mariadb/mysys/lf_dynarray.c

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2011-06-30 17:46:53 +02:00
/* Copyright (c) 2006, 2010, Oracle and/or its affiliates. All rights reserved.
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
2011-06-30 17:46:53 +02:00
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
/*
Analog of DYNAMIC_ARRAY that never reallocs
(so no pointer into the array may ever become invalid).
Memory is allocated in non-contiguous chunks.
This data structure is not space efficient for sparse arrays.
Every element is aligned to sizeof(element) boundary
(to avoid false sharing if element is big enough).
LF_DYNARRAY is a recursive structure. On the zero level
LF_DYNARRAY::level[0] it's an array of LF_DYNARRAY_LEVEL_LENGTH elements,
on the first level it's an array of LF_DYNARRAY_LEVEL_LENGTH pointers
to arrays of elements, on the second level it's an array of pointers
to arrays of pointers to arrays of elements. And so on.
With four levels the number of elements is limited to 4311810304
(but as in all functions index is uint, the real limit is 2^32-1)
Actually, it's wait-free, not lock-free ;-)
*/
#include <my_global.h>
#include <m_string.h>
#include <my_sys.h>
#include <lf.h>
void lf_dynarray_init(LF_DYNARRAY *array, uint element_size)
{
bzero(array, sizeof(*array));
array->size_of_element= element_size;
}
static void recursive_free(void **alloc, int level)
{
if (!alloc)
return;
if (level)
{
int i;
for (i= 0; i < LF_DYNARRAY_LEVEL_LENGTH; i++)
recursive_free(alloc[i], level-1);
Bug#34043: Server loops excessively in _checkchunk() when safemalloc is enabled Essentially, the problem is that safemalloc is excruciatingly slow as it checks all allocated blocks for overrun at each memory management primitive, yielding a almost exponential slowdown for the memory management functions (malloc, realloc, free). The overrun check basically consists of verifying some bytes of a block for certain magic keys, which catches some simple forms of overrun. Another minor problem is violation of aliasing rules and that its own internal list of blocks is prone to corruption. Another issue with safemalloc is rather the maintenance cost as the tool has a significant impact on the server code. Given the magnitude of memory debuggers available nowadays, especially those that are provided with the platform malloc implementation, maintenance of a in-house and largely obsolete memory debugger becomes a burden that is not worth the effort due to its slowness and lack of support for detecting more common forms of heap corruption. Since there are third-party tools that can provide the same functionality at a lower or comparable performance cost, the solution is to simply remove safemalloc. Third-party tools can provide the same functionality at a lower or comparable performance cost. The removal of safemalloc also allows a simplification of the malloc wrappers, removing quite a bit of kludge: redefinition of my_malloc, my_free and the removal of the unused second argument of my_free. Since free() always check whether the supplied pointer is null, redudant checks are also removed. Also, this patch adds unit testing for my_malloc and moves my_realloc implementation into the same file as the other memory allocation primitives. client/mysqldump.c: Pass my_free directly as its signature is compatible with the callback type -- which wasn't the case for free_table_ent.
2010-07-08 23:20:08 +02:00
my_free(alloc);
}
else
Bug#34043: Server loops excessively in _checkchunk() when safemalloc is enabled Essentially, the problem is that safemalloc is excruciatingly slow as it checks all allocated blocks for overrun at each memory management primitive, yielding a almost exponential slowdown for the memory management functions (malloc, realloc, free). The overrun check basically consists of verifying some bytes of a block for certain magic keys, which catches some simple forms of overrun. Another minor problem is violation of aliasing rules and that its own internal list of blocks is prone to corruption. Another issue with safemalloc is rather the maintenance cost as the tool has a significant impact on the server code. Given the magnitude of memory debuggers available nowadays, especially those that are provided with the platform malloc implementation, maintenance of a in-house and largely obsolete memory debugger becomes a burden that is not worth the effort due to its slowness and lack of support for detecting more common forms of heap corruption. Since there are third-party tools that can provide the same functionality at a lower or comparable performance cost, the solution is to simply remove safemalloc. Third-party tools can provide the same functionality at a lower or comparable performance cost. The removal of safemalloc also allows a simplification of the malloc wrappers, removing quite a bit of kludge: redefinition of my_malloc, my_free and the removal of the unused second argument of my_free. Since free() always check whether the supplied pointer is null, redudant checks are also removed. Also, this patch adds unit testing for my_malloc and moves my_realloc implementation into the same file as the other memory allocation primitives. client/mysqldump.c: Pass my_free directly as its signature is compatible with the callback type -- which wasn't the case for free_table_ent.
