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Re: Linux mis-reporting memory

From: Csaba Nagy <nagy(at)ecircle-ag(dot)com>
To: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
Cc: Gregory Stark <stark(at)enterprisedb(dot)com>, Decibel! <decibel(at)decibel(dot)org>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Linux mis-reporting memory
Date: 2007-09-21 11:34:22
Message-ID: 1190374462.4661.199.camel@PCD12478 (view raw or flat)
Thread:
Lists: pgsql-performance
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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