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/* Copyright (C) 2003 MySQL AB
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
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/* Key cache variable structures */
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FLUSH_KEEP, /* flush block and keep it in the cache */
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FLUSH_RELEASE, /* flush block and remove it from the cache */
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FLUSH_IGNORE_CHANGED, /* remove block from the cache */
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* As my_disable_flush_pagecache_blocks is always 0, the following option
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* is strictly equivalent to FLUSH_KEEP
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/* declare structures that is used by st_key_cache */
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typedef struct st_block_link BLOCK_LINK;
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struct st_keycache_page;
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typedef struct st_keycache_page KEYCACHE_PAGE;
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typedef struct st_hash_link HASH_LINK;
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typedef uint64_t my_off_t;
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struct st_my_thread_var;
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/* info about requests in a waiting queue */
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typedef struct st_keycache_wqueue
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drizzled::internal::st_my_thread_var *last_thread; /* circular list of waiting threads */
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#define CHANGED_BLOCKS_HASH 128 /* must be power of 2 */
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The key cache structure
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It also contains read-only statistics parameters.
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typedef struct st_key_cache
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bool key_cache_inited;
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bool can_be_used; /* usage of cache for read/write is allowed */
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uint32_t key_cache_block_size; /* size of the page buffer of a cache block */
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int blocks; /* max number of blocks in the cache */
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bool in_init; /* Set to 1 in MySQL during init/resize */
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key_cache_inited(false),
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key_cache_block_size(0),
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} /* namespace drizzled */
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/* The default key cache */
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extern int init_key_cache(drizzled::KEY_CACHE *keycache, uint32_t key_cache_block_size,
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size_t use_mem, uint32_t division_limit,
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uint32_t age_threshold);
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extern unsigned char *key_cache_read(drizzled::KEY_CACHE *keycache,
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int file, drizzled::internal::my_off_t filepos, int level,
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unsigned char *buff, uint32_t length,
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uint32_t block_length,int return_buffer);
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extern int key_cache_insert(drizzled::KEY_CACHE *keycache,
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int file, drizzled::internal::my_off_t filepos, int level,
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unsigned char *buff, uint32_t length);
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extern int key_cache_write(drizzled::KEY_CACHE *keycache,
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int file, drizzled::internal::my_off_t filepos, int level,
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unsigned char *buff, uint32_t length,
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uint32_t block_length,int force_write);
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extern int flush_key_blocks(drizzled::KEY_CACHE *keycache,
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int file, enum flush_type type);
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extern void end_key_cache(drizzled::KEY_CACHE *keycache, bool cleanup);
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Next highest power of two
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my_round_up_to_next_power()
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Next or equal power of 2
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Note: 0 will return 0
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Algorithm by Sean Anderson, according to:
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http://graphics.stanford.edu/~seander/bithacks.html
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(Orignal code public domain)
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Comments shows how this works with 01100000000000000000000000001011
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static inline uint32_t my_round_up_to_next_power(uint32_t v)
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v--; /* 01100000000000000000000000001010 */
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v|= v >> 1; /* 01110000000000000000000000001111 */
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v|= v >> 2; /* 01111100000000000000000000001111 */
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v|= v >> 4; /* 01111111110000000000000000001111 */
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v|= v >> 8; /* 01111111111111111100000000001111 */
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v|= v >> 16; /* 01111111111111111111111111111111 */
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return v+1; /* 10000000000000000000000000000000 */
added
removed
plugin/myisam/keycache.h
