Re: many backends hang on MultiXactOffsetSLRU

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.

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