From: Csaba Nagy <nagy@ecircle-ag.com>
To: Heikki Linnakangas <heikki@enterprisedb.com>
Cc: Gregory Stark <stark@enterprisedb.com>
Cc: Decibel! <decibel@decibel.org>
Cc: pgsql-performance@postgresql.org
Subject: Re: Linux mis-reporting memory
Date: Fri, 21 Sep 2007 13:34:22 +0200
Message-ID: <1190374462.4661.199.camel@PCD12478> (raw)
In-Reply-To: <46F39E4D.1080401@enterprisedb.com>
References: <20070920230400.GM95343@decibel.org>
<16213.1190329934@sss.pgh.pa.us>
<87r6ksa1jb.fsf@oxford.xeocode.com>
<1190363401.4661.116.camel@PCD12478>
<87r6ksuzf8.fsf@oxford.xeocode.com>
<1190369325.4661.178.camel@PCD12478>
<46F39E4D.1080401@enterprisedb.com>
On Fri, 2007-09-21 at 11:34 +0100, Heikki Linnakangas wrote:
> Which version of Postgres is this? In 8.3, a scan like that really won't
> suck it all into the shared buffer cache. For seq scans on tables larger
> than shared_buffers/4, it switches to the bulk read strategy, using only
> a few buffers, and choosing the starting point with the scan
> synchronization facility.
>
This was on 8.1.9 installed via apt-get on Debian 4.1.1-21. In any case
I'm pretty sure linux swaps shared buffers, as I always got worse
performance for shared buffers more than about 1/3 of the memory. But in
that case the output of top is misleading.
Cheers,
Csaba.
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To: pgsql-performance@postgresql.org
Cc: nagy@ecircle-ag.com, heikki@enterprisedb.com, stark@enterprisedb.com, decibel@decibel.org
Subject: Re: Linux mis-reporting memory
In-Reply-To: <1190374462.4661.199.camel@PCD12478>
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