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Re: Linux mis-reporting memory

From: Simon Riggs <simon(at)2ndquadrant(dot)com>
To: Csaba Nagy <nagy(at)ecircle-ag(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 11:01:18
Message-ID: 1190372478.4202.17.camel@ebony.site (view raw or flat)
Thread:
Lists: pgsql-performance
On Fri, 2007-09-21 at 12:08 +0200, Csaba Nagy wrote:
> On Fri, 2007-09-21 at 10:43 +0100, Gregory Stark wrote:
> > The other possibility is that Postgres just hasn't even touched a large part
> > of its shared buffers. 
> > 
> 
> But then how do you explain the example I gave, with a 5.5GB table
> seq-scanned 3 times, shared buffers set to 12 GB, and top still showing
> almost 100% memory as cached and no SWAP "used" ? In this case you can't
> say postgres didn't touch it's shared buffers - or a sequential scan
> won't use the shared buffers ?

Well, 6.5GB of shared_buffers could be swapped out and need not be
swapped back in to perform those 3 queries.

-- 
  Simon Riggs
  2ndQuadrant  http://www.2ndQuadrant.com


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