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Re: Potential memory usage issue

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Bill Moran <wmoran(at)collaborativefusion(dot)com>
Cc: David Brain <dbrain(at)bandwidth(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Potential memory usage issue
Date: 2007-03-22 15:35:36
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
Bill Moran <wmoran(at)collaborativefusion(dot)com> writes:
> In response to David Brain <dbrain(at)bandwidth(dot)com>:
>> I am curious as to why 'top' gives such different output on the two 
>> systems - the datasets are large and so I know I benefit from having 
>> high shared_buffers and effective_cache_size settings.

> Have you done any actual queries on the new system?  PG won't use the
> shm until it needs it -- and that doesn't occur until it gets a request
> for data via a query.

More accurately, top won't consider shared mem to be part of the process
address space until it's actually touched by that process.

			regards, tom lane

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