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From: Greg Smith <greg@2ndquadrant.com>
To: Jeff <threshar@torgo.978.org>
Cc: david@lang.hm, Hannu Krosing <hannu@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: Wed, 10 Feb 2010 01:37:04 -0500
Message-ID: <4B725410.5010000@2ndquadrant.com> (raw)
In-Reply-To: <39DDB34B-C375-46ED-83D2-688A32188100@torgo.978.org>
References: <4B6FDD26.9010106@2ndquadrant.com>
	<D960CB61B694CF459DCFB4B0128514C203938157@exadv11.host.magwien.gv.at>
	<4B6FD868020000250002F084@gw.wicourts.gov>
	<4B702E05.1000708@2ndquadrant.com>
	<1265652529.2153.13.camel@hvost>
	<4B70E18D.2040709@2ndquadrant.com>
	<alpine.DEB.2.00.1002082033090.6976@asgard.lang.hm>
	<39DDB34B-C375-46ED-83D2-688A32188100@torgo.978.org>

Jeff wrote:
> I'd done some testing a while ago on the schedulers and at the time 
> deadline or noop smashed cfq.  Now, it is 100% possible since then 
> that they've made vast improvements to cfq and or the VM to get better 
> or similar performance.  I recall a vintage of 2.6 where they severely 
> messed up the VM. Glad I didn't upgrade to that one :)
>
> Here's the old post: 
> http://archives.postgresql.org/pgsql-performance/2008-04/msg00155.php

pgiosim doesn't really mix writes into there though, does it?  The mixed 
read/write situations are the ones where the scheduler stuff gets messy.

-- 
Greg Smith    2ndQuadrant   Baltimore, MD
PostgreSQL Training, Services and Support
greg@2ndQuadrant.com  www.2ndQuadrant.com




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