| From: | James Pang <jamespang886(at)gmail(dot)com> |
|---|---|
| To: | pgsql-performance(at)lists(dot)postgresql(dot)org |
| Subject: | many sessions waiting DataFileRead and extend |
| Date: | 2025-06-25 03:15:08 |
| Message-ID: | CAHgTRfdDkiX5bLRCYhrP18kFJjcvs1eHvL+jUtX1Ep-Y3=cFVg@mail.gmail.com |
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| Lists: | pgsql-performance |
pgv14, RHEL8, xfs , we suddenly see tens of sessions waiting on
"DataFileRead" and "extend", it last about 2 seconds(based on
pg_stat_activity query) , during the waiting time, "%sys" cpu increased to
80% , but from "iostat" , no high iops and io read/write latency increased
either.
many sessions were running same "DELETE FROM xxxx" in parallel waiting
on "extend" and "DataFileRead", there are triggers in this table "After
delete" to insert/delete other tables in the tigger.
time wait_event
count(sessions)
2025-06-24 18:00:11.687245+00 | DataFileFlush | 1
2025-06-24 18:00:11.687245+00 | DataFileWrite | 1
2025-06-24 18:00:11.687245+00 | PgSleep | 1
2025-06-24 18:00:11.687245+00 | DataFileExtend | 7
2025-06-24 18:00:11.687245+00 | ProcArrayGroupUpdate | 1
2025-06-24 18:00:11.687245+00 | WALWrite | 5
2025-06-24 18:00:11.687245+00 | extend | 55
2025-06-24 18:00:11.687245+00 | DataFileRead | 45
2025-06-24 18:00:11.687245+00 | DataFilePrefetch | 2
Thanks,
James
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