/************************************************************************ The memory management (c) 1994, 1995 Innobase Oy Created 6/9/1994 Heikki Tuuri *************************************************************************/ #include "mem0mem.h" #ifdef UNIV_NONINL #include "mem0mem.ic" #endif #include "mach0data.h" #include "buf0buf.h" #include "btr0sea.h" #include "srv0srv.h" #include "mem0dbg.c" /* THE MEMORY MANAGEMENT ===================== The basic element of the memory management is called a memory heap. A memory heap is conceptually a stack from which memory can be allocated. The stack may grow infinitely. The top element of the stack may be freed, or the whole stack can be freed at one time. The advantage of the memory heap concept is that we can avoid using the malloc and free functions of C which are quite expensive, for example, on the Solaris + GCC system (50 MHz Sparc, 1993) the pair takes 3 microseconds, on Win NT + 100MHz Pentium, 2.5 microseconds. When we use a memory heap, we can allocate larger blocks of memory at a time and thus reduce overhead. Slightly more efficient the method is when we allocate the memory from the index page buffer pool, as we can claim a new page fast. This is called buffer allocation. When we allocate the memory from the dynamic memory of the C environment, that is called dynamic allocation. The default way of operation of the memory heap is the following. First, when the heap is created, an initial block of memory is allocated. In dynamic allocation this may be about 50 bytes. If more space is needed, additional blocks are allocated and they are put into a linked list. After the initial block, each allocated block is twice the size of the previous, until a threshold is attained, after which the sizes of the blocks stay the same. An exception is, of course, the case where the caller requests a memory buffer whose size is bigger than the threshold. In that case a block big enough must be allocated. The heap is physically arranged so that if the current block becomes full, a new block is allocated and always inserted in the chain of blocks as the last block. In the debug version of the memory management, all the allocated heaps are kept in a list (which is implemented as a hash table). Thus we can notice if the caller tries to free an already freed heap. In addition, each buffer given to the caller contains start field at the start and a trailer field at the end of the buffer. The start field has the following content: A. sizeof(ulint) bytes of field length (in the standard byte order) B. sizeof(ulint) bytes of check field (a random number) The trailer field contains: A. sizeof(ulint) bytes of check field (the same random number as at the start) Thus we can notice if something has been copied over the borders of the buffer, which is illegal. The memory in the buffers is initialized to a random byte sequence. After freeing, all the blocks in the heap are set to random bytes to help us discover errors which result from the use of buffers in an already freed heap. */ #ifdef MEM_PERIODIC_CHECK ibool mem_block_list_inited; /* List of all mem blocks allocated; protected by the mem_comm_pool mutex */ UT_LIST_BASE_NODE_T(mem_block_t) mem_block_list; #endif /******************************************************************* NOTE: Use the corresponding macro instead of this function. Allocates a single buffer of memory from the dynamic memory of the C compiler. Is like malloc of C. The buffer must be freed with mem_free. */ void* mem_alloc_func_noninline( /*=====================*/ /* out, own: free storage */ ulint n, /* in: desired number of bytes */ const char* file_name, /* in: file name where created */ ulint line) /* in: line where created */ { return(mem_alloc_func(n, file_name, line)); } /************************************************************************** Duplicates a NUL-terminated string, allocated from a memory heap. */ char* mem_heap_strdup( /*============*/ /* out, own: a copy of the string */ mem_heap_t* heap, /* in: memory heap where string is allocated */ const char* str) /* in: string to be copied */ { ulint len = strlen(str) + 1; return(memcpy(mem_heap_alloc(heap, len), str, len)); } /******************************************************************* Creates a memory heap block where data can be allocated. */ mem_block_t* mem_heap_create_block( /*==================*/ /* out, own: memory heap block, NULL if did not succeed (only possible for MEM_HEAP_BTR_SEARCH type heaps) */ mem_heap_t* heap, /* in: memory heap or NULL if first block should be created */ ulint n, /* in: number of bytes needed for user data, or if init_block is not NULL, its size in bytes */ void* init_block, /* in: init block in fast create, type must be MEM_HEAP_DYNAMIC */ ulint type, /* in: type of heap: MEM_HEAP_DYNAMIC or MEM_HEAP_BUFFER */ const char* file_name,/* in: file name where created */ ulint line) /* in: line where created */ { mem_block_t* block; ulint len; ut_ad((type == MEM_HEAP_DYNAMIC) || (type == MEM_HEAP_BUFFER) || (type == MEM_HEAP_BUFFER + MEM_HEAP_BTR_SEARCH)); if (heap && heap->magic_n != MEM_BLOCK_MAGIC_N) { mem_analyze_corruption(heap); } /* In dynamic allocation, calculate the size: block header + data. */ if (init_block != NULL) { ut_ad(type == MEM_HEAP_DYNAMIC); ut_ad(n > MEM_BLOCK_START_SIZE + MEM_BLOCK_HEADER_SIZE); len = n; block = init_block; } else if (type == MEM_HEAP_DYNAMIC) { len = MEM_BLOCK_HEADER_SIZE + MEM_SPACE_NEEDED(n); block = mem_area_alloc(len, mem_comm_pool); } else { ut_ad(n <= MEM_MAX_ALLOC_IN_BUF); len = MEM_BLOCK_HEADER_SIZE + MEM_SPACE_NEEDED(n); if (len < UNIV_PAGE_SIZE / 2) { block = mem_area_alloc(len, mem_comm_pool); } else { len = UNIV_PAGE_SIZE; if ((type & MEM_HEAP_BTR_SEARCH) && heap) { /* We cannot allocate the block from the buffer pool, but must get the free block from the heap header free block field */ block = (mem_block_t*)heap->free_block; heap->free_block = NULL; } else { block = (mem_block_t*)buf_frame_alloc(); } } } if (block == NULL) { /* Only MEM_HEAP_BTR_SEARCH allocation should ever fail. */ ut_a(type & MEM_HEAP_BTR_SEARCH); return(NULL); } block->magic_n = MEM_BLOCK_MAGIC_N; ut_strlcpy_rev(block->file_name, file_name, sizeof(block->file_name)); block->line = line; #ifdef MEM_PERIODIC_CHECK mem_pool_mutex_enter(); if (!mem_block_list_inited) { mem_block_list_inited = TRUE; UT_LIST_INIT(mem_block_list); } UT_LIST_ADD_LAST(mem_block_list, mem_block_list, block); mem_pool_mutex_exit(); #endif mem_block_set_len(block, len); mem_block_set_type(block, type); mem_block_set_free(block, MEM_BLOCK_HEADER_SIZE); mem_block_set_start(block, MEM_BLOCK_HEADER_SIZE); block->free_block = NULL; block->init_block = (init_block != NULL); ut_ad((ulint)MEM_BLOCK_HEADER_SIZE < len); return(block); } /******************************************************************* Adds a new block to a memory heap. */ mem_block_t* mem_heap_add_block( /*===============*/ /* out: created block, NULL if did not succeed (only possible for MEM_HEAP_BTR_SEARCH type heaps)*/ mem_heap_t* heap, /* in: memory heap */ ulint n) /* in: number of bytes user needs */ { mem_block_t* block; mem_block_t* new_block; ulint new_size; ut_ad(mem_heap_check(heap)); block = UT_LIST_GET_LAST(heap->base); /* We have to allocate a new block. The size is always at least doubled until the standard size is reached. After that the size stays the same, except in cases where the caller needs more space. */ new_size = 2 * mem_block_get_len(block); if (heap->type != MEM_HEAP_DYNAMIC) { /* From the buffer pool we allocate buffer frames */ ut_a(n <= MEM_MAX_ALLOC_IN_BUF); if (new_size > MEM_MAX_ALLOC_IN_BUF) { new_size = MEM_MAX_ALLOC_IN_BUF; } } else if (new_size > MEM_BLOCK_STANDARD_SIZE) { new_size = MEM_BLOCK_STANDARD_SIZE; } if (new_size < n) { new_size = n; } new_block = mem_heap_create_block(heap, new_size, NULL, heap->type, heap->file_name, heap->line); if (new_block == NULL) { return(NULL); } /* Add the new block as the last block */ UT_LIST_INSERT_AFTER(list, heap->base, block, new_block); return(new_block); } /********************************************************************** Frees a block from a memory heap. */ void mem_heap_block_free( /*================*/ mem_heap_t* heap, /* in: heap */ mem_block_t* block) /* in: block to free */ { ulint type; ulint len; ibool init_block; if (block->magic_n != MEM_BLOCK_MAGIC_N) { mem_analyze_corruption(block); } UT_LIST_REMOVE(list, heap->base, block); #ifdef MEM_PERIODIC_CHECK mem_pool_mutex_enter(); UT_LIST_REMOVE(mem_block_list, mem_block_list, block); mem_pool_mutex_exit(); #endif type = heap->type; len = block->len; init_block = block->init_block; block->magic_n = MEM_FREED_BLOCK_MAGIC_N; #ifdef UNIV_MEM_DEBUG /* In the debug version we set the memory to a random combination of hex 0xDE and 0xAD. */ mem_erase_buf((byte*)block, len); #endif if (init_block) { /* Do not have to free: do nothing */ } else if (type == MEM_HEAP_DYNAMIC) { mem_area_free(block, mem_comm_pool); } else { ut_ad(type & MEM_HEAP_BUFFER); if (len >= UNIV_PAGE_SIZE / 2) { buf_frame_free((byte*)block); } else { mem_area_free(block, mem_comm_pool); } } } /********************************************************************** Frees the free_block field from a memory heap. */ void mem_heap_free_block_free( /*=====================*/ mem_heap_t* heap) /* in: heap */ { if (heap->free_block) { buf_frame_free(heap->free_block); heap->free_block = NULL; } } #ifdef MEM_PERIODIC_CHECK /********************************************************************** Goes through the list of all allocated mem blocks, checks their magic numbers, and reports possible corruption. */ void mem_validate_all_blocks(void) /*=========================*/ { mem_block_t* block; mem_pool_mutex_enter(); block = UT_LIST_GET_FIRST(mem_block_list); while (block) { if (block->magic_n != MEM_BLOCK_MAGIC_N) { mem_analyze_corruption(block); } block = UT_LIST_GET_NEXT(mem_block_list, block); } mem_pool_mutex_exit(); } #endif