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Diffstat (limited to 'mysql/mysys/mf_keycache.c')
| -rw-r--r-- | mysql/mysys/mf_keycache.c | 4051 |
1 files changed, 0 insertions, 4051 deletions
diff --git a/mysql/mysys/mf_keycache.c b/mysql/mysys/mf_keycache.c deleted file mode 100644 index cb712ed..0000000 --- a/mysql/mysys/mf_keycache.c +++ /dev/null @@ -1,4051 +0,0 @@ -/* Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved. - - This program is free software; you can redistribute it and/or modify - it under the terms of the GNU General Public License as published by - the Free Software Foundation; version 2 of the License. - - This program is distributed in the hope that it will be useful, - but WITHOUT ANY WARRANTY; without even the implied warranty of - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - GNU General Public License for more details. - - You should have received a copy of the GNU General Public License - along with this program; if not, write to the Free Software - Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */ - -/** - @file - These functions handle keyblock cacheing for ISAM and MyISAM tables. - - One cache can handle many files. - It must contain buffers of the same blocksize. - init_key_cache() should be used to init cache handler. - - The free list (free_block_list) is a stack like structure. - When a block is freed by free_block(), it is pushed onto the stack. - When a new block is required it is first tried to pop one from the stack. - If the stack is empty, it is tried to get a never-used block from the pool. - If this is empty too, then a block is taken from the LRU ring, flushing it - to disk, if neccessary. This is handled in find_key_block(). - With the new free list, the blocks can have three temperatures: - hot, warm and cold (which is free). This is remembered in the block header - by the enum BLOCK_TEMPERATURE temperature variable. Remembering the - temperature is neccessary to correctly count the number of warm blocks, - which is required to decide when blocks are allowed to become hot. Whenever - a block is inserted to another (sub-)chain, we take the old and new - temperature into account to decide if we got one more or less warm block. - blocks_unused is the sum of never used blocks in the pool and of currently - free blocks. blocks_used is the number of blocks fetched from the pool and - as such gives the maximum number of in-use blocks at any time. -*/ - -/* - Key Cache Locking - ================= - - All key cache locking is done with a single mutex per key cache: - keycache->cache_lock. This mutex is locked almost all the time - when executing code in this file (mf_keycache.c). - However it is released for I/O and some copy operations. - - The cache_lock is also released when waiting for some event. Waiting - and signalling is done via condition variables. In most cases the - thread waits on its thread->suspend condition variable. Every thread - has a my_thread_var structure, which contains this variable and a - '*next' and '**prev' pointer. These pointers are used to insert the - thread into a wait queue. - - A thread can wait for one block and thus be in one wait queue at a - time only. - - Before starting to wait on its condition variable with - mysql_cond_wait(), the thread enters itself to a specific wait queue - with link_into_queue() (double linked with '*next' + '**prev') or - wait_on_queue() (single linked with '*next'). - - Another thread, when releasing a resource, looks up the waiting thread - in the related wait queue. It sends a signal with - mysql_cond_signal() to the waiting thread. - - NOTE: Depending on the particular wait situation, either the sending - thread removes the waiting thread from the wait queue with - unlink_from_queue() or release_whole_queue() respectively, or the waiting - thread removes itself. - - There is one exception from this locking scheme when one thread wants - to reuse a block for some other address. This works by first marking - the block reserved (status= BLOCK_IN_SWITCH) and then waiting for all - threads that are reading the block to finish. Each block has a - reference to a condition variable (condvar). It holds a reference to - the thread->suspend condition variable for the waiting thread (if such - a thread exists). When that thread is signaled, the reference is - cleared. The number of readers of a block is registered in - block->hash_link->requests. See wait_for_readers() / remove_reader() - for details. This is similar to the above, but it clearly means that - only one thread can wait for a particular block. There is no queue in - this case. Strangely enough block->convar is used for waiting for the - assigned hash_link only. More precisely it is used to wait for all - requests to be unregistered from the assigned hash_link. - - The resize_queue serves two purposes: - 1. Threads that want to do a resize wait there if in_resize is set. - This is not used in the server. The server refuses a second resize - request if one is already active. keycache->in_init is used for the - synchronization. See set_var.cc. - 2. Threads that want to access blocks during resize wait here during - the re-initialization phase. - When the resize is done, all threads on the queue are signalled. - Hypothetical resizers can compete for resizing, and read/write - requests will restart to request blocks from the freshly resized - cache. If the cache has been resized too small, it is disabled and - 'can_be_used' is false. In this case read/write requests bypass the - cache. Since they increment and decrement 'cnt_for_resize_op', the - next resizer can wait on the queue 'waiting_for_resize_cnt' until all - I/O finished. -*/ - -#include "mysys_priv.h" -#include "mysys_err.h" -#include <keycache.h> -#include "my_static.h" -#include <m_string.h> -#include <my_bit.h> -#include <errno.h> -#include <stdarg.h> -#include "probes_mysql.h" -#include "my_thread_local.h" - -#define STRUCT_PTR(TYPE, MEMBER, a) \ - (TYPE *) ((char *) (a) - offsetof(TYPE, MEMBER)) - -/* types of condition variables */ -#define COND_FOR_REQUESTED 0 -#define COND_FOR_SAVED 1 -#define COND_FOR_READERS 2 - -typedef mysql_cond_t KEYCACHE_CONDVAR; - -/* descriptor of the page in the key cache block buffer */ -struct st_keycache_page -{ - int file; /* file to which the page belongs to */ - my_off_t filepos; /* position of the page in the file */ -}; -typedef struct st_keycache_page KEYCACHE_PAGE; - -/* element in the chain of a hash table bucket */ -struct st_hash_link -{ - struct st_hash_link *next, **prev; /* to connect links in the same bucket */ - struct st_block_link *block; /* reference to the block for the page: */ - File file; /* from such a file */ - my_off_t diskpos; /* with such an offset */ - uint requests; /* number of requests for the page */ -}; - -/* simple states of a block */ -#define BLOCK_ERROR 1 /* an error occured when performing file i/o */ -#define BLOCK_READ 2 /* file block is in the block buffer */ -#define BLOCK_IN_SWITCH 4 /* block is preparing to read new page */ -#define BLOCK_REASSIGNED 8 /* blk does not accept requests for old page */ -#define BLOCK_IN_FLUSH 16 /* block is selected for flush */ -#define BLOCK_CHANGED 32 /* block buffer contains a dirty page */ -#define BLOCK_IN_USE 64 /* block is not free */ -#define BLOCK_IN_EVICTION 128 /* block is selected for eviction */ -#define BLOCK_IN_FLUSHWRITE 256 /* block is in write to file */ -#define BLOCK_FOR_UPDATE 512 /* block is selected for buffer modification */ - -/* page status, returned by find_key_block */ -#define PAGE_READ 0 -#define PAGE_TO_BE_READ 1 -#define PAGE_WAIT_TO_BE_READ 2 - -/* block temperature determines in which (sub-)chain the block currently is */ -enum BLOCK_TEMPERATURE { BLOCK_COLD /*free*/ , BLOCK_WARM , BLOCK_HOT }; - -/* key cache block */ -struct st_block_link -{ - struct st_block_link - *next_used, **prev_used; /* to connect links in the LRU chain (ring) */ - struct st_block_link - *next_changed, **prev_changed; /* for lists of file dirty/clean blocks */ - struct st_hash_link *hash_link; /* backward ptr to referring hash_link */ - KEYCACHE_WQUEUE wqueue[2]; /* queues on waiting requests for new/old pages */ - uint requests; /* number of requests for the block */ - uchar *buffer; /* buffer for the block page */ - uint offset; /* beginning of modified data in the buffer */ - uint length; /* end of data in the buffer */ - uint status; /* state of the block */ - enum BLOCK_TEMPERATURE temperature; /* block temperature: cold, warm, hot */ - uint hits_left; /* number of hits left until promotion */ - ulonglong last_hit_time; /* timestamp of the last hit */ - KEYCACHE_CONDVAR *condvar; /* condition variable for 'no readers' event */ -}; - -KEY_CACHE dflt_key_cache_var; -KEY_CACHE *dflt_key_cache= &dflt_key_cache_var; - -#define FLUSH_CACHE 2000 /* sort this many blocks at once */ - -static void change_key_cache_param(KEY_CACHE *keycache, - ulonglong division_limit, - ulonglong age_threshold); -static int flush_all_key_blocks(KEY_CACHE *keycache, - st_keycache_thread_var *thread_var); - -static void wait_on_queue(KEYCACHE_WQUEUE *wqueue, - mysql_mutex_t *mutex, - st_keycache_thread_var *thread); -static void release_whole_queue(KEYCACHE_WQUEUE *wqueue); - -static void free_block(KEY_CACHE *keycache, - st_keycache_thread_var *thread_var, - BLOCK_LINK *block); - -#define KEYCACHE_HASH(f, pos) \ -(((ulong) ((pos) / keycache->key_cache_block_size) + \ - (ulong) (f)) & (keycache->hash_entries-1)) -#define FILE_HASH(f) ((uint) (f) & (CHANGED_BLOCKS_HASH-1)) - -#define BLOCK_NUMBER(b) \ - ((uint) (((char*)(b)-(char *) keycache->block_root)/sizeof(BLOCK_LINK))) -#define HASH_LINK_NUMBER(h) \ - ((uint) (((char*)(h)-(char *) keycache->hash_link_root)/sizeof(HASH_LINK))) - -#if !defined(DBUG_OFF) -static int fail_block(BLOCK_LINK *block); -static int fail_hlink(HASH_LINK *hlink); -static int cache_empty(KEY_CACHE *keycache); -#endif - -static inline uint next_power(uint value) -{ - return (uint) my_round_up_to_next_power((uint32) value) << 1; -} - - -/* - Initialize a key cache - - SYNOPSIS - init_key_cache() - keycache pointer to a key cache data structure - key_cache_block_size size of blocks to keep cached data - use_mem total memory to use for the key cache - division_limit division limit (may be zero) - age_threshold age threshold (may be zero) - - RETURN VALUE - number of blocks in the key cache, if successful, - 0 - otherwise. - - NOTES. - if keycache->key_cache_inited != 0 we assume that the key cache - is already initialized. This is for now used by myisamchk, but shouldn't - be something that a program should rely on! - - It's assumed that no two threads call this function simultaneously - referring to the same key cache handle. - -*/ - -int init_key_cache(KEY_CACHE *keycache, ulonglong key_cache_block_size, - size_t use_mem, ulonglong division_limit, - ulonglong age_threshold) -{ - ulong blocks, hash_links; - size_t length; - int error; - DBUG_ENTER("init_key_cache"); - DBUG_ASSERT(key_cache_block_size >= 512); - - if (keycache->key_cache_inited && keycache->disk_blocks > 0) - { - DBUG_PRINT("warning",("key cache already in use")); - DBUG_RETURN(0); - } - - keycache->global_cache_w_requests= keycache->global_cache_r_requests= 0; - keycache->global_cache_read= keycache->global_cache_write= 0; - keycache->disk_blocks= -1; - if (! keycache->key_cache_inited) - { - keycache->key_cache_inited= 1; - /* - Initialize these variables once only. - Their value must survive re-initialization during resizing. - */ - keycache->in_resize= 0; - keycache->resize_in_flush= 0; - keycache->cnt_for_resize_op= 0; - keycache->waiting_for_resize_cnt.last_thread= NULL; - keycache->in_init= 0; - mysql_mutex_init(key_KEY_CACHE_cache_lock, - &keycache->cache_lock, MY_MUTEX_INIT_FAST); - keycache->resize_queue.last_thread= NULL; - } - - keycache->key_cache_mem_size= use_mem; - keycache->key_cache_block_size= (uint)key_cache_block_size; - DBUG_PRINT("info", ("key_cache_block_size: %llu", - key_cache_block_size)); - - blocks= (ulong) (use_mem / (sizeof(BLOCK_LINK) + 2 * sizeof(HASH_LINK) + - sizeof(HASH_LINK*) * 5/4 + key_cache_block_size)); - /* It doesn't make sense to have too few blocks (less than 8) */ - if (blocks >= 8) - { - for ( ; ; ) - { - /* Set my_hash_entries to the next bigger 2 power */ - if ((keycache->hash_entries= next_power(blocks)) < blocks * 5/4) - keycache->hash_entries<<= 1; - hash_links= 2 * blocks; - while ((length= (ALIGN_SIZE(blocks * sizeof(BLOCK_LINK)) + - ALIGN_SIZE(hash_links * sizeof(HASH_LINK)) + - ALIGN_SIZE(sizeof(HASH_LINK*) * - keycache->hash_entries))) + - ((size_t) blocks * keycache->key_cache_block_size) > use_mem) - blocks--; - /* Allocate memory for cache page buffers */ - if ((keycache->block_mem= - my_large_malloc(key_memory_KEY_CACHE, - (size_t) blocks * keycache->key_cache_block_size, - MYF(0)))) - { - /* - Allocate memory for blocks, hash_links and hash entries; - For each block 2 hash links are allocated - */ - if ((keycache->block_root= (BLOCK_LINK*) my_malloc(key_memory_KEY_CACHE, - length, - MYF(0)))) - break; - my_large_free(keycache->block_mem); - keycache->block_mem= 0; - } - if (blocks < 8) - { - set_my_errno(ENOMEM); - my_error(EE_OUTOFMEMORY, MYF(ME_FATALERROR), - blocks * keycache->key_cache_block_size); - goto err; - } - blocks= blocks / 4*3; - } - keycache->blocks_unused= blocks; - keycache->disk_blocks= (int) blocks; - keycache->hash_links= hash_links; - keycache->hash_root= (HASH_LINK**) ((char*) keycache->block_root + - ALIGN_SIZE(blocks*sizeof(BLOCK_LINK))); - keycache->hash_link_root= (HASH_LINK*) ((char*) keycache->hash_root + - ALIGN_SIZE((sizeof(HASH_LINK*) * - keycache->hash_entries))); - memset(keycache->block_root, 0, - keycache->disk_blocks * sizeof(BLOCK_LINK)); - memset(keycache->hash_root, 0, - keycache->hash_entries * sizeof(HASH_LINK*)); - memset(keycache->hash_link_root, 0, - keycache->hash_links * sizeof(HASH_LINK)); - keycache->hash_links_used= 0; - keycache->free_hash_list= NULL; - keycache->blocks_used= keycache->blocks_changed= 0; - - keycache->global_blocks_changed= 0; - keycache->blocks_available=0; /* For debugging */ - - /* The LRU chain is empty after initialization */ - keycache->used_last= NULL; - keycache->used_ins= NULL; - keycache->free_block_list= NULL; - keycache->keycache_time= 0; - keycache->warm_blocks= 0; - keycache->min_warm_blocks= (division_limit ? - blocks * division_limit / 100 + 1 : - blocks); - keycache->age_threshold= (age_threshold ? - blocks * age_threshold / 100 : - blocks); - - keycache->can_be_used= 1; - - keycache->waiting_for_hash_link.last_thread= NULL; - keycache->waiting_for_block.last_thread= NULL; - DBUG_PRINT("exit", - ("disk_blocks: %d block_root: 0x%lx hash_entries: %d\ - hash_root: 0x%lx hash_links: %d hash_link_root: 0x%lx", - keycache->disk_blocks, (long) keycache->block_root, - keycache->hash_entries, (long) keycache->hash_root, - keycache->hash_links, (long) keycache->hash_link_root)); - memset(keycache->changed_blocks, 0, - sizeof(keycache->changed_blocks[0]) * CHANGED_BLOCKS_HASH); - memset(keycache->file_blocks, 0, - sizeof(keycache->file_blocks[0]) * CHANGED_BLOCKS_HASH); - } - else - { - /* key_buffer_size is specified too small. Disable the cache. */ - keycache->can_be_used= 0; - } - - keycache->blocks= keycache->disk_blocks > 0 ? keycache->disk_blocks : 0; - DBUG_RETURN((int) keycache->disk_blocks); - -err: - error= my_errno(); - keycache->disk_blocks= 0; - keycache->blocks= 0; - if (keycache->block_mem) - { - my_large_free((uchar*) keycache->block_mem); - keycache->block_mem= NULL; - } - if (keycache->block_root) - { - my_free(keycache->block_root); - keycache->block_root= NULL; - } - set_my_errno(error); - keycache->can_be_used= 0; - DBUG_RETURN(0); -} - - -/* - Resize a key cache - - SYNOPSIS - resize_key_cache() - keycache pointer to a key cache data structure - thread_var pointer to thread specific variables - key_cache_block_size size of blocks to keep cached data - use_mem total memory to use for the new key cache - division_limit new division limit (if not zero) - age_threshold new age threshold (if not zero) - - RETURN VALUE - number of blocks in the key cache, if successful, - 0 - otherwise. - - NOTES. - The function first compares the memory size and the block size parameters - with the key cache values. - - If they differ the function free the the memory allocated for the - old key cache blocks by calling the end_key_cache function and - then rebuilds the key cache with new blocks by calling - init_key_cache. - - The function starts the operation only when all other threads - performing operations with the key cache let her to proceed - (when cnt_for_resize=0). -*/ - -int resize_key_cache(KEY_CACHE *keycache, - st_keycache_thread_var *thread_var, - ulonglong key_cache_block_size, - size_t use_mem, ulonglong division_limit, - ulonglong age_threshold) -{ - int blocks; - DBUG_ENTER("resize_key_cache"); - - if (!keycache->key_cache_inited) - DBUG_RETURN(keycache->disk_blocks); - - if(key_cache_block_size == keycache->key_cache_block_size && - use_mem == keycache->key_cache_mem_size) - { - change_key_cache_param(keycache, division_limit, age_threshold); - DBUG_RETURN(keycache->disk_blocks); - } - - mysql_mutex_lock(&keycache->cache_lock); - - /* - We may need to wait for another thread which is doing a resize - already. This cannot happen in the MySQL server though. It allows - one resizer only. In set_var.cc keycache->in_init is used to block - multiple attempts. - */ - while (keycache->in_resize) - { - /* purecov: begin inspected */ - wait_on_queue(&keycache->resize_queue, &keycache->cache_lock, - thread_var); - /* purecov: end */ - } - - /* - Mark the operation in progress. This blocks other threads from doing - a resize in parallel. It prohibits new blocks to enter the cache. - Read/write requests can bypass the cache during the flush phase. - */ - keycache->in_resize= 1; - - /* Need to flush only if keycache is enabled. */ - if (keycache->can_be_used) - { - /* Start the flush phase. */ - keycache->resize_in_flush= 1; - - if (flush_all_key_blocks(keycache, thread_var)) - { - /* TODO: if this happens, we should write a warning in the log file ! */ - keycache->resize_in_flush= 0; - blocks= 0; - keycache->can_be_used= 0; - goto finish; - } - DBUG_ASSERT(cache_empty(keycache)); - - /* End the flush phase. */ - keycache->resize_in_flush= 0; - } - - /* - Some direct read/write operations (bypassing the cache) may still be - unfinished. Wait until they are done. If the key cache can be used, - direct I/O is done in increments of key_cache_block_size. That is, - every block is checked if it is in the cache. We need to wait for - pending I/O before re-initializing the cache, because we may change - the block size. Otherwise they could check for blocks at file - positions where the new block division has none. We do also want to - wait for I/O done when (if) the cache was disabled. It must not - run in parallel with normal cache operation. - */ - while (keycache->cnt_for_resize_op) - wait_on_queue(&keycache->waiting_for_resize_cnt, &keycache->cache_lock, - thread_var); - - /* - Free old cache structures, allocate new structures, and initialize - them. Note that the cache_lock mutex and the resize_queue are left - untouched. We do not lose the cache_lock and will release it only at - the end of this function. - */ - end_key_cache(keycache, 0); /* Don't free mutex */ - /* The following will work even if use_mem is 0 */ - blocks= init_key_cache(keycache, key_cache_block_size, use_mem, - division_limit, age_threshold); - -finish: - /* - Mark the resize finished. This allows other threads to start a - resize or to request new cache blocks. - */ - keycache->in_resize= 0; - - /* Signal waiting threads. */ - release_whole_queue(&keycache->resize_queue); - - mysql_mutex_unlock(&keycache->cache_lock); - DBUG_RETURN(blocks); -} - - -/* - Increment counter blocking resize key cache operation -*/ -static inline void inc_counter_for_resize_op(KEY_CACHE *keycache) -{ - keycache->cnt_for_resize_op++; -} - - -/* - Decrement counter blocking resize key cache operation; - Signal the operation to proceed when counter becomes equal zero -*/ -static inline void dec_counter_for_resize_op(KEY_CACHE *keycache) -{ - if (!--keycache->cnt_for_resize_op) - release_whole_queue(&keycache->waiting_for_resize_cnt); -} - -/* - Change the key cache parameters - - SYNOPSIS - change_key_cache_param() - keycache pointer to a key cache data structure - division_limit new division limit (if not zero) - age_threshold new age threshold (if not zero) - - RETURN VALUE - none - - NOTES. - Presently the function resets the key cache parameters - concerning midpoint insertion strategy - division_limit and - age_threshold. -*/ - -static void change_key_cache_param(KEY_CACHE *keycache, - ulonglong division_limit, - ulonglong age_threshold) -{ - DBUG_ENTER("change_key_cache_param"); - - mysql_mutex_lock(&keycache->cache_lock); - if (division_limit) - keycache->min_warm_blocks= (keycache->disk_blocks * - division_limit / 100 + 1); - if (age_threshold) - keycache->age_threshold= (keycache->disk_blocks * - age_threshold / 100); - mysql_mutex_unlock(&keycache->cache_lock); - DBUG_VOID_RETURN; -} - - -/* - Remove key_cache from memory - - SYNOPSIS - end_key_cache() - keycache key cache handle - cleanup Complete free (Free also mutex for key cache) - - RETURN VALUE - none -*/ - -void end_key_cache(KEY_CACHE *keycache, my_bool cleanup) -{ - DBUG_ENTER("end_key_cache"); - DBUG_PRINT("enter", ("key_cache: 0x%lx", (long) keycache)); - - if (!keycache->key_cache_inited) - DBUG_VOID_RETURN; - - if (keycache->disk_blocks > 0) - { - if (keycache->block_mem) - { - my_large_free((uchar*) keycache->block_mem); - keycache->block_mem= NULL; - my_free(keycache->block_root); - keycache->block_root= NULL; - } - keycache->disk_blocks= -1; - /* Reset blocks_changed to be safe if flush_all_key_blocks is called */ - keycache->blocks_changed= 0; - } - - DBUG_PRINT("status", ("used: %lu changed: %lu w_requests: %lu " - "writes: %lu r_requests: %lu reads: %lu", - keycache->blocks_used, keycache->global_blocks_changed, - (ulong) keycache->global_cache_w_requests, - (ulong) keycache->global_cache_write, - (ulong) keycache->global_cache_r_requests, - (ulong) keycache->global_cache_read)); - - /* - Reset these values to be able to detect a disabled key cache. - See Bug#44068 (RESTORE can disable the MyISAM Key Cache). - */ - keycache->blocks_used= 0; - keycache->blocks_unused= 0; - - if (cleanup) - { - mysql_mutex_destroy(&keycache->cache_lock); - keycache->key_cache_inited= keycache->can_be_used= 0; - } - DBUG_VOID_RETURN; -} /* end_key_cache */ - - -/** - Link a thread into double-linked queue of waiting threads. - - @param wqueue pointer to the queue structure - @param thread pointer to the keycache variables for the - thread to be added to the queue - - Queue is represented by a circular list of the keycache variable structures. - Since each thread has its own keycache variables, this is equal to a list - of threads. The list is double-linked of the type (**prev,*next), accessed by - a pointer to the last element. -*/ - -static void link_into_queue(KEYCACHE_WQUEUE *wqueue, - st_keycache_thread_var *thread) -{ - st_keycache_thread_var *last; - - DBUG_ASSERT(!thread->next && !thread->prev); - if (! (last= wqueue->last_thread)) - { - /* Queue is empty */ - thread->next= thread; - thread->prev= &thread->next; - } - else - { - thread->prev= last->next->prev; - last->next->prev= &thread->next; - thread->next= last->next; - last->next= thread; - } - wqueue->last_thread= thread; -} - - -/** - Unlink a thread from double-linked queue of waiting threads - - @param wqueue pointer to the queue structure - @param thread pointer to the keycache variables for the - thread to be removed to the queue - - @note See link_into_queue -*/ - -static void unlink_from_queue(KEYCACHE_WQUEUE *wqueue, - st_keycache_thread_var *thread) -{ - DBUG_ASSERT(thread->next && thread->prev); - if (thread->next == thread) - /* The queue contains only one member */ - wqueue->last_thread= NULL; - else - { - thread->next->prev= thread->prev; - *thread->prev=thread->next; - if (wqueue->last_thread == thread) - wqueue->last_thread= STRUCT_PTR(st_keycache_thread_var, next, - thread->prev); - } - thread->next= NULL; -#if !defined(DBUG_OFF) - /* - This makes it easier to see it's not in a chain during debugging. - And some DBUG_ASSERT() rely on it. - */ - thread->prev= NULL; -#endif -} - - -/* - Add a thread to single-linked queue of waiting threads - - SYNOPSIS - wait_on_queue() - wqueue Pointer to the queue structure. - mutex Cache_lock to acquire after awake. - thread Thread to be added - - RETURN VALUE - none - - NOTES. - Queue is represented by a circular list of the thread structures - The list is single-linked of the type (*next), accessed by a pointer - to the last element. - - The function protects against stray signals by verifying that the - current thread is unlinked from the queue when awaking. However, - since several threads can wait for the same event, it might be - necessary for the caller of the function to check again if the - condition for awake is indeed matched. -*/ - -static void wait_on_queue(KEYCACHE_WQUEUE *wqueue, - mysql_mutex_t *mutex, - st_keycache_thread_var *thread) -{ - st_keycache_thread_var *last; - - /* Add to queue. */ - DBUG_ASSERT(!thread->next); - DBUG_ASSERT(!thread->prev); /* Not required, but must be true anyway. */ - if (! (last= wqueue->last_thread)) - thread->next= thread; - else - { - thread->next= last->next; - last->next= thread; - } - wqueue->last_thread= thread; - - /* - Wait until thread is removed from queue by the signalling thread. - The loop protects against stray signals. - */ - do - { - mysql_cond_wait(&thread->suspend, mutex); - } - while (thread->next); -} - - -/* - Remove all threads from queue signaling them to proceed - - SYNOPSIS - release_whole_queue() - wqueue pointer to the queue structure - - RETURN VALUE - none - - NOTES. - See notes for wait_on_queue(). - When removed from the queue each thread is signaled via condition - variable thread->suspend. -*/ - -static void release_whole_queue(KEYCACHE_WQUEUE *wqueue) -{ - st_keycache_thread_var *last; - st_keycache_thread_var *next; - st_keycache_thread_var *thread; - - /* Queue may be empty. */ - if (!(last= wqueue->last_thread)) - return; - - next= last->next; - do - { - thread=next; - /* Signal the thread. */ - mysql_cond_signal(&thread->suspend); - /* Take thread from queue. */ - next=thread->next; - thread->next= NULL; - } - while (thread != last); - - /* Now queue is definitely empty. */ - wqueue->last_thread= NULL; -} - - -/* - Unlink a block from the chain of dirty/clean blocks -*/ - -static inline void unlink_changed(BLOCK_LINK *block) -{ - DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); - if (block->next_changed) - block->next_changed->prev_changed= block->prev_changed; - *block->prev_changed= block->next_changed; - -#if !defined(DBUG_OFF) - /* - This makes it easier to see it's not in a chain during debugging. - And some DBUG_ASSERT() rely on it. - */ - block->next_changed= NULL; - block->prev_changed= NULL; -#endif -} - - -/* - Link a block into the chain of dirty/clean blocks -*/ - -static inline void link_changed(BLOCK_LINK *block, BLOCK_LINK **phead) -{ - DBUG_ASSERT(!block->next_changed); - DBUG_ASSERT(!block->prev_changed); - block->prev_changed= phead; - if ((block->next_changed= *phead)) - (*phead)->prev_changed= &block->next_changed; - *phead= block; -} - - -/* - Link a block in a chain of clean blocks of a file. - - SYNOPSIS - link_to_file_list() - keycache Key cache handle - block Block to relink - file File to be linked to - unlink If to unlink first - - DESCRIPTION - Unlink a block from whichever chain it is linked in, if it's - asked for, and link it to the chain of clean blocks of the - specified file. - - NOTE - Please do never set/clear BLOCK_CHANGED outside of - link_to_file_list() or link_to_changed_list(). - You would risk to damage correct counting of changed blocks - and to find blocks in the wrong hash. - - RETURN - void -*/ - -static void link_to_file_list(KEY_CACHE *keycache, - BLOCK_LINK *block, int file, - my_bool unlink_block) -{ - DBUG_ASSERT(block->status & BLOCK_IN_USE); - DBUG_ASSERT(block->hash_link && block->hash_link->block == block); - DBUG_ASSERT(block->hash_link->file == file); - if (unlink_block) - unlink_changed(block); - link_changed(block, &keycache->file_blocks[FILE_HASH(file)]); - if (block->status & BLOCK_CHANGED) - { - block->status&= ~BLOCK_CHANGED; - keycache->blocks_changed--; - keycache->global_blocks_changed--; - } -} - - -/* - Re-link a block from the clean chain to the dirty chain of a file. - - SYNOPSIS - link_to_changed_list() - keycache key cache handle - block block to relink - - DESCRIPTION - Unlink a block from the chain of clean blocks of a file - and link it to the chain of dirty blocks of the same file. - - NOTE - Please do never set/clear BLOCK_CHANGED outside of - link_to_file_list() or link_to_changed_list(). - You would risk to damage correct counting of changed blocks - and to find blocks in the wrong hash. - - RETURN - void -*/ - -static void link_to_changed_list(KEY_CACHE *keycache, - BLOCK_LINK *block) -{ - DBUG_ASSERT(block->status & BLOCK_IN_USE); - DBUG_ASSERT(!(block->status & BLOCK_CHANGED)); - DBUG_ASSERT(block->hash_link && block->hash_link->block == block); - - unlink_changed(block); - link_changed(block, - &keycache->changed_blocks[FILE_HASH(block->hash_link->file)]); - block->status|=BLOCK_CHANGED; - keycache->blocks_changed++; - keycache->global_blocks_changed++; -} - - -/* - Link a block to the LRU chain at the beginning or at the end of - one of two parts. - - SYNOPSIS - link_block() - keycache pointer to a key cache data structure - block pointer to the block to link to the LRU chain - hot <-> to link the block into the hot subchain - at_end <-> to link the block at the end of the subchain - - RETURN VALUE - none - - NOTES. - The LRU ring is represented by a circular list of block structures. - The list is double-linked of the type (**prev,*next) type. - The LRU ring is divided into two parts - hot and warm. - There are two pointers to access the last blocks of these two - parts. The beginning of the warm part follows right after the - end of the hot part. - Only blocks of the warm part can be used for eviction. - The first block from the beginning of this subchain is always - taken for eviction (keycache->last_used->next) - - LRU chain: +------+ H O T +------+ - +----| end |----...<----| beg |----+ - | +------+last +------+ | - v<-link in latest hot (new end) | - | link in latest warm (new end)->^ - | +------+ W A R M +------+ | - +----| beg |---->...