the hash_link. Someone tries to evict a block
for this hash_link (could have started before resizing started).
This means that the LRU ring is empty. Otherwise a block could
be assigned immediately. Behave like a thread that wants to
evict a block for this file/pos. Add to the queue of threads
waiting for a block. Wait until there is one assigned.
Refresh the request on the hash-link so that it cannot be reused
for another file/pos.
*/
thread= my_thread_var;
thread->keycache_link= (void *) hash_link;
link_into_queue(&keycache->waiting_for_block, thread);
do
{
KEYCACHE_DBUG_PRINT("find_key_block: wait",
("suspend thread %ld", (ulong) thread->id));
keycache_pthread_cond_wait(&thread->suspend,
&keycache->cache_lock);
} while (thread->next);
thread->keycache_link= NULL;
/*
A block should now be assigned to the hash_link. But it may
still need to be evicted. Anyway, we should re-check the
situation. page_status must be set correctly.
*/
hash_link->requests--;
goto restart;
} /* end of if (!block) */
/*
There is a block for this file/pos in the cache. Register a
request on it. This unlinks it from the LRU ring (if it is there)
and hence protects it against eviction (if not already in
eviction). We need this for returning the block to the caller, for
calling remove_reader() (for debugging purposes), and for calling
free_block(). The only case where we don't need the request is if
the block is in eviction. In that case we have to unregister the
request later.
*/
reg_requests(keycache, block, 1);
if (page_status != PAGE_READ)
{
/*
- block not assigned to this hash_link or
- block assigned but not yet read from file (invalid data).
This must be a block in eviction. It will be read soon. We need
to wait here until this happened. Otherwise the caller could
access a wrong block or a block which is in read. While waiting
we cannot lose hash_link nor block. We have registered a request
on the hash_link. Everything can happen to the block but changes
in the hash_link -> block relationship. In other words:
everything can happen to the block but free or another completed
eviction.
Note that we behave like a secondary requestor here. We just
cannot return with PAGE_WAIT_TO_BE_READ. This would work for
read requests and writes on dirty blocks that are not in flush
only. Waiting here on COND_FOR_REQUESTED works in all
situations.
*/
DBUG_ASSERT(((block->hash_link != hash_link) &&
(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH))) ||
((block->hash_link == hash_link) &&
!(block->status & BLOCK_READ)));
wait_on_queue(&block->wqueue[COND_FOR_REQUESTED], &keycache->cache_lock);
/*
Here we can trust that the block has been assigned to this
hash_link (block->hash_link == hash_link) and read into the
buffer (BLOCK_READ). The worst things possible here are that the
block is in free (BLOCK_REASSIGNED). But the block is still
assigned to the hash_link. The freeing thread waits until we
release our request on the hash_link. The block must not be
again in eviction because we registered an request on it before
starting to wait.
*/
DBUG_ASSERT(block->hash_link == hash_link);
DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
DBUG_ASSERT(!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH)));
}
/*
The block is in the cache. Assigned to the hash_link. Valid data.
Note that in case of page_st == PAGE_READ, the block can be marked
for eviction. In any case it can be marked for freeing.
*/
if (!wrmode)
{
/* A reader can just read the block. */
*page_st= PAGE_READ;
DBUG_ASSERT((hash_link->file == file) &&
(hash_link->diskpos == filepos) &&
(block->hash_link == hash_link));
DBUG_RETURN(block);
}
/*
This is a writer. No two writers for the same block can exist.
This must be assured by locks outside of the key cache.
*/
DBUG_ASSERT(!(block->status & BLOCK_FOR_UPDATE) || fail_block(block));
while (block->status & BLOCK_IN_FLUSH)
{
/*
Wait until the block is flushed to file. Do not release the
request on the hash_link yet to prevent that the block is freed
or reassigned while we wait. While we wait, several things can
happen to the block, including another flush. But the block
cannot be reassigned to another hash_link until we release our
request on it. But it can be marked BLOCK_REASSIGNED from free
or eviction, while they wait for us to release the hash_link.
*/
wait_on_queue(&block->wqueue[COND_FOR_SAVED], &keycache->cache_lock);
/*
If the flush phase failed, the resize could have finished while
we waited here.
*/
if (!keycache->in_resize)
{
remove_reader(block);
unreg_request(keycache, block, 1);
goto restart;
}
DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
DBUG_ASSERT(!(block->status & BLOCK_FOR_UPDATE) || fail_block(block));
DBUG_ASSERT(block->hash_link == hash_link);
}
if (block->status & BLOCK_CHANGED)
{
/*
We want to write a block with changed contents. If the cache
block size is bigger than the callers block size (e.g. MyISAM),
the caller may replace part of the block only. Changes of the
other part of the block must be preserved. Since the block has
not yet been selected for flush, we can still add our changes.
*/
*page_st= PAGE_READ;
DBUG_ASSERT((hash_link->file == file) &&
(hash_link->diskpos == filepos) &&
(block->hash_link == hash_link));
DBUG_RETURN(block);
}
/*
This is a write request for a clean block. We do not want to have
new dirty blocks in the cache while resizing. We will free the
block and write directly to file. If the block is in eviction or
in free, we just let it go.
Unregister from the hash_link. This must be done before freeing
the block. And it must be done if not freeing the block. Because
we could have waited above, we need to call remove_reader(). Other
threads could wait for us to release our request on the hash_link.
*/
remove_reader(block);
/* If the block is not in eviction and not in free, we can free it. */
if (!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH |
BLOCK_REASSIGNED)))
{
/*
Free block as we are going to write directly to file.
Although we have an exlusive lock for the updated key part,
the control can be yielded by the current thread as we might
have unfinished readers of other key parts in the block
buffer. Still we are guaranteed not to have any readers
of the key part we are writing into until the block is
removed from the cache as we set the BLOCK_REASSIGNED
flag (see the code below that handles reading requests).
*/
free_block(keycache, block);
}
else
{
/*
The block will be evicted/freed soon. Don't touch it in any way.
Unregister the request that we registered above.
*/
unreg_request(keycache, block, 1);
/*
The block is still assigned to the hash_link (the file/pos that
we are going to write to). Wait until the eviction/free is
complete. Otherwise the direct write could complete before all
readers are done with the block. So they could read outdated
data.
Since we released our request on the hash_link, it can be reused
for another file/pos. Hence we cannot just check for
block->hash_link == hash_link. As long as the resize is
proceeding the block cannot be reassigned to the same file/pos
again. So we can terminate the loop when the block is no longer
assigned to this file/pos.
*/
do
{
wait_on_queue(&block->wqueue[COND_FOR_SAVED],
&keycache->cache_lock);
/*
If the flush phase failed, the resize could have finished
while we waited here.
*/
if (!keycache->in_resize)
goto restart;
} while (block->hash_link &&
(block->hash_link->file == file) &&
(block->hash_link->diskpos == filepos));
}
DBUG_RETURN(0);
}
if (page_status == PAGE_READ &&
(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH |
BLOCK_REASSIGNED)))
{
/*
This is a request for a block to be removed from cache. The block
is assigned to this hash_link and contains valid data, but is
marked for eviction or to be freed. Possible reasons why it has
not yet been evicted/freed can be a flush before reassignment
(BLOCK_IN_SWITCH), readers of the block have not finished yet
(BLOCK_REASSIGNED), or the evicting thread did not yet awake after
the block has been selected for it (BLOCK_IN_EVICTION).
*/
KEYCACHE_DBUG_PRINT("find_key_block",
("request for old page in block %u "
"wrmode: %d block->status: %d",
BLOCK_NUMBER(block), wrmode, block->status));
/*
Only reading requests can proceed until the old dirty page is flushed,
all others are to be suspended, then resubmitted
*/
if (!wrmode && !(block->status & BLOCK_REASSIGNED))
{
/*
This is a read request and the block not yet reassigned. We can
register our request and proceed. This unlinks the block from
the LRU ring and protects it against eviction.
*/
reg_requests(keycache, block, 1);
}
else
{
/*
Either this is a write request for a block that is in eviction
or in free. We must not use it any more. Instead we must evict
another block. But we cannot do this before the eviction/free is
done. Otherwise we would find the same hash_link + block again
and again.
Or this is a read request for a block in eviction/free that does
not require a flush, but waits for readers to finish with the
block. We do not read this block to let the eviction/free happen
as soon as possible. Again we must wait so that we don't find
the same hash_link + block again and again.
*/
DBUG_ASSERT(hash_link->requests);
hash_link->requests--;
KEYCACHE_DBUG_PRINT("find_key_block",
("request waiting for old page to be saved"));
wait_on_queue(&block->wqueue[COND_FOR_SAVED], &keycache->cache_lock);
KEYCACHE_DBUG_PRINT("find_key_block",
("request for old page resubmitted"));
/*
The block is no longer assigned to this hash_link.
Get another one.
*/
goto restart;
}
}
else
{
/*
This is a request for a new block or for a block not to be removed.
Either
- block == NULL or
- block not assigned to this hash_link or
- block assigned but not yet read from file,
or
- block assigned with valid (changed or unchanged) data and
- it will not be reassigned/freed.
*/
if (! block)
{
/* No block is assigned to the hash_link yet. */
if (keycache->blocks_unused)
{
if (keycache->free_block_list)
{
/* There is a block in the free list. */
block= keycache->free_block_list;
keycache->free_block_list= block->next_used;
block->next_used= NULL;
}
else
{
size_t block_mem_offset;
/* There are some never used blocks, take first of them */
DBUG_ASSERT(keycache->blocks_used <
(ulong) keycache->disk_blocks);
block= &keycache->block_root[keycache->blocks_used];
block_mem_offset=
((size_t) keycache->blocks_used) * keycache->key_cache_block_size;
block->buffer= ADD_TO_PTR(keycache->block_mem,
block_mem_offset,
uchar*);
keycache->blocks_used++;
DBUG_ASSERT(!block->next_used);
}
DBUG_ASSERT(!block->prev_used);
DBUG_ASSERT(!block->next_changed);
DBUG_ASSERT(!block->prev_changed);
DBUG_ASSERT(!block->hash_link);
DBUG_ASSERT(!block->status);
DBUG_ASSERT(!block->requests);
keycache->blocks_unused--;
block->status= BLOCK_IN_USE;
block->length= 0;
block->offset= keycache->key_cache_block_size;
block->requests= 1;
block->temperature= BLOCK_COLD;
block->hits_left= init_hits_left;
block->last_hit_time= 0;
block->hash_link= hash_link;
hash_link->block= block;
link_to_file_list(keycache, block, file, 0);
page_status= PAGE_TO_BE_READ;
KEYCACHE_DBUG_PRINT("find_key_block",
("got free or never used block %u",
BLOCK_NUMBER(block)));
}
else
{
/*
There are no free blocks and no never used blocks, use a block
from the LRU ring.
*/
if (! keycache->used_last)
{
/*
The LRU ring is empty. Wait until a new block is added to
it. Several threads might wait here for the same hash_link,
all of them must get the same block. While waiting for a
block, after a block is selected for this hash_link, other
threads can run first before this one awakes. During this
time interval other threads find this hash_link pointing to
the block, which is still assigned to another hash_link. In
this case the block is not marked BLOCK_IN_SWITCH yet, but
it is marked BLOCK_IN_EVICTION.
*/
struct st_my_thread_var *thread= my_thread_var;
thread->keycache_link= (void *) hash_link;
link_into_queue(&keycache->waiting_for_block, thread);
do
{
KEYCACHE_DBUG_PRINT("find_key_block: wait",
("suspend thread %ld", (ulong) thread->id));
keycache_pthread_cond_wait(&thread->suspend,
&keycache->cache_lock);
}
while (thread->next);
thread->keycache_link= NULL;
/* Assert that block has a request registered. */
DBUG_ASSERT(hash_link->block->requests);
/* Assert that block is not in LRU ring. */
DBUG_ASSERT(!hash_link->block->next_used);
DBUG_ASSERT(!hash_link->block->prev_used);
}
/*
If we waited above, hash_link->block has been assigned by
link_block(). Otherwise it is still NULL. In the latter case
we need to grab a block from the LRU ring ourselves.
*/
block= hash_link->block;
if (! block)
{
/* Select the last block from the LRU ring. */
block= keycache->used_last->next_used;
block->hits_left= init_hits_left;
block->last_hit_time= 0;
hash_link->block= block;
/*
Register a request on the block. This unlinks it from the
LRU ring and protects it against eviction.
*/
DBUG_ASSERT(!block->requests);
reg_requests(keycache, block,1);
/*
We do not need to set block->status|= BLOCK_IN_EVICTION here
because we will set block->status|= BLOCK_IN_SWITCH
immediately without releasing the lock in between. This does
also support debugging. When looking at the block, one can
see if the block has been selected by link_block() after the
LRU ring was empty, or if it was grabbed directly from the
LRU ring in this branch.
*/
}
/*
If we had to wait above, there is a small chance that another
thread grabbed this block for the same file block already. But
in most cases the first condition is true.
*/
if (block->hash_link != hash_link &&
! (block->status & BLOCK_IN_SWITCH) )
{
/* this is a primary request for a new page */
block->status|= BLOCK_IN_SWITCH;
KEYCACHE_DBUG_PRINT("find_key_block",
("got block %u for new page", BLOCK_NUMBER(block)));
if (block->status & BLOCK_CHANGED)
{
/* The block contains a dirty page - push it out of the cache */
KEYCACHE_DBUG_PRINT("find_key_block", ("block is dirty"));
if (block->status & BLOCK_IN_FLUSH)
{
/*
The block is marked for flush. If we do not wait here,
it could happen that we write the block, reassign it to
another file block, then, before the new owner can read
the new file block, the flusher writes the cache block
(which still has the old contents) to the new file block!
*/
wait_on_queue(&block->wqueue[COND_FOR_SAVED],
&keycache->cache_lock);
/*
The block is marked BLOCK_IN_SWITCH. It should be left
alone except for reading. No free, no write.
*/
DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
DBUG_ASSERT(!(block->status & (BLOCK_REASSIGNED |
BLOCK_CHANGED |
BLOCK_FOR_UPDATE)));
}
else
{
block->status|= BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE;
/*
BLOCK_IN_EVICTION may be true or not. Other flags must
have a fixed value.
*/
DBUG_ASSERT((block->status & ~BLOCK_IN_EVICTION) ==
(BLOCK_READ | BLOCK_IN_SWITCH |
BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE |
BLOCK_CHANGED | BLOCK_IN_USE));
DBUG_ASSERT(block->hash_link);
keycache_pthread_mutex_unlock(&keycache->cache_lock);
/*
The call is thread safe because only the current
thread might change the block->hash_link value
*/
error= (int)my_pwrite(block->hash_link->file,
block->buffer + block->offset,
block->length - block->offset,
block->hash_link->diskpos + block->offset,
MYF(MY_NABP | MY_WAIT_IF_FULL));
keycache_pthread_mutex_lock(&keycache->cache_lock);
/* Block status must not have changed. */
DBUG_ASSERT((block->status & ~BLOCK_IN_EVICTION) ==
(BLOCK_READ | BLOCK_IN_SWITCH |
BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE |
BLOCK_CHANGED | BLOCK_IN_USE) || fail_block(block));
keycache->global_cache_write++;
}
}
block->status|= BLOCK_REASSIGNED;
/*
The block comes from the LRU ring. It must have a hash_link
assigned.
*/
DBUG_ASSERT(block->hash_link);
if (block->hash_link)
{
/*
All pending requests for this page must be resubmitted.
This must be done before waiting for readers. They could
wait for the flush to complete. And we must also do it
after the wait. Flushers might try to free the block while
we wait. They would wait until the reassignment is
complete. Also the block status must reflect the correct
situation: The block is not changed nor in flush any more.
Note that we must not change the BLOCK_CHANGED flag
outside of link_to_file_list() so that it is always in the
correct queue and the *blocks_changed counters are
correct.
*/
block->status&= ~(BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE);
link_to_file_list(keycache, block, block->hash_link->file, 1);
release_whole_queue(&block->wqueue[COND_FOR_SAVED]);
/*
The block is still assigned to its old hash_link.
Wait until all pending read requests
for this page are executed
(we could have avoided this waiting, if we had read
a page in the cache in a sweep, without yielding control)
*/
wait_for_readers(keycache, block);
DBUG_ASSERT(block->hash_link && block->hash_link->block == block &&
block->prev_changed);
/* The reader must not have been a writer. */
DBUG_ASSERT(!(block->status & BLOCK_CHANGED));
/* Wake flushers that might have found the block in between. */
release_whole_queue(&block->wqueue[COND_FOR_SAVED]);
/* Remove the hash link for the old file block from the hash. */
unlink_hash(keycache, block->hash_link);
/*
For sanity checks link_to_file_list() asserts that block
and hash_link refer to each other. Hence we need to assign
the hash_link first, but then we would not know if it was
linked before. Hence we would not know if to unlink it. So
unlink it here and call link_to_file_list(..., FALSE).
*/
unlink_changed(block);
}
block->status= error ? BLOCK_ERROR : BLOCK_IN_USE ;
block->length= 0;
block->offset= keycache->key_cache_block_size;
block->hash_link= hash_link;
link_to_file_list(keycache, block, file, 0);
page_status= PAGE_TO_BE_READ;
KEYCACHE_DBUG_ASSERT(block->hash_link->block == block);
KEYCACHE_DBUG_ASSERT(hash_link->block->hash_link == hash_link);
}
else
{
/*
Either (block->hash_link == hash_link),
or (block->status & BLOCK_IN_SWITCH).
This is for secondary requests for a new file block only.
Either it is already assigned to the new hash_link meanwhile
(if we had to wait due to empty LRU), or it is already in
eviction by another thread. Since this block has been
grabbed from the LRU ring and attached to this hash_link,
another thread cannot grab the same block from the LRU ring
anymore. If the block is in eviction already, it must become
attached to the same hash_link and as such destined for the
same file block.
*/
KEYCACHE_DBUG_PRINT("find_key_block",
("block->hash_link: %p hash_link: %p "
"block->status: %u", block->hash_link,
hash_link, block->status ));
page_status= (((block->hash_link == hash_link) &&
(block->status & BLOCK_READ)) ?
PAGE_READ : PAGE_WAIT_TO_BE_READ);
}
}
}
else
{
/*
Block is not NULL. This hash_link points to a block.
