Re: Potential memory usage issue - Mailing list pgsql-performance

From Tom Lane
Subject Re: Potential memory usage issue
Date
Msg-id 3701.1174577736@sss.pgh.pa.us
Whole thread Raw
In response to Re: Potential memory usage issue  (Bill Moran <wmoran@collaborativefusion.com>)
List pgsql-performance
Bill Moran <wmoran@collaborativefusion.com> writes:
> In response to David Brain <dbrain@bandwidth.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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