From: Wu Fengguang <fengguang.wu@gmail.com>
To: Andreas Dilger <adilger@dilger.ca>
Cc: Dave Chinner <david@fromorbit.com>,
Vivek Goyal <vgoyal@redhat.com>,
Andrea Arcangeli <aarcange@redhat.com>, Jan Kara <jack@suse.cz>,
"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
Mike Snitzer <snitzer@redhat.com>,
"neilb@suse.de" <neilb@suse.de>,
"dm-devel@redhat.com" <dm-devel@redhat.com>,
Christoph Hellwig <hch@infradead.org>,
Jeff Moyer <jmoyer@redhat.com>,
Boaz Harrosh <bharrosh@panasas.com>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
"lsf-pc@lists.linux-foundation.org"
<lsf-pc@lists.linux-foundation.org>,
Chris Mason <chris.mason@oracle.com>,
"Darrick J.Wong" <djwong@us.ibm.com>
Subject: Re: [Lsf-pc] [dm-devel] [LSF/MM TOPIC] a few storage topics
Date: Fri, 27 Jan 2012 15:53:07 +0800 [thread overview]
Message-ID: <20120127075306.GA8795@localhost> (raw)
In-Reply-To: <20C51818-5C53-4417-B62A-AD7C020CE283@dilger.ca>
On Thu, Jan 26, 2012 at 10:25:33PM -0700, Andreas Dilger wrote:
[snip]
> Doesn't the kernel derive at least some idea of the speed of a device
> due to the writeback changes that you made? It would be very useful
> if we could derive at least some rough metric for the device performance
> in the kernel and use that as input to the readahead window size as well.
Yeah we now have bdi->write_bandwidth (exported as "BdiWriteBandwidth"
in /debug/bdi/8:0/stats) for estimating the bdi write bandwidth.
However the value is not reflecting the sequential throughput in some
cases:
1) when doing random writes
2) when doing mixed reads+writes
3) when not enough IO have been issued
4) in the rare case, when writing to a small area repeatedly so that
it's effectively writing to the internal disk buffer at high speed
So there are still some challenges in getting a reliably usable
runtime estimation.
Thanks,
Fengguang
next prev parent reply other threads:[~2012-01-27 7:53 UTC|newest]
Thread overview: 96+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-21 17:26 [CFP] Linux Storage, Filesystem & Memory Management Summit 2012 (April 1-2) Williams, Dan J
2012-01-17 20:06 ` [LSF/MM TOPIC] a few storage topics Mike Snitzer
2012-01-17 21:36 ` [Lsf-pc] " Jan Kara
2012-01-18 22:58 ` Darrick J. Wong
2012-01-18 23:22 ` Jan Kara
2012-01-18 23:42 ` Boaz Harrosh
2012-01-19 9:46 ` Jan Kara
2012-01-19 15:08 ` Andrea Arcangeli
2012-01-19 20:52 ` Jan Kara
2012-01-19 21:39 ` Andrea Arcangeli
2012-01-22 11:31 ` Boaz Harrosh
2012-01-23 16:30 ` Jan Kara
2012-01-22 12:21 ` Boaz Harrosh
2012-01-23 16:18 ` Jan Kara
2012-01-23 17:53 ` Andrea Arcangeli
2012-01-23 18:28 ` Jeff Moyer
2012-01-23 18:56 ` Andrea Arcangeli
2012-01-23 19:19 ` Jeff Moyer
2012-01-24 15:15 ` Chris Mason