----| end |----+ - +------+ +------+ins - first for eviction - - It is also possible that the block is selected for eviction and thus - not linked in the LRU ring. -*/ - -static void link_block(KEY_CACHE *keycache, BLOCK_LINK *block, my_bool hot, - my_bool at_end) -{ - BLOCK_LINK *ins; - BLOCK_LINK **pins; - - DBUG_ASSERT((block->status & ~BLOCK_CHANGED) == (BLOCK_READ | BLOCK_IN_USE)); - DBUG_ASSERT(block->hash_link); /*backptr to block NULL from free_block()*/ - DBUG_ASSERT(!block->requests); - DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); - DBUG_ASSERT(!block->next_used); - DBUG_ASSERT(!block->prev_used); - - if (!hot && keycache->waiting_for_block.last_thread) - { - /* Signal that in the LRU warm sub-chain an available block has appeared */ - st_keycache_thread_var *last_thread= - keycache->waiting_for_block.last_thread; - st_keycache_thread_var *first_thread= last_thread->next; - st_keycache_thread_var *next_thread= first_thread; - HASH_LINK *hash_link= (HASH_LINK *) first_thread->opt_info; - st_keycache_thread_var *thread; - do - { - thread= next_thread; - next_thread= thread->next; - /* - We notify about the event all threads that ask - for the same page as the first thread in the queue - */ - if ((HASH_LINK *) thread->opt_info == hash_link) - { - mysql_cond_signal(&thread->suspend); - unlink_from_queue(&keycache->waiting_for_block, thread); - block->requests++; - } - } - while (thread != last_thread); - hash_link->block= block; - /* - NOTE: We assigned the block to the hash_link and signalled the - requesting thread(s). But it is possible that other threads runs - first. These threads see the hash_link assigned to a block which - is assigned to another hash_link and not marked BLOCK_IN_SWITCH. - This can be a problem for functions that do not select the block - via its hash_link: flush and free. They do only see a block which - is in a "normal" state and don't know that it will be evicted soon. - - We cannot set BLOCK_IN_SWITCH here because only one of the - requesting threads must handle the eviction. All others must wait - for it to complete. If we set the flag here, the threads would not - know who is in charge of the eviction. Without the flag, the first - thread takes the stick and sets the flag. - - But we need to note in the block that is has been selected for - eviction. It must not be freed. The evicting thread will not - expect the block in the free list. Before freeing we could also - check if block->requests > 1. But I think including another flag - in the check of block->status is slightly more efficient and - probably easier to read. - */ - block->status|= BLOCK_IN_EVICTION; - return; - } - - pins= hot ? &keycache->used_ins : &keycache->used_last; - ins= *pins; - if (ins) - { - ins->next_used->prev_used= &block->next_used; - block->next_used= ins->next_used; - block->prev_used= &ins->next_used; - ins->next_used= block; - if (at_end) - *pins= block; - } - else - { - /* The LRU ring is empty. Let the block point to itself. */ - keycache->used_last= keycache->used_ins= block->next_used= block; - block->prev_used= &block->next_used; - } - DBUG_ASSERT((ulong) keycache->blocks_available <= - keycache->blocks_used); -} - - -/* - Unlink a block from the LRU chain - - SYNOPSIS - unlink_block() - keycache pointer to a key cache data structure - block pointer to the block to unlink from the LRU chain - - RETURN VALUE - none - - NOTES. - See NOTES for link_block -*/ - -static void unlink_block(KEY_CACHE *keycache, BLOCK_LINK *block) -{ - DBUG_ASSERT((block->status & ~BLOCK_CHANGED) == (BLOCK_READ | BLOCK_IN_USE)); - DBUG_ASSERT(block->hash_link); /*backptr to block NULL from free_block()*/ - DBUG_ASSERT(!block->requests); - DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); - DBUG_ASSERT(block->next_used && block->prev_used && - (block->next_used->prev_used == &block->next_used) && - (*block->prev_used == block)); - if (block->next_used == block) - /* The list contains only one member */ - keycache->used_last= keycache->used_ins= NULL; - else - { - block->next_used->prev_used= block->prev_used; - *block->prev_used= block->next_used; - if (keycache->used_last == block) - keycache->used_last= STRUCT_PTR(BLOCK_LINK, next_used, block->prev_used); - if (keycache->used_ins == block) - keycache->used_ins=STRUCT_PTR(BLOCK_LINK, next_used, block->prev_used); - } - block->next_used= NULL; -#if !defined(DBUG_OFF) - /* - This makes it easier to see it's not in a chain during debugging. - And some DBUG_ASSERT() rely on it. - */ - block->prev_used= NULL; -#endif -} - - -/* - Register requests for a block. - - SYNOPSIS - reg_requests() - keycache Pointer to a key cache data structure. - block Pointer to the block to register a request on. - count Number of requests. Always 1. - - NOTE - The first request unlinks the block from the LRU ring. This means - that it is protected against eveiction. - - RETURN - void -*/ -static void reg_requests(KEY_CACHE *keycache, BLOCK_LINK *block, int count) -{ - DBUG_ASSERT(block->status & BLOCK_IN_USE); - DBUG_ASSERT(block->hash_link); - - if (!block->requests) - unlink_block(keycache, block); - block->requests+=count; -} - - -/* - Unregister request for a block - linking it to the LRU chain if it's the last request - - SYNOPSIS - unreg_request() - keycache pointer to a key cache data structure - block pointer to the block to link to the LRU chain - at_end <-> to link the block at the end of the LRU chain - - RETURN VALUE - none - - NOTES. - Every linking to the LRU ring decrements by one a special block - counter (if it's positive). If the at_end parameter is TRUE the block is - added either at the end of warm sub-chain or at the end of hot sub-chain. - It is added to the hot subchain if its counter is zero and number of - blocks in warm sub-chain is not less than some low limit (determined by - the division_limit parameter). Otherwise the block is added to the warm - sub-chain. If the at_end parameter is FALSE the block is always added - at beginning of the warm sub-chain. - Thus a warm block can be promoted to the hot sub-chain when its counter - becomes zero for the first time. - At the same time the block at the very beginning of the hot subchain - might be moved to the beginning of the warm subchain if it stays untouched - for a too long time (this time is determined by parameter age_threshold). - - It is also possible that the block is selected for eviction and thus - not linked in the LRU ring. -*/ - -static void unreg_request(KEY_CACHE *keycache, - BLOCK_LINK *block, int at_end) -{ - DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); - DBUG_ASSERT(block->hash_link); /*backptr to block NULL from free_block()*/ - DBUG_ASSERT(block->requests); - DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); - DBUG_ASSERT(!block->next_used); - DBUG_ASSERT(!block->prev_used); - /* - Unregister the request, but do not link erroneous blocks into the - LRU ring. - */ - if (!--block->requests && !(block->status & BLOCK_ERROR)) - { - my_bool hot; - if (block->hits_left) - block->hits_left--; - hot= !block->hits_left && at_end && - keycache->warm_blocks > keycache->min_warm_blocks; - if (hot) - { - if (block->temperature == BLOCK_WARM) - keycache->warm_blocks--; - block->temperature= BLOCK_HOT; - } - link_block(keycache, block, hot, (my_bool)at_end); - block->last_hit_time= keycache->keycache_time; - keycache->keycache_time++; - /* - At this place, the block might be in the LRU ring or not. If an - evicter was waiting for a block, it was selected for eviction and - not linked in the LRU ring. - */ - - /* - Check if we should link a hot block to the warm block sub-chain. - It is possible that we select the same block as above. But it can - also be another block. In any case a block from the LRU ring is - selected. In other words it works even if the above block was - selected for eviction and not linked in the LRU ring. Since this - happens only if the LRU ring is empty, the block selected below - would be NULL and the rest of the function skipped. - */ - block= keycache->used_ins; - if (block && keycache->keycache_time - block->last_hit_time > - keycache->age_threshold) - { - unlink_block(keycache, block); - link_block(keycache, block, 0, 0); - if (block->temperature != BLOCK_WARM) - { - keycache->warm_blocks++; - block->temperature= BLOCK_WARM; - } - } - } -} - -/* - Remove a reader of the page in block -*/ - -static void remove_reader(BLOCK_LINK *block) -{ - DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); - DBUG_ASSERT(block->hash_link && block->hash_link->block == block); - DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); - DBUG_ASSERT(!block->next_used); - DBUG_ASSERT(!block->prev_used); - DBUG_ASSERT(block->hash_link->requests); - - if (! --block->hash_link->requests && block->condvar) - mysql_cond_signal(block->condvar); -} - - -/* - Wait until the last reader of the page in block - signals on its termination -*/ - -static void wait_for_readers(KEY_CACHE *keycache, - BLOCK_LINK *block, - st_keycache_thread_var *thread) -{ - DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); - DBUG_ASSERT(!(block->status & (BLOCK_IN_FLUSH | BLOCK_CHANGED))); - DBUG_ASSERT(block->hash_link); - DBUG_ASSERT(block->hash_link->block == block); - /* Linked in file_blocks or changed_blocks hash. */ - DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); - /* Not linked in LRU ring. */ - DBUG_ASSERT(!block->next_used); - DBUG_ASSERT(!block->prev_used); - while (block->hash_link->requests) - { - /* There must be no other waiter. We have no queue here. */ - DBUG_ASSERT(!block->condvar); - block->condvar= &thread->suspend; - mysql_cond_wait(&thread->suspend, &keycache->cache_lock); - block->condvar= NULL; - } -} - - -/* - Add a hash link to a bucket in the hash_table -*/ - -static inline void link_hash(HASH_LINK **start, HASH_LINK *hash_link) -{ - if (*start) - (*start)->prev= &hash_link->next; - hash_link->next= *start; - hash_link->prev= start; - *start= hash_link; -} - - -/* - Remove a hash link from the hash table -*/ - -static void unlink_hash(KEY_CACHE *keycache, HASH_LINK *hash_link) -{ - DBUG_ASSERT(hash_link->requests == 0); - if ((*hash_link->prev= hash_link->next)) - hash_link->next->prev= hash_link->prev; - hash_link->block= NULL; - - if (keycache->waiting_for_hash_link.last_thread) - { - /* Signal that a free hash link has appeared */ - st_keycache_thread_var *last_thread= - keycache->waiting_for_hash_link.last_thread; - st_keycache_thread_var *first_thread= last_thread->next; - st_keycache_thread_var *next_thread= first_thread; - KEYCACHE_PAGE *first_page= (KEYCACHE_PAGE *) (first_thread->opt_info); - st_keycache_thread_var *thread; - - hash_link->file= first_page->file; - hash_link->diskpos= first_page->filepos; - do - { - KEYCACHE_PAGE *page; - thread= next_thread; - page= (KEYCACHE_PAGE *) thread->opt_info; - next_thread= thread->next; - /* - We notify about the event all threads that ask - for the same page as the first thread in the queue - */ - if (page->file == hash_link->file && page->filepos == hash_link->diskpos) - { - mysql_cond_signal(&thread->suspend); - unlink_from_queue(&keycache->waiting_for_hash_link, thread); - } - } - while (thread != last_thread); - link_hash(&keycache->hash_root[KEYCACHE_HASH(hash_link->file, - hash_link->diskpos)], - hash_link); - return; - } - hash_link->next= keycache->free_hash_list; - keycache->free_hash_list= hash_link; -} - - -/* - Get the hash link for a page -*/ - -static HASH_LINK *get_hash_link(KEY_CACHE *keycache, - int file, my_off_t filepos, - st_keycache_thread_var *thread) -{ - HASH_LINK *hash_link, **start; -#ifndef DBUG_OFF - int cnt; -#endif - -restart: - /* - Find the bucket in the hash table for the pair (file, filepos); - start contains the head of the bucket list, - hash_link points to the first member of the list - */ - hash_link= *(start= &keycache->hash_root[KEYCACHE_HASH(file, filepos)]); -#ifndef DBUG_OFF - cnt= 0; -#endif - /* Look for an element for the pair (file, filepos) in the bucket chain */ - while (hash_link && - (hash_link->diskpos != filepos || hash_link->file != file)) - { - hash_link= hash_link->next; -#ifndef DBUG_OFF - cnt++; - DBUG_ASSERT(cnt <= keycache->hash_links_used); -#endif - } - if (! hash_link) - { - /* There is no hash link in the hash table for the pair (file, filepos) */ - if (keycache->free_hash_list) - { - hash_link= keycache->free_hash_list; - keycache->free_hash_list= hash_link->next; - } - else if (keycache->hash_links_used < keycache->hash_links) - { - hash_link= &keycache->hash_link_root[keycache->hash_links_used++]; - } - else - { - /* Wait for a free hash link */ - KEYCACHE_PAGE page; - page.file= file; - page.filepos= filepos; - thread->opt_info= (void *) &page; - link_into_queue(&keycache->waiting_for_hash_link, thread); - mysql_cond_wait(&thread->suspend, - &keycache->cache_lock); - thread->opt_info= NULL; - goto restart; - } - hash_link->file= file; - hash_link->diskpos= filepos; - link_hash(start, hash_link); - } - /* Register the request for the page */ - hash_link->requests++; - - return hash_link; -} - - -/* - Get a block for the file page requested by a keycache read/write operation; - If the page is not in the cache return a free block, if there is none - return the lru block after saving its buffer if the page is dirty. - - SYNOPSIS - - find_key_block() - keycache pointer to a key cache data structure - thread pointer to thread specific variables - file handler for the file to read page from - filepos position of the page in the file - init_hits_left how initialize the block counter for the page - wrmode <-> get for writing - page_st out {PAGE_READ,PAGE_TO_BE_READ,PAGE_WAIT_TO_BE_READ} - - RETURN VALUE - Pointer to the found block if successful, 0 - otherwise - - NOTES. - For the page from file positioned at filepos the function checks whether - the page is in the key cache specified by the first parameter. - If this is the case it immediately returns the block. - If not, the function first chooses a block for this page. If there is - no not used blocks in the key cache yet, the function takes the block - at the very beginning of the warm sub-chain. It saves the page in that - block if it's dirty before returning the pointer to it. - The function returns in the page_st parameter the following values: - PAGE_READ - if page already in the block, - PAGE_TO_BE_READ - if it is to be read yet by the current thread - WAIT_TO_BE_READ - if it is to be read by another thread - If an error occurs THE BLOCK_ERROR bit is set in the block status. - It might happen that there are no blocks in LRU chain (in warm part) - - all blocks are unlinked for some read/write operations. Then the function - waits until first of this operations links any block back. -*/ - -static BLOCK_LINK *find_key_block(KEY_CACHE *keycache, - st_keycache_thread_var *thread, - File file, my_off_t filepos, - int init_hits_left, - int wrmode, int *page_st) -{ - HASH_LINK *hash_link; - BLOCK_LINK *block; - int error= 0; - int page_status; - - DBUG_ENTER("find_key_block"); - DBUG_PRINT("enter", ("fd: %d pos: %lu wrmode: %d", - file, (ulong) filepos, wrmode)); - -restart: - /* - If the flush phase of a resize operation fails, the cache is left - unusable. This will be detected only after "goto restart". - */ - if (!keycache->can_be_used) - DBUG_RETURN(0); - - /* - Find the hash_link for the requested file block (file, filepos). We - do always get a hash_link here. It has registered our request so - that no other thread can use it for another file block until we - release the request (which is done by remove_reader() usually). The - hash_link can have a block assigned to it or not. If there is a - block, it may be assigned to this hash_link or not. In cases where a - block is evicted from the cache, it is taken from the LRU ring and - referenced by the new hash_link. But the block can still be assigned - to its old hash_link for some time if it needs to be flushed first, - or if there are other threads still reading it. - - Summary: - hash_link is always returned. - hash_link->block can be: - - NULL or - - not assigned to this hash_link or - - assigned to this hash_link. If assigned, the block can have - - invalid data (when freshly assigned) or - - valid data. Valid data can be - - changed over the file contents (dirty) or - - not changed (clean). - */ - hash_link= get_hash_link(keycache, file, filepos, thread); - DBUG_ASSERT((hash_link->file == file) && (hash_link->diskpos == filepos)); - - page_status= -1; - if ((block= hash_link->block) && - block->hash_link == hash_link && (block->status & BLOCK_READ)) - { - /* Assigned block with valid (changed or unchanged) contents. */ - page_status= PAGE_READ; - } - /* - else (page_status == -1) - - block == NULL or - - block not assigned to this hash_link or - - block assigned but not yet read from file (invalid data). - */ - - if (keycache->in_resize) - { - /* This is a request during a resize operation */ - - if (!block) - { - /* - The file block is not in the cache. We don't need it in the - cache: we are going to read or write directly to file. Cancel - the request. We can simply decrement hash_link->requests because - we did not release cache_lock since increasing it. So no other - thread can wait for our request to become released. - */ - if (hash_link->requests == 1) - { - /* - We are the only one to request this hash_link (this file/pos). - Free the