From: Jeff Davis <pgsql@j-davis.com>
To: Josh Berkus <josh@agliodbs.com>
Cc: Greg Smith <greg@2ndquadrant.com>
Cc: Kevin Grittner <Kevin.Grittner@wicourts.gov>
Cc: pgsql-performance@postgresql.org, Albe Laurenz <laurenz.albe@wien.gv.at>
Subject: Re: Linux I/O tuning: CFQ vs. deadline
Date: Tue, 16 Feb 2010 13:34:11 -0800
Message-ID: <1266356051.20221.8.camel@monkey-cat.sm.truviso.com> (raw)
In-Reply-To: <4B704EA0.3050906@agliodbs.com>
References: <4B6FDD26.9010106@2ndquadrant.com>
<D960CB61B694CF459DCFB4B0128514C203938157@exadv11.host.magwien.gv.at>
<4B6FD868020000250002F084@gw.wicourts.gov>
<4B702E05.1000708@2ndquadrant.com>
<4B704EA0.3050906@agliodbs.com>
On Mon, 2010-02-08 at 09:49 -0800, Josh Berkus wrote:
> FWIW, back when deadline was first introduced Mark Wong did some tests
> and found Deadline to be the fastest of 4 on DBT2 ... but only by about
> 5%. If the read vs. checkpoint analysis is correct, what was happening
> is the penalty for checkpoints on deadline was almost wiping out the
> advantage for reads, but not quite.
I also did some tests when I was putting together my Synchronized Scan
benchmarks:
http://j-davis.com/postgresql/83v82_scans.html
CFQ was so slow that I didn't include it in the results at all.
The tests weren't intended to compare schedulers, so I did most of the
tests with anticipatory (at least the ones on linux; I also tested
freebsd). However, I have some raw data from the tests I did run with
CFQ:
http://j-davis.com/postgresql/results/
They will take some interpretation (again, not intended as scheduler
benchmarks). The server was modified to record a log message every N
page accesses.
Regards,
Jeff Davis
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Cc: pgsql@j-davis.com, josh@agliodbs.com, greg@2ndquadrant.com, Kevin.Grittner@wicourts.gov, laurenz.albe@wien.gv.at
Subject: Re: Linux I/O tuning: CFQ vs. deadline
In-Reply-To: <1266356051.20221.8.camel@monkey-cat.sm.truviso.com>
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