2012-01-24 16:56 ` [dm-devel] " Christoph Hellwig
2012-01-24 17:01 ` Andreas Dilger
2012-01-24 17:06 ` [Lsf-pc] [dm-devel] " Andrea Arcangeli
2012-01-24 17:08 ` Chris Mason
2012-01-24 17:08 ` [Lsf-pc] " Andreas Dilger
2012-01-24 18:05 ` [dm-devel] " Jeff Moyer
2012-01-24 18:05 ` Jeff Moyer
2012-01-24 18:40 ` Christoph Hellwig
2012-01-24 19:07 ` Chris Mason
2012-01-24 19:14 ` Jeff Moyer
2012-01-24 20:09 ` [Lsf-pc] [dm-devel] " Jan Kara
2012-01-24 20:13 ` [Lsf-pc] " Jeff Moyer
2012-01-24 20:39 ` [Lsf-pc] [dm-devel] " Jan Kara
2012-01-24 20:59 ` Jeff Moyer
2012-01-24 20:59 ` Jeff Moyer
2012-01-24 21:08 ` Jan Kara
2012-01-25 3:29 ` Wu Fengguang
2012-01-25 6:15 ` [Lsf-pc] " Andreas Dilger
2012-01-25 6:35 ` [Lsf-pc] [dm-devel] " Wu Fengguang
2012-01-25 14:00 ` Jan Kara
2012-01-26 12:29 ` Andreas Dilger
2012-01-27 17:03 ` Ted Ts'o
2012-01-26 16:25 ` Vivek Goyal
2012-01-26 20:37 ` Jan Kara
2012-01-26 22:34 ` Dave Chinner
2012-01-27 3:27 ` Wu Fengguang
2012-01-27 5:25 ` Andreas Dilger
2012-01-27 7:53 ` Wu Fengguang [this message]
2012-01-25 14:33 ` Steven Whitehouse
2012-01-25 14:45 ` Jan Kara
2012-01-25 16:22 ` Loke, Chetan
2012-01-25 16:22 ` Loke, Chetan
2012-01-25 16:40 ` Steven Whitehouse
2012-01-25 17:08 ` Loke, Chetan
2012-01-25 17:08 ` Loke, Chetan
2012-01-25 17:32 ` James Bottomley
2012-01-25 18:28 ` Loke, Chetan
2012-01-25 18:28 ` Loke, Chetan
2012-01-25 18:28 ` Loke, Chetan
2012-01-25 18:37 ` Loke, Chetan
2012-01-25 18:37 ` Loke, Chetan
2012-01-25 18:37 ` Loke, Chetan
2012-01-25 18:37 ` James Bottomley
2012-01-25 20:06 ` Chris Mason
2012-01-25 22:46 ` Andrea Arcangeli
2012-01-25 22:58 ` Jan Kara
2012-01-26 8:59 ` Boaz Harrosh
2012-01-26 8:59 ` Boaz Harrosh
2012-01-26 16:40 ` Loke, Chetan
2012-01-26 16:40 ` Loke, Chetan
2012-01-26 17:00 ` Andreas Dilger
2012-01-26 17:00 ` Andreas Dilger
2012-01-26 17:16 ` Loke, Chetan
2012-01-26 17:16 ` Loke, Chetan
2012-02-03 12:37 ` Wu Fengguang
2012-01-26 22:38 ` Dave Chinner
2012-01-26 22:38 ` Dave Chinner
2012-01-26 16:17 ` Loke, Chetan
2012-01-26 16:17 ` Loke, Chetan
2012-01-26 16:17 ` Loke, Chetan
2012-01-25 18:44 ` Boaz Harrosh
2012-01-25 18:44 ` Boaz Harrosh
2012-02-03 12:55 ` Wu Fengguang
2012-01-24 19:11 ` [dm-devel] [Lsf-pc] " Jeff Moyer
2012-01-24 19:11 ` Jeff Moyer
2012-01-26 22:31 ` Dave Chinner
2012-01-24 17:12 ` Jeff Moyer
2012-01-24 17:32 ` Chris Mason
2012-01-24 18:14 ` Jeff Moyer
2012-01-25 0:23 ` NeilBrown
2012-01-25 0:23 ` NeilBrown
2012-01-25 6:11 ` Andreas Dilger
2012-01-25 6:11 ` Andreas Dilger
2012-01-18 23:39 ` Dan Williams
2012-01-24 17:59 ` Martin K. Petersen
2012-01-24 19:48 ` Douglas Gilbert
2012-01-24 20:04 ` Martin K. Petersen
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