2010-07-08 23:20:08 +02:00
my_free(alloc[-1]);
}
void lf_dynarray_destroy(LF_DYNARRAY *array)
{
int i;
for (i= 0; i < LF_DYNARRAY_LEVELS; i++)
recursive_free(array->level[i], i);
}
static const ulong dynarray_idxes_in_prev_levels[LF_DYNARRAY_LEVELS]=
{
0, /* +1 here to to avoid -1's below */
LF_DYNARRAY_LEVEL_LENGTH,
LF_DYNARRAY_LEVEL_LENGTH * LF_DYNARRAY_LEVEL_LENGTH +
LF_DYNARRAY_LEVEL_LENGTH,
LF_DYNARRAY_LEVEL_LENGTH * LF_DYNARRAY_LEVEL_LENGTH *
LF_DYNARRAY_LEVEL_LENGTH + LF_DYNARRAY_LEVEL_LENGTH *
LF_DYNARRAY_LEVEL_LENGTH + LF_DYNARRAY_LEVEL_LENGTH
};
static const ulong dynarray_idxes_in_prev_level[LF_DYNARRAY_LEVELS]=
{
0, /* +1 here to to avoid -1's below */
LF_DYNARRAY_LEVEL_LENGTH,
LF_DYNARRAY_LEVEL_LENGTH * LF_DYNARRAY_LEVEL_LENGTH,
LF_DYNARRAY_LEVEL_LENGTH * LF_DYNARRAY_LEVEL_LENGTH *
LF_DYNARRAY_LEVEL_LENGTH,
};
/*
Returns a valid lvalue pointer to the element number 'idx'.
Allocates memory if necessary.
*/
void *lf_dynarray_lvalue(LF_DYNARRAY *array, uint idx)
{
void * ptr, * volatile * ptr_ptr= 0;
int i;
for (i= LF_DYNARRAY_LEVELS-1; idx < dynarray_idxes_in_prev_levels[i]; i--)
/* no-op */;
ptr_ptr= &array->level[i];
idx-= dynarray_idxes_in_prev_levels[i];
for (; i > 0; i--)
{
if (!(ptr= *ptr_ptr))
{
void *alloc= my_malloc(LF_DYNARRAY_LEVEL_LENGTH * sizeof(void *),
MYF(MY_WME|MY_ZEROFILL));
if (unlikely(!alloc))
return(NULL);
if (my_atomic_casptr(ptr_ptr, &ptr, alloc))
ptr= alloc;
else
Bug#34043: Server loops excessively in _checkchunk() when safemalloc is enabled Essentially, the problem is that safemalloc is excruciatingly slow as it checks all allocated blocks for overrun at each memory management primitive, yielding a almost exponential slowdown for the memory management functions (malloc, realloc, free). The overrun check basically consists of verifying some bytes of a block for certain magic keys, which catches some simple forms of overrun. Another minor problem is violation of aliasing rules and that its own internal list of blocks is prone to corruption. Another issue with safemalloc is rather the maintenance cost as the tool has a significant impact on the server code. Given the magnitude of memory debuggers available nowadays, especially those that are provided with the platform malloc implementation, maintenance of a in-house and largely obsolete memory debugger becomes a burden that is not worth the effort due to its slowness and lack of support for detecting more common forms of heap corruption. Since there are third-party tools that can provide the same functionality at a lower or comparable performance cost, the solution is to simply remove safemalloc. Third-party tools can provide the same functionality at a lower or comparable performance cost. The removal of safemalloc also allows a simplification of the malloc wrappers, removing quite a bit of kludge: redefinition of my_malloc, my_free and the removal of the unused second argument of my_free. Since free() always check whether the supplied pointer is null, redudant checks are also removed. Also, this patch adds unit testing for my_malloc and moves my_realloc implementation into the same file as the other memory allocation primitives. client/mysqldump.c: Pass my_free directly as its signature is compatible with the callback type -- which wasn't the case for free_table_ent.