Either
- block not assigned to this hash_link (yet) or
- block assigned but not yet read from file,
or
- block assigned with valid (changed or unchanged) data and
- it will not be reassigned/freed.
The first condition means hash_link points to a block in
eviction. This is not necessarily marked by BLOCK_IN_SWITCH yet.
But then it is marked BLOCK_IN_EVICTION. See the NOTE in
link_block(). In both cases it is destined for this hash_link
and its file block address. When this hash_link got its block
address, the block was removed from the LRU ring and cannot be
selected for eviction (for another hash_link) again.
Register a request on the block. This is another protection
against eviction.
*/
DBUG_ASSERT(((block->hash_link != hash_link) &&
(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH))) ||
((block->hash_link == hash_link) &&
!(block->status & BLOCK_READ)) ||
((block->status & BLOCK_READ) &&
!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH))));
reg_requests(keycache, block, 1);
KEYCACHE_DBUG_PRINT("find_key_block",
("block->hash_link: %p hash_link: %p "
"block->status: %u", block->hash_link,
hash_link, block->status ));
page_status= (((block->hash_link == hash_link) &&
(block->status & BLOCK_READ)) ?
PAGE_READ : PAGE_WAIT_TO_BE_READ);
}
}
KEYCACHE_DBUG_ASSERT(page_status != -1);
/* Same assert basically, but be very sure. */
KEYCACHE_DBUG_ASSERT(block);
/* Assert that block has a request and is not in LRU ring. */
DBUG_ASSERT(block->requests);
DBUG_ASSERT(!block->next_used);
DBUG_ASSERT(!block->prev_used);
/* Assert that we return the correct block. */
DBUG_ASSERT((page_status == PAGE_WAIT_TO_BE_READ) ||
((block->hash_link->file == file) &&
(block->hash_link->diskpos == filepos)));
*page_st=page_status;
KEYCACHE_DBUG_PRINT("find_key_block",
("fd: %d pos: %lu block->status: %u page_status: %d",
file, (ulong) filepos, block->status,
page_status));
#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG)
DBUG_EXECUTE("check_keycache2",
test_key_cache(keycache, "end of find_key_block",0););
#endif
KEYCACHE_THREAD_TRACE("find_key_block:end");
DBUG_RETURN(block);
}
/*
Read into a key cache block buffer from disk.
SYNOPSIS
read_block_{primary|secondary}()
keycache pointer to a key cache data structure
block block to which buffer the data is to be read
read_length size of data to be read
min_length at least so much data must be read
RETURN VALUE
None
NOTES.
The function either reads a page data from file to the block buffer,
or waits until another thread reads it. What page to read is determined
by a block parameter - reference to a hash link for this page.
If an error occurs THE BLOCK_ERROR bit is set in the block status.
We do not report error when the size of successfully read
portion is less than read_length, but not less than min_length.
*/
static void read_block_primary(SIMPLE_KEY_CACHE_CB *keycache,
BLOCK_LINK *block, uint read_length,
uint min_length)
{
size_t got_length;
/* On entry cache_lock is locked */
KEYCACHE_THREAD_TRACE("read_block_primary");
/*
This code is executed only by threads that submitted primary
requests. Until block->status contains BLOCK_READ, all other
request for the block become secondary requests. For a primary
request the block must be properly initialized.
*/
DBUG_ASSERT(((block->status & ~BLOCK_FOR_UPDATE) == BLOCK_IN_USE) ||
fail_block(block));
DBUG_ASSERT((block->length == 0) || fail_block(block));
DBUG_ASSERT((block->offset == keycache->key_cache_block_size) ||
fail_block(block));
DBUG_ASSERT((block->requests > 0) || fail_block(block));
KEYCACHE_DBUG_PRINT("read_block_primary",
("page to be read by primary request"));
keycache->global_cache_read++;
/* Page is not in buffer yet, is to be read from disk */
keycache_pthread_mutex_unlock(&keycache->cache_lock);
/*
Here other threads may step in and register as secondary readers.
They will register in block->wqueue[COND_FOR_REQUESTED].
*/
got_length= my_pread(block->hash_link->file, block->buffer,
read_length, block->hash_link->diskpos, MYF(0));
keycache_pthread_mutex_lock(&keycache->cache_lock);
/*
The block can now have been marked for free (in case of
FLUSH_RELEASE). Otherwise the state must be unchanged.
*/
DBUG_ASSERT(((block->status & ~(BLOCK_REASSIGNED |
BLOCK_FOR_UPDATE)) == BLOCK_IN_USE) ||
fail_block(block));
DBUG_ASSERT((block->length == 0) || fail_block(block));
DBUG_ASSERT((block->offset == keycache->key_cache_block_size) ||
fail_block(block));
DBUG_ASSERT((block->requests > 0) || fail_block(block));
if (got_length < min_length)
block->status|= BLOCK_ERROR;
else
{
block->status|= BLOCK_READ;
block->length= (uint)got_length;
/*
Do not set block->offset here. If this block is marked
BLOCK_CHANGED later, we want to flush only the modified part. So
only a writer may set block->offset down from
keycache->key_cache_block_size.
*/
}
KEYCACHE_DBUG_PRINT("read_block_primary",
("primary request: new page in cache"));
/* Signal that all pending requests for this page now can be processed */
release_whole_queue(&block->wqueue[COND_FOR_REQUESTED]);
DBUG_ASSERT(keycache->can_be_used);
}
static void read_block_secondary(SIMPLE_KEY_CACHE_CB *keycache,
BLOCK_LINK *block)
{
KEYCACHE_THREAD_TRACE("read_block_secondary");
/*
This code is executed only by threads that submitted secondary
requests. At this point it could happen that the cache block is
not yet assigned to the hash_link for the requested file block.
But at awake from the wait this should be the case. Unfortunately
we cannot assert this here because we do not know the hash_link
for the requested file block nor the file and position. So we have
to assert this in the caller.
*/
KEYCACHE_DBUG_PRINT("read_block_secondary",
("secondary request waiting for new page to be read"));
wait_on_queue(&block->wqueue[COND_FOR_REQUESTED], &keycache->cache_lock);
KEYCACHE_DBUG_PRINT("read_block_secondary",
("secondary request: new page in cache"));
DBUG_ASSERT(keycache->can_be_used);
DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
}
/*
Read a block of data from a simple key cache into a buffer
SYNOPSIS
simple_key_cache_read()
keycache pointer to the control block of a simple key cache
file handler for the file for the block of data to be read
filepos position of the block of data in the file
level determines the weight of the data
buff buffer to where the data must be placed
length length of the buffer
block_length length of the read data from a key cache block
return_buffer return pointer to the key cache buffer with the data
DESCRIPTION
This function is the implementation of the key_cache_read interface
function that is employed by simple (non-partitioned) key caches.
The function takes the parameter keycache as a pointer to the
control block structure of the type SIMPLE_KEY_CACHE_CB for a simple key
cache.
In a general case the function reads a block of data from the key cache
into the buffer buff of the size specified by the parameter length. The
beginning of the block of data to be read is specified by the parameters
file and filepos. The length of the read data is the same as the length
of the buffer. The data is read into the buffer in key_cache_block_size
increments. If the next portion of the data is not found in any key cache
block, first it is read from file into the key cache.
If the parameter return_buffer is not ignored and its value is TRUE, and
the data to be read of the specified size block_length can be read from one
key cache buffer, then the function returns a pointer to the data in the
key cache buffer.
The function takse into account parameters block_length and return buffer
only in a single-threaded environment.
The parameter 'level' is used only by the midpoint insertion strategy
when the data or its portion cannot be found in the key cache.
RETURN VALUE
Returns address from where the data is placed if successful, 0 - otherwise.
NOTES
Filepos must be a multiple of 'block_length', but it doesn't
have to be a multiple of key_cache_block_size;
*/
uchar *simple_key_cache_read(void *keycache_,
File file, my_off_t filepos, int level,
uchar *buff, uint length,
uint block_length __attribute__((unused)),
int return_buffer __attribute__((unused)))
{
SIMPLE_KEY_CACHE_CB *keycache= keycache_;
my_bool locked_and_incremented= FALSE;
int error=0;
uchar *start= buff;
DBUG_ENTER("simple_key_cache_read");
DBUG_PRINT("enter", ("fd: %u pos: %lu length: %u",
(uint) file, (ulong) filepos, length));
if (keycache->key_cache_inited)
{
/* Key cache is used */
reg1 BLOCK_LINK *block;
uint read_length;
uint offset;
int page_st;
if (MYSQL_KEYCACHE_READ_START_ENABLED())
{
MYSQL_KEYCACHE_READ_START(my_filename(file), length,
(ulong) (keycache->blocks_used *
keycache->key_cache_block_size),
(ulong) (keycache->blocks_unused *
keycache->key_cache_block_size));
}
/*
When the key cache is once initialized, we use the cache_lock to
reliably distinguish the cases of normal operation, resizing, and
disabled cache. We always increment and decrement
'cnt_for_resize_op' so that a resizer can wait for pending I/O.
*/
keycache_pthread_mutex_lock(&keycache->cache_lock);
/*
Cache resizing has two phases: Flushing and re-initializing. In
the flush phase read requests are allowed to bypass the cache for
blocks not in the cache. find_key_block() returns NULL in this
case.
After the flush phase new I/O requests must wait until the
re-initialization is done. The re-initialization can be done only
if no I/O request is in progress. The reason is that
key_cache_block_size can change. With enabled cache, I/O is done
in chunks of key_cache_block_size. Every chunk tries to use a
cache block first. If the block size changes in the middle, a
block could be missed and old data could be read.
*/
while (keycache->in_resize && !keycache->resize_in_flush)
wait_on_queue(&keycache->resize_queue, &keycache->cache_lock);
/* Register the I/O for the next resize. */
inc_counter_for_resize_op(keycache);
locked_and_incremented= TRUE;
/* Requested data may not always be aligned to cache blocks. */
offset= (uint) (filepos % keycache->key_cache_block_size);
/* Read data in key_cache_block_size increments */
do
{
/* Cache could be disabled in a later iteration. */
if (!keycache->can_be_used)
{
KEYCACHE_DBUG_PRINT("key_cache_read", ("keycache cannot be used"));
goto no_key_cache;
}
/* Start reading at the beginning of the cache block. */
filepos-= offset;
/* Do not read beyond the end of the cache block. */
read_length= length;
set_if_smaller(read_length, keycache->key_cache_block_size-offset);
KEYCACHE_DBUG_ASSERT(read_length > 0);
/* Request the cache block that matches file/pos. */
keycache->global_cache_r_requests++;
MYSQL_KEYCACHE_READ_BLOCK(keycache->key_cache_block_size);
block=find_key_block(keycache, file, filepos, level, 0, &page_st);
if (!block)
{
/*
This happens only for requests submitted during key cache
resize. The block is not in the cache and shall not go in.
Read directly from file.
*/
keycache->global_cache_read++;
keycache_pthread_mutex_unlock(&keycache->cache_lock);
error= (my_pread(file, (uchar*) buff, read_length,
filepos + offset, MYF(MY_NABP)) != 0);
keycache_pthread_mutex_lock(&keycache->cache_lock);
goto next_block;
}
if (!(block->status & BLOCK_ERROR))
{
if (page_st == PAGE_TO_BE_READ)
{
MYSQL_KEYCACHE_READ_MISS();
read_block_primary(keycache, block,
keycache->key_cache_block_size, read_length+offset);
}
else if (page_st == PAGE_WAIT_TO_BE_READ)
{
MYSQL_KEYCACHE_READ_MISS();
/* The requested page is to be read into the block buffer */
read_block_secondary(keycache, block);
/*
A secondary request must now have the block assigned to the
requested file block.
*/
DBUG_ASSERT(block->hash_link->file == file);
DBUG_ASSERT(block->hash_link->diskpos == filepos);
}
else if (block->length < read_length + offset)
{
/*
Impossible if nothing goes wrong:
this could only happen if we are using a file with
small key blocks and are trying to read outside the file
*/
my_errno= -1;
block->status|= BLOCK_ERROR;
}
else
{
MYSQL_KEYCACHE_READ_HIT();
}
}
/* block status may have added BLOCK_ERROR in the above 'if'. */
if (!(block->status & BLOCK_ERROR))
{
{
DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
#if !defined(SERIALIZED_READ_FROM_CACHE)
keycache_pthread_mutex_unlock(&keycache->cache_lock);
#endif
/* Copy data from the cache buffer */
memcpy(buff, block->buffer+offset, (size_t) read_length);
#if !defined(SERIALIZED_READ_FROM_CACHE)
keycache_pthread_mutex_lock(&keycache->cache_lock);
DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
#endif
}
}
remove_reader(block);
/* Error injection for coverage testing. */
DBUG_EXECUTE_IF("key_cache_read_block_error",
block->status|= BLOCK_ERROR;);
/* Do not link erroneous blocks into the LRU ring, but free them. */
if (!(block->status & BLOCK_ERROR))
{
/*
Link the block into the LRU ring if it's the last submitted
request for the block. This enables eviction for the block.
*/
unreg_request(keycache, block, 1);
}
else
{
free_block(keycache, block);
error= 1;
break;
}
next_block:
buff+= read_length;
filepos+= read_length+offset;
offset= 0;
} while ((length-= read_length));
if (MYSQL_KEYCACHE_READ_DONE_ENABLED())
{
MYSQL_KEYCACHE_READ_DONE((ulong) (keycache->blocks_used *
keycache->key_cache_block_size),
(ulong) (keycache->blocks_unused *
keycache->key_cache_block_size));
}
goto end;
}
KEYCACHE_DBUG_PRINT("key_cache_read", ("keycache not initialized"));
no_key_cache:
/* Key cache is not used */
keycache->global_cache_r_requests++;
keycache->global_cache_read++;
if (locked_and_incremented)
keycache_pthread_mutex_unlock(&keycache->cache_lock);
if (my_pread(file, (uchar*) buff, length, filepos, MYF(MY_NABP)))
error= 1;
if (locked_and_incremented)
keycache_pthread_mutex_lock(&keycache->cache_lock);
end:
if (locked_and_incremented)
{
dec_counter_for_resize_op(keycache);
keycache_pthread_mutex_unlock(&keycache->cache_lock);
}
DBUG_PRINT("exit", ("error: %d", error ));
DBUG_RETURN(error ? (uchar*) 0 : start);
}
/*
Insert a block of file data from a buffer into a simple key cache
SYNOPSIS
simple_key_cache_insert()
keycache pointer to the control block of a simple key cache
file handler for the file to insert data from
filepos position of the block of data in the file to insert
level determines the weight of the data
buff buffer to read data from
length length of the data in the buffer
DESCRIPTION
This function is the implementation of the key_cache_insert interface
function that is employed by simple (non-partitioned) key caches.
The function takes the parameter keycache as a pointer to the
control block structure of the type SIMPLE_KEY_CACHE_CB for a simple key
cache.
The function writes a block of file data from a buffer into the key cache.
The buffer is specified with the parameters buff and length - the pointer
to the beginning of the buffer and its size respectively. It's assumed
the buffer contains the data from 'file' allocated from the position
filepos. The data is copied from the buffer in key_cache_block_size
increments.
The parameter level is used to set one characteristic for the key buffers
loaded with the data from buff. The characteristic is used only by the
midpoint insertion strategy.
RETURN VALUE
0 if a success, 1 - otherwise.
NOTES
The function is used by MyISAM to move all blocks from a index file to
the key cache. It can be performed in parallel with reading the file data
from the key buffers by other threads.
*/
static
int simple_key_cache_insert(void *keycache_,
File file, my_off_t filepos, int level,
uchar *buff, uint length)
{
SIMPLE_KEY_CACHE_CB *keycache= keycache_;
int error= 0;
DBUG_ENTER("key_cache_insert");
DBUG_PRINT("enter", ("fd: %u pos: %lu length: %u",
(uint) file,(ulong) filepos, length));
if (keycache->key_cache_inited)
{
/* Key cache is used */
reg1 BLOCK_LINK *block;
uint read_length;
uint offset;
int page_st;
my_bool locked_and_incremented= FALSE;
/*
When the keycache is once initialized, we use the cache_lock to
reliably distinguish the cases of normal operation, resizing, and
disabled cache. We always increment and decrement
'cnt_for_resize_op' so that a resizer can wait for pending I/O.
*/
keycache_pthread_mutex_lock(&keycache->cache_lock);
/*
We do not load index data into a disabled cache nor into an
ongoing resize.
*/
if (!keycache->can_be_used || keycache->in_resize)
goto no_key_cache;
/* Register the pseudo I/O for the next resize. */
inc_counter_for_resize_op(keycache);
locked_and_incremented= TRUE;
/* Loaded data may not always be aligned to cache blocks. */
offset= (uint) (filepos % keycache->key_cache_block_size);
/* Load data in key_cache_block_size increments. */
do
{
/* Cache could be disabled or resizing in a later iteration. */
if (!keycache->can_be_used || keycache->in_resize)
goto no_key_cache;
/* Start loading at the beginning of the cache block. */
filepos-= offset;
/* Do not load beyond the end of the cache block. */
read_length= length;
set_if_smaller(read_length, keycache->key_cache_block_size-offset);
KEYCACHE_DBUG_ASSERT(read_length > 0);
/* The block has been read by the caller already. */
keycache->global_cache_read++;
/* Request the cache block that matches file/pos. */
keycache->global_cache_r_requests++;
block= find_key_block(keycache, file, filepos, level, 0, &page_st);
if (!block)
{
/*
This happens only for requests submitted during key cache
resize. The block is not in the cache and shall not go in.
Stop loading index data.
*/
goto no_key_cache;
}
if (!(block->status & BLOCK_ERROR))
{
if (page_st == PAGE_WAIT_TO_BE_READ)
{
/*
this is a secondary request for a block to be read into the
cache. The block is in eviction. It is not yet assigned to
the requested file block (It does not point to the right
hash_link). So we cannot call remove_reader() on the block.
And we cannot access the hash_link directly here. We need to
wait until the assignment is complete. read_block_secondary()
executes the correct wait.
*/
read_block_secondary(keycache, block);
/*
A secondary request must now have the block assigned to the
requested file block.
