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Diffstat (limited to 'mysql/mysys/mf_keycache.c')
| -rw-r--r-- | mysql/mysys/mf_keycache.c | 4051 |
1 files changed, 4051 insertions, 0 deletions
diff --git a/mysql/mysys/mf_keycache.c b/mysql/mysys/mf_keycache.c new file mode 100644 index 0000000..cb712ed --- /dev/null +++ b/mysql/mysys/mf_keycache.c @@ -0,0 +1,4051 @@ +/* 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 + |