/******************************************************************//** Returns a free block from the buf_pool. The block is taken off the free list. If it is empty, blocks are moved from the end of the LRU list to the free list. @return the free control block, in state BUF_BLOCK_READY_FOR_USE */ UNIV_INTERN buf_block_t* buf_LRU_get_free_block( /*===================*/ buf_pool_t* buf_pool) /*!< in/out: buffer pool instance */ { buf_block_t* block = NULL; ibool freed; ulint n_iterations = ; ibool mon_value_was = FALSE; ibool started_monitor = FALSE; loop: buf_pool_mutex_enter(buf_pool); if (!recv_recovery_on && UT_LIST_GET_LEN(buf_pool->free) + UT_LIST_GET_LEN(buf_pool->LRU) < buf_pool->curr_size / ) { ut_print_timestamp(stderr); fprintf(stderr, " InnoDB: ERROR: over 95 percent of the buffer pool" " is occupied by\n" "InnoDB: lock heaps or the adaptive hash index!" " Check that your\n" "InnoDB: transactions do not set too many row locks.\n" "InnoDB: Your buffer pool size is %lu MB." " Maybe you should make\n" "InnoDB: the buffer pool bigger?\n" "InnoDB: We intentionally generate a seg fault" " to print a stack trace\n" "InnoDB: on Linux!\n", (ulong) (buf_pool->curr_size / ( * / UNIV_PAGE_SIZE))); ut_error; } else if (!recv_recovery_on && (UT_LIST_GET_LEN(buf_pool->free) + UT_LIST_GET_LEN(buf_pool->LRU)) < buf_pool->curr_size / ) { if (!buf_lru_switched_on_innodb_mon) { /* Over 67 % of the buffer pool is occupied by lock heaps or the adaptive hash index. This may be a memory leak! */ ut_print_timestamp(stderr); fprintf(stderr, " InnoDB: WARNING: over 67 percent of" " the buffer pool is occupied by\n" "InnoDB: lock heaps or the adaptive" " hash index! Check that your\n" "InnoDB: transactions do not set too many" " row locks.\n" "InnoDB: Your buffer pool size is %lu MB." " Maybe you should make\n" "InnoDB: the buffer pool bigger?\n" "InnoDB: Starting the InnoDB Monitor to print" " diagnostics, including\n" "InnoDB: lock heap and hash index sizes.\n", (ulong) (buf_pool->curr_size / ( * / UNIV_PAGE_SIZE))); buf_lru_switched_on_innodb_mon = TRUE; srv_print_innodb_monitor = TRUE; os_event_set(srv_lock_timeout_thread_event); } } else if (buf_lru_switched_on_innodb_mon) { /* Switch off the InnoDB Monitor; this is a simple way to stop the monitor if the situation becomes less urgent, but may also surprise users if the user also switched on the monitor! */ buf_lru_switched_on_innodb_mon = FALSE; srv_print_innodb_monitor = FALSE; } /* If there is a block in the free list, take it */ block = buf_LRU_get_free_only(buf_pool); //这里 buf_pool_mutex_exit(buf_pool); if (block) { ut_ad(buf_pool_from_block(block) == buf_pool); memset(&block->page.zip, , sizeof block->page.zip); if (started_monitor) { srv_print_innodb_monitor = mon_value_was; } return(block); } /* If no block was in the free list, search from the end of the LRU list and try to free a block there */ freed = buf_LRU_search_and_free_block(buf_pool, n_iterations); //从lru中取一块 这里) { goto loop; } ) { ut_print_timestamp(stderr); fprintf(stderr, " InnoDB: Warning: difficult to find free blocks in\n" "InnoDB: the buffer pool (%lu search iterations)!" " Consider\n" "InnoDB: increasing the buffer pool size.\n" "InnoDB: It is also possible that" " in your Unix version\n" "InnoDB: fsync is very slow, or" " completely frozen inside\n" "InnoDB: the OS kernel. Then upgrading to" " a newer version\n" "InnoDB: of your operating system may help." " Look at the\n" "InnoDB: number of fsyncs in diagnostic info below.\n" "InnoDB: Pending flushes (fsync) log: %lu;" " buffer pool: %lu\n" "InnoDB: %lu OS file reads, %lu OS file writes," " %lu OS fsyncs\n" "InnoDB: Starting InnoDB Monitor to print further\n" "InnoDB: diagnostics to the standard output.\n", (ulong) n_iterations, (ulong) fil_n_pending_log_flushes, (ulong) fil_n_pending_tablespace_flushes, (ulong) os_n_file_reads, (ulong) os_n_file_writes, (ulong) os_n_fsyncs); mon_value_was = srv_print_innodb_monitor; started_monitor = TRUE; srv_print_innodb_monitor = TRUE; os_event_set(srv_lock_timeout_thread_event); } /* No free block was found: try to flush the LRU list */ buf_flush_free_margin(buf_pool); ++srv_buf_pool_wait_free; os_aio_simulated_wake_handler_threads(); buf_pool_mutex_enter(buf_pool); ) { /* We have written pages in an LRU flush. To make the insert buffer more efficient, we try to move these pages to the free list. */ buf_pool_mutex_exit(buf_pool); buf_LRU_try_free_flushed_blocks(buf_pool); } else { buf_pool_mutex_exit(buf_pool); } ) { os_thread_sleep(); } n_iterations++; goto loop; }
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