*/
DBUG_ASSERT(block->hash_link->file == file);
DBUG_ASSERT(block->hash_link->diskpos == filepos);
}
else if (page_st == PAGE_TO_BE_READ &&
(offset || (read_length < keycache->key_cache_block_size)))
{
/*
this is a primary request for a block to be read into the
cache and the supplied data does not fill the whole block.
This function is called on behalf of a LOAD INDEX INTO CACHE
statement, which is a read-only task and allows other
readers. It is possible that a parallel running reader tries
to access this block. If it needs more data than has been
supplied here, it would report an error. To be sure that we
have all data in the block that is available in the file, we
read the block ourselves.
Though reading again what the caller did read already is an
expensive operation, we need to do this for correctness.
*/
read_block_primary(keycache, block, keycache->key_cache_block_size,
read_length + offset);
}
else if (page_st == PAGE_TO_BE_READ)
{
/*
This is a new block in the cache. If we come here, we have
data for the whole block.
*/
DBUG_ASSERT(block->hash_link->requests);
DBUG_ASSERT(block->status & BLOCK_IN_USE);
DBUG_ASSERT((page_st == PAGE_TO_BE_READ) ||
(block->status & BLOCK_READ));
#if !defined(SERIALIZED_READ_FROM_CACHE)
keycache_pthread_mutex_unlock(&keycache->cache_lock);
/*
Here other threads may step in and register as secondary readers.
They will register in block->wqueue[COND_FOR_REQUESTED].
*/
#endif
/* Copy data from buff */
memcpy(block->buffer+offset, buff, (size_t) read_length);
#if !defined(SERIALIZED_READ_FROM_CACHE)
keycache_pthread_mutex_lock(&keycache->cache_lock);
DBUG_ASSERT(block->status & BLOCK_IN_USE);
DBUG_ASSERT((page_st == PAGE_TO_BE_READ) ||
(block->status & BLOCK_READ));
#endif
/*
After the data is in the buffer, we can declare the block
valid. Now other threads do not need to register as
secondary readers any more. They can immediately access the
block.
*/
block->status|= BLOCK_READ;
block->length= read_length+offset;
/*
Do not set block->offset here. If this block is marked
BLOCK_CHANGED later, we want to flush only the modified part. So
only a writer may set block->offset down from
keycache->key_cache_block_size.
*/
KEYCACHE_DBUG_PRINT("key_cache_insert",
("primary request: new page in cache"));
/* Signal all pending requests. */
release_whole_queue(&block->wqueue[COND_FOR_REQUESTED]);
}
else
{
/*
page_st == PAGE_READ. The block is in the buffer. All data
must already be present. Blocks are always read with all
data available on file. Assert that the block does not have
less contents than the preloader supplies. If the caller has
data beyond block->length, it means that a file write has
been done while this block was in cache and not extended
with the new data. If the condition is met, we can simply
ignore the block.
*/
DBUG_ASSERT((page_st == PAGE_READ) &&
(read_length + offset <= block->length));
}
/*
A secondary request must now have the block assigned to the
requested file block. It does not hurt to check it for primary
requests too.
*/
DBUG_ASSERT(block->hash_link->file == file);
DBUG_ASSERT(block->hash_link->diskpos == filepos);
DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
} /* end of if (!(block->status & BLOCK_ERROR)) */
remove_reader(block);
/* Error injection for coverage testing. */
DBUG_EXECUTE_IF("key_cache_insert_block_error",
block->status|= BLOCK_ERROR; errno=EIO;);
/* Do not link erroneous blocks into the LRU ring, but free them. */
if (!(block->status & BLOCK_ERROR))
{
/*
Link the block into the LRU ring if it's the last submitted
request for the block. This enables eviction for the block.
*/
unreg_request(keycache, block, 1);
}
else
{
free_block(keycache, block);
error= 1;
break;
}
buff+= read_length;
filepos+= read_length+offset;
offset= 0;
} while ((length-= read_length));
no_key_cache:
if (locked_and_incremented)
dec_counter_for_resize_op(keycache);
keycache_pthread_mutex_unlock(&keycache->cache_lock);
}
DBUG_RETURN(error);
}
/*
Write a buffer into a simple key cache
SYNOPSIS
simple_key_cache_write()
keycache pointer to the control block of a simple key cache
file handler for the file to write data to
file_extra maps of key cache partitions containing
dirty pages from file
filepos position in the file to write data to
level determines the weight of the data
buff buffer with the data
length length of the buffer
dont_write if is 0 then all dirty pages involved in writing
should have been flushed from key cache
DESCRIPTION
This function is the implementation of the key_cache_write interface
function that is employed by simple (non-partitioned) key caches.
The function takes the parameter keycache as a pointer to the
control block structure of the type SIMPLE_KEY_CACHE_CB for a simple key
cache.
In a general case the function copies data from a buffer into the key
cache. The buffer is specified with the parameters buff and length -
the pointer to the beginning of the buffer and its size respectively.
It's assumed the buffer contains the data to be written into 'file'
starting from the position filepos. The data is copied from the buffer
in key_cache_block_size increments.
If the value of the parameter dont_write is FALSE then the function
also writes the data into file.
The parameter level is used to set one characteristic for the key buffers
filled with the data from buff. The characteristic is employed only by
the midpoint insertion strategy.
The parameter file_extra currently makes sense only for simple key caches
that are elements of a partitioned key cache. It provides a pointer to the
shared bitmap of the partitions that may contains dirty pages for the file.
This bitmap is used to optimize the function
flush_partitioned_key_cache_blocks.
RETURN VALUE
0 if a success, 1 - otherwise.
NOTES
This implementation exploits the fact that the function is called only
when a thread has got an exclusive lock for the key file.
*/
static
int simple_key_cache_write(void *keycache_,
File file, void *file_extra __attribute__((unused)),
my_off_t filepos, int level,
uchar *buff, uint length,
uint block_length __attribute__((unused)),
int dont_write)
{
SIMPLE_KEY_CACHE_CB *keycache= keycache_;
my_bool locked_and_incremented= FALSE;
int error=0;
DBUG_ENTER("simple_key_cache_write");
DBUG_PRINT("enter",
("fd: %u pos: %lu length: %u block_length: %u"
" key_block_length: %u",
(uint) file, (ulong) filepos, length, block_length,
keycache ? keycache->key_cache_block_size : 0));
if (!dont_write)
{
/* purecov: begin inspected */
/* Not used in the server. */
/* Force writing from buff into disk. */
keycache->global_cache_w_requests++;
keycache->global_cache_write++;
if (my_pwrite(file, buff, length, filepos, MYF(MY_NABP | MY_WAIT_IF_FULL)))
DBUG_RETURN(1);
/* purecov: end */
}
#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG)
DBUG_EXECUTE("check_keycache",
test_key_cache(keycache, "start of key_cache_write", 1););
#endif
if (keycache->key_cache_inited)
{
/* Key cache is used */
reg1 BLOCK_LINK *block;
uint read_length;
uint offset;
int page_st;
if (MYSQL_KEYCACHE_WRITE_START_ENABLED())
{
MYSQL_KEYCACHE_WRITE_START(my_filename(file), length,
(ulong) (keycache->blocks_used *
keycache->key_cache_block_size),
(ulong) (keycache->blocks_unused *
keycache->key_cache_block_size));
}
/*
When the key cache is once initialized, we use the cache_lock to
reliably distinguish the cases of normal operation, resizing, and
disabled cache. We always increment and decrement
'cnt_for_resize_op' so that a resizer can wait for pending I/O.
*/
keycache_pthread_mutex_lock(&keycache->cache_lock);
/*
Cache resizing has two phases: Flushing and re-initializing. In
the flush phase write requests can modify dirty blocks that are
not yet in flush. Otherwise they are allowed to bypass the cache.
find_key_block() returns NULL in both cases (clean blocks and
non-cached blocks).
After the flush phase new I/O requests must wait until the
re-initialization is done. The re-initialization can be done only
if no I/O request is in progress. The reason is that
key_cache_block_size can change. With enabled cache I/O is done in
chunks of key_cache_block_size. Every chunk tries to use a cache
block first. If the block size changes in the middle, a block
could be missed and data could be written below a cached block.
*/
while (keycache->in_resize && !keycache->resize_in_flush)
wait_on_queue(&keycache->resize_queue, &keycache->cache_lock);
/* Register the I/O for the next resize. */
inc_counter_for_resize_op(keycache);
locked_and_incremented= TRUE;
/* Requested data may not always be aligned to cache blocks. */
offset= (uint) (filepos % keycache->key_cache_block_size);
/* Write data in key_cache_block_size increments. */
do
{
/* Cache could be disabled in a later iteration. */
if (!keycache->can_be_used)
goto no_key_cache;
MYSQL_KEYCACHE_WRITE_BLOCK(keycache->key_cache_block_size);
/* Start writing at the beginning of the cache block. */
filepos-= offset;
/* Do not write beyond the end of the cache block. */
read_length= length;
set_if_smaller(read_length, keycache->key_cache_block_size-offset);
KEYCACHE_DBUG_ASSERT(read_length > 0);
/* Request the cache block that matches file/pos. */
keycache->global_cache_w_requests++;
block= find_key_block(keycache, file, filepos, level, 1, &page_st);
if (!block)
{
/*
This happens only for requests submitted during key cache
resize. The block is not in the cache and shall not go in.
Write directly to file.
*/
if (dont_write)
{
/* Used in the server. */
keycache->global_cache_write++;
keycache_pthread_mutex_unlock(&keycache->cache_lock);
if (my_pwrite(file, (uchar*) buff, read_length, filepos + offset,
MYF(MY_NABP | MY_WAIT_IF_FULL)))
error=1;
keycache_pthread_mutex_lock(&keycache->cache_lock);
}
goto next_block;
}
/*
Prevent block from flushing and from being selected for to be
freed. This must be set when we release the cache_lock.
However, we must not set the status of the block before it is
assigned to this file/pos.
*/
if (page_st != PAGE_WAIT_TO_BE_READ)
block->status|= BLOCK_FOR_UPDATE;
/*
We must read the file block first if it is not yet in the cache
and we do not replace all of its contents.
In cases where the cache block is big enough to contain (parts
of) index blocks of different indexes, our request can be
secondary (PAGE_WAIT_TO_BE_READ). In this case another thread is
reading the file block. If the read completes after us, it
overwrites our new contents with the old contents. So we have to
wait for the other thread to complete the read of this block.
read_block_primary|secondary() takes care for the wait.
*/
if (!(block->status & BLOCK_ERROR))
{
if (page_st == PAGE_TO_BE_READ &&
(offset || read_length < keycache->key_cache_block_size))
{
read_block_primary(keycache, block,
offset + read_length >= keycache->key_cache_block_size?
offset : keycache->key_cache_block_size,
offset);
/*
Prevent block from flushing and from being selected for to be
freed. This must be set when we release the cache_lock.
Here we set it in case we could not set it above.
*/
block->status|= BLOCK_FOR_UPDATE;
}
else if (page_st == PAGE_WAIT_TO_BE_READ)
{
read_block_secondary(keycache, block);
block->status|= BLOCK_FOR_UPDATE;
}
}
/*
The block should always be assigned to the requested file block
here. It need not be BLOCK_READ when overwriting the whole block.
*/
DBUG_ASSERT(block->hash_link->file == file);
DBUG_ASSERT(block->hash_link->diskpos == filepos);
DBUG_ASSERT(block->status & BLOCK_IN_USE);
DBUG_ASSERT((page_st == PAGE_TO_BE_READ) || (block->status & BLOCK_READ));
/*
The block to be written must not be marked BLOCK_REASSIGNED.
Otherwise it could be freed in dirty state or reused without
another flush during eviction. It must also not be in flush.
Otherwise the old contens may have been flushed already and
the flusher could clear BLOCK_CHANGED without flushing the
new changes again.
*/
DBUG_ASSERT(!(block->status & BLOCK_REASSIGNED));
while (block->status & BLOCK_IN_FLUSHWRITE)
{
/*
Another thread is flushing the block. It was dirty already.
Wait until the block is flushed to file. Otherwise we could
modify the buffer contents just while it is written to file.
An unpredictable file block contents would be the result.
While we wait, several things can happen to the block,
including another flush. But the block cannot be reassigned to
another hash_link until we release our request on it.
*/
wait_on_queue(&block->wqueue[COND_FOR_SAVED], &keycache->cache_lock);
DBUG_ASSERT(keycache->can_be_used);
DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
/* Still must not be marked for free. */
DBUG_ASSERT(!(block->status & BLOCK_REASSIGNED));
DBUG_ASSERT(block->hash_link && (block->hash_link->block == block));
}
/*
We could perhaps release the cache_lock during access of the
data like in the other functions. Locks outside of the key cache
assure that readers and a writer do not access the same range of
data. Parallel accesses should happen only if the cache block
contains multiple index block(fragment)s. So different parts of
the buffer would be read/written. An attempt to flush during
memcpy() is prevented with BLOCK_FOR_UPDATE.
*/
if (!(block->status & BLOCK_ERROR))
{
#if !defined(SERIALIZED_READ_FROM_CACHE)
keycache_pthread_mutex_unlock(&keycache->cache_lock);
#endif
memcpy(block->buffer+offset, buff, (size_t) read_length);
#if !defined(SERIALIZED_READ_FROM_CACHE)
keycache_pthread_mutex_lock(&keycache->cache_lock);
#endif
}
if (!dont_write)
{
/* Not used in the server. buff has been written to disk at start. */
if ((block->status & BLOCK_CHANGED) &&
(!offset && read_length >= keycache->key_cache_block_size))
link_to_file_list(keycache, block, block->hash_link->file, 1);
}
else if (! (block->status & BLOCK_CHANGED))
link_to_changed_list(keycache, block);
block->status|=BLOCK_READ;
/*
Allow block to be selected for to be freed. Since it is marked
BLOCK_CHANGED too, it won't be selected for to be freed without
a flush.
*/
block->status&= ~BLOCK_FOR_UPDATE;
set_if_smaller(block->offset, offset);
set_if_bigger(block->length, read_length+offset);
/* Threads may be waiting for the changes to be complete. */
release_whole_queue(&block->wqueue[COND_FOR_REQUESTED]);
/*
If only a part of the cache block is to be replaced, and the
rest has been read from file, then the cache lock has been
released for I/O and it could be possible that another thread
wants to evict or free the block and waits for it to be
released. So we must not just decrement hash_link->requests, but
also wake a waiting thread.
*/
remove_reader(block);
/* Error injection for coverage testing. */
DBUG_EXECUTE_IF("key_cache_write_block_error",
block->status|= BLOCK_ERROR;);
/* Do not link erroneous blocks into the LRU ring, but free them. */
if (!(block->status & BLOCK_ERROR))
{
/*
Link the block into the LRU ring if it's the last submitted
request for the block. This enables eviction for the block.
*/
unreg_request(keycache, block, 1);
}
else
{
/* Pretend a "clean" block to avoid complications. */
block->status&= ~(BLOCK_CHANGED);
free_block(keycache, block);
error= 1;
break;
}
next_block:
buff+= read_length;
filepos+= read_length+offset;
offset= 0;
} while ((length-= read_length));
goto end;
}
no_key_cache:
/* Key cache is not used */
if (dont_write)
{
/* Used in the server. */
keycache->global_cache_w_requests++;
keycache->global_cache_write++;
if (locked_and_incremented)
keycache_pthread_mutex_unlock(&keycache->cache_lock);
if (my_pwrite(file, (uchar*) buff, length, filepos,
MYF(MY_NABP | MY_WAIT_IF_FULL)))
error=1;
if (locked_and_incremented)
keycache_pthread_mutex_lock(&keycache->cache_lock);
}
end:
if (locked_and_incremented)
{
dec_counter_for_resize_op(keycache);
keycache_pthread_mutex_unlock(&keycache->cache_lock);
}
if (MYSQL_KEYCACHE_WRITE_DONE_ENABLED())
{
MYSQL_KEYCACHE_WRITE_DONE((ulong) (keycache->blocks_used *
keycache->key_cache_block_size),
(ulong) (keycache->blocks_unused *
keycache->key_cache_block_size));
}
#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG)
DBUG_EXECUTE("exec",
test_key_cache(keycache, "end of key_cache_write", 1););
#endif
DBUG_RETURN(error);
}
/*
Free block.
SYNOPSIS
free_block()
keycache Pointer to a key cache data structure
block Pointer to the block to free
DESCRIPTION
Remove reference to block from hash table.
Remove block from the chain of clean blocks.
Add block to the free list.
NOTE
Block must not be free (status == 0).
Block must not be in free_block_list.
Block must not be in the LRU ring.
Block must not be in eviction (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH).
Block must not be in free (BLOCK_REASSIGNED).
Block must not be in flush (BLOCK_IN_FLUSH).
Block must not be dirty (BLOCK_CHANGED).
Block must not be in changed_blocks (dirty) hash.
Block must be in file_blocks (clean) hash.
Block must refer to a hash_link.
Block must have a request registered on it.
*/
static void free_block(SIMPLE_KEY_CACHE_CB *keycache, BLOCK_LINK *block)
{
KEYCACHE_THREAD_TRACE("free block");
KEYCACHE_DBUG_PRINT("free_block",
("block %u to be freed, hash_link %p status: %u",
BLOCK_NUMBER(block), block->hash_link,
block->status));
/*
Assert that the block is not free already. And that it is in a clean
state. Note that the block might just be assigned to a hash_link and
not yet read (BLOCK_READ may not be set here). In this case a reader
is registered in the hash_link and free_block() will wait for it
below.
*/
DBUG_ASSERT((block->status & BLOCK_IN_USE) &&
!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH |
BLOCK_REASSIGNED | BLOCK_IN_FLUSH |
BLOCK_CHANGED | BLOCK_FOR_UPDATE)));
/* Assert that the block is in a file_blocks chain. */
DBUG_ASSERT(block->prev_changed && *block->prev_changed == block);
/* Assert that the block is not in the LRU ring. */
DBUG_ASSERT(!block->next_used && !block->prev_used);
/*
IMHO the below condition (if()) makes no sense. I can't see how it
could be possible that free_block() is entered with a NULL hash_link
pointer. The only place where it can become NULL is in free_block()
(or before its first use ever, but for those blocks free_block() is
not called). I don't remove the conditional as it cannot harm, but
place an DBUG_ASSERT to confirm my hypothesis. Eventually the
condition (if()) can be removed.
