Message-ID: <450A75DE.6050102@logix-tt.com>
Date: Fri, 15 Sep 2006 11:43:58 +0200
From: Markus Schaber <schabi@logix-tt.com>
Organization: Logical Tracking and Tracing International AG, Switzerland
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To: pgsql-performance@postgresql.org
Subject: Re: High CPU Load
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Hi, J=E9r=F4me,

J=E9r=F4me BENOIS wrote:

> max_connections =3D 512

Do you really have that much concurrent connections? Then you should
think about getting a larger machine, probably.

You will definitely want to play with commit_delay and commit_siblings
settings in that case, especially if you have write access.

> work_mem =3D 65536
> effective_cache_size =3D 131072

hmm, 131072*8*1024 + 512*65536*1024 =3D 35433480192 - thats 33 Gig of
Memory you assume here, not counting OS usage, and the fact that certain
queries can use up a multiple of work_mem.

Even on amachine that big, I'd be inclined to dedicate more memory to
caching, and less to the backends, unless specific needs dictate it. You
could try to use sqlrelay or pgpool to cut down the number of backends
you need.

> My Server is Dual Xeon 3.06GHz

For xeons, there were rumours about "context switch storms" which kill
performance.

> with 2 Go RAM and good SCSI disks.

For 2 Gigs of ram, you should cut down the number of concurrent backends.=


Does your machine go into swap?

Markus
--=20
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf.     | Software Development GIS

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