Re: Excessive PostmasterIsAlive calls slow down WAL redo

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От Andres Freund
Тема Re: Excessive PostmasterIsAlive calls slow down WAL redo
Дата
Msg-id 20180406163929.g3jho4t776k75qlg@alap3.anarazel.de
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Ответ на Re: Excessive PostmasterIsAlive calls slow down WAL redo  (Stephen Frost <sfrost@snowman.net>)
Ответы Re: Excessive PostmasterIsAlive calls slow down WAL redo  (Heikki Linnakangas <hlinnaka@iki.fi>)
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Hi,

On 2018-04-06 07:39:28 -0400, Stephen Frost wrote:
> While I tend to agree that it'd be nice to just make it cheaper, that
> doesn't seem like something that we'd be likely to back-patch and I tend
> to share Heikki's feelings that this is a performance regression we
> should be considering fixing in released versions.

I'm doubtful about fairly characterizing this as a performance bug. It's
not like we've O(n^2) behaviour on our hand, and if your replay isn't of
a toy workload normally that one syscall isn't going to make a huge
difference because you've actual IO and such going on.

I'm also doubtful that it's sane to just check every 32 records. There's
records that can take a good chunk of time, and just continuing for
another 31 records seems like a bad idea.

Greetings,

Andres Freund


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