From: Tom Lane <tgl@sss.pgh.pa.us>
To: Jordan Hurwich <jhurwich@pulsasensors.com>
Cc: Samed YILDIRIM <samed@reddoc.net>
Cc: pgsql-performance@lists.postgresql.org, Gautam Bellary <gautam@pulsasensors.com>
Subject: Re: Increased iowait and blk_read_time with higher shared_buffers
Date: Wed, 14 Dec 2022 13:27:23 -0500
Message-ID: <2784235.1671042443@sss.pgh.pa.us> (raw)
In-Reply-To: <CAJKqsjvsuFWoBD7++aPRmdfrr7UmsZbc2Whg6zqd3VQB02FTmg@mail.gmail.com>
References: <CAJKqsjvU3Er=FKwS8wc1E3QOUmJK8bPWVUfZXzm=Nzg55FULcQ@mail.gmail.com>
<CAAo1mbmDJctnPfxY_85Zm+-koTDhWJQp3Pmu9kARMzy40ryMEA@mail.gmail.com>
<CAJKqsjvsuFWoBD7++aPRmdfrr7UmsZbc2Whg6zqd3VQB02FTmg@mail.gmail.com>
Jordan Hurwich <jhurwich@pulsasensors.com> writes:
> I'm familiar with the article you linked to, and part of my surprise is
> that with these 32GB RAM machines we're seeing better performance at 12.5%
> (4GB) than the commonly recommended 25% (8GB) of system memory for
> shared_buffers. Your notes about disk read stats from Postgres potentially
> actually representing blocks read from the OS cache make sense, I just
> imagined that Postgres would be better at managing the memory when it was
> dedicated to it via shared_buffers than the OS (obviously with some point
> of diminishing returns); and I'm still hoping there's some Postgres
> configuration change we can make that enables better performance through
> improved utilization of shared_buffers at the commonly recommended 25% of
> system memory.
Keep in mind that 25% was never some kind of golden number. It is
a rough rule of thumb that was invented for far smaller machines than
what you're talking about here.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, jhurwich@pulsasensors.com, samed@reddoc.net, gautam@pulsasensors.com
Subject: Re: Increased iowait and blk_read_time with higher shared_buffers
In-Reply-To: <2784235.1671042443@sss.pgh.pa.us>
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