✏ 编辑: keycache.h

This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.

This program is also distributed with certain software (including
   but not limited to OpenSSL) that is licensed under separate terms,
   as designated in a particular file or component or in included license
   documentation.  The authors of MySQL hereby grant you an additional
   permission to link the program and your derivative works with the
   separately licensed software that they have included with MySQL.

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, version 2.0, 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 */

/* Key cache variable structures */

#ifndef _keycache_h
#define _keycache_h

#include "my_sys.h"                             /* flush_type */

C_MODE_START

/* declare structures that is used by st_key_cache */

struct st_block_link;
typedef struct st_block_link BLOCK_LINK;
struct st_hash_link;
typedef struct st_hash_link HASH_LINK;

/* Thread specific variables */
typedef struct st_keycache_thread_var
{
  mysql_cond_t suspend;
  struct st_keycache_thread_var *next,**prev;
  void *opt_info;
} st_keycache_thread_var;

/* info about requests in a waiting queue */
typedef struct st_keycache_wqueue
{
  st_keycache_thread_var *last_thread;  /* circular list of waiting threads */
} KEYCACHE_WQUEUE;

#define CHANGED_BLOCKS_HASH 128             /* must be power of 2 */

/*
  The key cache structure
  It also contains read-only statistics parameters.
*/

typedef struct st_key_cache
{
  my_bool key_cache_inited;
  my_bool in_resize;             /* true during resize operation             */
  my_bool resize_in_flush;       /* true during flush of resize operation    */
  my_bool can_be_used;           /* usage of cache for read/write is allowed */
  size_t key_cache_mem_size;      /* specified size of the cache memory       */
  uint key_cache_block_size;     /* size of the page buffer of a cache block */
  ulonglong min_warm_blocks;     /* min number of warm blocks;               */
  ulonglong age_threshold;       /* age threshold for hot blocks             */
  ulonglong keycache_time;       /* total number of block link operations    */
  uint hash_entries;             /* max number of entries in the hash table  */
  int hash_links;                /* max number of hash links                 */
  int hash_links_used;           /* number of hash links currently used      */
  int disk_blocks;               /* max number of blocks in the cache        */
  ulong blocks_used; /* maximum number of concurrently used blocks */
  ulong blocks_unused; /* number of currently unused blocks */
  ulong blocks_changed;          /* number of currently dirty blocks         */
  ulong warm_blocks;             /* number of blocks in warm sub-chain       */
  ulong cnt_for_resize_op;       /* counter to block resize operation        */
  long blocks_available;      /* number of blocks available in the LRU chain */
  HASH_LINK **hash_root;         /* arr. of entries into hash table buckets  */
  HASH_LINK *hash_link_root;     /* memory for hash table links              */
  HASH_LINK *free_hash_list;     /* list of free hash links                  */
  BLOCK_LINK *free_block_list;   /* list of free blocks */
  BLOCK_LINK *block_root;        /* memory for block links                   */
  uchar *block_mem;              /* memory for block buffers                 */
  BLOCK_LINK *used_last;         /* ptr to the last block of the LRU chain   */
  BLOCK_LINK *used_ins;          /* ptr to the insertion block in LRU chain  */
  mysql_mutex_t cache_lock;      /* to lock access to the cache structure    */
  KEYCACHE_WQUEUE resize_queue;  /* threads waiting during resize operation  */
  /*
    Waiting for a zero resize count. Using a queue for symmetry though
    only one thread can wait here.
  */
  KEYCACHE_WQUEUE waiting_for_resize_cnt;
  KEYCACHE_WQUEUE waiting_for_hash_link; /* waiting for a free hash link     */
  KEYCACHE_WQUEUE waiting_for_block;    /* requests waiting for a free block */
  BLOCK_LINK *changed_blocks[CHANGED_BLOCKS_HASH]; /* hash for dirty file bl.*/
  BLOCK_LINK *file_blocks[CHANGED_BLOCKS_HASH];    /* hash for other file bl.*/

/*
    The following variables are and variables used to hold parameters for
    initializing the key cache.
  */

ulonglong param_buff_size;      /* size the memory allocated for the cache  */
  ulonglong param_block_size;     /* size of the blocks in the key cache      */
  ulonglong param_division_limit; /* min. percentage of warm blocks           */
  ulonglong param_age_threshold;  /* determines when hot block is downgraded  */

/* Statistics variables. These are reset in reset_key_cache_counters(). */
  ulong global_blocks_changed;	/* number of currently dirty blocks         */
  ulonglong global_cache_w_requests;/* number of write requests (write hits) */
  ulonglong global_cache_write;     /* number of writes from cache to files  */
  ulonglong global_cache_r_requests;/* number of read requests (read hits)   */
  ulonglong global_cache_read;      /* number of reads from files to cache   */

int blocks;                   /* max number of blocks in the cache        */
  my_bool in_init;		/* Set to 1 in MySQL during init/resize     */
} KEY_CACHE;

/* The default key cache */
extern KEY_CACHE dflt_key_cache_var, *dflt_key_cache;

extern int init_key_cache(KEY_CACHE *keycache, ulonglong key_cache_block_size,
			  size_t use_mem, ulonglong division_limit,
			  ulonglong age_threshold);
extern 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);
extern 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,int return_buffer);
extern 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);
extern 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,int force_write);
extern int flush_key_blocks(KEY_CACHE *keycache,
                            st_keycache_thread_var *thread_var,
                            int file, enum flush_type type);
extern void end_key_cache(KEY_CACHE *keycache, my_bool cleanup);

/* Functions to handle multiple key caches */
extern my_bool multi_keycache_init(void);
extern void multi_keycache_free(void);
extern KEY_CACHE *multi_key_cache_search(uchar *key, uint length);
extern my_bool multi_key_cache_set(const uchar *key, uint length,
				   KEY_CACHE *key_cache);
extern void multi_key_cache_change(KEY_CACHE *old_data,
				   KEY_CACHE *new_data);
extern int reset_key_cache_counters(const char *name,
                                    KEY_CACHE *key_cache);
C_MODE_END
#endif /* _keycache_h */

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