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Re: PG 8.3 and large shared buffer settings

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Dan Sugalski <dan(at)sidhe(dot)org>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: PG 8.3 and large shared buffer settings
Date: 2009-09-25 04:36:28
Message-ID: 10057.1253853388@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Dan Sugalski <dan(at)sidhe(dot)org> writes:
> Is there any practical limit to the number of shared buffers PG 8.3.7 
> can handle before more becomes counter-productive?

Probably, but I've not heard any definitive measurements showing an
upper limit.  The traditional wisdom of limiting it to 1G or so dates
from before the last rounds of revisions to the bufmgr logic.

> My production DB's around 200G, and the box hosting it has 192G of 
> memory on it, running a 64 bit AIX build of 8.3.7.

Yowza.  You might be able to do measurements that no one has done
before.  Let us know what you find out.

BTW, does AIX have any provision for locking shared memory into RAM?
One of the gotchas for large shared memory has always been the risk
that the kernel would decide to swap some of it out.

			regards, tom lane

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