*/
DBUG_ASSERT(block->hash_link && block->hash_link->block == block);
if (block->hash_link)
{
/*
While waiting for readers to finish, new readers might request the
block. But since we set block->status|= BLOCK_REASSIGNED, they
will wait on block->wqueue[COND_FOR_SAVED]. They must be signalled
later.
*/
block->status|= BLOCK_REASSIGNED;
wait_for_readers(keycache, block);
/*
The block must not have been freed by another thread. Repeat some
checks. An additional requirement is that it must be read now
(BLOCK_READ).
*/
DBUG_ASSERT(block->hash_link && block->hash_link->block == block);
DBUG_ASSERT((block->status & (BLOCK_READ | BLOCK_IN_USE |
BLOCK_REASSIGNED)) &&
!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH |
BLOCK_IN_FLUSH | BLOCK_CHANGED |
BLOCK_FOR_UPDATE)));
DBUG_ASSERT(block->prev_changed && *block->prev_changed == block);
DBUG_ASSERT(!block->prev_used);
/*
Unset BLOCK_REASSIGNED again. If we hand the block to an evicting
thread (through unreg_request() below), other threads must not see
this flag. They could become confused.
*/
block->status&= ~BLOCK_REASSIGNED;
/*
Do not release the hash_link until the block is off all lists.
At least not if we hand it over for eviction in unreg_request().
*/
}
/*
Unregister the block request and link the block into the LRU ring.
This enables eviction for the block. If the LRU ring was empty and
threads are waiting for a block, then the block will be handed over
for eviction immediately. Otherwise we will unlink it from the LRU
ring again, without releasing the lock in between. So decrementing
the request counter and updating statistics are the only relevant
operation in this case. Assert that there are no other requests
registered.
*/
DBUG_ASSERT(block->requests == 1);
unreg_request(keycache, block, 0);
/*
Note that even without releasing the cache lock it is possible that
the block is immediately selected for eviction by link_block() and
thus not added to the LRU ring. In this case we must not touch the
block any more.
*/
if (block->status & BLOCK_IN_EVICTION)
return;
/* Error blocks are not put into the LRU ring. */
if (!(block->status & BLOCK_ERROR))
{
/* Here the block must be in the LRU ring. Unlink it again. */
DBUG_ASSERT(block->next_used && block->prev_used &&
*block->prev_used == block);
unlink_block(keycache, block);
}
if (block->temperature == BLOCK_WARM)
keycache->warm_blocks--;
block->temperature= BLOCK_COLD;
/* Remove from file_blocks hash. */
unlink_changed(block);
/* Remove reference to block from hash table. */
unlink_hash(keycache, block->hash_link);
block->hash_link= NULL;
block->status= 0;
block->length= 0;
block->offset= keycache->key_cache_block_size;
KEYCACHE_THREAD_TRACE("free block");
KEYCACHE_DBUG_PRINT("free_block", ("block is freed"));
/* Enforced by unlink_changed(), but just to be sure. */
DBUG_ASSERT(!block->next_changed && !block->prev_changed);
/* Enforced by unlink_block(): not in LRU ring nor in free_block_list. */
DBUG_ASSERT(!block->next_used && !block->prev_used);
/* Insert the free block in the free list. */
block->next_used= keycache->free_block_list;
keycache->free_block_list= block;
/* Keep track of the number of currently unused blocks. */
keycache->blocks_unused++;
/* All pending requests for this page must be resubmitted. */
release_whole_queue(&block->wqueue[COND_FOR_SAVED]);
}
static int cmp_sec_link(const void *_a, const void *_b)
{
const BLOCK_LINK *a= *(const BLOCK_LINK **)_a;
const BLOCK_LINK *b= *(const BLOCK_LINK **)_b;
return (a->hash_link->diskpos < b->hash_link->diskpos) ? -1 :
(a->hash_link->diskpos > b->hash_link->diskpos) ? 1 : 0;
}
/*
Flush a portion of changed blocks to disk,
free used blocks if requested
*/
static int flush_cached_blocks(SIMPLE_KEY_CACHE_CB *keycache,
File file, BLOCK_LINK **cache,
BLOCK_LINK **end,
enum flush_type type)
{
int error;
int last_errno= 0;
uint count= (uint) (end-cache);
/* Don't lock the cache during the flush */
keycache_pthread_mutex_unlock(&keycache->cache_lock);
/*
As all blocks referred in 'cache' are marked by BLOCK_IN_FLUSH
we are guaranteed no thread will change them
*/
my_qsort((uchar*) cache, count, sizeof(*cache), (qsort_cmp) cmp_sec_link);
keycache_pthread_mutex_lock(&keycache->cache_lock);
/*
Note: Do not break the loop. We have registered a request on every
block in 'cache'. These must be unregistered by free_block() or
unreg_request().
*/
for ( ; cache != end ; cache++)
{
BLOCK_LINK *block= *cache;
KEYCACHE_DBUG_PRINT("flush_cached_blocks",
("block %u to be flushed", BLOCK_NUMBER(block)));
/*
If the block contents is going to be changed, we abandon the flush
for this block. flush_key_blocks_int() will restart its search and
handle the block properly.
*/
if (!(block->status & BLOCK_FOR_UPDATE))
{
/* Blocks coming here must have a certain status. */
DBUG_ASSERT(block->hash_link);
DBUG_ASSERT(block->hash_link->block == block);
DBUG_ASSERT(block->hash_link->file == file);
DBUG_ASSERT((block->status & ~BLOCK_IN_EVICTION) ==
(BLOCK_READ | BLOCK_IN_FLUSH | BLOCK_CHANGED | BLOCK_IN_USE));
block->status|= BLOCK_IN_FLUSHWRITE;
keycache_pthread_mutex_unlock(&keycache->cache_lock);
error= (int)my_pwrite(file, block->buffer + block->offset,
block->length - block->offset,
block->hash_link->diskpos + block->offset,
MYF(MY_NABP | MY_WAIT_IF_FULL));
keycache_pthread_mutex_lock(&keycache->cache_lock);
keycache->global_cache_write++;
if (error)
{
block->status|= BLOCK_ERROR;
if (!last_errno)
last_errno= errno ? errno : -1;
}
block->status&= ~BLOCK_IN_FLUSHWRITE;
/* Block must not have changed status except BLOCK_FOR_UPDATE. */
DBUG_ASSERT(block->hash_link);
DBUG_ASSERT(block->hash_link->block == block);
DBUG_ASSERT(block->hash_link->file == file);
DBUG_ASSERT((block->status & ~(BLOCK_FOR_UPDATE | BLOCK_IN_EVICTION)) ==
(BLOCK_READ | BLOCK_IN_FLUSH | BLOCK_CHANGED | BLOCK_IN_USE));
/*
Set correct status and link in right queue for free or later use.
free_block() must not see BLOCK_CHANGED and it may need to wait
for readers of the block. These should not see the block in the
wrong hash. If not freeing the block, we need to have it in the
right queue anyway.
*/
link_to_file_list(keycache, block, file, 1);
}
block->status&= ~BLOCK_IN_FLUSH;
/*
Let to proceed for possible waiting requests to write to the block page.
It might happen only during an operation to resize the key cache.
*/
release_whole_queue(&block->wqueue[COND_FOR_SAVED]);
/* type will never be FLUSH_IGNORE_CHANGED here */
if (!(type == FLUSH_KEEP || type == FLUSH_FORCE_WRITE) &&
!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH |
BLOCK_FOR_UPDATE)))
{
/*
Note that a request has been registered against the block in
flush_key_blocks_int().
*/
free_block(keycache, block);
}
else
{
/*
Link the block into the LRU ring if it's the last submitted
request for the block. This enables eviction for the block.
Note that a request has been registered against the block in
flush_key_blocks_int().
*/
unreg_request(keycache, block, 1);
}
} /* end of for ( ; cache != end ; cache++) */
return last_errno;
}
/*
Flush all key blocks for a file to disk, but don't do any mutex locks
SYNOPSIS
flush_key_blocks_int()
keycache pointer to a key cache data structure
file handler for the file to flush to
flush_type type of the flush
NOTES
This function doesn't do any mutex locks because it needs to be called both
from flush_key_blocks and flush_all_key_blocks (the later one does the
mutex lock in the resize_key_cache() function).
We do only care about changed blocks that exist when the function is
entered. We do not guarantee that all changed blocks of the file are
flushed if more blocks change while this function is running.
RETURN
0 ok
1 error
*/
static int flush_key_blocks_int(SIMPLE_KEY_CACHE_CB *keycache,
File file, enum flush_type type)
{
BLOCK_LINK *cache_buff[FLUSH_CACHE],**cache;
int last_errno= 0;
int last_errcnt= 0;
DBUG_ENTER("flush_key_blocks_int");
DBUG_PRINT("enter",("file: %d blocks_used: %lu blocks_changed: %lu",
file, keycache->blocks_used, keycache->blocks_changed));
#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG)
DBUG_EXECUTE("check_keycache",
test_key_cache(keycache, "start of flush_key_blocks", 0););
#endif
DBUG_ASSERT(type != FLUSH_KEEP_LAZY);
cache= cache_buff;
if (keycache->disk_blocks > 0 &&
(!my_disable_flush_key_blocks || type != FLUSH_KEEP))
{
/* Key cache exists and flush is not disabled */
int error= 0;
uint count= FLUSH_CACHE;
BLOCK_LINK **pos,**end;
BLOCK_LINK *first_in_switch= NULL;
BLOCK_LINK *last_in_flush;
BLOCK_LINK *last_for_update;
BLOCK_LINK *block, *next;
#if defined(KEYCACHE_DEBUG)
uint cnt=0;
#endif
if (type != FLUSH_IGNORE_CHANGED)
{
/*
Count how many key blocks we have to cache to be able
to flush all dirty pages with minimum seek moves
*/
count= 0;
for (block= keycache->changed_blocks[FILE_HASH(file, keycache)] ;
block ;
block= block->next_changed)
{
if ((block->hash_link->file == file) &&
!(block->status & BLOCK_IN_FLUSH))
{
count++;
KEYCACHE_DBUG_ASSERT(count<= keycache->blocks_used);
}
}
/*
Allocate a new buffer only if its bigger than the one we have.
Assure that we always have some entries for the case that new
changed blocks appear while we need to wait for something.
*/
if ((count > FLUSH_CACHE) &&
!(cache= (BLOCK_LINK**) my_malloc(key_memory_KEY_CACHE,
sizeof(BLOCK_LINK*)*count, MYF(0))))
cache= cache_buff;
/*
After a restart there could be more changed blocks than now.
So we should not let count become smaller than the fixed buffer.
*/
if (cache == cache_buff)
count= FLUSH_CACHE;
}
/* Retrieve the blocks and write them to a buffer to be flushed */
restart:
last_in_flush= NULL;
last_for_update= NULL;
end= (pos= cache)+count;
for (block= keycache->changed_blocks[FILE_HASH(file, keycache)] ;
block ;
block= next)
{
#if defined(KEYCACHE_DEBUG)
cnt++;
KEYCACHE_DBUG_ASSERT(cnt <= keycache->blocks_used);
#endif
next= block->next_changed;
if (block->hash_link->file == file)
{
if (!(block->status & (BLOCK_IN_FLUSH | BLOCK_FOR_UPDATE)))
{
/*
Note: The special handling of BLOCK_IN_SWITCH is obsolete
since we set BLOCK_IN_FLUSH if the eviction includes a
flush. It can be removed in a later version.
*/
if (!(block->status & BLOCK_IN_SWITCH))
{
/*
We care only for the blocks for which flushing was not
initiated by another thread and which are not in eviction.
Registering a request on the block unlinks it from the LRU
ring and protects against eviction.
*/
reg_requests(keycache, block, 1);
if (type != FLUSH_IGNORE_CHANGED)
{
/* It's not a temporary file */
if (pos == end)
{
/*
This should happen relatively seldom. Remove the
request because we won't do anything with the block
but restart and pick it again in the next iteration.
*/
unreg_request(keycache, block, 0);
/*
This happens only if there is not enough
memory for the big block
*/
if ((error= flush_cached_blocks(keycache, file, cache,
end,type)))
{
/* Do not loop infinitely trying to flush in vain. */
if ((last_errno == error) && (++last_errcnt > 5))
goto err;
last_errno= error;
}
/*
Restart the scan as some other thread might have changed
the changed blocks chain: the blocks that were in switch
state before the flush started have to be excluded
*/
goto restart;
}
/*
Mark the block with BLOCK_IN_FLUSH in order not to let
other threads to use it for new pages and interfere with
our sequence of flushing dirty file pages. We must not
set this flag before actually putting the block on the
write burst array called 'cache'.
*/
block->status|= BLOCK_IN_FLUSH;
/* Add block to the array for a write burst. */
*pos++= block;
}
else
{
/* It's a temporary file */
DBUG_ASSERT(!(block->status & BLOCK_REASSIGNED));
/*
free_block() must not be called with BLOCK_CHANGED. Note
that we must not change the BLOCK_CHANGED flag outside of
link_to_file_list() so that it is always in the correct
queue and the *blocks_changed counters are correct.
*/
link_to_file_list(keycache, block, file, 1);
if (!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH)))
{
/* A request has been registered against the block above. */
free_block(keycache, block);
}
else
{
/*
Link the block into the LRU ring if it's the last
submitted request for the block. This enables eviction
for the block. A request has been registered against
the block above.
*/
unreg_request(keycache, block, 1);
}
}
}
else
{
/*
Link the block into a list of blocks 'in switch'.
WARNING: Here we introduce a place where a changed block
is not in the changed_blocks hash! This is acceptable for
a BLOCK_IN_SWITCH. Never try this for another situation.
Other parts of the key cache code rely on changed blocks
being in the changed_blocks hash.
*/
unlink_changed(block);
link_changed(block, &first_in_switch);
}
}
else if (type != FLUSH_KEEP)
{
/*
During the normal flush at end of statement (FLUSH_KEEP) we
do not need to ensure that blocks in flush or update by
other threads are flushed. They will be flushed by them
later. In all other cases we must assure that we do not have
any changed block of this file in the cache when this
function returns.
*/
if (block->status & BLOCK_IN_FLUSH)
{
/* Remember the last block found to be in flush. */
last_in_flush= block;
}
else
{
/* Remember the last block found to be selected for update. */
last_for_update= block;
}
}
}
}
if (pos != cache)
{
if ((error= flush_cached_blocks(keycache, file, cache, pos, type)))
{
/* Do not loop infinitely trying to flush in vain. */
if ((last_errno == error) && (++last_errcnt > 5))
goto err;
last_errno= error;
}
/*
Do not restart here during the normal flush at end of statement
(FLUSH_KEEP). We have now flushed at least all blocks that were
changed when entering this function. In all other cases we must
assure that we do not have any changed block of this file in the
cache when this function returns.
*/
if (type != FLUSH_KEEP)
goto restart;
}
if (last_in_flush)
{
/*
There are no blocks to be flushed by this thread, but blocks in
flush by other threads. Wait until one of the blocks is flushed.
Re-check the condition for last_in_flush. We may have unlocked
the cache_lock in flush_cached_blocks(). The state of the block
could have changed.
*/
if (last_in_flush->status & BLOCK_IN_FLUSH)
wait_on_queue(&last_in_flush->wqueue[COND_FOR_SAVED],
&keycache->cache_lock);
/* Be sure not to lose a block. They may be flushed in random order. */
goto restart;
}
if (last_for_update)
{
/*
There are no blocks to be flushed by this thread, but blocks for
update by other threads. Wait until one of the blocks is updated.
Re-check the condition for last_for_update. We may have unlocked
the cache_lock in flush_cached_blocks(). The state of the block
could have changed.
*/
if (last_for_update->status & BLOCK_FOR_UPDATE)
wait_on_queue(&last_for_update->wqueue[COND_FOR_REQUESTED],
&keycache->cache_lock);
/* The block is now changed. Flush it. */
goto restart;
}
/*
Wait until the list of blocks in switch is empty. The threads that
are switching these blocks will relink them to clean file chains
while we wait and thus empty the 'first_in_switch' chain.
*/
while (first_in_switch)
{
#if defined(KEYCACHE_DEBUG)
cnt= 0;
#endif
wait_on_queue(&first_in_switch->wqueue[COND_FOR_SAVED],
&keycache->cache_lock);
#if defined(KEYCACHE_DEBUG)
cnt++;
KEYCACHE_DBUG_ASSERT(cnt <= keycache->blocks_used);
#endif
/*
Do not restart here. We have flushed all blocks that were
changed when entering this function and were not marked for
eviction. Other threads have now flushed all remaining blocks in
the course of their eviction.
*/
}
if (! (type == FLUSH_KEEP || type == FLUSH_FORCE_WRITE))
{
BLOCK_LINK *last_in_switch= NULL;
uint total_found= 0;
uint found;
last_for_update= NULL;
/*
Finally free all clean blocks for this file.
During resize this may be run by two threads in parallel.
*/
do
{
found= 0;
for (block= keycache->file_blocks[FILE_HASH(file, keycache)] ;
block ;
block= next)
{
/* Remember the next block. After freeing we cannot get at it. */
next= block->next_changed;
/* Changed blocks cannot appear in the file_blocks hash. */
DBUG_ASSERT(!(block->status & BLOCK_CHANGED));
if (block->hash_link->file == file)
{
/* We must skip blocks that will be changed. */
if (block->status & BLOCK_FOR_UPDATE)
{
last_for_update= block;
continue;
}
/*
We must not free blocks in eviction (BLOCK_IN_EVICTION |
BLOCK_IN_SWITCH) or blocks intended to be freed
(BLOCK_REASSIGNED).
*/
if (!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH |
BLOCK_REASSIGNED)))
{
struct st_hash_link *UNINIT_VAR(next_hash_link);
my_off_t UNINIT_VAR(next_diskpos);
File UNINIT_VAR(next_file);
uint UNINIT_VAR(next_status);
uint UNINIT_VAR(hash_requests);
total_found++;
found++;
KEYCACHE_DBUG_ASSERT(found <= keycache->blocks_used);
/*
Register a request. This unlinks the block from the LRU
ring and protects it against eviction. This is required
by free_block().
