Re: Logical Replica ReorderBuffer Size Accounting Issues

Le 16/02/2023 à 19:08, Alex Richman a écrit :
> Hi all,
>
> Looping back to say we updated to 15.2 and are still seeing this
> issue, though it is less prevalent.
>
> Thanks,
> - Alex.
>
> On Wed, 18 Jan 2023 at 11:16, Alex Richman <alexrichman(at)onesignal(dot)com>
> wrote:
>
>
>
> On Wed, 18 Jan 2023 at 10:10, Amit Kapila
> <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> Alex,
> Do we see this problem with small tuples as well? I see from your
> earlier email that tuple size is ~800 bytes in the production
> environment. It is possible that after commit 1b0d9aa4 such
> kind of
> problems are not there with small tuple sizes but that commit
> happened
> in PG15 whereas your production environment might be on a prior
> release.
>
>
> Hi Amit,
>
> Our prod environment is also on 15.1, which is where we first saw
> the issue, so I'm afraid the issue still seems to be present here.
>
> Looping back on the earlier discussion, we applied the malloc
> patch from [1] ([2]) to a prod server, which also fixes the issue
> there.  Attached is a graph of the last 48 hours of memory usage,
> the ~200GB spikes are instances of the LR walsender memory issue.
> After patch is applied (blue mark), baseline memory drops and we
> no longer see the spikes.  Per-process memory stats corroborate
> that the LR walsender memory is now never more than a few MB RSS
> per process.
>
> Thanks,
> - Alex.
>
> [1]
> https://www.postgresql.org/message-id/CAMnUB3pwknqoe5s-bGuRD8nX1bWkZRbFF%3DjWNLTWbm_etFigkA%40mail.gmail.com
> [2]
> https://gist.github.com/alex-richman-onesignal/4ad147b37eaab99f41a150b51899a564
>

Hi,

Amit / Wang Wei do you have a better patch to fix this bug or should we
use the one provided by Alex? I have tried some other fixes but it's a
fail, you may have better understanding of the problem and the way to
fix it.

Best regards

--
Gilles Darold