Re: Mapping a database completly into Memory

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Franco Bruno Borghesi <franco(at)akyasociados(dot)com(dot)ar>
Cc: Josh Berkus <josh(at)agliodbs(dot)com>, Daniel Migowski <postgresql(at)Mig-O(dot)de>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Mapping a database completly into Memory
Date: 2003-07-28 16:25:57
Message-ID: 10185.1059409557@sss.pgh.pa.us
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Franco Bruno Borghesi <franco(at)akyasociados(dot)com(dot)ar> writes:
> wouldn't also increasing shared_buffers to 64 or 128 MB be a good
> performance improvement? This way, pages belonging to heavily used
> indexes would be already cached by the database itself.

Not necessarily. The trouble with large shared_buffers settings is you
end up with lots of pages being doubly cached (both in PG's buffers and
in the kernel's disk cache), thus wasting RAM. If we had a portable way
of preventing the kernel from caching the same page, it would make more
sense to run with large shared_buffers.

regards, tom lane

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