linux-kernel - Re: Performance regression in IO scheduler still there

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Date:	Tue, 10 Nov 2009 19:37:30 +0100
From:	Jan Kara <jack@...e.cz>
To:	Jeff Moyer <jmoyer@...hat.com>
Cc:	Corrado Zoccolo <czoccolo@...il.com>, Jan Kara <jack@...e.cz>,
	jens.axboe@...cle.com, LKML <linux-kernel@...r.kernel.org>,
	Chris Mason <chris.mason@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Galbraith <efault@....de>
Subject: Re: Performance regression in IO scheduler still there

On Fri 06-11-09 09:14:53, Jeff Moyer wrote:
> Corrado Zoccolo <czoccolo@...il.com> writes:
> 
> > Hi Jeff,
> > what hardware are you using for tests?
> > I see aggregated random read bandwidth is larger than sequential read
> > bandwidth, and write bandwidth greater than read.
> > Is this a SAN with multiple independent spindles?
> 
> Yeah, this is a single path to an HP EVA storage array.  There are 24 or
> so disks striped in the pool used to create the volume I am using.  Jan,
> could you repeat your tests with /sys/block/sdX/queue/iosched/low_latency
> set to 0?
  I'll give it a spin tomorrow...

									Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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