Re: PANIC: could not fsync file "pg_multixact/..." since commit dee663f7843

On Wed, Nov 04, 2020 at 05:36:46PM +1300, Thomas Munro wrote:
>On Wed, Nov 4, 2020 at 2:57 PM Tomas Vondra
><tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
>> On Wed, Nov 04, 2020 at 02:49:24PM +1300, Thomas Munro wrote:
>> >On Wed, Nov 4, 2020 at 2:32 PM Tomas Vondra
>> ><tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
>> >> After a while (~1h on my machine) the pg_multixact gets over 10GB, which
>> >> triggers a more aggressive cleanup (per MultiXactMemberFreezeThreshold).
>> >> My guess is that this discards some of the files, but checkpointer is
>> >> not aware of that, or something like that. Not sure.
>> >
>> >Urgh. Thanks. Looks like perhaps the problem is that I have
>> >RegisterSyncRequest(&tag, SYNC_FORGET_REQUEST, true) in one codepath
>> >that unlinks files, but not another. Looking.
>>
>> Maybe. I didn't have time to investigate this more deeply, and it takes
>> quite a bit of time to reproduce. I can try again with extra logging or
>> test some proposed fixes, if you give me a patch.
>
>I think this should be fixed by doing all unlinking through a common
>code path. Does this pass your test?

Seems to be working - without the patch it failed after ~1h, now it's
running for more than 2h without a crash. I'll let it run for a few more
hours (on both machines).

regards

--
Tomas Vondra http://www.2ndQuadrant.com
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