On 11/10/20 7:16 AM, Andrey Borodin wrote: > > >> 10 нояб. 2020 г., в 05:13, Tomas Vondra <tomas.von...@enterprisedb.com> >> написал(а): >> After the issue reported in [1] got fixed, I've restarted the multi-xact >> stress test, hoping to reproduce the issue. But so far no luck :-( > > > Tomas, many thanks for looking into this. I figured out that to make > multixact sets bigger transactions must hang for a while and lock large set > of tuples. But not continuous range to avoid locking on buffer_content. > I did not manage to implement this via pgbench, that's why I was trying to > hack on separate go program. But, essentially, no luck either. > I was observing something resemblant though > > пятница, 8 мая 2020 г. 15:08:37 (every > 1s) > > pid | wait_event | wait_event_type | state | > query > -------+----------------------------+-----------------+--------+---------------------------------------------------- > 41344 | ClientRead | Client | idle | insert into > t1 select generate_series(1,1000000,1) > 41375 | MultiXactOffsetControlLock | LWLock | active | select * > from t1 where i = ANY ($1) for share > 41377 | MultiXactOffsetControlLock | LWLock | active | select * > from t1 where i = ANY ($1) for share > 41378 | | | active | select * > from t1 where i = ANY ($1) for share > 41379 | MultiXactOffsetControlLock | LWLock | active | select * > from t1 where i = ANY ($1) for share > 41381 | | | active | select * > from t1 where i = ANY ($1) for share > 41383 | MultiXactOffsetControlLock | LWLock | active | select * > from t1 where i = ANY ($1) for share > 41385 | MultiXactOffsetControlLock | LWLock | active | select * > from t1 where i = ANY ($1) for share > (8 rows) > > but this picture was not stable. > Seems we haven't made much progress in reproducing the issue :-( I guess we'll need to know more about the machine where this happens. Is there anything special about the hardware/config? Are you monitoring size of the pg_multixact directory? > How do you collect wait events for aggregation? just insert into some table > with cron? > No, I have a simple shell script (attached) sampling data from pg_stat_activity regularly. Then I load it into a table and aggregate to get a summary. regards -- Tomas Vondra EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
collect-wait-events.sh
Description: application/shellscript
