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Remove unnecessary global mutex in parallel replication.

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The function apply_event_and_update_pos() is called with the
rli->data_lock mutex held. However, there seems to be nothing in the
function actually needing the mutex to be held. Certainly not in the
parallel replication case, where sql_slave_skip_counter is always 0
since the non-zero case is handled by the SQL driver thread.

So this patch makes parallel replication use a variant of
apply_event_and_update_pos() without the need to take the
rli->data_lock mutex. This avoids one contended global mutex for each
event executed, which might improve performance on CPU-bound workloads
somewhat.

Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>
This commit is contained in:
Kristian Nielsen
2016-09-20 15:30:57 +02:00
parent 7e0c9de864
commit 50f19ca809
3 changed files with 96 additions and 43 deletions
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4
sql/rpl_parallel.cc
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@@ -47,9 +47,7 @@ rpt_handle_event(rpl_parallel_thread::queued_event *qev,
if (!(ev->is_artificial_event() || ev->is_relay_log_event() ||
(ev->when == 0)))
rgi->last_master_timestamp= ev->when + (time_t)ev->exec_time;
mysql_mutex_lock(&rli->data_lock);
/* Mutex will be released in apply_event_and_update_pos(). */
err= apply_event_and_update_pos(ev, thd, rgi, rpt);
err= apply_event_and_update_pos_for_parallel(ev, thd, rgi);
thread_safe_increment64(&rli->executed_entries);
/* ToDo: error handling. */