From: Michael Paquier <michael@paquier.xyz>
To: Joao Junior <jcoj2006@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: shared buffers and startup process
Date: Wed, 15 Jan 2020 11:48:00 +0900
Message-ID: <20200115024800.GD2243@paquier.xyz> (raw)
In-Reply-To: <CABnPa_iu8LB=g-Cau8BhvJ1M4rOKRxZK-qzKdzvoG=1=2rbZbQ@mail.gmail.com>
References: <CABnPa_iu8LB=g-Cau8BhvJ1M4rOKRxZK-qzKdzvoG=1=2rbZbQ@mail.gmail.com>
On Tue, Jan 14, 2020 at 04:29:51PM +0100, Joao Junior wrote:
> I would like to know if increasing the amount of shared-buffers could help
> the startup process applying the wals. I would like to know if in
> the process of reading the wals and applying them, blocks that should be
> written will be brought to shared buffer or not??
Please feel free to look at XLogReadBufferForRedo() in xlogutils.c and
check what the routine does, and when/where it gets called. The code
is well-documented, so you will find your answer easily.
> If yes, having a bigger
> shared buffer will keep as much as possible the amount of pages there and
> increase the startup process's speed avoiding pages's replacement and going
> to the OS cache and maybe to the disk .
> Does it make sense?
It does. Even if relying on the OS cache would be enough in most
cases, it is good to keep a certain of pages hot enough, and you need
to be careful with not setting shared_buffers too high either.
--
Michael
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To: pgsql-performance@postgresql.org
Cc: michael@paquier.xyz, jcoj2006@gmail.com
Subject: Re: shared buffers and startup process
In-Reply-To: <20200115024800.GD2243@paquier.xyz>
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