hash_link. - */ - hash_link->requests--; - unlink_hash(keycache, hash_link); - DBUG_RETURN(0); - } - - /* - More requests on the hash_link. Someone tries to evict a block - for this hash_link (could have started before resizing started). - This means that the LRU ring is empty. Otherwise a block could - be assigned immediately. Behave like a thread that wants to - evict a block for this file/pos. Add to the queue of threads - waiting for a block. Wait until there is one assigned. - - Refresh the request on the hash-link so that it cannot be reused - for another file/pos. - */ - thread->opt_info= (void *) hash_link; - link_into_queue(&keycache->waiting_for_block, thread); - do - { - mysql_cond_wait(&thread->suspend, - &keycache->cache_lock); - } while (thread->next); - thread->opt_info= NULL; - /* - A block should now be assigned to the hash_link. But it may - still need to be evicted. Anyway, we should re-check the - situation. page_status must be set correctly. - */ - hash_link->requests--; - goto restart; - } /* end of if (!block) */ - - /* - There is a block for this file/pos in the cache. Register a - request on it. This unlinks it from the LRU ring (if it is there) - and hence protects it against eviction (if not already in - eviction). We need this for returning the block to the caller, for - calling remove_reader() (for debugging purposes), and for calling - free_block(). The only case where we don't need the request is if - the block is in eviction. In that case we have to unregister the - request later. - */ - reg_requests(keycache, block, 1); - - if (page_status != PAGE_READ) - { - /* - - block not assigned to this hash_link or - - block assigned but not yet read from file (invalid data). - - This must be a block in eviction. It will be read soon. We need - to wait here until this happened. Otherwise the caller could - access a wrong block or a block which is in read. While waiting - we cannot lose hash_link nor block. We have registered a request - on the hash_link. Everything can happen to the block but changes - in the hash_link -> block relationship. In other words: - everything can happen to the block but free or another completed - eviction. - - Note that we bahave like a secondary requestor here. We just - cannot return with PAGE_WAIT_TO_BE_READ. This would work for - read requests and writes on dirty blocks that are not in flush - only. Waiting here on COND_FOR_REQUESTED works in all - situations. - */ - DBUG_ASSERT(((block->hash_link != hash_link) && - (block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH))) || - ((block->hash_link == hash_link) && - !(block->status & BLOCK_READ))); - wait_on_queue(&block->wqueue[COND_FOR_REQUESTED], &keycache->cache_lock, - thread); - /* - Here we can trust that the block has been assigned to this - hash_link (block->hash_link == hash_link) and read into the - buffer (BLOCK_READ). The worst things possible here are that the - block is in free (BLOCK_REASSIGNED). But the block is still - assigned to the hash_link. The freeing thread waits until we - release our request on the hash_link. The block must not be - again in eviction because we registered an request on it before - starting to wait. - */ - DBUG_ASSERT(block->hash_link == hash_link); - DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); - DBUG_ASSERT(!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH))); - } - /* - The block is in the cache. Assigned to the hash_link. Valid data. - Note that in case of page_st == PAGE_READ, the block can be marked - for eviction. In any case it can be marked for freeing. - */ - - if (!wrmode) - { - /* A reader can just read the block. */ - *page_st= PAGE_READ; - DBUG_ASSERT((hash_link->file == file) && - (hash_link->diskpos == filepos) && - (block->hash_link == hash_link)); - DBUG_RETURN(block); - } - - /* - This is a writer. No two writers for the same block can exist. - This must be assured by locks outside of the key cache. - */ - DBUG_ASSERT(!(block->status & BLOCK_FOR_UPDATE) || fail_block(block)); - - while (block->status & BLOCK_IN_FLUSH) - { - /* - Wait until the block is flushed to file. Do not release the - request on the hash_link yet to prevent that the block is freed - or reassigned while we wait. While we wait, several things can - happen to the block, including another flush. But the block - cannot be reassigned to another hash_link until we release our - request on it. But it can be marked BLOCK_REASSIGNED from free - or eviction, while they wait for us to release the hash_link. - */ - wait_on_queue(&block->wqueue[COND_FOR_SAVED], &keycache->cache_lock, - thread); - /* - If the flush phase failed, the resize could have finished while - we waited here. - */ - if (!keycache->in_resize) - { - remove_reader(block); - unreg_request(keycache, block, 1); - goto restart; - } - DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); - DBUG_ASSERT(!(block->status & BLOCK_FOR_UPDATE) || fail_block(block)); - DBUG_ASSERT(block->hash_link == hash_link); - } - - if (block->status & BLOCK_CHANGED) - { - /* - We want to write a block with changed contents. If the cache - block size is bigger than the callers block size (e.g. MyISAM), - the caller may replace part of the block only. Changes of the - other part of the block must be preserved. Since the block has - not yet been selected for flush, we can still add our changes. - */ - *page_st= PAGE_READ; - DBUG_ASSERT((hash_link->file == file) && - (hash_link->diskpos == filepos) && - (block->hash_link == hash_link)); - DBUG_RETURN(block); - } - - /* - This is a write request for a clean block. We do not want to have - new dirty blocks in the cache while resizing. We will free the - block and write directly to file. If the block is in eviction or - in free, we just let it go. - - Unregister from the hash_link. This must be done before freeing - the block. And it must be done if not freeing the block. Because - we could have waited above, we need to call remove_reader(). Other - threads could wait for us to release our request on the hash_link. - */ - remove_reader(block); - - /* If the block is not in eviction and not in free, we can free it. */ - if (!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | - BLOCK_REASSIGNED))) - { - /* - Free block as we are going to write directly to file. - Although we have an exlusive lock for the updated key part, - the control can be yielded by the current thread as we might - have unfinished readers of other key parts in the block - buffer. Still we are guaranteed not to have any readers - of the key part we are writing into until the block is - removed from the cache as we set the BLOCK_REASSIGNED - flag (see the code below that handles reading requests). - */ - free_block(keycache, thread, block); - } - else - { - /* - The block will be evicted/freed soon. Don't touch it in any way. - Unregister the request that we registered above. - */ - unreg_request(keycache, block, 1); - - /* - The block is still assigned to the hash_link (the file/pos that - we are going to write to). Wait until the eviction/free is - complete. Otherwise the direct write could complete before all - readers are done with the block. So they could read outdated - data. - - Since we released our request on the hash_link, it can be reused - for another file/pos. Hence we cannot just check for - block->hash_link == hash_link. As long as the resize is - proceeding the block cannot be reassigned to the same file/pos - again. So we can terminate the loop when the block is no longer - assigned to this file/pos. - */ - do - { - wait_on_queue(&block->wqueue[COND_FOR_SAVED], - &keycache->cache_lock, thread); - /* - If the flush phase failed, the resize could have finished - while we waited here. - */ - if (!keycache->in_resize) - goto restart; - } while (block->hash_link && - (block->hash_link->file == file) && - (block->hash_link->diskpos == filepos)); - } - DBUG_RETURN(0); - } - - if (page_status == PAGE_READ && - (block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | - BLOCK_REASSIGNED))) - { - /* - This is a request for a block to be removed from cache. The block - is assigned to this hash_link and contains valid data, but is - marked for eviction or to be freed. Possible reasons why it has - not yet been evicted/freed can be a flush before reassignment - (BLOCK_IN_SWITCH), readers of the block have not finished yet - (BLOCK_REASSIGNED), or the evicting thread did not yet awake after - the block has been selected for it (BLOCK_IN_EVICTION). - */ - - /* - Only reading requests can proceed until the old dirty page is flushed, - all others are to be suspended, then resubmitted - */ - if (!wrmode && !(block->status & BLOCK_REASSIGNED)) - { - /* - This is a read request and the block not yet reassigned. We can - register our request and proceed. This unlinks the block from - the LRU ring and protects it against eviction. - */ - reg_requests(keycache, block, 1); - } - else - { - /* - Either this is a write request for a block that is in eviction - or in free. We must not use it any more. Instead we must evict - another block. But we cannot do this before the eviction/free is - done. Otherwise we would find the same hash_link + block again - and again. - - Or this is a read request for a block in eviction/free that does - not require a flush, but waits for readers to finish with the - block. We do not read this block to let the eviction/free happen - as soon as possible. Again we must wait so that we don't find - the same hash_link + block again and again. - */ - DBUG_ASSERT(hash_link->requests); - hash_link->requests--; - wait_on_queue(&block->wqueue[COND_FOR_SAVED], &keycache->cache_lock, - thread); - /* - The block is no longer assigned to this hash_link. - Get another one. - */ - goto restart; - } - } - else - { - /* - This is a request for a new block or for a block not to be removed. - Either - - block == NULL or - - block not assigned to this hash_link or - - block assigned but not yet read from file, - or - - block assigned with valid (changed or unchanged) data and - - it will not be reassigned/freed. - */ - if (! block) - { - /* No block is assigned to the hash_link yet. */ - if (keycache->blocks_unused) - { - if (keycache->free_block_list) - { - /* There is a block in the free list. */ - block= keycache->free_block_list; - keycache->free_block_list= block->next_used; - block->next_used= NULL; - } - else - { - size_t block_mem_offset; - /* There are some never used blocks, take first of them */ - DBUG_ASSERT(keycache->blocks_used < - (ulong) keycache->disk_blocks); - block= &keycache->block_root[keycache->blocks_used]; - block_mem_offset= - ((size_t) keycache->blocks_used) * keycache->key_cache_block_size; - block->buffer= ADD_TO_PTR(keycache->block_mem, - block_mem_offset, - uchar*); - keycache->blocks_used++; - DBUG_ASSERT(!block->next_used); - } - DBUG_ASSERT(!block->prev_used); - DBUG_ASSERT(!block->next_changed); - DBUG_ASSERT(!block->prev_changed); - DBUG_ASSERT(!block->hash_link); - DBUG_ASSERT(!block->status); - DBUG_ASSERT(!block->requests); - keycache->blocks_unused--; - block->status= BLOCK_IN_USE; - block->length= 0; - block->offset= keycache->key_cache_block_size; - block->requests= 1; - block->temperature= BLOCK_COLD; - block->hits_left= init_hits_left; - block->last_hit_time= 0; - block->hash_link= hash_link; - hash_link->block= block; - link_to_file_list(keycache, block, file, 0); - page_status= PAGE_TO_BE_READ; - } - else - { - /* - There are no free blocks and no never used blocks, use a block - from the LRU ring. - */ - - if (! keycache->used_last) - { - /* - The LRU ring is empty. Wait until a new block is added to - it. Several threads might wait here for the same hash_link, - all of them must get the same block. While waiting for a - block, after a block is selected for this hash_link, other - threads can run first before this one awakes. During this - time interval other threads find this hash_link pointing to - the block, which is still assigned to another hash_link. In - this case the block is not marked BLOCK_IN_SWITCH yet, but - it is marked BLOCK_IN_EVICTION. - */ - - thread->opt_info= (void *) hash_link; - link_into_queue(&keycache->waiting_for_block, thread); - do - { - mysql_cond_wait(&thread->suspend, - &keycache->cache_lock); - } - while (thread->next); - thread->opt_info= NULL; - /* Assert that block has a request registered. */ - DBUG_ASSERT(hash_link->block->requests); - /* Assert that block is not in LRU ring. */ - DBUG_ASSERT(!hash_link->block->next_used); - DBUG_ASSERT(!hash_link->block->prev_used); - } - - /* - If we waited above, hash_link->block has been assigned by - link_block(). Otherwise it is still NULL. In the latter case - we need to grab a block from the LRU ring ourselves. - */ - block= hash_link->block; - if (! block) - { - /* Select the last block from the LRU ring. */ - block= keycache->used_last->next_used; - block->hits_left= init_hits_left; - block->last_hit_time= 0; - hash_link->block= block; - /* - Register a request on the block. This unlinks it from the - LRU ring and protects it against eviction. - */ - DBUG_ASSERT(!block->requests); - reg_requests(keycache, block,1); - /* - We do not need to set block->status|= BLOCK_IN_EVICTION here - because we will set block->status|= BLOCK_IN_SWITCH - immediately without releasing the lock in between. This does - also support debugging. When looking at the block, one can - see if the block has been selected by link_block() after the - LRU ring was empty, or if it was grabbed directly from the - LRU ring in this branch. - */ - } - - /* - If we had to wait above, there is a small chance that another - thread grabbed this block for the same file block already. But - in most cases the first condition is true. - */ - if (block->hash_link != hash_link && - ! (block->status & BLOCK_IN_SWITCH) ) - { - /* this is a primary request for a new page */ - block->status|= BLOCK_IN_SWITCH; - - if (block->status & BLOCK_CHANGED) - { - /* The block contains a dirty page - push it out of the cache */ - - if (block->status & BLOCK_IN_FLUSH) - { - /* - The block is marked for flush. If we do not wait here, - it could happen that we write the block, reassign it to - another file block, then, before the new owner can read - the new file block, the flusher writes the cache block - (which still has the old contents) to the new file block! - */ - wait_on_queue(&block->wqueue[COND_FOR_SAVED], - &keycache->cache_lock, thread); - /* - The block is marked BLOCK_IN_SWITCH. It should be left - alone except for reading. No free, no write. - */ - DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); - DBUG_ASSERT(!(block->status & (BLOCK_REASSIGNED | - BLOCK_CHANGED | - BLOCK_FOR_UPDATE))); - } - else - { - block->status|= BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE; - /* - BLOCK_IN_EVICTION may be true or not. Other flags must - have a fixed value. - */ - DBUG_ASSERT((block->status & ~BLOCK_IN_EVICTION) == - (BLOCK_READ | BLOCK_IN_SWITCH | - BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE | - BLOCK_CHANGED | BLOCK_IN_USE)); - DBUG_ASSERT(block->hash_link); - - mysql_mutex_unlock(&keycache->cache_lock); - /* - The call is thread safe because only the current - thread might change the block->hash_link value - */ - error= (int)my_pwrite(block->hash_link->file, - block->buffer + block->offset, - block->length - block->offset, - block->hash_link->diskpos + block->offset, - MYF(MY_NABP | MY_WAIT_IF_FULL)); - mysql_mutex_lock(&keycache->cache_lock); - - /* Block status must not have changed. */ - DBUG_ASSERT((block->status & ~BLOCK_IN_EVICTION) == - (BLOCK_READ | BLOCK_IN_SWITCH | - BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE | - BLOCK_CHANGED | BLOCK_IN_USE) || fail_block(block)); - keycache->global_cache_write++; - } - } - - block->status|= BLOCK_REASSIGNED; - /* - The block comes from the LRU ring. It must have a hash_link - assigned. - */ - DBUG_ASSERT(block->hash_link); - if (block->hash_link) - { - /* - All pending requests for this page must be resubmitted. - This must be done before waiting for readers. They could - wait for the flush to complete. And we must also do it - after the wait. Flushers might try to free the block while - we wait. They would wait until the reassignment is - complete. Also the block status must reflect the correct - situation: The block is not changed nor in flush any more. - Note that we must not change the BLOCK_CHANGED flag - outside of link_to_file_list() so that it is always in the - correct queue and the *blocks_changed counters are - correct. - */ - block->status&= ~(BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE); - link_to_file_list(keycache, block, block->hash_link->file, 1); - release_whole_queue(&block->wqueue[COND_FOR_SAVED]); - /* - The block is still assigned to its old hash_link. - Wait until all pending read requests - for this page are executed - (we could have avoided this waiting, if we had read - a page in the cache in a sweep, without yielding control) - */ - wait_for_readers(keycache, block, thread); - DBUG_ASSERT(block->hash_link && block->hash_link->block == block && - block->prev_changed); - /* The reader must not have been a writer. */ - DBUG_ASSERT(!