Re: MultiXact\SLRU buffers configuration

> 10 нояб. 2020 г., в 05:13, Tomas Vondra <tomas.vondra@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.

How do you collect wait events for aggregation? just insert into some table with cron?

Thanks!

Best regards, Andrey Borodin.