| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Aleksander Alekseev <aleksander(at)timescale(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com> |
| Subject: | Re: Background writer and checkpointer in crash recovery |
| Date: | 2021-08-02 13:07:18 |
| Message-ID: | CA+TgmoZmXLn6SFzxmPqVx2h4Nf2SzCePCzxA-K0J9ikO2LvUCg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Jul 30, 2021 at 4:00 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> I don't agree with that? If (user+system) << wall then it is very likely
> that recovery is IO bound. If system is a large percentage of wall, then
> shared buffers is likely too small (or we're replacing the wrong
> buffers) because you spend a lot of time copying data in/out of the
> kernel page cache. If user is the majority, you're CPU bound.
>
> Without user & system time it's much harder to figure that out - at
> least for me.
Oh, that's an interesting point. At least now I'll know why I am
supposed to care about that log line the next time I see it. I guess
we could include both things, though the line might get a little long.
Or maybe there's some other subset that would make sense.
--
Robert Haas
EDB: http://www.enterprisedb.com
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