2010-07-08 23:20:08 +02:00
my_free(alloc);
}
ptr_ptr= ((void **)ptr) + idx / dynarray_idxes_in_prev_level[i];
idx%= dynarray_idxes_in_prev_level[i];
}
if (!(ptr= *ptr_ptr))
{
uchar *alloc, *data;
alloc= my_malloc(LF_DYNARRAY_LEVEL_LENGTH * array->size_of_element +
2013-03-25 23:03:13 +01:00
MY_MAX(array->size_of_element, sizeof(void *)),
MYF(MY_WME|MY_ZEROFILL));
if (unlikely(!alloc))
return(NULL);
/* reserve the space for free() address */
data= alloc + sizeof(void *);
{ /* alignment */
intptr mod= ((intptr)data) % array->size_of_element;
if (mod)
data+= array->size_of_element - mod;
}
((void **)data)[-1]= alloc; /* free() will need the original pointer */
if (my_atomic_casptr(ptr_ptr, &ptr, data))
ptr= data;
else
Bug#34043: Server loops excessively in _checkchunk() when safemalloc is enabled Essentially, the problem is that safemalloc is excruciatingly slow as it checks all allocated blocks for overrun at each memory management primitive, yielding a almost exponential slowdown for the memory management functions (malloc, realloc, free). The overrun check basically consists of verifying some bytes of a block for certain magic keys, which catches some simple forms of overrun. Another minor problem is violation of aliasing rules and that its own internal list of blocks is prone to corruption. Another issue with safemalloc is rather the maintenance cost as the tool has a significant impact on the server code. Given the magnitude of memory debuggers available nowadays, especially those that are provided with the platform malloc implementation, maintenance of a in-house and largely obsolete memory debugger becomes a burden that is not worth the effort due to its slowness and lack of support for detecting more common forms of heap corruption. Since there are third-party tools that can provide the same functionality at a lower or comparable performance cost, the solution is to simply remove safemalloc. Third-party tools can provide the same functionality at a lower or comparable performance cost. The removal of safemalloc also allows a simplification of the malloc wrappers, removing quite a bit of kludge: redefinition of my_malloc, my_free and the removal of the unused second argument of my_free. Since free() always check whether the supplied pointer is null, redudant checks are also removed. Also, this patch adds unit testing for my_malloc and moves my_realloc implementation into the same file as the other memory allocation primitives. client/mysqldump.c: Pass my_free directly as its signature is compatible with the callback type -- which wasn't the case for free_table_ent.
2010-07-08 23:20:08 +02:00
my_free(alloc);
}
return ((uchar*)ptr) + array->size_of_element * idx;
}
/*
Returns a pointer to the element number 'idx'
or NULL if an element does not exists
*/
void *lf_dynarray_value(LF_DYNARRAY *array, uint idx)
{
void * ptr, * volatile * ptr_ptr= 0;
int i;
for (i= LF_DYNARRAY_LEVELS-1; idx < dynarray_idxes_in_prev_levels[i]; i--)
/* no-op */;
ptr_ptr= &array->level[i];
idx-= dynarray_idxes_in_prev_levels[i];
for (; i > 0; i--)
{
if (!(ptr= *ptr_ptr))
return(NULL);
ptr_ptr= ((void **)ptr) + idx / dynarray_idxes_in_prev_level[i];
idx %= dynarray_idxes_in_prev_level[i];
}
if (!(ptr= *ptr_ptr))
return(NULL);
return ((uchar*)ptr) + array->size_of_element * idx;
}
static int recursive_iterate(LF_DYNARRAY *array, void *ptr, int level,
lf_dynarray_func func, void *arg)
{
int res, i;
if (!ptr)
return 0;
if (!level)
return func(ptr, arg);
for (i= 0; i < LF_DYNARRAY_LEVEL_LENGTH; i++)
if ((res= recursive_iterate(array, ((void **)ptr)[i], level-1, func, arg)))
return res;
return 0;
}
/*
Calls func(array, arg) on every array of LF_DYNARRAY_LEVEL_LENGTH elements
in lf_dynarray.
DESCRIPTION
lf_dynarray consists of a set of arrays, LF_DYNARRAY_LEVEL_LENGTH elements
each. lf_dynarray_iterate() calls user-supplied function on every array
from the set. It is the fastest way to scan the array, faster than
for (i=0; i < N; i++) { func(lf_dynarray_value(dynarray, i)); }
NOTE
if func() returns non-zero, the scan is aborted
*/
int lf_dynarray_iterate(LF_DYNARRAY *array, lf_dynarray_func func, void *arg)
{
int i, res;
for (i= 0; i < LF_DYNARRAY_LEVELS; i++)
if ((res= recursive_iterate(array, array->level[i], i, func, arg)))
return res;
return 0;
}