(block->status & BLOCK_CHANGED)); - - /* Wake flushers that might have found the block in between. */ - release_whole_queue(&block->wqueue[COND_FOR_SAVED]); - - /* Remove the hash link for the old file block from the hash. */ - unlink_hash(keycache, block->hash_link); - - /* - For sanity checks link_to_file_list() asserts that block - and hash_link refer to each other. Hence we need to assign - the hash_link first, but then we would not know if it was - linked before. Hence we would not know if to unlink it. So - unlink it here and call link_to_file_list(..., FALSE). - */ - unlink_changed(block); - } - block->status= error ? BLOCK_ERROR : BLOCK_IN_USE ; - block->length= 0; - block->offset= keycache->key_cache_block_size; - block->hash_link= hash_link; - link_to_file_list(keycache, block, file, 0); - page_status= PAGE_TO_BE_READ; - - DBUG_ASSERT(block->hash_link->block == block); - DBUG_ASSERT(hash_link->block->hash_link == hash_link); - } - else - { - /* - Either (block->hash_link == hash_link), - or (block->status & BLOCK_IN_SWITCH). - - This is for secondary requests for a new file block only. - Either it is already assigned to the new hash_link meanwhile - (if we had to wait due to empty LRU), or it is already in - eviction by another thread. Since this block has been - grabbed from the LRU ring and attached to this hash_link, - another thread cannot grab the same block from the LRU ring - anymore. If the block is in eviction already, it must become - attached to the same hash_link and as such destined for the - same file block. - */ - page_status= (((block->hash_link == hash_link) && - (block->status & BLOCK_READ)) ? - PAGE_READ : PAGE_WAIT_TO_BE_READ); - } - } - } - else - { - /* - Block is not NULL. This hash_link points to a block. - Either - - block not assigned to this hash_link (yet) or - - block assigned but not yet read from file, - or - - block assigned with valid (changed or unchanged) data and - - it will not be reassigned/freed. - - The first condition means hash_link points to a block in - eviction. This is not necessarily marked by BLOCK_IN_SWITCH yet. - But then it is marked BLOCK_IN_EVICTION. See the NOTE in - link_block(). In both cases it is destined for this hash_link - and its file block address. When this hash_link got its block - address, the block was removed from the LRU ring and cannot be - selected for eviction (for another hash_link) again. - - Register a request on the block. This is another protection - against eviction. - */ - DBUG_ASSERT(((block->hash_link != hash_link) && - (block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH))) || - ((block->hash_link == hash_link) && - !(block->status & BLOCK_READ)) || - ((block->status & BLOCK_READ) && - !(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH)))); - reg_requests(keycache, block, 1); - page_status= (((block->hash_link == hash_link) && - (block->status & BLOCK_READ)) ? - PAGE_READ : PAGE_WAIT_TO_BE_READ); - } - } - - DBUG_ASSERT(page_status != -1); - /* Same assert basically, but be very sure. */ - DBUG_ASSERT(block); - /* Assert that block has a request and is not in LRU ring. */ - DBUG_ASSERT(block->requests); - DBUG_ASSERT(!block->next_used); - DBUG_ASSERT(!block->prev_used); - /* Assert that we return the correct block. */ - DBUG_ASSERT((page_status == PAGE_WAIT_TO_BE_READ) || - ((block->hash_link->file == file) && - (block->hash_link->diskpos == filepos))); - *page_st=page_status; - DBUG_RETURN(block); -} - - -/* - Read into a key cache block buffer from disk. - - SYNOPSIS - - read_block() - keycache pointer to a key cache data structure - thread_var pointer to thread specific variables - block block to which buffer the data is to be read - read_length size of data to be read - min_length at least so much data must be read - primary <-> the current thread will read the data - - RETURN VALUE - None - - NOTES. - The function either reads a page data from file to the block buffer, - or waits until another thread reads it. What page to read is determined - by a block parameter - reference to a hash link for this page. - If an error occurs THE BLOCK_ERROR bit is set in the block status. - We do not report error when the size of successfully read - portion is less than read_length, but not less than min_length. -*/ - -static void read_block(KEY_CACHE *keycache, - st_keycache_thread_var *thread_var, - BLOCK_LINK *block, uint read_length, - uint min_length, my_bool primary) -{ - size_t got_length; - - /* On entry cache_lock is locked */ - - if (primary) - { - /* - This code is executed only by threads that submitted primary - requests. Until block->status contains BLOCK_READ, all other - request for the block become secondary requests. For a primary - request the block must be properly initialized. - */ - DBUG_ASSERT(((block->status & ~BLOCK_FOR_UPDATE) == BLOCK_IN_USE) || - fail_block(block)); - DBUG_ASSERT((block->length == 0) || fail_block(block)); - DBUG_ASSERT((block->offset == keycache->key_cache_block_size) || - fail_block(block)); - DBUG_ASSERT((block->requests > 0) || fail_block(block)); - - keycache->global_cache_read++; - /* Page is not in buffer yet, is to be read from disk */ - mysql_mutex_unlock(&keycache->cache_lock); - /* - Here other threads may step in and register as secondary readers. - They will register in block->wqueue[COND_FOR_REQUESTED]. - */ - got_length= my_pread(block->hash_link->file, block->buffer, - read_length, block->hash_link->diskpos, MYF(0)); - mysql_mutex_lock(&keycache->cache_lock); - /* - The block can now have been marked for free (in case of - FLUSH_RELEASE). Otherwise the state must be unchanged. - */ - DBUG_ASSERT(((block->status & ~(BLOCK_REASSIGNED | - BLOCK_FOR_UPDATE)) == BLOCK_IN_USE) || - fail_block(block)); - DBUG_ASSERT((block->length == 0) || fail_block(block)); - DBUG_ASSERT((block->offset == keycache->key_cache_block_size) || - fail_block(block)); - DBUG_ASSERT((block->requests > 0) || fail_block(block)); - - if (got_length < min_length) - block->status|= BLOCK_ERROR; - else - { - block->status|= BLOCK_READ; - block->length= (int)got_length; - /* - Do not set block->offset here. If this block is marked - BLOCK_CHANGED later, we want to flush only the modified part. So - only a writer may set block->offset down from - keycache->key_cache_block_size. - */ - } - /* Signal that all pending requests for this page now can be processed */ - release_whole_queue(&block->wqueue[COND_FOR_REQUESTED]); - } - else - { - /* - This code is executed only by threads that submitted secondary - requests. At this point it could happen that the cache block is - not yet assigned to the hash_link for the requested file block. - But at awake from the wait this should be the case. Unfortunately - we cannot assert this here because we do not know the hash_link - for the requested file block nor the file and position. So we have - to assert this in the caller. - */ - wait_on_queue(&block->wqueue[COND_FOR_REQUESTED], &keycache->cache_lock, - thread_var); - } -} - - -/* - Read a block of data from a cached file into a buffer; - - SYNOPSIS - - key_cache_read() - keycache pointer to a key cache data structure - thread_var pointer to thread specific variables - file handler for the file for the block of data to be read - filepos position of the block of data in the file - level determines the weight of the data - buff buffer to where the data must be placed - length length of the buffer - block_length length of the block in the key cache buffer - return_buffer return pointer to the key cache buffer with the data - - RETURN VALUE - Returns address from where the data is placed if sucessful, 0 - otherwise. - - NOTES. - The function ensures that a block of data of size length from file - positioned at filepos is in the buffers for some key cache blocks. - Then the function either copies the data into the buffer buff, or, - if return_buffer is TRUE, it just returns the pointer to the key cache - buffer with the data. - Filepos must be a multiple of 'block_length', but it doesn't - have to be a multiple of key_cache_block_size; -*/ - -uchar *key_cache_read(KEY_CACHE *keycache, - st_keycache_thread_var *thread_var, - File file, my_off_t filepos, int level, - uchar *buff, uint length, - uint block_length MY_ATTRIBUTE((unused)), - int return_buffer MY_ATTRIBUTE((unused))) -{ - my_bool locked_and_incremented= FALSE; - int error=0; - uchar *start= buff; - DBUG_ENTER("key_cache_read"); - DBUG_PRINT("enter", ("fd: %u pos: %lu length: %u", - (uint) file, (ulong) filepos, length)); - - if (keycache->key_cache_inited) - { - /* Key cache is used */ - BLOCK_LINK *block; - uint read_length; - uint offset; - int page_st; - - if (MYSQL_KEYCACHE_READ_START_ENABLED()) - { - MYSQL_KEYCACHE_READ_START(my_filename(file), length, - (ulong) (keycache->blocks_used * - keycache->key_cache_block_size), - (ulong) (keycache->blocks_unused * - keycache->key_cache_block_size)); - } - - /* - When the key cache is once initialized, we use the cache_lock to - reliably distinguish the cases of normal operation, resizing, and - disabled cache. We always increment and decrement - 'cnt_for_resize_op' so that a resizer can wait for pending I/O. - */ - mysql_mutex_lock(&keycache->cache_lock); - /* - Cache resizing has two phases: Flushing and re-initializing. In - the flush phase read requests are allowed to bypass the cache for - blocks not in the cache. find_key_block() returns NULL in this - case. - - After the flush phase new I/O requests must wait until the - re-initialization is done. The re-initialization can be done only - if no I/O request is in progress. The reason is that - key_cache_block_size can change. With enabled cache, I/O is done - in chunks of key_cache_block_size. Every chunk tries to use a - cache block first. If the block size changes in the middle, a - block could be missed and old data could be read. - */ - while (keycache->in_resize && !keycache->resize_in_flush) - wait_on_queue(&keycache->resize_queue, &keycache->cache_lock, - thread_var); - /* Register the I/O for the next resize. */ - inc_counter_for_resize_op(keycache); - locked_and_incremented= TRUE; - /* Requested data may not always be aligned to cache blocks. */ - offset= (uint) (filepos % keycache->key_cache_block_size); - /* Read data in key_cache_block_size increments */ - do - { - /* Cache could be disabled in a later iteration. */ - if (!keycache->can_be_used) - { - goto no_key_cache; - } - /* Start reading at the beginning of the cache block. */ - filepos-= offset; - /* Do not read beyond the end of the cache block. */ - read_length= length; - set_if_smaller(read_length, keycache->key_cache_block_size-offset); - DBUG_ASSERT(read_length > 0); - - if (block_length > keycache->key_cache_block_size || offset) - return_buffer=0; - - /* Request the cache block that matches file/pos. */ - keycache->global_cache_r_requests++; - - MYSQL_KEYCACHE_READ_BLOCK(keycache->key_cache_block_size); - - block= find_key_block(keycache, thread_var, file, filepos, level, 0, - &page_st); - if (!block) - { - /* - This happens only for requests submitted during key cache - resize. The block is not in the cache and shall not go in. - Read directly from file. - */ - keycache->global_cache_read++; - mysql_mutex_unlock(&keycache->cache_lock); - error= (my_pread(file, (uchar*) buff, read_length, - filepos + offset, MYF(MY_NABP)) != 0); - mysql_mutex_lock(&keycache->cache_lock); - goto next_block; - } - if (!(block->status & BLOCK_ERROR)) - { - if (page_st != PAGE_READ) - { - MYSQL_KEYCACHE_READ_MISS(); - /* The requested page is to be read into the block buffer */ - read_block(keycache, thread_var, block, - keycache->key_cache_block_size, read_length+offset, - (my_bool)(page_st == PAGE_TO_BE_READ)); - /* - A secondary request must now have the block assigned to the - requested file block. It does not hurt to check it for - primary requests too. - */ - DBUG_ASSERT(keycache->can_be_used); - DBUG_ASSERT(block->hash_link->file == file); - DBUG_ASSERT(block->hash_link->diskpos == filepos); - DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); - } - else if (block->length < read_length + offset) - { - /* - Impossible if nothing goes wrong: - this could only happen if we are using a file with - small key blocks and are trying to read outside the file - */ - set_my_errno(-1); - block->status|= BLOCK_ERROR; - } - else - { - MYSQL_KEYCACHE_READ_HIT(); - } - } - - /* block status may have added BLOCK_ERROR in the above 'if'. */ - if (!(block->status & BLOCK_ERROR)) - { - { - DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); - mysql_mutex_unlock(&keycache->cache_lock); - - /* Copy data from the cache buffer */ - memcpy(buff, block->buffer+offset, (size_t) read_length); - - mysql_mutex_lock(&keycache->cache_lock); - DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); - } - } - - remove_reader(block); - - /* Error injection for coverage testing. */ - DBUG_EXECUTE_IF("key_cache_read_block_error", - block->status|= BLOCK_ERROR;); - - /* Do not link erroneous blocks into the LRU ring, but free them. */ - if (!