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From: Craig James <craig_james@emolecules.com>
To: Kevin Grittner <Kevin.Grittner@wicourts.gov>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-performance@postgresql.org
Subject: Re: Occasional giant spikes in CPU load
Date: Fri, 25 Jun 2010 10:01:21 -0700
Message-ID: <4C24E0E1.7020301@emolecules.com> (raw)
In-Reply-To: <4C2495D70200002500032B16@gw.wicourts.gov>
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	<4BBCFB12.1010306@emolecules.com>
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	<23596.1277438692@sss.pgh.pa.us>
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	<4C24D679.7030701@emolecules.com>
	<4C2495D70200002500032B16@gw.wicourts.gov>

On 6/25/10 9:41 AM, Kevin Grittner wrote:
> Craig James<craig_james@emolecules.com>  wrote:
>
>> I always just assumed that lots of backends that would be harmless
>> if each one was doing very little.
>
> Even if each is doing very little, if a large number of them happen
> to make a request at the same time, you can have problems.  This is
> exactly where a connection pool can massively improve both
> throughput and response time.  If you can arrange it, you want a
> connection pool which will put a limit on active database
> transactions and queue requests to start a new transaction until one
> of the pending ones finishes.

No, that's doesn't seem to be the case.  There is no external activity that triggers this huge spike in usage.  It even happens to our backup server when only one of us is using it to do a single query.  This problem seems to be triggered by Postgres itself, not by anything external.

Per Tom's suggestion, I think upgrading to 8.4.4 is the answer.  I'll learn more when our new hardware comes into use with a shiny new 8.4.4 installation.

Craig



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