| From: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
|---|---|
| To: | Amine Tengilimoglu <aminetengilimoglu(at)gmail(dot)com> |
| Cc: | James Pang <jamespang886(at)gmail(dot)com>, pgsql-performance(at)lists(dot)postgresql(dot)org |
| Subject: | Re: many backends hang on MultiXactOffsetSLRU |
| Date: | 2024-09-10 08:15:42 |
| Message-ID: | 202409100815.7i32l2unwhgy@alvherre.pgsql |
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| Thread: | |
| Lists: | pgsql-performance |
On 2024-Sep-10, Amine Tengilimoglu wrote:
> Hi,
>
> I encountered this in a project we migrated to PostgreSQL
> before, and unfortunately, it’s a situation that completely degrades
> performance. We identified the cause as savepoints being used excessively
> and without control. Once they reduced the number of savepoints, the issue
> was resolved. However, the documentation also mentions that it could be
> caused by foreign keys.
Yeah, it's exactly the same problem; when it comes from savepoints the
issue is pg_subtrans, and when foreign keys are involved, it is
pg_multixact. Both of those use the SLRU subsystem, which was heavily
modified in pg17 as I mentioned in my reply to James.
--
Álvaro Herrera 48°01'N 7°57'E — https://www.EnterpriseDB.com/
"I think my standards have lowered enough that now I think 'good design'
is when the page doesn't irritate the living f*ck out of me." (JWZ)
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