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82b7c561b7
In the parent commit, dict_sys.latch could theoretically have been
replaced with a mutex. But, we can do better and merge dict_sys.mutex
into dict_sys.latch. Generally, every occurrence of dict_sys.mutex_lock()
will be replaced with dict_sys.lock().
The PERFORMANCE_SCHEMA instrumentation for dict_sys_mutex
will be removed along with dict_sys.mutex. The dict_sys.latch
will remain instrumented as dict_operation_lock.
Some use of dict_sys.lock() will be replaced with dict_sys.freeze(),
which we will reintroduce for the new shared mode. Most notably,
concurrent table lookups are possible as long as the tables are present
in the dict_sys cache. In particular, this will allow more concurrency
among InnoDB purge workers.
Because dict_sys.mutex will no longer 'throttle' the threads that purge
InnoDB transaction history, a performance degradation may be observed
unless innodb_purge_threads=1.
The table cache eviction policy will become FIFO-like,
similar to what happened to fil_system.LRU
in commit 45ed9dd957.
The name of the list dict_sys.table_LRU will become somewhat misleading;
that list contains tables that may be evicted, even though the
eviction policy no longer is least-recently-used but first-in-first-out.
(Note: Tables can never be evicted as long as locks exist on them or
the tables are in use by some thread.)
As demonstrated by the test perfschema.sxlock_func, there
will be less contention on dict_sys.latch, because some previous
use of exclusive latches will be replaced with shared latches.
fts_parse_sql_no_dict_lock(): Replaced with pars_sql().
fts_get_table_name_prefix(): Merged to fts_optimize_create().
dict_stats_update_transient_for_index(): Deduplicated some code.
ha_innobase::info_low(), dict_stats_stop_bg(): Use a combination
of dict_sys.latch and table->stats_mutex_lock() to cover the
changes of BG_STAT_SHOULD_QUIT, because the flag is being read
in dict_stats_update_persistent() while not holding dict_sys.latch.
row_discard_tablespace_for_mysql(): Protect stats_bg_flag by
exclusive dict_sys.latch, like most other code does.
row_quiesce_table_has_fts_index(): Remove unnecessary mutex
acquisition. FLUSH TABLES...FOR EXPORT is protected by MDL.
row_import::set_root_by_heuristic(): Remove unnecessary mutex
acquisition. ALTER TABLE...IMPORT TABLESPACE is protected by MDL.
row_ins_sec_index_entry_low(): Replace a call
to dict_set_corrupted_index_cache_only(). Reads of index->type
were not really protected by dict_sys.mutex, and writes
(flagging an index corrupted) should be extremely rare.
dict_stats_process_entry_from_defrag_pool(): Only freeze the dictionary,
do not lock it exclusively.
dict_stats_wait_bg_to_stop_using_table(), DICT_BG_YIELD: Remove trx.
We can simply invoke dict_sys.unlock() and dict_sys.lock() directly.
dict_acquire_mdl_shared()<trylock=false>: Assert that dict_sys.latch is
only held in shared more, not exclusive mode. Only acquire it in
exclusive mode if the table needs to be loaded to the cache.
dict_sys_t::acquire(): Remove. Relocating elements in dict_sys.table_LRU
would require holding an exclusive latch, which we want to avoid
for performance reasons.
dict_sys_t::allow_eviction(): Add the table first to dict_sys.table_LRU,
to compensate for the removal of dict_sys_t::acquire(). This function
is only invoked by INFORMATION_SCHEMA.INNODB_SYS_TABLESTATS.
dict_table_open_on_id(), dict_table_open_on_name(): If dict_locked=false,
try to acquire dict_sys.latch in shared mode. Only acquire the latch in
exclusive mode if the table is not found in the cache.
Reviewed by: Thirunarayanan Balathandayuthapani
70 lines
2.4 KiB
Plaintext
70 lines
2.4 KiB
Plaintext
# Performance schema tests, for SX-lock
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# Note that only Innodb provides instrumented SX-locks,
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# so this test depends largely on the innodb instrumentation.
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--source include/not_embedded.inc
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--source include/have_perfschema.inc
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--source include/have_innodb.inc
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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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UPDATE performance_schema.setup_instruments SET enabled = 'YES'
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WHERE name like 'wait/synch/rwlock/innodb/%';
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SELECT DISTINCT name FROM performance_schema.setup_instruments
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WHERE name LIKE 'wait/synch/rwlock/innodb/%'
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AND name!='wait/synch/rwlock/innodb/btr_search_latch' ORDER BY name;
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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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# Check some SX-locks classes are instrumented
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select name from performance_schema.setup_instruments
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where name like "wait/synch/sxlock/%" order by name;
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# Check some SX-locks instances are instrumented
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SELECT DISTINCT name FROM performance_schema.rwlock_instances
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WHERE name LIKE 'wait/synch/sxlock/innodb/%'
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ORDER BY name;
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# Some Innodb payload, to produce data
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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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# Make sure some rw-lock operations have been executed
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# (there will only occasionally be waits on some rw-locks)
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SELECT DISTINCT event_name FROM performance_schema.events_waits_history_long
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WHERE event_name LIKE 'wait/synch/rwlock/innodb/%'
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AND event_name NOT IN
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('wait/synch/rwlock/innodb/btr_search_latch',
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'wait/synch/rwlock/innodb/dict_operation_lock',
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'wait/synch/rwlock/innodb/trx_purge_latch')
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ORDER BY event_name;
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# Make sure some shared_lock operations have been executed
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SELECT event_name FROM performance_schema.events_waits_history_long
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WHERE event_name = 'wait/synch/sxlock/innodb/index_tree_rw_lock'
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AND operation IN ('try_shared_lock','shared_lock') LIMIT 1;
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# Make sure some exclusive_lock operations have been executed
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SELECT event_name from performance_schema.events_waits_history_long
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WHERE event_name = 'wait/synch/sxlock/innodb/index_tree_rw_lock'
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AND operation IN ('try_exclusive_lock','exclusive_lock') LIMIT 1;
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# Cleanup
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UPDATE performance_schema.setup_instruments SET enabled = 'YES', timed = 'YES';
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