From: Jeff Moyer <jmoyer@redhat.com>
To: Corrado Zoccolo <czoccolo@gmail.com>
Cc: Jan Kara <jack@suse.cz>, jens.axboe@oracle.com,
       LKML <linux-kernel@vger.kernel.org>,
       Chris Mason <chris.mason@oracle.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       Mike Galbraith <efault@gmx.de>
Subject: Re: Performance regression in IO scheduler still there
References: <20091026172012.GC7233@duck.suse.cz>
	<x49zl7020mr.fsf@segfault.boston.devel.redhat.com>
	<4e5e476b0911051500j7587dd6dh975148475418efcf@mail.gmail.com>
Date: Fri, 06 Nov 2009 09:14:53 -0500
In-Reply-To: <4e5e476b0911051500j7587dd6dh975148475418efcf@mail.gmail.com>
	(Corrado Zoccolo's message of "Fri, 6 Nov 2009 00:00:40 +0100")
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Corrado Zoccolo <czoccolo@gmail.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?

Cheers,
Jeff
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