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From: Andrey M. Borodin <[email protected]>
To: Thom Brown <[email protected]>
Cc: Michael Paquier <[email protected]>
Cc: Alvaro Herrera <[email protected]>
Cc: vignesh C <[email protected]>
Cc: Andrew Borodin <[email protected]>
Cc: Yura Sokolov <[email protected]>
Cc: Andres Freund <[email protected]>
Cc: Thomas Munro <[email protected]>
Cc: Gilles Darold <[email protected]>
Cc: Alexander Korotkov <[email protected]>
Cc: Daniel Gustafsson <[email protected]>
Cc: Kyotaro Horiguchi <[email protected]>
Cc: pgsql-hackers mailing list <[email protected]>
Subject: Re: MultiXact\SLRU buffers configuration
Date: Tue, 5 Nov 2024 19:11:07 +0500
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAA-aLv7-fs32r7v8znJ=uPPtQNqZ9_sH2REn=cu1pyEQ=tuEhw@mail.gmail.com>
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> On 1 Nov 2024, at 00:25, Thom Brown <[email protected]> wrote:
> 
> Unfortunately I didn't gather much information when it was occuring, and prioritised getting rid of the process blocking replay. I just attached gdb to it, got a backtrace and then "print ProcessInterrupts()".
> 

Currently I do not see how this wait can result in a deadlock.
But I did observe standby in a pathological sequential scan encountering recent multixact again and again (new each time).
I hope this situation will be alleviated by recent cahnges - now there is not a millisecond wait, but hopefully smaller amount of time.

In v17 we also added injection point test which reproduces reading very recent multixact. If there is a deadlock I hope buildfarm will show it to us.


Best regards, Andrey Borodin.

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