Message-ID: <4909D989.5020905@technocon.com>
Date: Thu, 30 Oct 2008 16:58:01 +0100
From: Christiaan Willemsen <cwillemsen@technocon.com>
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To: "Joshua D. Drake" <jd@commandprompt.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Configuring for maximum memory usage
References: <4909CF9C.80701@technocon.com>
 <4909D688.1090806@commandprompt.com>
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Joshua D. Drake wrote:
>
> PostgreSQL is only going to use what it needs. It relies on the OS for 
> much of the caching etc...
>
So that would actually mean that I could raise the setting of the ARC 
cache to far more than 8 GB? As I said, our database is 250 GB, So I 
would expect that postgres needs more than it is using right now... 
Several tables have over 500 million  records (obviously partitioned). 
At the moment we are doing queries over large datasets, So I would 
assume that postgress would need a bit more memory than this..
>
> You are missing effective_cache_size. Try setting that to 32G.
That one was set to 24 GB. But this setting only tells posgres how much 
caching it can expect from the OS? This is not actually memory that it 
will allocate, is it?
>
> You also didn't mention checkpoint_segments (which isn't memory but 
> still important) and default_statistics_target (which isn't memory but 
> still important).
>
is at the moment set to:

checkpoint_segments = 40
default_statistics_target is set to default (I think that is 10)

Thanks already,

Christiaan