From: Ho Fat Tsang <namiwf@gmail.com>
To: Greg Smith <gsmith@gregsmith.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: PostgreSQL 8.0 occasionally slow down
Date: Wed, 4 Jul 2007 01:03:17 +0800
Message-ID: <97e6e20f0707031003q69f7bb32kf69531f39cd416cd@mail.gmail.com> (raw)
In-Reply-To: <Pine.GSO.4.64.0706280942320.6275@westnet.com>
References: <97e6e20f0706272354m5e42c91em177c8b80abb2ea52@mail.gmail.com>
<468361A9.1040308@archonet.com>
<97e6e20f0706280101y543b871ao4cbf85e57f07f7e9@mail.gmail.com>
<Pine.GSO.4.64.0706280942320.6275@westnet.com>
Hi Greg.
2007/6/28, Greg Smith <gsmith@gregsmith.com>:
>
> On Thu, 28 Jun 2007, Ho Fat Tsang wrote:
>
> > I have tuned the checkpoint_timeout to 30 second which is ten times less
> > than default and the issue is still reproduced.
Doing a checkpoint every 30 seconds is crazy; no wonder your system is
> pausing so much. Put the timeout back to the default. What you should do
> here is edit your config file and set checkpoint_warning to its maximum of
> 3600. After that, take a look at the log files; you'll then get a warning
> message every time a checkpoint happens. If those line up with when
> you're getting the slowdowns, then at least you'll have narrowed the cause
> of your problem, and you can get some advice here on how to make the
> overhead of checkpoints less painful.
>
> The hint it will give is probably the first thing to try: increase
> checkpoint_segments from the default to something much larger (if it's at
> 3 now, try 10 instead to start), and see if the problem stops happening as
> frequently. Your problem looks exactly like a pause at every checkpoint,
> and I'm not sure what Richard was thinking when he suggested having them
> more often would improve things.
Yes, Thank you for your suggestion. i have found that the slowdown time does
not align to checkpoint after i turned on the warning. The issue is related
what Richard has been mentioned - Something outsides PG doing many write
operations to pages.
--
> * Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD
>
> ---------------------------(end of broadcast)---------------------------
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>
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To: pgsql-performance@postgresql.org
Cc: namiwf@gmail.com, gsmith@gregsmith.com
Subject: Re: PostgreSQL 8.0 occasionally slow down
In-Reply-To: <97e6e20f0707031003q69f7bb32kf69531f39cd416cd@mail.gmail.com>
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