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b1d81974b2
This is useful for thing like Item_true and Item_false that we allocated and initalize once and want to ensure that nothing can change them Main changes: - Memory protection is achived by allocating memory with mmap() and protect it from write with mprotect() - init_alloc_root(...,MY_ROOT_USE_MPROTECT) will create a memroot that one can later use with protect_root() to turn it read only or turn it back to read-write. All allocations to this memroot is done with mmap() to ensure page alligned allocations. - alloc_root() code was rearranged to combine normal and valgrind code. - init_alloc_root() now changes block size to be power of 2's, to get less memory fragmentation. - Changed MEM_ROOT structure to make it smaller. Also renamed MEM_ROOT m_psi_key to psi_key. - Moved MY_THREAD_SPECIFIC marker in MEM_ROOT from block size (old hack) to flags. - Added global variable my_system_page_size. This is initialized at startup.
65 lines
2 KiB
C
65 lines
2 KiB
C
/* Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */
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/*
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Data structures for mysys/my_alloc.c (root memory allocator)
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*/
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#ifndef _my_alloc_h
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#define _my_alloc_h
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#include <mysql/psi/psi_memory.h>
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#define ALLOC_MAX_BLOCK_TO_DROP 4096
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#define ALLOC_MAX_BLOCK_USAGE_BEFORE_DROP 10
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#ifdef __cplusplus
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extern "C" {
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#endif
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typedef struct st_used_mem
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{ /* struct for once_alloc (block) */
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struct st_used_mem *next; /* Next block in use */
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size_t left; /* memory left in block */
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size_t size; /* size of block */
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} USED_MEM;
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typedef struct st_mem_root
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{
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USED_MEM *free; /* blocks with free memory in it */
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USED_MEM *used; /* blocks almost without free memory */
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USED_MEM *pre_alloc; /* preallocated block */
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/* if block have less memory it will be put in 'used' list */
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size_t min_malloc;
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size_t block_size; /* initial block size */
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unsigned int block_num; /* allocated blocks counter */
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/*
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first free block in queue test counter (if it exceed
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MAX_BLOCK_USAGE_BEFORE_DROP block will be dropped in 'used' list)
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*/
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unsigned short first_block_usage;
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unsigned short flags;
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void (*error_handler)(void);
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PSI_memory_key psi_key;
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} MEM_ROOT;
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#ifdef __cplusplus
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}
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#endif
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#endif
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