From: Wu Fengguang <fengguang.wu@intel.com>
To: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Jan Kara <jack@suse.cz>, Christoph Hellwig <hch@lst.de>,
Dave Chinner <david@fromorbit.com>, Theodore Ts'o <tytso@mit.edu>,
Chris Mason <chris.mason@oracle.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Mel Gorman <mel@csn.ul.ie>, Rik van Riel <riel@redhat.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Greg Thelen <gthelen@google.com>,
Minchan Kim <minchan.kim@gmail.com>,
linux-mm <linux-mm@kvack.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 29/35] nfs: in-commit pages accounting and wait queue
Date: Tue, 14 Dec 2010 23:40:26 +0800 [thread overview]
Message-ID: <20101214154026.GA8959@localhost> (raw)
In-Reply-To: <1292274951.8795.28.camel@heimdal.trondhjem.org>
On Tue, Dec 14, 2010 at 05:15:51AM +0800, Trond Myklebust wrote:
> On Mon, 2010-12-13 at 22:47 +0800, Wu Fengguang wrote:
> > plain text document attachment (writeback-nfs-in-commit.patch)
> > When doing 10+ concurrent dd's, I observed very bumpy commits submission
> > (partly because the dd's are started at the same time, and hence reached
> > 4MB to-commit pages at the same time). Basically we rely on the server
> > to complete and return write/commit requests, and want both to progress
> > smoothly and not consume too many pages. The write request wait queue is
> > not enough as it's mainly network bounded. So add another commit request
> > wait queue. Only async writes need to sleep on this queue.
> >
>
> I'm not understanding the above reasoning. Why should we serialise
> commits at the per-filesystem level (and only for non-blocking flushes
> at that)?
I did the commit wait queue after seeing this graph, where there is
very bursty pattern of commit submission and hence completion:
http://www.kernel.org/pub/linux/kernel/people/wfg/writeback/tests/3G/nfs-100dd-1M-8p-2953M-2.6.37-rc3+-2010-12-03-01/nfs-commit-1000.png
leading to big fluctuations, eg. the almost straight up/straight down
lines below
http://www.kernel.org/pub/linux/kernel/people/wfg/writeback/tests/3G/nfs-100dd-1M-8p-2953M-2.6.37-rc3+-2010-12-03-01/vmstat-dirty-300.png
http://www.kernel.org/pub/linux/kernel/people/wfg/writeback/tests/3G/nfs-100dd-1M-8p-2953M-2.6.37-rc3+-2010-12-03-01/dirty-pages.png
http://www.kernel.org/pub/linux/kernel/people/wfg/writeback/tests/3G/nfs-100dd-1M-8p-2953M-2.6.37-rc3+-2010-12-03-01/dirty-pages-200.png
A commit wait queue will help wipe out the "peaks". The "fixed" graph
is
http://www.kernel.org/pub/linux/kernel/people/wfg/writeback/tests/3G/nfs-100dd-1M-8p-2952M-2.6.37-rc5+-2010-12-09-03-23/vmstat-dirty-300.png
http://www.kernel.org/pub/linux/kernel/people/wfg/writeback/tests/3G/nfs-100dd-1M-8p-2952M-2.6.37-rc5+-2010-12-09-03-23/dirty-pages.png
Blocking flushes don't need to wait on this queue because they already
throttle themselves by waiting on the inode commit lock before/after
the commit. They actually should not wait on this queue, to prevent
sync requests being unnecessarily blocked by async ones.
Thanks,
Fengguang
next prev parent reply other threads:[~2010-12-14 15:40 UTC|newest]
Thread overview: 87+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-13 14:46 [PATCH 00/35] IO-less dirty throttling v4 Wu Fengguang
2010-12-13 14:46 ` [PATCH 01/35] writeback: enabling gate limit for light dirtied bdi Wu Fengguang
2011-01-12 21:43 ` Jan Kara
2011-01-13 3:44 ` Wu Fengguang
2011-01-13 3:58 ` Wu Fengguang
2011-01-13 19:26 ` Peter Zijlstra
2011-01-14 3:21 ` Wu Fengguang
2010-12-13 14:46 ` [PATCH 02/35] writeback: safety margin for bdi stat error Wu Fengguang
2011-01-12 21:59 ` Jan Kara
2011-01-13 4:14 ` Wu Fengguang
2011-01-13 10:38 ` Jan Kara
2011-01-13 10:41 ` Wu Fengguang
2010-12-13 14:46 ` [PATCH 03/35] writeback: prevent duplicate balance_dirty_pages_ratelimited() calls Wu Fengguang
2010-12-13 14:46 ` [PATCH 04/35] writeback: reduce per-bdi dirty threshold ramp up time Wu Fengguang
2010-12-14 13:37 ` Richard Kennedy
2010-12-14 13:59 ` Wu Fengguang
2010-12-14 14:33 ` Wu Fengguang
2010-12-14 14:39 ` Wu Fengguang
2010-12-14 14:50 ` Peter Zijlstra
2010-12-14 15:15 ` Wu Fengguang
