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The rw_lock_s_lock() calls for the buf_pool.page_hash became a clear bottleneck after MDEV-15053 reduced the contention on buf_pool.mutex. We will replace that use of rw_lock_t with a special implementation that is optimized for memory bus traffic. The hash_table_locks instrumentation will be removed. buf_pool_t::page_hash: Use a special implementation whose API is compatible with hash_table_t, and store the custom rw-locks directly in buf_pool.page_hash.array, intentionally sharing cache lines with the hash table pointers. rw_lock: A low-level rw-lock implementation based on std::atomic<uint32_t> where read_trylock() becomes a simple fetch_add(1). buf_pool_t::page_hash_latch: The special of rw_lock for the page_hash. buf_pool_t::page_hash_latch::read_lock(): Assert that buf_pool.mutex is not being held by the caller. buf_pool_t::page_hash_latch::write_lock() may be called while not holding buf_pool.mutex. buf_pool_t::watch_set() is such a caller. buf_pool_t::page_hash_latch::read_lock_wait(), page_hash_latch::write_lock_wait(): The spin loops. These will obey the global parameters innodb_sync_spin_loops and innodb_sync_spin_wait_delay. buf_pool_t::freed_page_hash: A singly linked list of copies of buf_pool.page_hash that ever existed. The fact that we never free any buf_pool.page_hash.array guarantees that all page_hash_latch that ever existed will remain valid until shutdown. buf_pool_t::resize_hash(): Replaces buf_pool_resize_hash(). Prepend a shallow copy of the old page_hash to freed_page_hash. buf_pool_t::page_hash_table::n_cells: Declare as Atomic_relaxed. buf_pool_t::page_hash_table::lock(): Explain what prevents a race condition with buf_pool_t::resize_hash().
65 lines
2.4 KiB
Plaintext
65 lines
2.4 KiB
Plaintext
UPDATE performance_schema.setup_instruments SET enabled = 'NO', timed = 'YES';
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UPDATE performance_schema.setup_instruments SET enabled = 'YES'
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WHERE name like 'wait/synch/sxlock/%';
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TRUNCATE TABLE performance_schema.events_waits_history_long;
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TRUNCATE TABLE performance_schema.events_waits_history;
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TRUNCATE TABLE performance_schema.events_waits_current;
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select name from performance_schema.setup_instruments
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where name like "wait/synch/sxlock/%"
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and name not in
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("wait/synch/sxlock/innodb/buf_block_lock",
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"wait/synch/sxlock/innodb/buf_block_debug_latch")
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order by name;
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name
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wait/synch/sxlock/innodb/btr_search_latch
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wait/synch/sxlock/innodb/dict_operation_lock
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wait/synch/sxlock/innodb/dict_table_stats
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wait/synch/sxlock/innodb/fil_space_latch
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wait/synch/sxlock/innodb/fts_cache_init_rw_lock
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wait/synch/sxlock/innodb/fts_cache_rw_lock
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wait/synch/sxlock/innodb/index_online_log
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wait/synch/sxlock/innodb/index_tree_rw_lock
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wait/synch/sxlock/innodb/trx_i_s_cache_lock
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wait/synch/sxlock/innodb/trx_purge_latch
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select name from performance_schema.rwlock_instances
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where name in
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(
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'wait/synch/sxlock/innodb/btr_search_latch',
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'wait/synch/sxlock/innodb/checkpoint_lock',
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'wait/synch/sxlock/innodb/dict_operation_lock',
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'wait/synch/sxlock/innodb/trx_i_s_cache_lock',
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'wait/synch/sxlock/innodb/trx_purge_latch'
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)
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order by name;
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name
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wait/synch/sxlock/innodb/btr_search_latch
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wait/synch/sxlock/innodb/btr_search_latch
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wait/synch/sxlock/innodb/btr_search_latch
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wait/synch/sxlock/innodb/btr_search_latch
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wait/synch/sxlock/innodb/btr_search_latch
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wait/synch/sxlock/innodb/btr_search_latch
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wait/synch/sxlock/innodb/btr_search_latch
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wait/synch/sxlock/innodb/btr_search_latch
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wait/synch/sxlock/innodb/dict_operation_lock
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wait/synch/sxlock/innodb/trx_i_s_cache_lock
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wait/synch/sxlock/innodb/trx_purge_latch
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drop table if exists t1;
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create table t1(a int) engine=innodb;
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begin;
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insert into t1 values (1), (2), (3);
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insert into t1 values (1), (2), (3);
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insert into t1 values (1), (2), (3);
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commit;
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drop table t1;
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select operation from performance_schema.events_waits_history_long
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where event_name like "wait/synch/sxlock/%"
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and operation = "shared_lock" limit 1;
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operation
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shared_lock
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select operation from performance_schema.events_waits_history_long
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where event_name like "wait/synch/sxlock/%"
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and operation = "exclusive_lock" limit 1;
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operation
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exclusive_lock
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UPDATE performance_schema.setup_instruments SET enabled = 'YES', timed = 'YES';
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