| From: | "Bossart, Nathan" <bossartn(at)amazon(dot)com> |
|---|---|
| To: | "alvherre(at)alvh(dot)no-ip(dot)org" <alvherre(at)alvh(dot)no-ip(dot)org>, Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, "x4mmm(at)yandex-team(dot)ru" <x4mmm(at)yandex-team(dot)ru>, "a(dot)lubennikova(at)postgrespro(dot)ru" <a(dot)lubennikova(at)postgrespro(dot)ru>, "hlinnaka(at)iki(dot)fi" <hlinnaka(at)iki(dot)fi>, "matsumura(dot)ryo(at)fujitsu(dot)com" <matsumura(dot)ryo(at)fujitsu(dot)com>, "masao(dot)fujii(at)gmail(dot)com" <masao(dot)fujii(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: archive status ".ready" files may be created too early |
| Date: | 2021-08-30 19:59:48 |
| Message-ID: | B8282B41-7699-46D9-A517-B671A3266425@amazon.com |
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| Lists: | pgsql-hackers |
On 8/30/21, 12:52 PM, "alvherre(at)alvh(dot)no-ip(dot)org" <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> On 2021-Aug-28, Andres Freund wrote:
>
>> While rebasing the aio patchset ontop of HEAD I noticed that this commit added
>> another atomic operation to XLogWrite() with archiving enabled. The WAL write
>> path is really quite hot, and at least some of the
>> NotifySegmentsReadyForArchive() calls are done while WALWriteLock is held.
>>
>> I think we should at least try to make the fast-path where no segment
>> boundaries were crossed use no atomic operations.
>
> I think the best way to achieve this is is to rely completely on
> walwriter doing the segment notification, so that the WAL write done by
> backend would only do a latch set.
+1. If we do that, we may also want to move
NotifySegmentsReadyForArchive() to after the call to
XLogBackgroundFlush() in the WAL writer.
Nathan
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