(block->status & BLOCK_ERROR)) - { - /* - Link the block into the LRU ring if it's the last submitted - request for the block. This enables eviction for the block. - */ - unreg_request(keycache, block, 1); - } - else - { - free_block(keycache, thread_var, block); - error= 1; - break; - } - - next_block: - buff+= read_length; - filepos+= read_length+offset; - offset= 0; - - } while ((length-= read_length)); - if (MYSQL_KEYCACHE_READ_DONE_ENABLED()) - { - MYSQL_KEYCACHE_READ_DONE((ulong) (keycache->blocks_used * - keycache->key_cache_block_size), - (ulong) (keycache->blocks_unused * - keycache->key_cache_block_size)); - } - goto end; - } - -no_key_cache: - /* Key cache is not used */ - - keycache->global_cache_r_requests++; - keycache->global_cache_read++; - - if (locked_and_incremented) - mysql_mutex_unlock(&keycache->cache_lock); - if (my_pread(file, (uchar*) buff, length, filepos, MYF(MY_NABP))) - error= 1; - if (locked_and_incremented) - mysql_mutex_lock(&keycache->cache_lock); - -end: - if (locked_and_incremented) - { - dec_counter_for_resize_op(keycache); - mysql_mutex_unlock(&keycache->cache_lock); - } - DBUG_PRINT("exit", ("error: %d", error )); - DBUG_RETURN(error ? (uchar*) 0 : start); -} - - -/* - Insert a block of file data from a buffer into key cache - - SYNOPSIS - key_cache_insert() - keycache pointer to a key cache data structure - thread_var pointer to thread specific variables - file handler for the file to insert data from - filepos position of the block of data in the file to insert - level determines the weight of the data - buff buffer to read data from - length length of the data in the buffer - - NOTES - This is used by MyISAM to move all blocks from a index file to the key - cache - - RETURN VALUE - 0 if a success, 1 - otherwise. -*/ - -int key_cache_insert(KEY_CACHE *keycache, - st_keycache_thread_var *thread_var, - File file, my_off_t filepos, int level, - uchar *buff, uint length) -{ - int error= 0; - DBUG_ENTER("key_cache_insert"); - DBUG_PRINT("enter", ("fd: %u pos: %lu length: %u", - (uint) file,(ulong) filepos, length)); - - if (keycache->key_cache_inited) - { - /* Key cache is used */ - BLOCK_LINK *block; - uint read_length; - uint offset; - int page_st; - my_bool locked_and_incremented= FALSE; - - /* - When the keycache is once initialized, we use the cache_lock to - reliably distinguish the cases of normal operation, resizing, and - disabled cache. We always increment and decrement - 'cnt_for_resize_op' so that a resizer can wait for pending I/O. - */ - mysql_mutex_lock(&keycache->cache_lock); - /* - We do not load index data into a disabled cache nor into an - ongoing resize. - */ - if (!keycache->can_be_used || keycache->in_resize) - goto no_key_cache; - /* Register the pseudo I/O for the next resize. */ - inc_counter_for_resize_op(keycache); - locked_and_incremented= TRUE; - /* Loaded data may not always be aligned to cache blocks. */ - offset= (uint) (filepos % keycache->key_cache_block_size); - /* Load data in key_cache_block_size increments. */ - do - { - /* Cache could be disabled or resizing in a later iteration. */ - if (!keycache->can_be_used || keycache->in_resize) - goto no_key_cache; - /* Start loading at the beginning of the cache block. */ - filepos-= offset; - /* Do not load beyond the end of the cache block. */ - read_length= length; - set_if_smaller(read_length, keycache->key_cache_block_size-offset); - DBUG_ASSERT(read_length > 0); - - /* The block has been read by the caller already. */ - keycache->global_cache_read++; - /* Request the cache block that matches file/pos. */ - keycache->global_cache_r_requests++; - block= find_key_block(keycache, thread_var, file, filepos, level, 0, - &page_st); - if (!block) - { - /* - This happens only for requests submitted during key cache - resize. The block is not in the cache and shall not go in. - Stop loading index data. - */ - goto no_key_cache; - } - if (!(block->status & BLOCK_ERROR)) - { - if ((page_st == PAGE_WAIT_TO_BE_READ) || - ((page_st == PAGE_TO_BE_READ) && - (offset || (read_length < keycache->key_cache_block_size)))) - { - /* - Either - - this is a secondary request for a block to be read into the - cache. The block is in eviction. It is not yet assigned to - the requested file block (It does not point to the right - hash_link). So we cannot call remove_reader() on the block. - And we cannot access the hash_link directly here. We need to - wait until the assignment is complete. read_block() executes - the correct wait when called with primary == FALSE. - - Or - - this is a primary request for a block to be read into the - cache and the supplied data does not fill the whole block. - - This function is called on behalf of a LOAD INDEX INTO CACHE - statement, which is a read-only task and allows other - readers. It is possible that a parallel running reader tries - to access this block. If it needs more data than has been - supplied here, it would report an error. To be sure that we - have all data in the block that is available in the file, we - read the block ourselves. - - Though reading again what the caller did read already is an - expensive operation, we need to do this for correctness. - */ - read_block(keycache, thread_var, block, - keycache->key_cache_block_size, - read_length + offset, (page_st == PAGE_TO_BE_READ)); - /* - A secondary request must now have the block assigned to the - requested file block. It does not hurt to check it for - primary requests too. - */ - DBUG_ASSERT(keycache->can_be_used); - DBUG_ASSERT(block->hash_link->file == file); - DBUG_ASSERT(block->hash_link->diskpos == filepos); - DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); - } - else if (page_st == PAGE_TO_BE_READ) - { - /* - This is a new block in the cache. If we come here, we have - data for the whole block. - */ - DBUG_ASSERT(block->hash_link->requests); - DBUG_ASSERT(block->status & BLOCK_IN_USE); - DBUG_ASSERT((page_st == PAGE_TO_BE_READ) || - (block->status & BLOCK_READ)); - - mysql_mutex_unlock(&keycache->cache_lock); - /* - Here other threads may step in and register as secondary readers. - They will register in block->wqueue[COND_FOR_REQUESTED]. - */ - - /* Copy data from buff */ - memcpy(block->buffer+offset, buff, (size_t) read_length); - - mysql_mutex_lock(&keycache->cache_lock); - DBUG_ASSERT(block->status & BLOCK_IN_USE); - DBUG_ASSERT((page_st == PAGE_TO_BE_READ) || - (block->status & BLOCK_READ)); - /* - After the data is in the buffer, we can declare the block - valid. Now other threads do not need to register as - secondary readers any more. They can immediately access the - block. - */ - block->status|= BLOCK_READ; - block->length= read_length+offset; - /* - Do not set block->offset here. If this block is marked - BLOCK_CHANGED later, we want to flush only the modified part. So - only a writer may set block->offset down from - keycache->key_cache_block_size. - */ - /* Signal all pending requests. */ - release_whole_queue(&block->wqueue[COND_FOR_REQUESTED]); - } - else - { - /* - page_st == PAGE_READ. The block is in the buffer. All data - must already be present. Blocks are always read with all - data available on file. Assert that the block does not have - less contents than the preloader supplies. If the caller has - data beyond block->length, it means that a file write has - been done while this block was in cache and not extended - with the new data. If the condition is met, we can simply - ignore the block. - */ - DBUG_ASSERT((page_st == PAGE_READ) && - (read_length + offset <= block->length)); - } - - /* - A secondary request must now have the block assigned to the - requested file block. It does not hurt to check it for primary - requests too. - */ - DBUG_ASSERT(block->hash_link->file == file); - DBUG_ASSERT(block->hash_link->diskpos == filepos); - DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); - } /* end of if (!(block->status & BLOCK_ERROR)) */ - - remove_reader(block); - - /* Error injection for coverage testing. */ - DBUG_EXECUTE_IF("key_cache_insert_block_error", - block->status|= BLOCK_ERROR; errno=EIO;); - - /* Do not link erroneous blocks into the LRU ring, but free them. */ - if (!(block->status & BLOCK_ERROR)) - { - /* - Link the block into the LRU ring if it's the last submitted - request for the block. This enables eviction for the block. - */ - unreg_request(keycache, block, 1); - } - else - { - free_block(keycache, thread_var, block); - error= 1; - break; - } - - buff+= read_length; - filepos+= read_length+offset; - offset= 0; - - } while ((length-= read_length)); - - no_key_cache: - if (locked_and_incremented) - dec_counter_for_resize_op(keycache); - mysql_mutex_unlock(&keycache->cache_lock); - } - DBUG_RETURN(error); -} - - -/* - Write a buffer into a cached file. - - SYNOPSIS - - key_cache_write() - keycache pointer to a key cache data structure - thread_var pointer to thread specific variables - file handler for the file to write data to - filepos position in the file to write data to - level determines the weight of the data - buff buffer with the data - length length of the buffer - dont_write if is 0 then all dirty pages involved in writing - should have been flushed from key cache - - RETURN VALUE - 0 if a success, 1 - otherwise. - - NOTES. - The function copies the data of size length from buff into buffers - for key cache blocks that are assigned to contain the portion of - the file starting with position filepos. - It ensures that this data is flushed to the file if dont_write is FALSE. - Filepos must be a multiple of 'block_length', but it doesn't - have to be a multiple of key_cache_block_size; - - dont_write is always TRUE in the server (info->lock_type is never F_UNLCK). -*/ - -int key_cache_write(KEY_CACHE *keycache, - st_keycache_thread_var *thread_var, - File file, my_off_t filepos, int level, - uchar *buff, uint length, - uint block_length MY_ATTRIBUTE((unused)), - int dont_write) -{ - my_bool locked_and_incremented= FALSE; - int error=0; - DBUG_ENTER("key_cache_write"); - DBUG_PRINT("enter", - ("fd: %u pos: %lu length: %u block_length: %u" - " key_block_length: %u", - (uint) file, (ulong) filepos, length, block_length, - keycache ? keycache->key_cache_block_size : 0)); - - if (!dont_write) - { - /* purecov: begin inspected */ - /* Not used in the server. */ - /* Force writing from buff into disk. */ - keycache->global_cache_w_requests++; - keycache->global_cache_write++; - if (my_pwrite(file, buff, length, filepos, MYF(MY_NABP | MY_WAIT_IF_FULL))) - DBUG_RETURN(1); - /* purecov: end */ - } - - if (keycache->key_cache_inited) - { - /* Key cache is used */ - BLOCK_LINK *block; - uint read_length; - uint offset; - int page_st; - - if (MYSQL_KEYCACHE_WRITE_START_ENABLED()) - { - MYSQL_KEYCACHE_WRITE_START(my_filename(file), length, - (ulong) (keycache->blocks_used * - keycache->key_cache_block_size), - (ulong) (keycache->blocks_unused * - keycache->key_cache_block_size)); - } - - /* - When the key cache is once initialized, we use the cache_lock to - reliably distinguish the cases of normal operation, resizing, and - disabled cache. We always increment and decrement - 'cnt_for_resize_op' so that a resizer can wait for pending I/O. - */ - mysql_mutex_lock(&keycache->cache_lock); - /* - Cache resizing has two phases: Flushing and re-initializing. In - the flush phase write requests can modify dirty blocks that are - not yet in flush. Otherwise they are allowed to bypass the cache. - find_key_block() returns NULL in both cases (clean blocks and - non-cached blocks). - - After the flush phase new I/O requests must wait until the - re-initialization is done. The re-initialization can be done only - if no I/O request is in progress. The reason is that - key_cache_block_size can change. With enabled cache I/O is done in - chunks of key_cache_block_size. Every chunk tries to use a cache - block first. If the block size changes in the middle, a block - could be missed and data could be written below a cached block. - */ - while (keycache->in_resize && !keycache->resize_in_flush) - wait_on_queue(&keycache->resize_queue, &keycache->cache_lock, - thread_var); - /* Register the I/O for the next resize. */ - inc_counter_for_resize_op(keycache); - locked_and_incremented= TRUE; - /* Requested data may not always be aligned to cache blocks. */ - offset= (uint) (filepos % keycache->key_cache_block_size); - /* Write data in key_cache_block_size increments. */ - do - { - /* Cache could be disabled in a later iteration. */ - if (!keycache->can_be_used) - goto no_key_cache; - - MYSQL_KEYCACHE_WRITE_BLOCK(keycache->key_cache_block_size); - /* Start writing at the beginning of the cache block. */ - filepos-= offset; - /* Do not write beyond the end of the cache block. */ - read_length= length; - set_if_smaller(read_length, keycache->key_cache_block_size-offset); - DBUG_ASSERT(read_length > 0); - - /* Request the cache block that matches file/pos. */ - keycache->global_cache_w_requests++; - block= find_key_block(keycache, thread_var, file, filepos, level, 1, - &page_st); - if (!block) - { - /* - This happens only for requests submitted during key cache - resize. The block is not in the cache and shall not go in. - Write directly to file. - */ - if (dont_write) - { - /* Used in the server. */ - keycache->global_cache_write++; - mysql_mutex_unlock(&keycache->cache_lock); - if (my_pwrite(file, (uchar*) buff, read_length, filepos + offset, - MYF(MY_NABP | MY_WAIT_IF_FULL))) - error=1; - mysql_mutex_lock(&keycache->cache_lock); - } - goto next_block; - } - /* - Prevent block from flushing and from being selected for to be - freed. This must be set when we release the cache_lock. - However, we must not set the status of the block before it is - assigned to this file/pos. - */ - if (page_st != PAGE_WAIT_TO_BE_READ) - block->status|= BLOCK_FOR_UPDATE; - /* - We must read the file block first if it is not yet in the cache - and we do not replace all of its contents. - - In cases where the cache block is big enough to contain (parts - of) index blocks of different indexes, our request can be - secondary (PAGE_WAIT_TO_BE_READ). In this case another thread is - reading the file block. If the read completes after us, it - overwrites our new contents with the old contents. So we have to - wait for the other thread to complete the read of this block. - read_block() takes care for the wait. - */ - if (!(block->status & BLOCK_ERROR) && - ((page_st == PAGE_TO_BE_READ && - (offset || read_length < keycache->key_cache_block_size)) || - (page_st == PAGE_WAIT_TO_BE_READ))) - { - read_block(keycache, thread_var, block, - offset + read_length >= keycache->key_cache_block_size? - offset : keycache->key_cache_block_size, - offset, (page_st == PAGE_TO_BE_READ)); - DBUG_ASSERT(keycache->can_be_used); - DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); - /* - Prevent block from flushing and from being selected for to be - freed. This must be set when we release the cache_lock. - Here we set it in case we could not set it above. - */ - block->status|= BLOCK_FOR_UPDATE; - } - /* - The block should always be assigned to the requested file block - here. It need not be BLOCK_READ when overwriting the whole block. - */ - DBUG_ASSERT(block->hash_link->file == file); - DBUG_ASSERT(block->hash_link->diskpos == filepos); - DBUG_ASSERT(block->status & BLOCK_IN_USE); - DBUG_ASSERT((page_st == PAGE_TO_BE_READ) || (block->status & BLOCK_READ)); - /* - The block to be written must not be marked BLOCK_REASSIGNED. - Otherwise it could be freed in dirty state or reused without - another flush during eviction. It must also not be in flush. - Otherwise the old contens may have been flushed already and - the flusher could clear BLOCK_CHANGED without flushing the - new changes again. - */ - DBUG_ASSERT(!(block->status & BLOCK_REASSIGNED)); - - while (block->status & BLOCK_IN_FLUSHWRITE) - { - /* - Another thread is flushing the block. It was dirty already. - Wait until the block is flushed to file. Otherwise we could - modify the buffer contents just while it is written to file. - An unpredictable file block contents would be the result. - While we wait, several things can happen to the block, - including another flush. But the block cannot be reassigned to - another hash_link until we release our request on it. - */ - wait_on_queue(&block->wqueue[COND_FOR_SAVED], &keycache->cache_lock, - thread_var); - DBUG_ASSERT(keycache->can_be_used); - DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); - /* Still must not be marked for free. */ - DBUG_ASSERT(!(block->status & BLOCK_REASSIGNED)); - DBUG_ASSERT(block->hash_link && (block->hash_link->block == block)); - } - - /* - We could perhaps release the cache_lock during access of the - data like in the other functions. Locks outside of the key cache - assure that readers and a writer do not access the same range of - data. Parallel accesses should happen only if the cache block - contains multiple index block(fragment)s. So different parts of - the buffer would be read/written. An attempt to flush during - memcpy() is prevented with BLOCK_FOR_UPDATE. - */ - if (!(block->status & BLOCK_ERROR)) - { - mysql_mutex_unlock(&keycache->cache_lock); - memcpy(block->buffer+offset, buff, (size_t) read_length); - - mysql_mutex_lock(&keycache->cache_lock); - } - - if (!dont_write) - { - /* Not used in the server. buff has been written to disk at start. */ - if ((block->status & BLOCK_CHANGED) && - (!offset && read_length >= keycache->key_cache_block_size)) - link_to_file_list(keycache, block, block->hash_link->file, 1); - } - else if (! (block->status & BLOCK_CHANGED)) - link_to_changed_list(keycache, block); - block->status|=BLOCK_READ; - /* - Allow block to be selected for to be freed. Since it is marked - BLOCK_CHANGED too, it won't be selected for to be freed without - a flush. - */ - block->status&= ~BLOCK_FOR_UPDATE; - set_if_smaller(block->offset, offset); - set_if_bigger(block->length, read_length+offset); - - /* Threads may be waiting for the changes to be complete. */ - release_whole_queue(&block->wqueue[COND_FOR_REQUESTED]); - - /* - If only a part of the cache block is to be replaced, and the - rest has been read from file, then the cache lock has been - released for I/O and it could be possible that another thread - wants to evict or free the block and waits for it to be - released. So we must not just decrement hash_link->requests, but - also wake a waiting thread. - */ - remove_reader(block); - - /* Error injection for coverage testing. */ - DBUG_EXECUTE_IF("key_cache_write_block_error", - block->status|= BLOCK_ERROR;); - - /* Do not link erroneous blocks into the LRU ring, but free them. */ - if (!