*/
reg_requests(keycache, block, 1);
/*
free_block() may need to wait for readers of the block.
This is the moment where the other thread can move the
'next' block from the chain. free_block() needs to wait
if there are requests for the block pending.
*/
if (next && (hash_requests= block->hash_link->requests))
{
/* Copy values from the 'next' block and its hash_link. */
next_status= next->status;
next_hash_link= next->hash_link;
next_diskpos= next_hash_link->diskpos;
next_file= next_hash_link->file;
DBUG_ASSERT(next == next_hash_link->block);
}
free_block(keycache, block);
/*
If we had to wait and the state of the 'next' block
changed, break the inner loop. 'next' may no longer be
part of the current chain.
We do not want to break the loop after every free_block(),
not even only after waits. The chain might be quite long
and contain blocks for many files. Traversing it again and
again to find more blocks for this file could become quite
inefficient.
*/
if (next && hash_requests &&
((next_status != next->status) ||
(next_hash_link != next->hash_link) ||
(next_file != next_hash_link->file) ||
(next_diskpos != next_hash_link->diskpos) ||
(next != next_hash_link->block)))
break;
}
else
{
last_in_switch= block;
}
}
} /* end for block in file_blocks */
} while (found);
/*
If any clean block has been found, we may have waited for it to
become free. In this case it could be possible that another clean
block became dirty. This is possible if the write request existed
before the flush started (BLOCK_FOR_UPDATE). Re-check the hashes.
*/
if (total_found)
goto restart;
/*
To avoid an infinite loop, wait until one of the blocks marked
for update is updated.
*/
if (last_for_update)
{
/* We did not wait. Block must not have changed status. */
DBUG_ASSERT(last_for_update->status & BLOCK_FOR_UPDATE);
wait_on_queue(&last_for_update->wqueue[COND_FOR_REQUESTED],
&keycache->cache_lock);
goto restart;
}
/*
To avoid an infinite loop wait until one of the blocks marked
for eviction is switched.
*/
if (last_in_switch)
{
/* We did not wait. Block must not have changed status. */
DBUG_ASSERT(last_in_switch->status & (BLOCK_IN_EVICTION |
BLOCK_IN_SWITCH |
BLOCK_REASSIGNED));
wait_on_queue(&last_in_switch->wqueue[COND_FOR_SAVED],
&keycache->cache_lock);
goto restart;
}
} /* if (! (type == FLUSH_KEEP || type == FLUSH_FORCE_WRITE)) */
} /* if (keycache->disk_blocks > 0 */
DBUG_EXECUTE("check_keycache",
test_key_cache(keycache, "end of flush_key_blocks", 0););
err:
if (cache != cache_buff)
my_free(cache);
if (last_errno)
errno=last_errno; /* Return first error */
DBUG_RETURN(last_errno != 0);
}
/*
Flush all blocks for a file from key buffers of a simple key cache
SYNOPSIS
flush_simple_key_blocks()
keycache pointer to the control block of a simple key cache
file handler for the file to flush to
file_extra maps of key cache partitions containing
dirty pages from file (not used)
flush_type type of the flush operation
DESCRIPTION
This function is the implementation of the flush_key_blocks interface
function that is employed by simple (non-partitioned) key caches.
The function takes the parameter keycache as a pointer to the
control block structure of the type S_KEY_CACHE_CB for a simple key
cache.
In a general case the function flushes the data from all dirty key
buffers related to the file 'file' into this file. The function does
exactly this if the value of the parameter type is FLUSH_KEEP. If the
value of this parameter is FLUSH_RELEASE, the function additionally
releases the key buffers containing data from 'file' for new usage.
If the value of the parameter type is FLUSH_IGNORE_CHANGED the function
just releases the key buffers containing data from 'file'.
The parameter file_extra currently is not used by this function.
RETURN
0 ok
1 error
NOTES
This implementation exploits the fact that the function is called only
when a thread has got an exclusive lock for the key file.
*/
static
int flush_simple_key_cache_blocks(void *keycache_,
File file,
void *file_extra __attribute__((unused)),
enum flush_type type)
{
SIMPLE_KEY_CACHE_CB *keycache= keycache_;
int res= 0;
DBUG_ENTER("flush_key_blocks");
DBUG_PRINT("enter", ("keycache: %p", keycache));
if (!keycache->key_cache_inited)
DBUG_RETURN(0);
keycache_pthread_mutex_lock(&keycache->cache_lock);
/* While waiting for lock, keycache could have been ended. */
if (keycache->disk_blocks > 0)
{
inc_counter_for_resize_op(keycache);
res= flush_key_blocks_int(keycache, file, type);
dec_counter_for_resize_op(keycache);
}
keycache_pthread_mutex_unlock(&keycache->cache_lock);
DBUG_RETURN(res);
}
/*
Flush all blocks in the key cache to disk.
SYNOPSIS
flush_all_key_blocks()
keycache pointer to key cache root structure
DESCRIPTION
Flushing of the whole key cache is done in two phases.
1. Flush all changed blocks, waiting for them if necessary. Loop
until there is no changed block left in the cache.
2. Free all clean blocks. Normally this means free all blocks. The
changed blocks were flushed in phase 1 and became clean. However we
may need to wait for blocks that are read by other threads. While we
wait, a clean block could become changed if that operation started
before the resize operation started. To be safe we must restart at
phase 1.
When we can run through the changed_blocks and file_blocks hashes
without finding a block any more, then we are done.
Note that we hold keycache->cache_lock all the time unless we need
to wait for something.
RETURN
0 OK
!= 0 Error
*/
static int flush_all_key_blocks(SIMPLE_KEY_CACHE_CB *keycache)
{
BLOCK_LINK *block;
uint total_found;
uint found;
uint idx;
uint changed_blocks_hash_size= keycache->changed_blocks_hash_size;
DBUG_ENTER("flush_all_key_blocks");
do
{
mysql_mutex_assert_owner(&keycache->cache_lock);
total_found= 0;
/*
Phase1: Flush all changed blocks, waiting for them if necessary.
Loop until there is no changed block left in the cache.
*/
do
{
found= 0;
/* Step over the whole changed_blocks hash array. */
for (idx= 0; idx < changed_blocks_hash_size; idx++)
{
/*
If an array element is non-empty, use the first block from its
chain to find a file for flush. All changed blocks for this
file are flushed. So the same block will not appear at this
place again with the next iteration. New writes for blocks are
not accepted during the flush. If multiple files share the
same hash bucket, one of them will be flushed per iteration
of the outer loop of phase 1.
*/
while ((block= keycache->changed_blocks[idx]))
{
found++;
/*
Flush dirty blocks but do not free them yet. They can be used
for reading until all other blocks are flushed too.
*/
if (flush_key_blocks_int(keycache, block->hash_link->file,
FLUSH_FORCE_WRITE))
DBUG_RETURN(1);
}
}
} while (found);
/*
Phase 2: Free all clean blocks. Normally this means free all
blocks. The changed blocks were flushed in phase 1 and became
clean. However we may need to wait for blocks that are read by
other threads. While we wait, a clean block could become changed
if that operation started before the resize operation started. To
be safe we must restart at phase 1.
*/
do
{
found= 0;
/* Step over the whole file_blocks hash array. */
for (idx= 0; idx < changed_blocks_hash_size; idx++)
{
/*
If an array element is non-empty, use the first block from its
chain to find a file for flush. All blocks for this file are
freed. So the same block will not appear at this place again
with the next iteration. If multiple files share the
same hash bucket, one of them will be flushed per iteration
of the outer loop of phase 2.
*/
while ((block= keycache->file_blocks[idx]))
{
total_found++;
found++;
if (flush_key_blocks_int(keycache, block->hash_link->file,
FLUSH_RELEASE))
DBUG_RETURN(1);
}
}
} while (found);
/*
If any clean block has been found, we may have waited for it to
become free. In this case it could be possible that another clean
block became dirty. This is possible if the write request existed
before the resize started (BLOCK_FOR_UPDATE). Re-check the hashes.
*/
} while (total_found);
#ifndef DBUG_OFF
/* Now there should not exist any block any more. */
for (idx= 0; idx < changed_blocks_hash_size; idx++)
{
DBUG_ASSERT(!keycache->changed_blocks[idx]);
DBUG_ASSERT(!keycache->file_blocks[idx]);
}
#endif
DBUG_RETURN(0);
}
/*
Reset the counters of a simple key cache
SYNOPSIS
reset_simple_key_cache_counters()
name the name of a key cache
keycache pointer to the control block of a simple key cache
DESCRIPTION
This function is the implementation of the reset_key_cache_counters
interface function that is employed by simple (non-partitioned) key caches.
The function takes the parameter keycache as a pointer to the
control block structure of the type S_KEY_CACHE_CB for a simple key cache.
This function resets the values of all statistical counters for the key
cache to 0.
The parameter name is currently not used.
RETURN
0 on success (always because it can't fail)
*/
static
int reset_simple_key_cache_counters(const char *name __attribute__((unused)),
void *keycache_)
{
SIMPLE_KEY_CACHE_CB *keycache= keycache_;
DBUG_ENTER("reset_simple_key_cache_counters");
if (!keycache->key_cache_inited)
{
DBUG_PRINT("info", ("Key cache %s not initialized.", name));
DBUG_RETURN(0);
}
DBUG_PRINT("info", ("Resetting counters for key cache %s.", name));
keycache->global_blocks_changed= 0; /* Key_blocks_not_flushed */
keycache->global_cache_r_requests= 0; /* Key_read_requests */
keycache->global_cache_read= 0; /* Key_reads */
keycache->global_cache_w_requests= 0; /* Key_write_requests */
keycache->global_cache_write= 0; /* Key_writes */
DBUG_RETURN(0);
}
#ifndef DBUG_OFF
/*
Test if disk-cache is ok
*/
static
void test_key_cache(SIMPLE_KEY_CACHE_CB *keycache __attribute__((unused)),
const char *where __attribute__((unused)),
my_bool lock __attribute__((unused)))
{
/* TODO */
}
#endif
#if defined(KEYCACHE_TIMEOUT)
#define KEYCACHE_DUMP_FILE "keycache_dump.txt"
#define MAX_QUEUE_LEN 100
static void keycache_dump(SIMPLE_KEY_CACHE_CB *keycache)
{
FILE *keycache_dump_file=fopen(KEYCACHE_DUMP_FILE, "w");
struct st_my_thread_var *last;
struct st_my_thread_var *thread;
BLOCK_LINK *block;
HASH_LINK *hash_link;
KEYCACHE_PAGE *page;
uint i;
fprintf(keycache_dump_file, "thread:%lu\n", (ulong) thread->id);
i=0;
thread=last=waiting_for_hash_link.last_thread;
fprintf(keycache_dump_file, "queue of threads waiting for hash link\n");
if (thread)
do
{
thread=thread->next;
page= (KEYCACHE_PAGE *) thread->keycache_link;
fprintf(keycache_dump_file,
"thread:%lu, (file,filepos)=(%u,%lu)\n",
(ulong) thread->id,(uint) page->file,(ulong) page->filepos);
if (++i == MAX_QUEUE_LEN)
break;
}
while (thread != last);
i=0;
thread=last=waiting_for_block.last_thread;
fprintf(keycache_dump_file, "queue of threads waiting for block\n");
if (thread)
do
{
thread=thread->next;
hash_link= (HASH_LINK *) thread->keycache_link;
fprintf(keycache_dump_file,
"thread:%lu hash_link:%u (file,filepos)=(%u,%lu)\n",
(ulong) thread->id, (uint) HASH_LINK_NUMBER(hash_link),
(uint) hash_link->file,(ulong) hash_link->diskpos);
if (++i == MAX_QUEUE_LEN)
break;
}
while (thread != last);
for (i=0 ; i< keycache->blocks_used ; i++)
{
int j;
block= &keycache->block_root[i];
hash_link= block->hash_link;
fprintf(keycache_dump_file,
"block:%u hash_link:%d status:%x #requests=%u waiting_for_readers:%d\n",
i, (int) (hash_link ? HASH_LINK_NUMBER(hash_link) : -1),
block->status, block->requests, block->condvar ? 1 : 0);
for (j=0 ; j < 2; j++)
{
KEYCACHE_WQUEUE *wqueue=&block->wqueue[j];
thread= last= wqueue->last_thread;
fprintf(keycache_dump_file, "queue #%d\n", j);
if (thread)
{
do
{
thread=thread->next;
fprintf(keycache_dump_file,
"thread:%lu\n", (ulong) thread->id);
if (++i == MAX_QUEUE_LEN)
break;
}
while (thread != last);
}
}
}
fprintf(keycache_dump_file, "LRU chain:");
block= keycache= used_last;
if (block)
{
do
{
block= block->next_used;
fprintf(keycache_dump_file,
"block:%u, ", BLOCK_NUMBER(block));
}
while (block != keycache->used_last);
}
fprintf(keycache_dump_file, "\n");
fclose(keycache_dump_file);
}
#endif /* defined(KEYCACHE_TIMEOUT) */
#if defined(KEYCACHE_TIMEOUT) && !defined(_WIN32)
static int keycache_pthread_cond_wait(mysql_cond_t *cond,
mysql_mutex_t *mutex)
{
int rc;
struct timeval now; /* time when we started waiting */
struct timespec timeout; /* timeout value for the wait function */
struct timezone tz;
#if defined(KEYCACHE_DEBUG)
int cnt=0;
#endif
/* Get current time */
gettimeofday(&now, &tz);
/* Prepare timeout value */
timeout.tv_sec= now.tv_sec + KEYCACHE_TIMEOUT;
/*
timeval uses microseconds.
timespec uses nanoseconds.
1 nanosecond = 1000 micro seconds
*/
timeout.tv_nsec= now.tv_usec * 1000;
KEYCACHE_THREAD_TRACE_END("started waiting");
#if defined(KEYCACHE_DEBUG)
cnt++;
if (cnt % 100 == 0)
fprintf(keycache_debug_log, "waiting...\n");
fflush(keycache_debug_log);
#endif
rc= mysql_cond_timedwait(cond, mutex, &timeout);
KEYCACHE_THREAD_TRACE_BEGIN("finished waiting");
if (rc == ETIMEDOUT || rc == ETIME)
{
#if defined(KEYCACHE_DEBUG)
fprintf(keycache_debug_log,"aborted by keycache timeout\n");
fclose(keycache_debug_log);
abort();
#endif
keycache_dump();
}
#if defined(KEYCACHE_DEBUG)
KEYCACHE_DBUG_ASSERT(rc != ETIMEDOUT);
#else
assert(rc != ETIMEDOUT);
#endif
return rc;
}
#else
#if defined(KEYCACHE_DEBUG)
static int keycache_pthread_cond_wait(mysql_cond_t *cond,
mysql_mutex_t *mutex)
{
int rc;
KEYCACHE_THREAD_TRACE_END("started waiting");
rc= mysql_cond_wait(cond, mutex);
KEYCACHE_THREAD_TRACE_BEGIN("finished waiting");
return rc;
}
#endif
#endif /* defined(KEYCACHE_TIMEOUT) && !defined(_WIN32) */
#if defined(KEYCACHE_DEBUG)
static int keycache_pthread_mutex_lock(mysql_mutex_t *mutex)
{
int rc;
rc= mysql_mutex_lock(mutex);
KEYCACHE_THREAD_TRACE_BEGIN("");
return rc;
}
static void keycache_pthread_mutex_unlock(mysql_mutex_t *mutex)
{
KEYCACHE_THREAD_TRACE_END("");
mysql_mutex_unlock(mutex);
}
static int keycache_pthread_cond_signal(mysql_cond_t *cond)
{
int rc;
KEYCACHE_THREAD_TRACE("signal");
rc= mysql_cond_signal(cond);
return rc;
}
#if defined(KEYCACHE_DEBUG_LOG)
static void keycache_debug_print(const char * fmt,...)
{
va_list args;
va_start(args,fmt);
if (keycache_debug_log)
{
(void) vfprintf(keycache_debug_log, fmt, args);
(void) fputc('\n',keycache_debug_log);
}
va_end(args);
}
#endif /* defined(KEYCACHE_DEBUG_LOG) */
#if defined(KEYCACHE_DEBUG_LOG)
void keycache_debug_log_close(void)
{
if (keycache_debug_log)
fclose(keycache_debug_log);
}
#endif /* defined(KEYCACHE_DEBUG_LOG) */
#endif /* defined(KEYCACHE_DEBUG) */
#ifdef DBUG_ASSERT_EXISTS
#define F_B_PRT(_f_, _v_) DBUG_PRINT("assert_fail", (_f_, _v_))
static int fail_block(BLOCK_LINK *block __attribute__((unused)))
{
#ifndef DBUG_OFF
F_B_PRT("block->next_used: %p\n", block->next_used);
F_B_PRT("block->prev_used: %p\n", block->prev_used);
F_B_PRT("block->next_changed: %p\n", block->next_changed);
F_B_PRT("block->prev_changed: %p\n", block->prev_changed);
F_B_PRT("block->hash_link: %p\n", block->hash_link);
F_B_PRT("block->status: %u\n", block->status);
F_B_PRT("block->length: %u\n", block->length);
F_B_PRT("block->offset: %u\n", block->offset);
F_B_PRT("block->requests: %u\n", block->requests);
F_B_PRT("block->temperature: %u\n", block->temperature);
#endif
return 0; /* Let the assert fail. */
}
#endif
#ifndef DBUG_OFF
static int fail_hlink(HASH_LINK *hlink __attribute__((unused)))
{
F_B_PRT("hlink->next: %p\n", hlink->next);
F_B_PRT("hlink->prev: %p\n", hlink->prev);
F_B_PRT("hlink->block: %p\n", hlink->block);
F_B_PRT("hlink->diskpos: %lu\n", (ulong) hlink->diskpos);
F_B_PRT("hlink->file: %d\n", hlink->file);
return 0; /* Let the assert fail. */
}
static int cache_empty(SIMPLE_KEY_CACHE_CB *keycache)
{
int errcnt= 0;
int idx;
if (keycache->disk_blocks <= 0)
return 1;
for (idx= 0; idx < keycache->disk_blocks; idx++)
{
BLOCK_LINK *block= keycache->block_root + idx;
if (block->status || block->requests || block->hash_link)
{
fprintf(stderr, "block index: %u\n", idx);
fail_block(block);
errcnt++;
}
}
for (idx= 0; idx < keycache->hash_links; idx++)
{
HASH_LINK *hash_link= keycache->hash_link_root + idx;
if (hash_link->requests || hash_link->block)
{
fprintf(stderr, "hash_link index: %u\n", idx);
fail_hlink(hash_link);
errcnt++;
}
}
if (errcnt)
{
fprintf(stderr, "blocks: %d used: %zu\n",
keycache->disk_blocks, keycache->blocks_used);
fprintf(stderr, "hash_links: %d used: %d\n",
keycache->hash_links, keycache->hash_links_used);
fprintf(stderr, "\n");
}
return !errcnt;
}
#endif
/*
Get statistics for a simple key cache
SYNOPSIS
get_simple_key_cache_statistics()
keycache pointer to the control block of a simple key cache
partition_no partition number (not used)
key_cache_stats OUT pointer to the structure for the returned statistics
DESCRIPTION
This function is the implementation of the get_key_cache_statistics
interface function that is employed by simple (non-partitioned) key caches.
