From: Sam R. <samruohola@yahoo.com>
To: david.rowley@2ndquadrant.com <david.rowley@2ndquadrant.com>
Cc: pgsql-performance@lists.postgresql.org <pgsql-performance@lists.postgresql.org>
Cc: Jeff Janes <jeff.janes@gmail.com>
Subject: Re: To keep indexes in memory, is large enough effective_cache_size enough?
Date: Fri, 28 Sep 2018 04:45:25 +0000 (UTC)
Message-ID: <740776989.746571.1538109925380@mail.yahoo.com> (raw)
In-Reply-To: <CAKJS1f9W+nhzj_CV2wP++XH8j-onnv8boBqzqvu1vpe=uH2pQA@mail.gmail.com>
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<CAKJS1f9W+nhzj_CV2wP++XH8j-onnv8boBqzqvu1vpe=uH2pQA@mail.gmail.com>
Hi!
> The double buffering> itself does not slow anything down.
That was what I was suspecting a little. Double buffering may not matter in our case, because the whole server is meant for PostgreSQL only.
In our case, we can e.g. reserve almost "all memory" for PostgreSQL (shared buffers etc.).
Please correct me if I am wrong.
BR Sam
On ti, syysk. 25, 2018 at 23:55, David Rowley<david.rowley@2ndquadrant.com> wrote: On Tue, 25 Sep 2018 at 18:36, Sam R. <samruohola@yahoo.com> wrote:
> Regarding double buffering: I do not know how much double buffering would slow down operations.
> It could also be possible to turn off kernel page cache on our DB server, to avoid double buffering. Although, we may still keep it in use.
I think you've misunderstood double buffering. The double buffering
itself does not slow anything down. If the buffer is in shared buffers
already then it does not need to look any further for it. Double
buffering only becomes an issue when buffers existing 2 times in
memory causes other useful buffers to appear 0 times.
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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To: pgsql-performance@postgresql.org
Cc: samruohola@yahoo.com, david.rowley@2ndquadrant.com, pgsql-performance@lists.postgresql.org, jeff.janes@gmail.com
Subject: Re: To keep indexes in memory, is large enough effective_cache_size enough?
In-Reply-To: <740776989.746571.1538109925380@mail.yahoo.com>
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