(block->status & BLOCK_ERROR)) - { - /* - Link the block into the LRU ring if it's the last submitted - request for the block. This enables eviction for the block. - */ - unreg_request(keycache, block, 1); - } - else - { - /* Pretend a "clean" block to avoid complications. */ - block->status&= ~(BLOCK_CHANGED); - free_block(keycache, thread_var, block); - error= 1; - break; - } - - next_block: - buff+= read_length; - filepos+= read_length+offset; - offset= 0; - - } while ((length-= read_length)); - goto end; - } - -no_key_cache: - /* Key cache is not used */ - if (dont_write) - { - /* Used in the server. */ - keycache->global_cache_w_requests++; - keycache->global_cache_write++; - if (locked_and_incremented) - mysql_mutex_unlock(&keycache->cache_lock); - if (my_pwrite(file, (uchar*) buff, length, filepos, - MYF(MY_NABP | MY_WAIT_IF_FULL))) - error=1; - if (locked_and_incremented) - mysql_mutex_lock(&keycache->cache_lock); - } - -end: - if (locked_and_incremented) - { - dec_counter_for_resize_op(keycache); - mysql_mutex_unlock(&keycache->cache_lock); - } - - if (MYSQL_KEYCACHE_WRITE_DONE_ENABLED()) - { - MYSQL_KEYCACHE_WRITE_DONE((ulong) (keycache->blocks_used * - keycache->key_cache_block_size), - (ulong) (keycache->blocks_unused * - keycache->key_cache_block_size)); - } - - DBUG_RETURN(error); -} - - -/* - Free block. - - SYNOPSIS - free_block() - keycache Pointer to a key cache data structure - thread_var Pointer to thread specific variables - block Pointer to the block to free - - DESCRIPTION - Remove reference to block from hash table. - Remove block from the chain of clean blocks. - Add block to the free list. - - NOTE - Block must not be free (status == 0). - Block must not be in free_block_list. - Block must not be in the LRU ring. - Block must not be in eviction (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH). - Block must not be in free (BLOCK_REASSIGNED). - Block must not be in flush (BLOCK_IN_FLUSH). - Block must not be dirty (BLOCK_CHANGED). - Block must not be in changed_blocks (dirty) hash. - Block must be in file_blocks (clean) hash. - Block must refer to a hash_link. - Block must have a request registered on it. -*/ - -static void free_block(KEY_CACHE *keycache, - st_keycache_thread_var *thread_var, - BLOCK_LINK *block) -{ - /* - Assert that the block is not free already. And that it is in a clean - state. Note that the block might just be assigned to a hash_link and - not yet read (BLOCK_READ may not be set here). In this case a reader - is registered in the hash_link and free_block() will wait for it - below. - */ - DBUG_ASSERT((block->status & BLOCK_IN_USE) && - !(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | - BLOCK_REASSIGNED | BLOCK_IN_FLUSH | - BLOCK_CHANGED | BLOCK_FOR_UPDATE))); - /* Assert that the block is in a file_blocks chain. */ - DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); - /* Assert that the block is not in the LRU ring. */ - DBUG_ASSERT(!block->next_used && !block->prev_used); - /* - IMHO the below condition (if()) makes no sense. I can't see how it - could be possible that free_block() is entered with a NULL hash_link - pointer. The only place where it can become NULL is in free_block() - (or before its first use ever, but for those blocks free_block() is - not called). I don't remove the conditional as it cannot harm, but - place an DBUG_ASSERT to confirm my hypothesis. Eventually the - condition (if()) can be removed. - */ - DBUG_ASSERT(block->hash_link && block->hash_link->block == block); - if (block->hash_link) - { - /* - While waiting for readers to finish, new readers might request the - block. But since we set block->status|= BLOCK_REASSIGNED, they - will wait on block->wqueue[COND_FOR_SAVED]. They must be signalled - later. - */ - block->status|= BLOCK_REASSIGNED; - wait_for_readers(keycache, block, thread_var); - /* - The block must not have been freed by another thread. Repeat some - checks. An additional requirement is that it must be read now - (BLOCK_READ). - */ - DBUG_ASSERT(block->hash_link && block->hash_link->block == block); - DBUG_ASSERT((block->status & (BLOCK_READ | BLOCK_IN_USE | - BLOCK_REASSIGNED)) && - !(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | - BLOCK_IN_FLUSH | BLOCK_CHANGED | - BLOCK_FOR_UPDATE))); - DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); - DBUG_ASSERT(!block->prev_used); - /* - Unset BLOCK_REASSIGNED again. If we hand the block to an evicting - thread (through unreg_request() below), other threads must not see - this flag. They could become confused. - */ - block->status&= ~BLOCK_REASSIGNED; - /* - Do not release the hash_link until the block is off all lists. - At least not if we hand it over for eviction in unreg_request(). - */ - } - - /* - Unregister the block request and link the block into the LRU ring. - This enables eviction for the block. If the LRU ring was empty and - threads are waiting for a block, then the block wil be handed over - for eviction immediately. Otherwise we will unlink it from the LRU - ring again, without releasing the lock in between. So decrementing - the request counter and updating statistics are the only relevant - operation in this case. Assert that there are no other requests - registered. - */ - DBUG_ASSERT(block->requests == 1); - unreg_request(keycache, block, 0); - /* - Note that even without releasing the cache lock it is possible that - the block is immediately selected for eviction by link_block() and - thus not added to the LRU ring. In this case we must not touch the - block any more. - */ - if (block->status & BLOCK_IN_EVICTION) - return; - - /* Error blocks are not put into the LRU ring. */ - if (!(block->status & BLOCK_ERROR)) - { - /* Here the block must be in the LRU ring. Unlink it again. */ - DBUG_ASSERT(block->next_used && block->prev_used && - *block->prev_used == block); - unlink_block(keycache, block); - } - if (block->temperature == BLOCK_WARM) - keycache->warm_blocks--; - block->temperature= BLOCK_COLD; - - /* Remove from file_blocks hash. */ - unlink_changed(block); - - /* Remove reference to block from hash table. */ - unlink_hash(keycache, block->hash_link); - block->hash_link= NULL; - - block->status= 0; - block->length= 0; - block->offset= keycache->key_cache_block_size; - - /* Enforced by unlink_changed(), but just to be sure. */ - DBUG_ASSERT(!block->next_changed && !block->prev_changed); - /* Enforced by unlink_block(): not in LRU ring nor in free_block_list. */ - DBUG_ASSERT(!block->next_used && !block->prev_used); - /* Insert the free block in the free list. */ - block->next_used= keycache->free_block_list; - keycache->free_block_list= block; - /* Keep track of the number of currently unused blocks. */ - keycache->blocks_unused++; - - /* All pending requests for this page must be resubmitted. */ - release_whole_queue(&block->wqueue[COND_FOR_SAVED]); -} - - -static int cmp_sec_link(BLOCK_LINK **a, BLOCK_LINK **b) -{ - return (((*a)->hash_link->diskpos < (*b)->hash_link->diskpos) ? -1 : - ((*a)->hash_link->diskpos > (*b)->hash_link->diskpos) ? 1 : 0); -} - - -/* - Flush a portion of changed blocks to disk, - free used blocks if requested -*/ - -static int flush_cached_blocks(KEY_CACHE *keycache, - st_keycache_thread_var *thread_var, - File file, BLOCK_LINK **cache, - BLOCK_LINK **end, - enum flush_type type) -{ - int error; - int last_errno= 0; - uint count= (uint) (end-cache); - - /* Don't lock the cache during the flush */ - mysql_mutex_unlock(&keycache->cache_lock); - /* - As all blocks referred in 'cache' are marked by BLOCK_IN_FLUSH - we are guarunteed no thread will change them - */ - my_qsort((uchar*) cache, count, sizeof(*cache), (qsort_cmp) cmp_sec_link); - - mysql_mutex_lock(&keycache->cache_lock); - /* - Note: Do not break the loop. We have registered a request on every - block in 'cache'. These must be unregistered by free_block() or - unreg_request(). - */ - for ( ; cache != end ; cache++) - { - BLOCK_LINK *block= *cache; - - /* - If the block contents is going to be changed, we abandon the flush - for this block. flush_key_blocks_int() will restart its search and - handle the block properly. - */ - if (!(block->status & BLOCK_FOR_UPDATE)) - { - /* Blocks coming here must have a certain status. */ - DBUG_ASSERT(block->hash_link); - DBUG_ASSERT(block->hash_link->block == block); - DBUG_ASSERT(block->hash_link->file == file); - DBUG_ASSERT((block->status & ~BLOCK_IN_EVICTION) == - (BLOCK_READ | BLOCK_IN_FLUSH | BLOCK_CHANGED | BLOCK_IN_USE)); - block->status|= BLOCK_IN_FLUSHWRITE; - mysql_mutex_unlock(&keycache->cache_lock); - error= (int)my_pwrite(file, block->buffer+block->offset, - block->length - block->offset, - block->hash_link->diskpos+ block->offset, - MYF(MY_NABP | MY_WAIT_IF_FULL)); - mysql_mutex_lock(&keycache->cache_lock); - keycache->global_cache_write++; - if (error) - { - block->status|= BLOCK_ERROR; - if (!last_errno) - last_errno= errno ? errno : -1; - } - block->status&= ~BLOCK_IN_FLUSHWRITE; - /* Block must not have changed status except BLOCK_FOR_UPDATE. */ - DBUG_ASSERT(block->hash_link); - DBUG_ASSERT(block->hash_link->block == block); - DBUG_ASSERT(block->hash_link->file == file); - DBUG_ASSERT((block->status & ~(BLOCK_FOR_UPDATE | BLOCK_IN_EVICTION)) == - (BLOCK_READ | BLOCK_IN_FLUSH | BLOCK_CHANGED | BLOCK_IN_USE)); - /* - Set correct status and link in right queue for free or later use. - free_block() must not see BLOCK_CHANGED and it may need to wait - for readers of the block. These should not see the block in the - wrong hash. If not freeing the block, we need to have it in the - right queue anyway. - */ - link_to_file_list(keycache, block, file, 1); - } - block->status&= ~BLOCK_IN_FLUSH; - /* - Let to proceed for possible waiting requests to write to the block page. - It might happen only during an operation to resize the key cache. - */ - release_whole_queue(&block->wqueue[COND_FOR_SAVED]); - /* type will never be FLUSH_IGNORE_CHANGED here */ - if (!(type == FLUSH_KEEP || type == FLUSH_FORCE_WRITE) && - !(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | - BLOCK_FOR_UPDATE))) - { - /* - Note that a request has been registered against the block in - flush_key_blocks_int(). - */ - free_block(keycache, thread_var, block); - } - else - { - /* - Link the block into the LRU ring if it's the last submitted - request for the block. This enables eviction for the block. - Note that a request has been registered against the block in - flush_key_blocks_int(). - */ - unreg_request(keycache, block, 1); - } - - } /* end of for ( ; cache != end ; cache++) */ - return last_errno; -} - - -/* - Flush all key blocks for a file to disk, but don't do any mutex locks. - - SYNOPSIS - flush_key_blocks_int() - keycache pointer to a key cache data structure - thread_var pointer to thread specific variables - file handler for the file to flush to - flush_type type of the flush - - NOTES - This function doesn't do any mutex locks because it needs to be called both - from flush_key_blocks and flush_all_key_blocks (the later one does the - mutex lock in the resize_key_cache() function). - - We do only care about changed blocks that exist when the function is - entered. We do not guarantee that all changed blocks of the file are - flushed if more blocks change while this function is running. - - RETURN - 0 ok - 1 error -*/ - -static int flush_key_blocks_int(KEY_CACHE *keycache, - st_keycache_thread_var *thread_var, - File file, enum flush_type type) -{ - BLOCK_LINK *cache_buff[FLUSH_CACHE],**cache; - int last_errno= 0; - int last_errcnt= 0; - DBUG_ENTER("flush_key_blocks_int"); - DBUG_PRINT("enter",("file: %d blocks_used: %lu blocks_changed: %lu", - file, keycache->blocks_used, keycache->blocks_changed)); - - cache= cache_buff; - if (keycache->disk_blocks > 0) - { - /* Key cache exists and flush is not disabled */ - int error= 0; - uint count= FLUSH_CACHE; - BLOCK_LINK **pos,**end; - BLOCK_LINK *first_in_switch= NULL; - BLOCK_LINK *last_in_flush; - BLOCK_LINK *last_for_update; - BLOCK_LINK *block, *next; -#ifndef DBUG_OFF - uint cnt=0; -#endif - - if (type != FLUSH_IGNORE_CHANGED) - { - /* - Count how many key blocks we have to cache to be able - to flush all dirty pages with minimum seek moves - */ - count= 0; - for (block= keycache->changed_blocks[FILE_HASH(file)] ; - block ; - block= block->next_changed) - { - if ((block->hash_link->file == file) && - !(block->status & BLOCK_IN_FLUSH)) - { - count++; - DBUG_ASSERT(count<= keycache->blocks_used); - } - } - /* - Allocate a new buffer only if its bigger than the one we have. - Assure that we always have some entries for the case that new - changed blocks appear while we need to wait for something. - */ - if ((count > FLUSH_CACHE) && - !(cache= (BLOCK_LINK**) my_malloc(key_memory_KEY_CACHE, - sizeof(BLOCK_LINK*)*count, - MYF(0)))) - cache= cache_buff; - /* - After a restart there could be more changed blocks than now. - So we should not let count become smaller than the fixed buffer. - */ - if (cache == cache_buff) - count= FLUSH_CACHE; - } - - /* Retrieve the blocks and write them to a buffer to be flushed */ -restart: - last_in_flush= NULL; - last_for_update= NULL; - end= (pos= cache)+count; - for (block= keycache->changed_blocks[FILE_HASH(file)] ; - block ; - block= next) - { -#ifndef DBUG_OFF - cnt++; - DBUG_ASSERT(cnt <= keycache->blocks_used); -#endif - next= block->next_changed; - if (block->hash_link->file == file) - { - if (!(block->status & (BLOCK_IN_FLUSH | BLOCK_FOR_UPDATE))) - { - /* - Note: The special handling of BLOCK_IN_SWITCH is obsolete - since we set BLOCK_IN_FLUSH if the eviction includes a - flush. It can be removed in a later version. - */ - if (!(block->status & BLOCK_IN_SWITCH)) - { - /* - We care only for the blocks for which flushing was not - initiated by another thread and which are not in eviction. - Registering a request on the block unlinks it from the LRU - ring and protects against eviction. - */ - reg_requests(keycache, block, 1); - if (type != FLUSH_IGNORE_CHANGED) - { - /* It's not a temporary file */ - if (pos == end) - { - /* - This should happen relatively seldom. Remove the - request because we won't do anything with the block - but restart and pick it again in the next iteration. - */ - unreg_request(keycache, block, 0); - /* - This happens only if there is not enough - memory for the big block - */ - if ((error= flush_cached_blocks(keycache, thread_var, file, - cache, end, type))) - { - /* Do not loop infinitely trying to flush in vain. */ - if ((last_errno == error) && (++last_errcnt > 5)) - goto err; - last_errno= error; - } - /* - Restart the scan as some other thread might have changed - the changed blocks chain: the blocks that were in switch - state before the flush started have to be excluded - */ - goto restart; - } - /* - Mark the block with BLOCK_IN_FLUSH in order not to let - other threads to use it for new pages and interfere with - our sequence of flushing dirty file pages. We must not - set this flag before actually putting the block on the - write burst array called 'cache'. - */ - block->status|= BLOCK_IN_FLUSH; - /* Add block to the array for a write burst. */ - *pos++= block; - } - else - { - /* It's a temporary file */ - DBUG_ASSERT(!(block->status & BLOCK_REASSIGNED)); - /* - free_block() must not be called with BLOCK_CHANGED. Note - that we must not change the BLOCK_CHANGED flag outside of - link_to_file_list() so that it is always in the correct - queue and the *blocks_changed counters are correct. - */ - link_to_file_list(keycache, block, file, 1); - if (!