The function takes the parameter keycache as a pointer to the
control block structure of the type SIMPLE_KEY_CACHE_CB for a simple key
cache. This function returns the statistical data for the key cache.
The parameter partition_no is not used by this function.
RETURN
none
*/
static
void get_simple_key_cache_statistics(void *keycache_,
uint partition_no __attribute__((unused)),
KEY_CACHE_STATISTICS *keycache_stats)
{
SIMPLE_KEY_CACHE_CB *keycache= keycache_;
DBUG_ENTER("simple_get_key_cache_statistics");
keycache_stats->mem_size= (longlong) keycache->key_cache_mem_size;
keycache_stats->block_size= (longlong) keycache->key_cache_block_size;
keycache_stats->blocks_used= keycache->blocks_used;
keycache_stats->blocks_unused= keycache->blocks_unused;
keycache_stats->blocks_changed= keycache->global_blocks_changed;
keycache_stats->blocks_warm= keycache->warm_blocks;
keycache_stats->read_requests= keycache->global_cache_r_requests;
keycache_stats->reads= keycache->global_cache_read;
keycache_stats->write_requests= keycache->global_cache_w_requests;
keycache_stats->writes= keycache->global_cache_write;
DBUG_VOID_RETURN;
}
/*
The array of pointer to the key cache interface functions used for simple
key caches. Any simple key cache objects including those incorporated into
partitioned keys caches exploit this array.
The current implementation of these functions allows to call them from
the MySQL server code directly. We don't do it though.
*/
static KEY_CACHE_FUNCS simple_key_cache_funcs =
{
(INIT_KEY_CACHE) init_simple_key_cache,
(RESIZE_KEY_CACHE) resize_simple_key_cache,
(CHANGE_KEY_CACHE_PARAM) change_simple_key_cache_param,
(KEY_CACHE_READ) simple_key_cache_read,
(KEY_CACHE_INSERT) simple_key_cache_insert,
(KEY_CACHE_WRITE) simple_key_cache_write,
(FLUSH_KEY_BLOCKS) flush_simple_key_cache_blocks,
(RESET_KEY_CACHE_COUNTERS) reset_simple_key_cache_counters,
(END_KEY_CACHE) end_simple_key_cache,
(GET_KEY_CACHE_STATISTICS) get_simple_key_cache_statistics,
};
/******************************************************************************
Partitioned Key Cache Module
The module contains implementations of all key cache interface functions
employed by partitioned key caches.
A partitioned key cache is a collection of structures for simple key caches
called key cache partitions. Any page from a file can be placed into a buffer
of only one partition. The number of the partition is calculated from
the file number and the position of the page in the file, and it's always the
same for the page. The function that maps pages into partitions takes care
of even distribution of pages among partitions.
Partition key cache mitigate one of the major problem of simple key cache:
thread contention for key cache lock (mutex). Every call of a key cache
interface function must acquire this lock. So threads compete for this lock
even in the case when they have acquired shared locks for the file and
pages they want read from are in the key cache buffers.
When working with a partitioned key cache any key cache interface function
that needs only one page has to acquire the key cache lock only for the
partition the page is ascribed to. This makes the chances for threads not
compete for the same key cache lock better. Unfortunately if we use a
partitioned key cache with N partitions for B-tree indexes we can't say
that the chances becomes N times less. The fact is that any index lookup
operation requires reading from the root page that, for any index, is always
ascribed to the same partition. To resolve this problem we should have
employed more sophisticated mechanisms of working with root pages.
Currently the number of partitions in a partitioned key cache is limited
by 64. We could increase this limit. Simultaneously we would have to increase
accordingly the size of the bitmap dirty_part_map from the MYISAM_SHARE
structure.
******************************************************************************/
/* Control block for a partitioned key cache */
typedef struct st_partitioned_key_cache_cb
{
my_bool key_cache_inited; /*<=> control block is allocated */
SIMPLE_KEY_CACHE_CB **partition_array; /* the key cache partitions */
size_t key_cache_mem_size; /* specified size of the cache memory */
uint key_cache_block_size; /* size of the page buffer of a cache block */
uint partitions; /* number of partitions in the key cache */
} PARTITIONED_KEY_CACHE_CB;
static
void end_partitioned_key_cache(void *keycache_,
my_bool cleanup);
static int
reset_partitioned_key_cache_counters(const char *name,
void *keycache_);
/*
Determine the partition to which the index block to read is ascribed
SYNOPSIS
get_key_cache_partition()
keycache pointer to the control block of a partitioned key cache
file handler for the file for the block of data to be read
filepos position of the block of data in the file
DESCRIPTION
The function determines the number of the partition in whose buffer the
block from 'file' at the position filepos has to be placed for reading.
The function returns the control block of the simple key cache for this
partition to the caller.
RETURN VALUE
The pointer to the control block of the partition to which the specified
file block is ascribed.
*/
static
SIMPLE_KEY_CACHE_CB *
get_key_cache_partition(PARTITIONED_KEY_CACHE_CB *keycache,
File file, my_off_t filepos)
{
uint i= KEYCACHE_BASE_EXPR(file, filepos) % keycache->partitions;
return keycache->partition_array[i];
}
/*
Determine the partition to which the index block to write is ascribed
SYNOPSIS
get_key_cache_partition()
keycache pointer to the control block of a partitioned key cache
file handler for the file for the block of data to be read
filepos position of the block of data in the file
dirty_part_map pointer to the bitmap of dirty partitions for the file
DESCRIPTION
The function determines the number of the partition in whose buffer the
block from 'file' at the position filepos has to be placed for writing and
marks the partition as dirty in the dirty_part_map bitmap.
The function returns the control block of the simple key cache for this
partition to the caller.
RETURN VALUE
The pointer to the control block of the partition to which the specified
file block is ascribed.
*/
static SIMPLE_KEY_CACHE_CB
*get_key_cache_partition_for_write(PARTITIONED_KEY_CACHE_CB *keycache,
File file, my_off_t filepos,
ulonglong* dirty_part_map)
{
uint i= KEYCACHE_BASE_EXPR( file, filepos) % keycache->partitions;
*dirty_part_map|= 1ULL << i;
return keycache->partition_array[i];
}
/*
Initialize a partitioned key cache
SYNOPSIS
init_partitioned_key_cache()
keycache pointer to the control block of a partitioned key cache
key_cache_block_size size of blocks to keep cached data
use_mem total memory to use for all key cache partitions
division_limit division limit (may be zero)
age_threshold age threshold (may be zero)
DESCRIPTION
This function is the implementation of the init_key_cache
interface function that is employed by partitioned key caches.
The function builds and initializes an array of simple key caches,
and then initializes the control block structure of the type
PARTITIONED_KEY_CACHE_CB that is used for a partitioned key
cache. The parameter keycache is supposed to point to this
structure. The number of partitions in the partitioned key cache
to be built must be passed through the field 'partitions' of this
structure.
The parameter key_cache_block_size specifies the size of the
blocks in the the simple key caches to be built.
The parameters division_limit and age_threshold determine the initial
values of those characteristics of the simple key caches that are used for
midpoint insertion strategy. The parameter use_mem specifies the total
amount of memory to be allocated for the key cache blocks in all simple key
caches and for all auxiliary structures.
RETURN VALUE
total number of blocks in key cache partitions, if successful,
<= 0 - otherwise.
NOTES
If keycache->key_cache_inited != 0 then we assume that the memory for
the array of partitions has been already allocated.
It's assumed that no two threads call this function simultaneously
referring to the same key cache handle.
*/
static
int init_partitioned_key_cache(void *keycache_,
uint key_cache_block_size,
size_t use_mem, uint division_limit,
uint age_threshold, uint changed_blocks_hash_size)
{
PARTITIONED_KEY_CACHE_CB *keycache= keycache_;
int i;
size_t mem_per_cache;
size_t mem_decr;
int cnt;
SIMPLE_KEY_CACHE_CB *partition;
SIMPLE_KEY_CACHE_CB **partition_ptr;
uint partitions= keycache->partitions;
int blocks= 0;
DBUG_ENTER("partitioned_init_key_cache");
keycache->key_cache_block_size = key_cache_block_size;
if (keycache->key_cache_inited)
partition_ptr= keycache->partition_array;
else
{
if(!(partition_ptr=
(SIMPLE_KEY_CACHE_CB **) my_malloc(key_memory_KEY_CACHE,
sizeof(SIMPLE_KEY_CACHE_CB *) *
partitions, MYF(MY_WME))))
DBUG_RETURN(-1);
bzero(partition_ptr, sizeof(SIMPLE_KEY_CACHE_CB *) * partitions);
keycache->partition_array= partition_ptr;
}
mem_per_cache = use_mem / partitions;
mem_decr= mem_per_cache / 5;
for (i= 0; i < (int) partitions; i++)
{
my_bool key_cache_inited= keycache->key_cache_inited;
if (key_cache_inited)
partition= *partition_ptr;
else
{
if (!(partition=
(SIMPLE_KEY_CACHE_CB *) my_malloc(key_memory_KEY_CACHE,
sizeof(SIMPLE_KEY_CACHE_CB),
MYF(MY_WME))))
continue;
partition->key_cache_inited= 0;
}
cnt= init_simple_key_cache(partition, key_cache_block_size, mem_per_cache,
division_limit, age_threshold,
changed_blocks_hash_size);
if (cnt <= 0)
{
end_simple_key_cache(partition, 1);
if (!key_cache_inited)
{
my_free(partition);
partition= 0;
}
if ((i == 0 && cnt < 0) || i > 0)
{
/*
Here we have two cases:
1. i == 0 and cnt < 0
cnt < 0 => mem_per_cache is not big enough to allocate minimal
number of key blocks in the key cache of the partition.
Decrease the the number of the partitions by 1 and start again.
2. i > 0
There is not enough memory for one of the succeeding partitions.
Just skip this partition decreasing the number of partitions in
the key cache by one.
Do not change the value of mem_per_cache in both cases.
*/
if (key_cache_inited)
{
my_free(partition);
partition= 0;
if(key_cache_inited)
memmove(partition_ptr, partition_ptr+1,
sizeof(partition_ptr)*(partitions-i-1));
}
if (!--partitions)
break;
}
else
{
/*
We come here when i == 0 && cnt == 0.
cnt == 0 => the memory allocator fails to allocate a block of
memory of the size mem_per_cache. Decrease the value of
mem_per_cache without changing the current number of partitions
and start again. Make sure that such a decrease may happen not
more than 5 times in total.
*/
if (use_mem <= mem_decr)
break;
use_mem-= mem_decr;
}
i--;
mem_per_cache= use_mem/partitions;
continue;
}
else
{
blocks+= cnt;
*partition_ptr++= partition;
}
}
keycache->partitions= partitions= (uint) (partition_ptr-keycache->partition_array);
keycache->key_cache_mem_size= mem_per_cache * partitions;
for (i= 0; i < (int) partitions; i++)
keycache->partition_array[i]->hash_factor= partitions;
keycache->key_cache_inited= 1;
if (!partitions)
blocks= -1;
DBUG_RETURN(blocks);
}
/*
Resize a partitioned key cache
SYNOPSIS
resize_partitioned_key_cache()
keycache pointer to the control block of a partitioned key cache
key_cache_block_size size of blocks to keep cached data
use_mem total memory to use for the new key cache
division_limit new division limit (if not zero)
age_threshold new age threshold (if not zero)
DESCRIPTION
This function is the implementation of the resize_key_cache interface
function that is employed by partitioned key caches.
The function takes the parameter keycache as a pointer to the
control block structure of the type PARTITIONED_KEY_CACHE_CB for the
partitioned key cache to be resized.
The parameter key_cache_block_size specifies the new size of the blocks in
the simple key caches that comprise the partitioned key cache.
The parameters division_limit and age_threshold determine the new initial
values of those characteristics of the simple key cache that are used for
midpoint insertion strategy. The parameter use-mem specifies the total
amount of memory to be allocated for the key cache blocks in all new
simple key caches and for all auxiliary structures.
RETURN VALUE
number of blocks in the key cache, if successful,
0 - otherwise.
NOTES.
The function first calls prepare_resize_simple_key_cache for each simple
key cache effectively flushing all dirty pages from it and destroying
the key cache. Then init_partitioned_key_cache is called. This call builds
a new array of simple key caches containing the same number of elements
as the old one. After this the function calls the function
finish_resize_simple_key_cache for each simple key cache from this array.
This implementation doesn't block the calls and executions of other
functions from the key cache interface. However it assumes that the
calls of resize_partitioned_key_cache itself are serialized.
*/
static
int resize_partitioned_key_cache(void *keycache_,
uint key_cache_block_size,
size_t use_mem, uint division_limit,
uint age_threshold,
uint changed_blocks_hash_size)
{
PARTITIONED_KEY_CACHE_CB *keycache= keycache_;
uint i;
uint partitions= keycache->partitions;
my_bool cleanup= use_mem == 0;
int blocks= -1;
int err= 0;
DBUG_ENTER("partitioned_resize_key_cache");
if (cleanup)
{
end_partitioned_key_cache(keycache, 0);
DBUG_RETURN(-1);
}
for (i= 0; i < partitions; i++)
{
err|= prepare_resize_simple_key_cache(keycache->partition_array[i], 1);
}
if (!err)
blocks= init_partitioned_key_cache(keycache, key_cache_block_size,
use_mem, division_limit, age_threshold,
changed_blocks_hash_size);
if (blocks > 0)
{
for (i= 0; i < partitions; i++)
{
keycache_pthread_mutex_lock(&keycache->partition_array[i]->cache_lock);
finish_resize_simple_key_cache(keycache->partition_array[i]);
}
}
DBUG_RETURN(blocks);
}
/*
Change key cache parameters of a partitioned key cache
SYNOPSIS
partitioned_change_key_cache_param()
keycache pointer to the control block of a partitioned key cache
division_limit new division limit (if not zero)
age_threshold new age threshold (if not zero)
DESCRIPTION
This function is the implementation of the change_key_cache_param interface
function that is employed by partitioned key caches.
The function takes the parameter keycache as a pointer to the
control block structure of the type PARTITIONED_KEY_CACHE_CB for the simple
key cache where new values of the division limit and the age threshold used
for midpoint insertion strategy are to be set. The parameters
division_limit and age_threshold provide these new values.
RETURN VALUE
none
NOTES
The function just calls change_simple_key_cache_param for each element from
the array of simple caches that comprise the partitioned key cache.
*/
static
void change_partitioned_key_cache_param(void *keycache_,
uint division_limit,
uint age_threshold)
{
PARTITIONED_KEY_CACHE_CB *keycache= keycache_;
uint i;
uint partitions= keycache->partitions;
DBUG_ENTER("partitioned_change_key_cache_param");
for (i= 0; i < partitions; i++)
{
change_simple_key_cache_param(keycache->partition_array[i], division_limit,
age_threshold);
}
DBUG_VOID_RETURN;
}
/*
Destroy a partitioned key cache
SYNOPSIS
end_partitioned_key_cache()
keycache pointer to the control block of a partitioned key cache
cleanup <=> complete free (free also control block structures
for all simple key caches)
DESCRIPTION
This function is the implementation of the end_key_cache interface
function that is employed by partitioned key caches.
The function takes the parameter keycache as a pointer to the
control block structure of the type PARTITIONED_KEY_CACHE_CB for the
partitioned key cache to be destroyed.
The function frees the memory allocated for the cache blocks and
auxiliary structures used by simple key caches that comprise the
partitioned key cache. If the value of the parameter cleanup is TRUE
then even the memory used for control blocks of the simple key caches
and the array of pointers to them are freed.
RETURN VALUE
none
*/
static
void end_partitioned_key_cache(void *keycache_,
my_bool cleanup)
{
PARTITIONED_KEY_CACHE_CB *keycache= keycache_;
uint i;
uint partitions= keycache->partitions;
DBUG_ENTER("partitioned_end_key_cache");
DBUG_PRINT("enter", ("key_cache: %p", keycache));
for (i= 0; i < partitions; i++)
{
end_simple_key_cache(keycache->partition_array[i], cleanup);
}
if (cleanup)
{
for (i= 0; i < partitions; i++)
my_free(keycache->partition_array[i]);
my_free(keycache->partition_array);
keycache->key_cache_inited= 0;
}
DBUG_VOID_RETURN;
}
/*
Read a block of data from a partitioned key cache into a buffer
SYNOPSIS
partitioned_key_cache_read()
keycache pointer to the control block of a partitioned key cache
file handler for the file for the block of data to be read
filepos position of the block of data in the file
level determines the weight of the data
buff buffer to where the data must be placed
length length of the buffer
block_length length of the read data from a key cache block
return_buffer return pointer to the key cache buffer with the data
DESCRIPTION
This function is the implementation of the key_cache_read interface
function that is employed by partitioned key caches.
The function takes the parameter keycache as a pointer to the
control block structure of the type PARTITIONED_KEY_CACHE_CB for a
partitioned key cache.
