Re: "pgstat wait timeout" warnings

From: Andres Freund <andres(at)anarazel(dot)de>
To: pgsql-hackers(at)postgresql(dot)org
Cc: Bernd Helmle <mailings(at)oopsware(dot)de>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: "pgstat wait timeout" warnings
Date: 2011-08-11 10:03:52
Message-ID: 2785503.QPqdNFJ4MH@alap2
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On Thursday, August 11, 2011 11:49:12 Bernd Helmle wrote:
> --On 10. August 2011 21:54:06 +0300 Heikki Linnakangas
>
> <heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> > So my theory is that if the I/O is really busy, write() on the stats
> > file
> > blocks for more than 5 seconds, and you get the timeout.
>
> I've seen it on customer instances with very high INSERT peak loads (several
> dozens backends INSERTing/UPDATEing data concurrently). We are using a RAM
> disk for stats_temp_directory now for a while, and the timeout never
> occured again.
Yes, I have seen it several times as well. I can actually reproduce it without
much problems, so if you have some idea to test...

I also routinely use stats_temp_directory + tmpfs to solve this (and related
issues). I really think the stats file mechanism should be improved
fundamentally.

Andres

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