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH))) - { - /* A request has been registered against the block above. */ - free_block(keycache, thread_var, block); - } - else - { - /* - Link the block into the LRU ring if it's the last - submitted request for the block. This enables eviction - for the block. A request has been registered against - the block above. - */ - unreg_request(keycache, block, 1); - } - } - } - else - { - /* - Link the block into a list of blocks 'in switch'. - - WARNING: Here we introduce a place where a changed block - is not in the changed_blocks hash! This is acceptable for - a BLOCK_IN_SWITCH. Never try this for another situation. - Other parts of the key cache code rely on changed blocks - being in the changed_blocks hash. - */ - unlink_changed(block); - link_changed(block, &first_in_switch); - } - } - else if (type != FLUSH_KEEP) - { - /* - During the normal flush at end of statement (FLUSH_KEEP) we - do not need to ensure that blocks in flush or update by - other threads are flushed. They will be flushed by them - later. In all other cases we must assure that we do not have - any changed block of this file in the cache when this - function returns. - */ - if (block->status & BLOCK_IN_FLUSH) - { - /* Remember the last block found to be in flush. */ - last_in_flush= block; - } - else - { - /* Remember the last block found to be selected for update. */ - last_for_update= block; - } - } - } - } - if (pos != cache) - { - if ((error= - flush_cached_blocks(keycache, thread_var, file, cache, pos, type))) - { - /* Do not loop inifnitely trying to flush in vain. */ - if ((last_errno == error) && (++last_errcnt > 5)) - goto err; - last_errno= error; - } - /* - Do not restart here during the normal flush at end of statement - (FLUSH_KEEP). We have now flushed at least all blocks that were - changed when entering this function. In all other cases we must - assure that we do not have any changed block of this file in the - cache when this function returns. - */ - if (type != FLUSH_KEEP) - goto restart; - } - if (last_in_flush) - { - /* - There are no blocks to be flushed by this thread, but blocks in - flush by other threads. Wait until one of the blocks is flushed. - Re-check the condition for last_in_flush. We may have unlocked - the cache_lock in flush_cached_blocks(). The state of the block - could have changed. - */ - if (last_in_flush->status & BLOCK_IN_FLUSH) - wait_on_queue(&last_in_flush->wqueue[COND_FOR_SAVED], - &keycache->cache_lock, thread_var); - /* Be sure not to lose a block. They may be flushed in random order. */ - goto restart; - } - if (last_for_update) - { - /* - There are no blocks to be flushed by this thread, but blocks for - update by other threads. Wait until one of the blocks is updated. - Re-check the condition for last_for_update. We may have unlocked - the cache_lock in flush_cached_blocks(). The state of the block - could have changed. - */ - if (last_for_update->status & BLOCK_FOR_UPDATE) - wait_on_queue(&last_for_update->wqueue[COND_FOR_REQUESTED], - &keycache->cache_lock, thread_var); - /* The block is now changed. Flush it. */ - goto restart; - } - - /* - Wait until the list of blocks in switch is empty. The threads that - are switching these blocks will relink them to clean file chains - while we wait and thus empty the 'first_in_switch' chain. - */ - while (first_in_switch) - { -#ifndef DBUG_OFF - cnt= 0; -#endif - wait_on_queue(&first_in_switch->wqueue[COND_FOR_SAVED], - &keycache->cache_lock, thread_var); -#ifndef DBUG_OFF - cnt++; - DBUG_ASSERT(cnt <= keycache->blocks_used); -#endif - /* - Do not restart here. We have flushed all blocks that were - changed when entering this function and were not marked for - eviction. Other threads have now flushed all remaining blocks in - the course of their eviction. - */ - } - - if (! (type == FLUSH_KEEP || type == FLUSH_FORCE_WRITE)) - { - BLOCK_LINK *last_for_update= NULL; - BLOCK_LINK *last_in_switch= NULL; - uint total_found= 0; - uint found; - - /* - Finally free all clean blocks for this file. - During resize this may be run by two threads in parallel. - */ - do - { - found= 0; - for (block= keycache->file_blocks[FILE_HASH(file)] ; - block ; - block= next) - { - /* Remember the next block. After freeing we cannot get at it. */ - next= block->next_changed; - - /* Changed blocks cannot appear in the file_blocks hash. */ - DBUG_ASSERT(!(block->status & BLOCK_CHANGED)); - if (block->hash_link->file == file) - { - /* We must skip blocks that will be changed. */ - if (block->status & BLOCK_FOR_UPDATE) - { - last_for_update= block; - continue; - } - - /* - We must not free blocks in eviction (BLOCK_IN_EVICTION | - BLOCK_IN_SWITCH) or blocks intended to be freed - (BLOCK_REASSIGNED). - */ - if (!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | - BLOCK_REASSIGNED))) - { - struct st_hash_link *next_hash_link= NULL; - my_off_t next_diskpos= 0; - File next_file= 0; - uint next_status= 0; - uint hash_requests= 0; - - total_found++; - found++; - DBUG_ASSERT(found <= keycache->blocks_used); - - /* - Register a request. This unlinks the block from the LRU - ring and protects it against eviction. This is required - by free_block(). - */ - reg_requests(keycache, block, 1); - - /* - free_block() may need to wait for readers of the block. - This is the moment where the other thread can move the - 'next' block from the chain. free_block() needs to wait - if there are requests for the block pending. - */ - if (next && (hash_requests= block->hash_link->requests)) - { - /* Copy values from the 'next' block and its hash_link. */ - next_status= next->status; - next_hash_link= next->hash_link; - next_diskpos= next_hash_link->diskpos; - next_file= next_hash_link->file; - DBUG_ASSERT(next == next_hash_link->block); - } - - free_block(keycache, thread_var, block); - /* - If we had to wait and the state of the 'next' block - changed, break the inner loop. 'next' may no longer be - part of the current chain. - - We do not want to break the loop after every free_block(), - not even only after waits. The chain might be quite long - and contain blocks for many files. Traversing it again and - again to find more blocks for this file could become quite - inefficient. - */ - if (next && hash_requests && - ((next_status != next->status) || - (next_hash_link != next->hash_link) || - (next_file != next_hash_link->file) || - (next_diskpos != next_hash_link->diskpos) || - (next != next_hash_link->block))) - break; - } - else - { - last_in_switch= block; - } - } - } /* end for block in file_blocks */ - } while (found); - - /* - If any clean block has been found, we may have waited for it to - become free. In this case it could be possible that another clean - block became dirty. This is possible if the write request existed - before the flush started (BLOCK_FOR_UPDATE). Re-check the hashes. - */ - if (total_found) - goto restart; - - /* - To avoid an infinite loop, wait until one of the blocks marked - for update is updated. - */ - if (last_for_update) - { - /* We did not wait. Block must not have changed status. */ - DBUG_ASSERT(last_for_update->status & BLOCK_FOR_UPDATE); - wait_on_queue(&last_for_update->wqueue[COND_FOR_REQUESTED], - &keycache->cache_lock, thread_var); - goto restart; - } - - /* - To avoid an infinite loop wait until one of the blocks marked - for eviction is switched. - */ - if (last_in_switch) - { - /* We did not wait. Block must not have changed status. */ - DBUG_ASSERT(last_in_switch->status & (BLOCK_IN_EVICTION | - BLOCK_IN_SWITCH | - BLOCK_REASSIGNED)); - wait_on_queue(&last_in_switch->wqueue[COND_FOR_SAVED], - &keycache->cache_lock, thread_var); - goto restart; - } - - } /* if (! (type == FLUSH_KEEP || type == FLUSH_FORCE_WRITE)) */ - - } /* if (keycache->disk_blocks > 0 */ - -err: - if (cache != cache_buff) - my_free(cache); - if (last_errno) - errno=last_errno; /* Return first error */ - DBUG_RETURN(last_errno != 0); -} - - -/* - Flush all blocks for a file to disk - - SYNOPSIS - - flush_key_blocks() - keycache pointer to a key cache data structure - thread_var pointer to thread specific variables - file handler for the file to flush to - flush_type type of the flush - - RETURN - 0 ok - 1 error -*/ - -int flush_key_blocks(KEY_CACHE *keycache, - st_keycache_thread_var *thread_var, - File file, enum flush_type type) -{ - int res= 0; - DBUG_ENTER("flush_key_blocks"); - DBUG_PRINT("enter", ("keycache: 0x%lx", (long) keycache)); - - if (!keycache->key_cache_inited) - DBUG_RETURN(0); - - mysql_mutex_lock(&keycache->cache_lock); - /* While waiting for lock, keycache could have been ended. */ - if (keycache->disk_blocks > 0) - { - inc_counter_for_resize_op(keycache); - res= flush_key_blocks_int(keycache, thread_var, file, type); - dec_counter_for_resize_op(keycache); - } - mysql_mutex_unlock(&keycache->cache_lock); - DBUG_RETURN(res); -} - - -/* - Flush all blocks in the key cache to disk. - - SYNOPSIS - flush_all_key_blocks() - keycache pointer to key cache root structure - thread_var pointer to thread specific variables - - DESCRIPTION - - Flushing of the whole key cache is done in two phases. - - 1. Flush all changed blocks, waiting for them if necessary. Loop - until there is no changed block left in the cache. - - 2. Free all clean blocks. Normally this means free all blocks. The - changed blocks were flushed in phase 1 and became clean. However we - may need to wait for blocks that are read by other threads. While we - wait, a clean block could become changed if that operation started - before the resize operation started. To be safe we must restart at - phase 1. - - When we can run through the changed_blocks and file_blocks hashes - without finding a block any more, then we are done. - - Note that we hold keycache->cache_lock all the time unless we need - to wait for something. - - RETURN - 0 OK - != 0 Error -*/ - -static int flush_all_key_blocks(KEY_CACHE *keycache, - st_keycache_thread_var *thread_var) -{ - BLOCK_LINK *block; - uint total_found; - uint found; - uint idx; - DBUG_ENTER("flush_all_key_blocks"); - - do - { - mysql_mutex_assert_owner(&keycache->cache_lock); - total_found= 0; - - /* - Phase1: Flush all changed blocks, waiting for them if necessary. - Loop until there is no changed block left in the cache. - */ - do - { - found= 0; - /* Step over the whole changed_blocks hash array. */ - for (idx= 0; idx < CHANGED_BLOCKS_HASH; idx++) - { - /* - If an array element is non-empty, use the first block from its - chain to find a file for flush. All changed blocks for this - file are flushed. So the same block will not appear at this - place again with the next iteration. New writes for blocks are - not accepted during the flush. If multiple files share the - same hash bucket, one of them will be flushed per iteration - of the outer loop of phase 1. - */ - if ((block= keycache->changed_blocks[idx])) - { - found++; - /* - Flush dirty blocks but do not free them yet. They can be used - for reading until all other blocks are flushed too. - */ - if (flush_key_blocks_int(keycache, thread_var, - block->hash_link->file, - FLUSH_FORCE_WRITE)) - DBUG_RETURN(1); - } - } - - } while (found); - - /* - Phase 2: Free all clean blocks. Normally this means free all - blocks. The changed blocks were flushed in phase 1 and became - clean. However we may need to wait for blocks that are read by - other threads. While we wait, a clean block could become changed - if that operation started before the resize operation started. To - be safe we must restart at phase 1. - */ - do - { - found= 0; - /* Step over the whole file_blocks hash array. */ - for (idx= 0; idx < CHANGED_BLOCKS_HASH; idx++) - { - /* - If an array element is non-empty, use the first block from its - chain to find a file for flush. All blocks for this file are - freed. So the same block will not appear at this place again - with the next iteration. If multiple files share the - same hash bucket, one of them will be flushed per iteration - of the outer loop of phase 2. - */ - if ((block= keycache->file_blocks[idx])) - { - total_found++; - found++; - if (flush_key_blocks_int(keycache, thread_var, - block->hash_link->file, - FLUSH_RELEASE)) - DBUG_RETURN(1); - } - } - - } while (found); - - /* - If any clean block has been found, we may have waited for it to - become free. In this case it could be possible that another clean - block became dirty. This is possible if the write request existed - before the resize started (BLOCK_FOR_UPDATE). Re-check the hashes. - */ - } while (total_found); - -#ifndef DBUG_OFF - /* Now there should not exist any block any more. */ - for (idx= 0; idx < CHANGED_BLOCKS_HASH; idx++) - { - DBUG_ASSERT(!keycache->changed_blocks[idx]); - DBUG_ASSERT(!keycache->file_blocks[idx]); - } -#endif - - DBUG_RETURN(0); -} - - -/* - Reset the counters of a key cache. - - SYNOPSIS - reset_key_cache_counters() - name the name of a key cache - key_cache pointer to the key kache to be reset - - DESCRIPTION - This procedure is used by process_key_caches() to reset the counters of all - currently used key caches, both the default one and the named ones. - - RETURN - 0 on success (always because it can't fail) -*/ - -int reset_key_cache_counters(const char *name MY_ATTRIBUTE((unused)), - KEY_CACHE *key_cache) -{ - DBUG_ENTER("reset_key_cache_counters"); - if (!key_cache->key_cache_inited) - { - DBUG_PRINT("info", ("Key cache %s not initialized.", name)); - DBUG_RETURN(0); - } - DBUG_PRINT("info", ("Resetting counters for key cache %s.", name)); - - key_cache->global_blocks_changed= 0; /* Key_blocks_not_flushed */ - key_cache->global_cache_r_requests= 0; /* Key_read_requests */ - key_cache->global_cache_read= 0; /* Key_reads */ - key_cache->global_cache_w_requests= 0; /* Key_write_requests */ - key_cache->global_cache_write= 0; /* Key_writes */ - DBUG_RETURN(0); -} - - -#if !defined(DBUG_OFF) -#define F_B_PRT(_f_, _v_) DBUG_PRINT("assert_fail", (_f_, _v_)) - -static int fail_block(BLOCK_LINK *block) -{ - F_B_PRT("block->next_used: %lx\n", (ulong) block->next_used); - F_B_PRT("block->prev_used: %lx\n", (ulong) block->prev_used); - F_B_PRT("block->next_changed: %lx\n", (ulong) block->next_changed); - F_B_PRT("block->prev_changed: %lx\n", (ulong) block->prev_changed); - F_B_PRT("block->hash_link: %lx\n", (ulong) block->hash_link); - F_B_PRT("block->status: %u\n", block->status); - F_B_PRT("block->length: %u\n", block->length); - F_B_PRT("block->offset: %u\n", block->offset); - F_B_PRT("block->requests: %u\n", block->requests); - F_B_PRT("block->temperature: %u\n", block->temperature); - return 0; /* Let the assert fail. */ -} - -static int fail_hlink(HASH_LINK *hlink) -{ - F_B_PRT("hlink->next: %lx\n", (ulong) hlink->next); - F_B_PRT("hlink->prev: %lx\n", (ulong) hlink->prev); - F_B_PRT("hlink->block: %lx\n", (ulong) hlink->block); - F_B_PRT("hlink->diskpos: %lu\n", (ulong) hlink->diskpos); - F_B_PRT("hlink->file: %d\n", hlink->file); - return 0; /* Let the assert fail. */ -} - -static int cache_empty(KEY_CACHE *keycache) -{ - int errcnt= 0; - int idx; - if (keycache->disk_blocks <= 0) - return 1; - for (idx= 0; idx < keycache->disk_blocks; idx++) - { - BLOCK_LINK *block= keycache->block_root + idx; - if (block->status || block->requests || block->hash_link) - { - my_message_local(INFORMATION_LEVEL, "block index: %u", idx); - fail_block(block); - errcnt++; - } - } - for (idx= 0; idx < keycache->hash_links; idx++) - { - HASH_LINK *hash_link= keycache->hash_link_root + idx; - if (hash_link->requests || hash_link->block) - { - my_message_local(INFORMATION_LEVEL, "hash_link index: %u", idx); - fail_hlink(hash_link); - errcnt++; - } - } - if (errcnt) - { - my_message_local(INFORMATION_LEVEL, "blocks: %d used: %lu", - keycache->disk_blocks, keycache->blocks_used); - my_message_local(INFORMATION_LEVEL, "hash_links: %d used: %d", - keycache->hash_links, keycache->hash_links_used); - } - return !errcnt; -} -#endif - |