mariadb/storage/ibmdb2i/db2i_global.h
Davi Arnaut f56dd32bf7 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 18:20:08 -03:00

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4.5 KiB
C

/*
Licensed Materials - Property of IBM
DB2 Storage Engine Enablement
Copyright IBM Corporation 2007,2008
All rights reserved
Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:
(a) Redistributions of source code must retain this list of conditions, the
copyright notice in section {d} below, and the disclaimer following this
list of conditions.
(b) Redistributions in binary form must reproduce this list of conditions, the
copyright notice in section (d) below, and the disclaimer following this
list of conditions, in the documentation and/or other materials provided
with the distribution.
(c) The name of IBM may not be used to endorse or promote products derived from
this software without specific prior written permission.
(d) The text of the required copyright notice is:
Licensed Materials - Property of IBM
DB2 Storage Engine Enablement
Copyright IBM Corporation 2007,2008
All rights reserved
THIS SOFTWARE IS PROVIDED BY IBM CORPORATION "AS IS" AND ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
SHALL IBM CORPORATION BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
OF SUCH DAMAGE.
*/
#ifndef DB2I_GLOBAL_H
#define DB2I_GLOBAL_H
#define MYSQL_SERVER 1
#include "my_global.h"
#include "my_sys.h"
const uint MAX_DB2_KEY_PARTS=120;
const int MAX_DB2_V5R4_LIBNAME_LENGTH = 10;
const int MAX_DB2_V6R1_LIBNAME_LENGTH = 30;
const int MAX_DB2_SCHEMANAME_LENGTH=258;
const int MAX_DB2_FILENAME_LENGTH=258;
const int MAX_DB2_COLNAME_LENGTH=128;
const int MAX_DB2_SAVEPOINTNAME_LENGTH=128;
const int MAX_DB2_QUALIFIEDNAME_LENGTH=MAX_DB2_V6R1_LIBNAME_LENGTH + 1 + MAX_DB2_FILENAME_LENGTH;
const uint32 MAX_CHAR_LENGTH = 32765;
const uint32 MAX_VARCHAR_LENGTH = 32739;
const uint32 MAX_DEC_PRECISION = 63;
const uint32 MAX_BLOB_LENGTH = 2147483646;
const uint32 MAX_BINARY_LENGTH = MAX_CHAR_LENGTH;
const uint32 MAX_VARBINARY_LENGTH = MAX_VARCHAR_LENGTH;
const uint32 MAX_FULL_ALLOCATE_BLOB_LENGTH = 65536;
const uint32 MAX_FOREIGN_LEN = 64000;
const char* DB2I_TEMP_TABLE_SCHEMA = "QTEMP";
const char DB2I_ADDL_INDEX_NAME_DELIMITER[5] = {'_','_','_','_','_'};
const char DB2I_DEFAULT_INDEX_NAME_DELIMITER[3] = {'_','_','_'};
const int DB2I_INDEX_NAME_LENGTH_TO_PRESERVE = 110;
enum enum_DB2I_INDEX_TYPE
{
typeNone = 0,
typeDefault = 'D',
typeHex = 'H',
typeAscii = 'A'
};
void* roundToQuadWordBdy(void* ptr)
{
return (void*)(((uint64)(ptr)+0xf) & ~0xf);
}
typedef uint64_t ILEMemHandle;
struct OSVersion
{
uint8 v;
uint8 r;
};
extern OSVersion osVersion;
/**
Allocate 16-byte aligned space using the MySQL heap allocator
@details Many of the spaces used by the QMY_* APIS are required to be
aligned on 16 byte boundaries. The standard system malloc will do this
alignment by default. However, in order to use the heap debug and tracking
features of the mysql allocator, we chose to implement an aligning wrapper
around my_malloc. Essentially, we overallocate the storage space, find the
first aligned address in the space, store a pointer to the true malloc
allocation in the bytes immediately preceding the aligned address, and return
the aligned address to the caller.
@parm size The size of heap storage needed
@return A 16-byte aligned pointer to the storage requested.
*/
void* malloc_aligned(size_t size)
{
char* p;
char* base;
base = (char*)my_malloc(size + sizeof(void*) + 15, MYF(MY_WME));
if (likely(base))
{
p = (char*)roundToQuadWordBdy(base + sizeof(void*));
char** p2 = (char**)(p - sizeof(void*));
*p2 = base;
}
else
p = NULL;
return p;
}
/**
Free a 16-byte aligned space alloced by malloc_aligned
@details We know that a pointer to the true malloced storage immediately
precedes the aligned address, so we pull that out and call my_free().
@parm p A 16-byte aligned pointer generated by malloc_aligned
*/
void free_aligned(void* p)
{
if (likely(p))
{
my_free(*(char**)((char*)p-sizeof(void*)));
}
}
#endif