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