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

On 11/4/20 2:50 PM, Tomas Vondra wrote:
> 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).
>

It's been running for hours on both machines, without any crashes etc.
While that's not a definitive proof the fix is correct, it certainly
behaves differently.

regards

--
Tomas Vondra
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