| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Stephen Frost <sfrost(at)snowman(dot)net> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Excessive PostmasterIsAlive calls slow down WAL redo |
| Date: | 2018-04-06 16:39:29 |
| Message-ID: | 20180406163929.g3jho4t776k75qlg@alap3.anarazel.de |
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| Thread: | |
| Lists: | pgsql-hackers |
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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