In a general case the function reads a block of data from the key cache
into the buffer buff of the size specified by the parameter length. The
beginning of the block of data to be read is specified by the parameters
file and filepos. The length of the read data is the same as the length
of the buffer. The data is read into the buffer in key_cache_block_size
increments. To read each portion the function first finds out in what
partition of the key cache this portion(page) is to be saved, and calls
simple_key_cache_read with the pointer to the corresponding simple key as
its first parameter.
If the parameter return_buffer is not ignored and its value is TRUE, and
the data to be read of the specified size block_length can be read from one
key cache buffer, then the function returns a pointer to the data in the
key cache buffer.
The function takes into account parameters block_length and return buffer
only in a single-threaded environment.
The parameter 'level' is used only by the midpoint insertion strategy
when the data or its portion cannot be found in the key cache.
RETURN VALUE
Returns address from where the data is placed if successful, 0 - otherwise.
*/
static
uchar *partitioned_key_cache_read(void *keycache_,
File file, my_off_t filepos, int level,
uchar *buff, uint length,
uint block_length __attribute__((unused)),
int return_buffer __attribute__((unused)))
{
PARTITIONED_KEY_CACHE_CB *keycache= keycache_;
uint r_length;
uint offset= (uint) (filepos % keycache->key_cache_block_size);
uchar *start= buff;
DBUG_ENTER("partitioned_key_cache_read");
DBUG_PRINT("enter", ("fd: %u pos: %lu length: %u",
(uint) file, (ulong) filepos, length));
/* Read data in key_cache_block_size increments */
do
{
SIMPLE_KEY_CACHE_CB *partition= get_key_cache_partition(keycache,
file, filepos);
uchar *ret_buff= 0;
r_length= length;
set_if_smaller(r_length, keycache->key_cache_block_size - offset);
ret_buff= simple_key_cache_read((void *) partition,
file, filepos, level,
buff, r_length,
block_length, return_buffer);
if (ret_buff == 0)
DBUG_RETURN(0);
filepos+= r_length;
buff+= r_length;
offset= 0;
} while ((length-= r_length));
DBUG_RETURN(start);
}
/*
Insert a block of file data from a buffer into a partitioned key cache
SYNOPSIS
partitioned_key_cache_insert()
keycache pointer to the control block of a partitioned key cache
file handler for the file to insert data from
filepos position of the block of data in the file to insert
level determines the weight of the data
buff buffer to read data from
length length of the data in the buffer
DESCRIPTION
This function is the implementation of the key_cache_insert interface
function that is employed by partitioned key caches.
The function takes the parameter keycache as a pointer to the
control block structure of the type PARTITIONED_KEY_CACHE_CB for a
partitioned key cache.
The function writes a block of file data from a buffer into the key cache.
The buffer is specified with the parameters buff and length - the pointer
to the beginning of the buffer and its size respectively. It's assumed
that the buffer contains the data from 'file' allocated from the position
filepos. The data is copied from the buffer in key_cache_block_size
increments. For every portion of data the function finds out in what simple
key cache from the array of partitions the data must be stored, and after
this calls simple_key_cache_insert to copy the data into a key buffer of
this simple key cache.
The parameter level is used to set one characteristic for the key buffers
loaded with the data from buff. The characteristic is used only by the
midpoint insertion strategy.
RETURN VALUE
0 if a success, 1 - otherwise.
NOTES
The function is used by MyISAM to move all blocks from a index file to
the key cache. It can be performed in parallel with reading the file data
from the key buffers by other threads.
*/
static
int partitioned_key_cache_insert(void *keycache_,
File file, my_off_t filepos, int level,
uchar *buff, uint length)
{
PARTITIONED_KEY_CACHE_CB *keycache= keycache_;
uint w_length;
uint offset= (uint) (filepos % keycache->key_cache_block_size);
DBUG_ENTER("partitioned_key_cache_insert");
DBUG_PRINT("enter", ("fd: %u pos: %lu length: %u",
(uint) file,(ulong) filepos, length));
/* Write data in key_cache_block_size increments */
do
{
SIMPLE_KEY_CACHE_CB *partition= get_key_cache_partition(keycache,
file, filepos);
w_length= length;
set_if_smaller(w_length, keycache->key_cache_block_size - offset);
if (simple_key_cache_insert((void *) partition,
file, filepos, level,
buff, w_length))
DBUG_RETURN(1);
filepos+= w_length;
buff+= w_length;
offset = 0;
} while ((length-= w_length));
DBUG_RETURN(0);
}
/*
Write data from a buffer into a partitioned key cache
SYNOPSIS
partitioned_key_cache_write()
keycache pointer to the control block of a partitioned key cache
file handler for the file to write data to
filepos position in the file to write data to
level determines the weight of the data
buff buffer with the data
length length of the buffer
dont_write if is 0 then all dirty pages involved in writing
should have been flushed from key cache
file_extra maps of key cache partitions containing
dirty pages from file
DESCRIPTION
This function is the implementation of the key_cache_write interface
function that is employed by partitioned key caches.
The function takes the parameter keycache as a pointer to the
control block structure of the type PARTITIONED_KEY_CACHE_CB for a
partitioned key cache.
In a general case the function copies data from a buffer into the key
cache. The buffer is specified with the parameters buff and length -
the pointer to the beginning of the buffer and its size respectively.
It's assumed the buffer contains the data to be written into 'file'
starting from the position filepos. The data is copied from the buffer
in key_cache_block_size increments. For every portion of data the
function finds out in what simple key cache from the array of partitions
the data must be stored, and after this calls simple_key_cache_write to
copy the data into a key buffer of this simple key cache.
If the value of the parameter dont_write is FALSE then the function
also writes the data into file.
The parameter level is used to set one characteristic for the key buffers
filled with the data from buff. The characteristic is employed only by
the midpoint insertion strategy.
The parameter file_expra provides a pointer to the shared bitmap of
the partitions that may contains dirty pages for the file. This bitmap
is used to optimize the function flush_partitioned_key_cache_blocks.
RETURN VALUE
0 if a success, 1 - otherwise.
NOTES
This implementation exploits the fact that the function is called only
when a thread has got an exclusive lock for the key file.
*/
static
int partitioned_key_cache_write(void *keycache_,
File file, void *file_extra,
my_off_t filepos, int level,
uchar *buff, uint length,
uint block_length __attribute__((unused)),
int dont_write)
{
PARTITIONED_KEY_CACHE_CB *keycache= keycache_;
uint w_length;
ulonglong *part_map= (ulonglong *) file_extra;
uint offset= (uint) (filepos % keycache->key_cache_block_size);
DBUG_ENTER("partitioned_key_cache_write");
DBUG_PRINT("enter",
("fd: %u pos: %lu length: %u block_length: %u"
" key_block_length: %u",
(uint) file, (ulong) filepos, length, block_length,
keycache ? keycache->key_cache_block_size : 0));
/* Write data in key_cache_block_size increments */
do
{
SIMPLE_KEY_CACHE_CB *partition= get_key_cache_partition_for_write(keycache,
file,
filepos,
part_map);
w_length = length;
set_if_smaller(w_length, keycache->key_cache_block_size - offset );
if (simple_key_cache_write(partition,
file, 0, filepos, level,
buff, w_length, block_length,
dont_write))
DBUG_RETURN(1);
filepos+= w_length;
buff+= w_length;
offset= 0;
} while ((length-= w_length));
DBUG_RETURN(0);
}
/*
Flush all blocks for a file from key buffers of a partitioned key cache
SYNOPSIS
flush_partitioned_key_cache_blocks()
keycache pointer to the control block of a partitioned key cache
file handler for the file to flush to
file_extra maps of key cache partitions containing
dirty pages from file (not used)
flush_type type of the flush operation
DESCRIPTION
This function is the implementation of the flush_key_blocks interface
function that is employed by partitioned key caches.
The function takes the parameter keycache as a pointer to the
control block structure of the type PARTITIONED_KEY_CACHE_CB for a
partitioned key cache.
In a general case the function flushes the data from all dirty key
buffers related to the file 'file' into this file. The function does
exactly this if the value of the parameter type is FLUSH_KEEP. If the
value of this parameter is FLUSH_RELEASE, the function additionally
releases the key buffers containing data from 'file' for new usage.
If the value of the parameter type is FLUSH_IGNORE_CHANGED the function
just releases the key buffers containing data from 'file'.
The function performs the operation by calling the function
flush_simple_key_cache_blocks for the elements of the array of the
simple key caches that comprise the partitioned key_cache. If the value
of the parameter type is FLUSH_KEEP s_flush_key_blocks is called only
for the partitions with possibly dirty pages marked in the bitmap
pointed to by the parameter file_extra.
RETURN
0 ok
1 error
NOTES
This implementation exploits the fact that the function is called only
when a thread has got an exclusive lock for the key file.
*/
static
int flush_partitioned_key_cache_blocks(void *keycache_,
File file, void *file_extra,
enum flush_type type)
{
PARTITIONED_KEY_CACHE_CB *keycache= keycache_;
uint i;
uint partitions= keycache->partitions;
int err= 0;
ulonglong *dirty_part_map= (ulonglong *) file_extra;
DBUG_ENTER("partitioned_flush_key_blocks");
DBUG_PRINT("enter", ("keycache: %p", keycache));
for (i= 0; i < partitions; i++)
{
SIMPLE_KEY_CACHE_CB *partition= keycache->partition_array[i];
if ((type == FLUSH_KEEP || type == FLUSH_FORCE_WRITE) &&
!((*dirty_part_map) & ((ulonglong) 1 << i)))
continue;
err|= MY_TEST(flush_simple_key_cache_blocks(partition, file, 0, type));
}
*dirty_part_map= 0;
DBUG_RETURN(err);
}
/*
Reset the counters of a partitioned key cache
SYNOPSIS
reset_partitioned_key_cache_counters()
name the name of a key cache
keycache pointer to the control block of a partitioned key cache
DESCRIPTION
This function is the implementation of the reset_key_cache_counters
interface function that is employed by partitioned key caches.
The function takes the parameter keycache as a pointer to the
control block structure of the type PARTITIONED_KEY_CACHE_CB for a partitioned
key cache.
This function resets the values of the statistical counters of the simple
key caches comprising partitioned key cache to 0. It does it by calling
reset_simple_key_cache_counters for each key cache partition.
The parameter name is currently not used.
RETURN
0 on success (always because it can't fail)
*/
static int
reset_partitioned_key_cache_counters(const char *name __attribute__((unused)),
void *keycache_)
{
PARTITIONED_KEY_CACHE_CB *keycache= keycache_;
uint i;
uint partitions= keycache->partitions;
DBUG_ENTER("partitioned_reset_key_cache_counters");
for (i = 0; i < partitions; i++)
{
reset_simple_key_cache_counters(name, keycache->partition_array[i]);
}
DBUG_RETURN(0);
}
/*
Get statistics for a partition key cache
SYNOPSIS
get_partitioned_key_cache_statistics()
keycache pointer to the control block of a partitioned key cache
partition_no partition number to get statistics for
key_cache_stats OUT pointer to the structure for the returned statistics
DESCRIPTION
This function is the implementation of the get_key_cache_statistics
interface function that is employed by partitioned key caches.
The function takes the parameter keycache as a pointer to the
control block structure of the type PARTITIONED_KEY_CACHE_CB for
a partitioned key cache.
If the value of the parameter partition_no is equal to 0 then aggregated
statistics for all partitions is returned in the fields of the
structure key_cache_stat of the type KEY_CACHE_STATISTICS . Otherwise
the function returns data for the partition number partition_no of the
key cache in the structure key_cache_stat. (Here partitions are numbered
starting from 1.)
RETURN
none
*/
static
void
get_partitioned_key_cache_statistics(void *keycache_,
uint partition_no,
KEY_CACHE_STATISTICS *keycache_stats)
{
PARTITIONED_KEY_CACHE_CB *keycache= keycache_;
uint i;
SIMPLE_KEY_CACHE_CB *partition;
uint partitions= keycache->partitions;
DBUG_ENTER("get_partitioned_key_cache_statistics");
if (partition_no != 0)
{
partition= keycache->partition_array[partition_no-1];
get_simple_key_cache_statistics((void *) partition, 0, keycache_stats);
DBUG_VOID_RETURN;
}
bzero(keycache_stats, sizeof(KEY_CACHE_STATISTICS));
keycache_stats->mem_size= (longlong) keycache->key_cache_mem_size;
keycache_stats->block_size= (longlong) keycache->key_cache_block_size;
for (i = 0; i < partitions; i++)
{
partition= keycache->partition_array[i];
keycache_stats->blocks_used+= partition->blocks_used;
keycache_stats->blocks_unused+= partition->blocks_unused;
keycache_stats->blocks_changed+= partition->global_blocks_changed;
keycache_stats->blocks_warm+= partition->warm_blocks;
keycache_stats->read_requests+= partition->global_cache_r_requests;
keycache_stats->reads+= partition->global_cache_read;
keycache_stats->write_requests+= partition->global_cache_w_requests;
keycache_stats->writes+= partition->global_cache_write;
}
DBUG_VOID_RETURN;
}
/*
The array of pointers to the key cache interface functions used by
partitioned key caches. Any partitioned key cache object caches exploits
this array.
The current implementation of these functions does not allow to call
them from the MySQL server code directly. The key cache interface
wrappers must be used for this purpose.
*/
static KEY_CACHE_FUNCS partitioned_key_cache_funcs =
{
(INIT_KEY_CACHE) init_partitioned_key_cache,
(RESIZE_KEY_CACHE) resize_partitioned_key_cache,
(CHANGE_KEY_CACHE_PARAM) change_partitioned_key_cache_param,
(KEY_CACHE_READ) partitioned_key_cache_read,
(KEY_CACHE_INSERT) partitioned_key_cache_insert,
(KEY_CACHE_WRITE) partitioned_key_cache_write,
(FLUSH_KEY_BLOCKS) flush_partitioned_key_cache_blocks,
(RESET_KEY_CACHE_COUNTERS) reset_partitioned_key_cache_counters,
(END_KEY_CACHE) end_partitioned_key_cache,
(GET_KEY_CACHE_STATISTICS) get_partitioned_key_cache_statistics,
};
/******************************************************************************
Key Cache Interface Module
The module contains wrappers for all key cache interface functions.
Currently there are key caches of two types: simple key caches and
partitioned key caches. Each type (class) has its own implementation of the
basic key cache operations used the MyISAM storage engine. The pointers
to the implementation functions are stored in two static structures of the
type KEY_CACHE_FUNC: simple_key_cache_funcs - for simple key caches, and
partitioned_key_cache_funcs - for partitioned key caches. When a key cache
object is created the constructor procedure init_key_cache places a pointer
to the corresponding table into one of its fields. The procedure also
initializes a control block for the key cache oject and saves the pointer
to this block in another field of the key cache object.
When a key cache wrapper function is invoked for a key cache object to
perform a basic key cache operation it looks into the interface table
associated with the key cache oject and calls the corresponding
implementation of the operation. It passes the saved key cache control
block to this implementation. If, for some reasons, the control block
has not been fully initialized yet, the wrapper function either does not
do anything or, in the case when it perform a read/write operation, the
function do it directly through the system i/o functions.
As we can see the model with which the key cache interface is supported
as quite conventional for interfaces in general.
******************************************************************************/
static
int repartition_key_cache_internal(KEY_CACHE *keycache,
uint key_cache_block_size, size_t use_mem,
uint division_limit, uint age_threshold,
uint changed_blocks_hash_size,
uint partitions, my_bool use_op_lock);
/*
Initialize a key cache : internal
SYNOPSIS
init_key_cache_internal()
keycache pointer to the key cache to be initialized
key_cache_block_size size of blocks to keep cached data
use_mem total memory to use for cache buffers/structures
division_limit division limit (may be zero)
age_threshold age threshold (may be zero)
changed_blocks_hash_size Number of hash buckets to hold a link of different
files. Should be proportional to number of different
files sused.
partitions Number of partitions in the key cache
use_op_lock if TRUE use keycache->op_lock, otherwise - ignore it
DESCRIPTION
The function performs the actions required from init_key_cache().
It has an additional parameter: use_op_lock. When the parameter
is TRUE than the function initializes keycache->op_lock if needed,
then locks it, and unlocks it before the return. Otherwise the actions
with the lock are omitted.
RETURN VALUE
total number of blocks in key cache partitions, if successful,
<= 0 - otherwise.
NOTES
if keycache->key_cache_inited != 0 we assume that the memory
for the control block of the key cache has been already allocated.
*/
static
int init_key_cache_internal(KEY_CACHE *keycache, uint key_cache_block_size,
size_t use_mem, uint division_limit,
uint age_threshold, uint changed_blocks_hash_size,
uint partitions,
my_bool use_op_lock)
{
void *keycache_cb;
int blocks;
if (keycache->key_cache_inited)
{
if (use_op_lock)
pthread_mutex_lock(&keycache->op_lock);
keycache_cb= keycache->keycache_cb;
}
else
{
if (partitions == 0)
{
if (!(keycache_cb= (void *) my_malloc(key_memory_KEY_CACHE,
sizeof(SIMPLE_KEY_CACHE_CB),
MYF(0))))
return 0;
((SIMPLE_KEY_CACHE_CB *) keycache_cb)->key_cache_inited= 0;
keycache->key_cache_type= SIMPLE_KEY_CACHE;
keycache->interface_funcs= &simple_key_cache_funcs;
}
else
{
if (!(keycache_cb= (void *) my_malloc(key_memory_KEY_CACHE,
sizeof(PARTITIONED_KEY_CACHE_CB),
MYF(0))))
return 0;
((PARTITIONED_KEY_CACHE_CB *) keycache_cb)->key_cache_inited= 0;
keycache->key_cache_type= PARTITIONED_KEY_CACHE;
keycache->interface_funcs= &partitioned_key_cache_funcs;
}
/*
Initialize op_lock if it's not initialized before.
The mutex may have been initialized before if we are being called
from repartition_key_cache_internal().
*/
if (use_op_lock)
pthread_mutex_init(&keycache->op_lock, MY_MUTEX_INIT_FAST);
keycache->keycache_cb= keycache_cb;
keycache->key_cache_inited= 1;
if (use_op_lock)
pthread_mutex_lock(&keycache->op_lock);
}
if (partitions != 0)
{
((PARTITIONED_KEY_CACHE_CB *) keycache_cb)->partitions= partitions;
}
keycache->can_be_used= 0;
blocks= keycache->interface_funcs->init(keycache_cb, key_cache_block_size,
use_mem, division_limit,
age_threshold, changed_blocks_hash_size);
keycache->partitions= partitions ?
