From: Martin Sustrik <sustrik@fastmq.com>
To: Jeff Moyer <jmoyer@redhat.com>
Cc: Roger Heflin <rogerheflin@gmail.com>,
Martin Lucina <mato@kotelna.sk>,
linux-kernel@vger.kernel.org
Subject: Re: Higher than expected disk write(2) latency
Date: Wed, 02 Jul 2008 20:20:39 +0200 [thread overview]
Message-ID: <486BC6F7.2090709@fastmq.com> (raw)
In-Reply-To: <x49abh0p2y1.fsf@segfault.boston.devel.redhat.com>
> I thought you were doing I/O to the underlying block device. If so,
> there's no need to open with O_SYNC. You do, however, need to open the
> device with O_DIRECT and align your buffers (and buffer lengths)
> properly.
Yes, we are using O_DIRECT + aligning the buffers. However, usign O_SYNC
vs. O_ASYNC seems to matter (different latency). Maybe this is because
we are using librt?
> Which AIO interface are you using, libaio or librt? How many I/Os are
> you queueing to the device? You may want to take a look at aio-stress.c
> as a way to test your device (this uses libaio, the in-kernel AIO
> interface).
We are using librt, queueing 10240 writes, 512 bytes each.
We'll retry with libaio. Thanks for advice.
Martin
next prev parent reply other threads:[~2008-07-02 18:20 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-28 12:11 Higher than expected disk write(2) latency Martin Lucina
2008-06-28 13:11 ` Roger Heflin
2008-06-30 18:10 ` Martin Sustrik
2008-06-30 19:02 ` Roger Heflin
2008-06-30 22:20 ` Martin Sustrik
2008-07-01 0:11 ` Bernd Eckenfels
2008-07-02 16:48 ` Martin Sustrik
2008-07-02 18:15 ` Jeff Moyer
2008-07-02 18:20 ` Martin Sustrik [this message]
2008-07-04 3:16 ` David Dillow
2008-07-02 21:33 ` Roger Heflin
2008-06-28 14:47 ` David Newall
2008-06-29 11:34 ` Martin Sustrik
2008-07-10 5:27 ` Andrew Morton
2008-07-10 8:12 ` Martin Sustrik
2008-07-10 8:14 ` Andrew Morton
2008-07-10 13:29 ` Chris Mason
2008-07-10 13:41 ` Martin Lucina
2008-07-10 14:01 ` Arjan van de Ven
2008-07-10 14:18 ` Chris Mason
2008-07-10 8:31 ` Alan Cox
2008-07-10 13:17 ` Martin Sustrik
2008-07-10 13:18 ` Andrew Morton
2008-07-11 15:17 ` Martin Sustrik
[not found] <fa.OZMA74BZPX46rhnjz1am4hB786M@ifi.uio.no>
2008-06-30 6:41 ` Robert Hancock
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