((PARTITIONED_KEY_CACHE_CB *) keycache_cb)->partitions :
0;
DBUG_ASSERT(partitions <= MAX_KEY_CACHE_PARTITIONS);
keycache->key_cache_mem_size=
keycache->partitions ?
((PARTITIONED_KEY_CACHE_CB *) keycache_cb)->key_cache_mem_size :
((SIMPLE_KEY_CACHE_CB *) keycache_cb)->key_cache_mem_size;
if (blocks > 0)
keycache->can_be_used= 1;
if (use_op_lock)
pthread_mutex_unlock(&keycache->op_lock);
return blocks;
}
/*
Initialize a key cache
SYNOPSIS
init_key_cache()
keycache pointer to the key cache to be initialized
key_cache_block_size size of blocks to keep cached data
use_mem total memory to use for cache buffers/structures
division_limit division limit (may be zero)
age_threshold age threshold (may be zero)
partitions number of partitions in the key cache
DESCRIPTION
The function creates a control block structure for a key cache and
places the pointer to this block in the structure keycache.
If the value of the parameter 'partitions' is 0 then a simple key cache
is created. Otherwise a partitioned key cache with the specified number
of partitions is created.
The parameter key_cache_block_size specifies the size of the blocks in
the key cache to be created. The parameters division_limit and
age_threshold determine the initial values of those characteristics of
the key cache that are used for midpoint insertion strategy. The parameter
use_mem specifies the total amount of memory to be allocated for the
key cache buffers and for all auxiliary structures.
The function calls init_key_cache_internal() to perform all these actions
with the last parameter set to TRUE.
RETURN VALUE
total number of blocks in key cache partitions, if successful,
<= 0 - otherwise.
NOTES
It's assumed that no two threads call this function simultaneously
referring to the same key cache handle.
*/
int init_key_cache(KEY_CACHE *keycache, uint key_cache_block_size,
size_t use_mem, uint division_limit,
uint age_threshold, uint changed_blocks_hash_size,
uint partitions)
{
return init_key_cache_internal(keycache, key_cache_block_size, use_mem,
division_limit, age_threshold,
changed_blocks_hash_size, partitions, 1);
}
/*
Resize a key cache
SYNOPSIS
resize_key_cache()
keycache pointer to the key cache to be resized
key_cache_block_size size of blocks to keep cached data
use_mem total memory to use for the new key cache
division_limit new division limit (if not zero)
age_threshold new age threshold (if not zero)
DESCRIPTION
The function operates over the key cache key cache.
The parameter key_cache_block_size specifies the new size of the block
buffers in the key cache. The parameters division_limit and age_threshold
determine the new initial values of those characteristics of the key cache
that are used for midpoint insertion strategy. The parameter use_mem
specifies the total amount of memory to be allocated for the key cache
buffers and for all auxiliary structures.
RETURN VALUE
number of blocks in the key cache, if successful,
0 - otherwise.
NOTES
The function does not block the calls and executions of other functions
from the key cache interface. However it assumes that the calls of
resize_key_cache itself are serialized.
Currently the function is called when the values of the variables
key_buffer_size and/or key_cache_block_size are being reset for
the key cache keycache.
*/
int resize_key_cache(KEY_CACHE *keycache, uint key_cache_block_size,
size_t use_mem, uint division_limit, uint age_threshold,
uint changed_blocks_hash_size)
{
int blocks= -1;
if (keycache->key_cache_inited)
{
pthread_mutex_lock(&keycache->op_lock);
if ((uint) keycache->param_partitions != keycache->partitions && use_mem)
blocks= repartition_key_cache_internal(keycache,
key_cache_block_size, use_mem,
division_limit, age_threshold,
changed_blocks_hash_size,
(uint) keycache->param_partitions,
0);
else
{
blocks= keycache->interface_funcs->resize(keycache->keycache_cb,
key_cache_block_size,
use_mem, division_limit,
age_threshold,
changed_blocks_hash_size);
if (keycache->partitions)
keycache->partitions=
((PARTITIONED_KEY_CACHE_CB *)(keycache->keycache_cb))->partitions;
}
keycache->key_cache_mem_size=
keycache->partitions ?
((PARTITIONED_KEY_CACHE_CB *)(keycache->keycache_cb))->key_cache_mem_size :
((SIMPLE_KEY_CACHE_CB *)(keycache->keycache_cb))->key_cache_mem_size;
keycache->can_be_used= (blocks >= 0);
pthread_mutex_unlock(&keycache->op_lock);
}
return blocks;
}
/*
Change key cache parameters of a key cache
SYNOPSIS
change_key_cache_param()
keycache pointer to the key cache to change parameters for
division_limit new division limit (if not zero)
age_threshold new age threshold (if not zero)
DESCRIPTION
The function sets new values of the division limit and the age threshold
used when the key cache keycache employs midpoint insertion strategy.
The parameters division_limit and age_threshold provide these new values.
RETURN VALUE
none
NOTES
Currently the function is called when the values of the variables
key_cache_division_limit and/or key_cache_age_threshold are being reset
for the key cache keycache.
*/
void change_key_cache_param(KEY_CACHE *keycache, uint division_limit,
uint age_threshold)
{
if (keycache->key_cache_inited)
{
pthread_mutex_lock(&keycache->op_lock);
keycache->interface_funcs->change_param(keycache->keycache_cb,
division_limit,
age_threshold);
pthread_mutex_unlock(&keycache->op_lock);
}
}
/*
Destroy a key cache : internal
SYNOPSIS
end_key_cache_internal()
keycache pointer to the key cache to be destroyed
cleanup <=> complete free
use_op_lock if TRUE use keycache->op_lock, otherwise - ignore it
DESCRIPTION
The function performs the actions required from end_key_cache().
It has an additional parameter: use_op_lock. When the parameter
is TRUE than the function destroys keycache->op_lock if cleanup is true.
Otherwise the action with the lock is omitted.
RETURN VALUE
none
*/
static
void end_key_cache_internal(KEY_CACHE *keycache, my_bool cleanup,
my_bool use_op_lock)
{
if (keycache->key_cache_inited)
{
keycache->interface_funcs->end(keycache->keycache_cb, cleanup);
if (cleanup)
{
if (keycache->keycache_cb)
{
my_free(keycache->keycache_cb);
keycache->keycache_cb= 0;
}
/*
We do not destroy op_lock if we are going to reuse the same key cache.
This happens if we are called from repartition_key_cache_internal().
*/
if (use_op_lock)
pthread_mutex_destroy(&keycache->op_lock);
keycache->key_cache_inited= 0;
}
keycache->can_be_used= 0;
}
}
/*
Destroy a key cache
SYNOPSIS
end_key_cache()
keycache pointer to the key cache to be destroyed
cleanup <=> complete free
DESCRIPTION
The function frees the memory allocated for the cache blocks and
auxiliary structures used by the key cache keycache. If the value
of the parameter cleanup is TRUE then all resources used by the key
cache are to be freed.
The function calls end_key_cache_internal() to perform all these actions
with the last parameter set to TRUE.
RETURN VALUE
none
*/
void end_key_cache(KEY_CACHE *keycache, my_bool cleanup)
{
end_key_cache_internal(keycache, cleanup, 1);
}
/*
Read a block of data from a key cache into a buffer
SYNOPSIS
key_cache_read()
keycache pointer to the key cache to read data from
file handler for the file for the block of data to be read
filepos position of the block of data in the file
level determines the weight of the data
buff buffer to where the data must be placed
length length of the buffer
block_length length of the data read from a key cache block
return_buffer return pointer to the key cache buffer with the data
DESCRIPTION
The function operates over buffers of the key cache keycache.
In a general case the function reads a block of data from the key cache
into the buffer buff of the size specified by the parameter length. The
beginning of the block of data to be read is specified by the parameters
file and filepos. The length of the read data is the same as the length
of the buffer.
If the parameter return_buffer is not ignored and its value is TRUE, and
the data to be read of the specified size block_length can be read from one
key cache buffer, then the function returns a pointer to the data in the
key cache buffer.
The parameter 'level' is used only by the midpoint insertion strategy
when the data or its portion cannot be found in the key cache.
The function reads data into the buffer directly from file if the control
block of the key cache has not been initialized yet.
RETURN VALUE
Returns address from where the data is placed if successful, 0 - otherwise.
NOTES.
Filepos must be a multiple of 'block_length', but it doesn't
have to be a multiple of key_cache_block_size;
*/
uchar *key_cache_read(KEY_CACHE *keycache,
File file, my_off_t filepos, int level,
uchar *buff, uint length,
uint block_length, int return_buffer)
{
if (keycache->can_be_used)
return keycache->interface_funcs->read(keycache->keycache_cb,
file, filepos, level,
buff, length,
block_length, return_buffer);
/* We can't use mutex here as the key cache may not be initialized */
if (my_pread(file, (uchar*) buff, length, filepos, MYF(MY_NABP)))
return (uchar *) 0;
return buff;
}
/*
Insert a block of file data from a buffer into a key cache
SYNOPSIS
key_cache_insert()
keycache pointer to the key cache to insert data into
file handler for the file to insert data from
filepos position of the block of data in the file to insert
level determines the weight of the data
buff buffer to read data from
length length of the data in the buffer
DESCRIPTION
The function operates over buffers of the key cache keycache.
The function writes a block of file data from a buffer into the key cache.
The buffer is specified with the parameters buff and length - the pointer
to the beginning of the buffer and its size respectively. It's assumed
that the buffer contains the data from 'file' allocated from the position
filepos.
The parameter level is used to set one characteristic for the key buffers
loaded with the data from buff. The characteristic is used only by the
midpoint insertion strategy.
RETURN VALUE
0 if a success, 1 - otherwise.
NOTES
The function is used by MyISAM to move all blocks from a index file to
the key cache.
It is assumed that it may be performed in parallel with reading the file
data from the key buffers by other threads.
*/
int key_cache_insert(KEY_CACHE *keycache,
File file, my_off_t filepos, int level,
uchar *buff, uint length)
{
if (keycache->can_be_used)
return keycache->interface_funcs->insert(keycache->keycache_cb,
file, filepos, level,
buff, length);
return 0;
}
/*
Write data from a buffer into a key cache
SYNOPSIS
key_cache_write()
keycache pointer to the key cache to write data to
file handler for the file to write data to
filepos position in the file to write data to
level determines the weight of the data
buff buffer with the data
length length of the buffer
dont_write if is 0 then all dirty pages involved in writing
should have been flushed from key cache
file_extra pointer to optional file attributes
DESCRIPTION
The function operates over buffers of the key cache keycache.
In a general case the function writes data from a buffer into the key
cache. The buffer is specified with the parameters buff and length -
the pointer to the beginning of the buffer and its size respectively.
It's assumed the buffer contains the data to be written into 'file'
starting from the position filepos.
If the value of the parameter dont_write is FALSE then the function
also writes the data into file.
The parameter level is used to set one characteristic for the key buffers
filled with the data from buff. The characteristic is employed only by
the midpoint insertion strategy.
The parameter file_expra may point to additional file attributes used
for optimization or other purposes.
The function writes data from the buffer directly into file if the control
block of the key cache has not been initialized yet.
RETURN VALUE
0 if a success, 1 - otherwise.
NOTES
This implementation may exploit the fact that the function is called only
when a thread has got an exclusive lock for the key file.
*/
int key_cache_write(KEY_CACHE *keycache,
File file, void *file_extra,
my_off_t filepos, int level,
uchar *buff, uint length,
uint block_length, int force_write)
{
if (keycache->can_be_used)
return keycache->interface_funcs->write(keycache->keycache_cb,
file, file_extra,
filepos, level,
buff, length,
block_length, force_write);
/* We can't use mutex here as the key cache may not be initialized */
if (my_pwrite(file, buff, length, filepos, MYF(MY_NABP | MY_WAIT_IF_FULL)))
return 1;
return 0;
}
/*
Flush all blocks for a file from key buffers of a key cache
SYNOPSIS
flush_key_blocks()
keycache pointer to the key cache whose blocks are to be flushed
file handler for the file to flush to
file_extra maps of key cache (used for partitioned key caches)
flush_type type of the flush operation
DESCRIPTION
The function operates over buffers of the key cache keycache.
In a general case the function flushes the data from all dirty key
buffers related to the file 'file' into this file. The function does
exactly this if the value of the parameter type is FLUSH_KEEP. If the
value of this parameter is FLUSH_RELEASE, the function additionally
releases the key buffers containing data from 'file' for new usage.
If the value of the parameter type is FLUSH_IGNORE_CHANGED the function
just releases the key buffers containing data from 'file'.
If the value of the parameter type is FLUSH_KEEP the function may use
the value of the parameter file_extra pointing to possibly dirty
partitions to optimize the operation for partitioned key caches.
RETURN
0 ok
1 error
NOTES
Any implementation of the function may exploit the fact that the function
is called only when a thread has got an exclusive lock for the key file.
*/
int flush_key_blocks(KEY_CACHE *keycache,
int file, void *file_extra,
enum flush_type type)
{
if (keycache->can_be_used)
return keycache->interface_funcs->flush(keycache->keycache_cb,
file, file_extra, type);
return 0;
}
/*
Reset the counters of a key cache
SYNOPSIS
reset_key_cache_counters()
name the name of a key cache (unused)
keycache pointer to the key cache for which to reset counters
DESCRIPTION
This function resets the values of the statistical counters for the key
cache keycache.
The parameter name is currently not used.
RETURN
0 on success (always because it can't fail)
NOTES
This procedure is used by process_key_caches() to reset the counters of all
currently used key caches, both the default one and the named ones.
*/
int reset_key_cache_counters(const char *name __attribute__((unused)),
KEY_CACHE *keycache,
void *unused __attribute__((unused)))
{
int rc= 0;
if (keycache->key_cache_inited)
{
pthread_mutex_lock(&keycache->op_lock);
rc= keycache->interface_funcs->reset_counters(name,
keycache->keycache_cb);
pthread_mutex_unlock(&keycache->op_lock);
}
return rc;
}
/*
Get statistics for a key cache
SYNOPSIS
get_key_cache_statistics()
keycache pointer to the key cache to get statistics for
partition_no partition number to get statistics for
key_cache_stats OUT pointer to the structure for the returned statistics
DESCRIPTION
If the value of the parameter partition_no is equal to 0 then statistics
for the whole key cache keycache (aggregated statistics) is returned in the
fields of the structure key_cache_stat of the type KEY_CACHE_STATISTICS.
Otherwise the value of the parameter partition_no makes sense only for
a partitioned key cache. In this case the function returns statistics
for the partition with the specified number partition_no.
RETURN
none
*/
void get_key_cache_statistics(KEY_CACHE *keycache, uint partition_no,
KEY_CACHE_STATISTICS *key_cache_stats)
{
if (keycache->key_cache_inited)
{
pthread_mutex_lock(&keycache->op_lock);
keycache->interface_funcs->get_stats(keycache->keycache_cb,
partition_no, key_cache_stats);
pthread_mutex_unlock(&keycache->op_lock);
}
}
/*
Repartition a key cache : internal
SYNOPSIS
repartition_key_cache_internal()
keycache pointer to the key cache to be repartitioned
key_cache_block_size size of blocks to keep cached data
use_mem total memory to use for the new key cache
division_limit new division limit (if not zero)
age_threshold new age threshold (if not zero)
partitions new number of partitions in the key cache
use_op_lock if TRUE use keycache->op_lock, otherwise - ignore it
DESCRIPTION
The function performs the actions required from repartition_key_cache().
It has an additional parameter: use_op_lock. When the parameter
is TRUE then the function locks keycache->op_lock at start and
unlocks it before the return. Otherwise the actions with the lock
are omitted.
RETURN VALUE
number of blocks in the key cache, if successful,
0 - otherwise.
*/
static
int repartition_key_cache_internal(KEY_CACHE *keycache,
uint key_cache_block_size, size_t use_mem,
uint division_limit, uint age_threshold,
uint changed_blocks_hash_size,
uint partitions, my_bool use_op_lock)
{
uint blocks= -1;
if (keycache->key_cache_inited)
{
if (use_op_lock)
pthread_mutex_lock(&keycache->op_lock);
keycache->interface_funcs->resize(keycache->keycache_cb,
key_cache_block_size, 0,
division_limit, age_threshold,
changed_blocks_hash_size);
end_key_cache_internal(keycache, 1, 0);
blocks= init_key_cache_internal(keycache, key_cache_block_size, use_mem,
division_limit, age_threshold,
changed_blocks_hash_size, partitions,
0);
if (use_op_lock)
pthread_mutex_unlock(&keycache->op_lock);
}
return blocks;
}
/*
Repartition a key cache
SYNOPSIS
repartition_key_cache()
keycache pointer to the key cache to be repartitioned
key_cache_block_size size of blocks to keep cached data
use_mem total memory to use for the new key cache
division_limit new division limit (if not zero)
age_threshold new age threshold (if not zero)
partitions new number of partitions in the key cache
DESCRIPTION
The function operates over the key cache keycache.
The parameter partitions specifies the number of partitions in the key
cache after repartitioning. If the value of this parameter is 0 then
a simple key cache must be created instead of the old one.
The parameter key_cache_block_size specifies the new size of the block
buffers in the key cache. The parameters division_limit and age_threshold
determine the new initial values of those characteristics of the key cache
that are used for midpoint insertion strategy. The parameter use_mem
specifies the total amount of memory to be allocated for the new key
cache buffers and for all auxiliary structures.
The function calls repartition_key_cache_internal() to perform all these
actions with the last parameter set to TRUE.
RETURN VALUE
number of blocks in the key cache, if successful,
0 - otherwise.
NOTES
Currently the function is called when the value of the variable
key_cache_partitions is being reset for the key cache keycache.
*/
int repartition_key_cache(KEY_CACHE *keycache, uint key_cache_block_size,
size_t use_mem, uint division_limit,
uint age_threshold, uint changed_blocks_hash_size,
uint partitions)
{
return repartition_key_cache_internal(keycache, key_cache_block_size, use_mem,
division_limit, age_threshold,
changed_blocks_hash_size,
partitions, 1);
}
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