2010-12-14 15:26 ` Wu Fengguang
2010-12-14 14:56 ` Wu Fengguang
2010-12-15 18:48 ` Richard Kennedy
2010-12-17 13:07 ` Wu Fengguang
2010-12-13 14:46 ` [PATCH 05/35] writeback: IO-less balance_dirty_pages() Wu Fengguang
2010-12-13 14:46 ` [PATCH 06/35] writeback: consolidate variable names in balance_dirty_pages() Wu Fengguang
2010-12-13 14:46 ` [PATCH 07/35] writeback: per-task rate limit on balance_dirty_pages() Wu Fengguang
2010-12-13 14:46 ` [PATCH 08/35] writeback: user space think time compensation Wu Fengguang
2010-12-13 14:46 ` [PATCH 09/35] writeback: account per-bdi accumulated written pages Wu Fengguang
2010-12-13 14:46 ` [PATCH 10/35] writeback: bdi write bandwidth estimation Wu Fengguang
2010-12-13 14:46 ` [PATCH 11/35] writeback: show bdi write bandwidth in debugfs Wu Fengguang
2010-12-13 14:46 ` [PATCH 12/35] writeback: scale down max throttle bandwidth on concurrent dirtiers Wu Fengguang
2010-12-14 1:21 ` Yan, Zheng
2010-12-14 7:00 ` Wu Fengguang
2010-12-14 13:00 ` Wu Fengguang
2010-12-13 14:46 ` [PATCH 13/35] writeback: bdi base throttle bandwidth Wu Fengguang
2010-12-13 14:47 ` [PATCH 14/35] writeback: smoothed bdi dirty pages Wu Fengguang
2010-12-13 14:47 ` [PATCH 15/35] writeback: adapt max balance pause time to memory size Wu Fengguang
2010-12-13 14:47 ` [PATCH 16/35] writeback: increase min pause time on concurrent dirtiers Wu Fengguang
2010-12-13 18:23 ` Valdis.Kletnieks
2010-12-14 6:51 ` Wu Fengguang
2010-12-14 18:42 ` Valdis.Kletnieks
2010-12-14 18:55 ` Peter Zijlstra
2010-12-14 20:13 ` Valdis.Kletnieks
2010-12-14 20:24 ` Peter Zijlstra
2010-12-14 20:37 ` Valdis.Kletnieks
2010-12-13 14:47 ` [PATCH 17/35] writeback: quit throttling when bdi dirty pages dropped low Wu Fengguang
2010-12-16 5:17 ` Wu Fengguang
2010-12-13 14:47 ` [PATCH 18/35] writeback: start background writeback earlier Wu Fengguang
2010-12-16 5:37 ` Wu Fengguang
2010-12-13 14:47 ` [PATCH 19/35] writeback: make nr_to_write a per-file limit Wu Fengguang
2010-12-13 14:47 ` [PATCH 20/35] writeback: scale IO chunk size up to device bandwidth Wu Fengguang
2010-12-13 14:47 ` [PATCH 21/35] writeback: trace balance_dirty_pages() Wu Fengguang
2010-12-13 14:47 ` [PATCH 22/35] writeback: trace global dirty page states Wu Fengguang
2010-12-17 2:19 ` Wu Fengguang
2010-12-17 3:11 ` Wu Fengguang
2010-12-17 6:52 ` Hugh Dickins
2010-12-17 9:31 ` Wu Fengguang
2010-12-17 11:21 ` [PATCH] writeback: skip balance_dirty_pages() for in-memory fs Wu Fengguang
2010-12-17 14:21 ` Rik van Riel
2010-12-17 15:34 ` Minchan Kim
2010-12-17 15:42 ` Minchan Kim
2010-12-21 5:59 ` Hugh Dickins
2010-12-21 9:39 ` Wu Fengguang
2010-12-30 3:15 ` Hugh Dickins
2010-12-13 14:47 ` [PATCH 23/35] writeback: trace writeback_single_inode() Wu Fengguang
2010-12-13 14:47 ` [PATCH 24/35] btrfs: dont call balance_dirty_pages_ratelimited() on already dirty pages Wu Fengguang
2010-12-13 14:47 ` [PATCH 25/35] btrfs: lower the dirty balacing rate limit Wu Fengguang
2010-12-13 14:47 ` [PATCH 26/35] btrfs: wait on too many nr_async_bios Wu Fengguang
2010-12-13 14:47 ` [PATCH 27/35] nfs: livelock prevention is now done in VFS Wu Fengguang
2010-12-13 14:47 ` [PATCH 28/35] nfs: writeback pages wait queue Wu Fengguang
2010-12-13 14:47 ` [PATCH 29/35] nfs: in-commit pages accounting and " Wu Fengguang
2010-12-13 21:15 ` Trond Myklebust
2010-12-14 15:40 ` Wu Fengguang [this message]
2010-12-14 15:57 ` Trond Myklebust
2010-12-15 15:07 ` Wu Fengguang
2010-12-13 14:47 ` [PATCH 30/35] nfs: heuristics to avoid commit Wu Fengguang
2010-12-13 20:53 ` Trond Myklebust
2010-12-14 8:20 ` Wu Fengguang
2010-12-13 14:47 ` [PATCH 31/35] nfs: dont change wbc->nr_to_write in write_inode() Wu Fengguang
2010-12-13 21:01 ` Trond Myklebust
2010-12-14 15:53 ` Wu Fengguang
2010-12-13 14:47 ` [PATCH 32/35] nfs: limit the range of commits Wu Fengguang
2010-12-13 14:47 ` [PATCH 33/35] nfs: adapt congestion threshold to dirty threshold Wu Fengguang
2010-12-13 14:47 ` [PATCH 34/35] nfs: trace nfs_commit_unstable_pages() Wu Fengguang
2010-12-13 14:47 ` [PATCH 35/35] nfs: trace nfs_commit_release() Wu Fengguang
[not found] ` <AANLkTinFeu7LMaDFgUcP3r2oqVHE5bei3T5JTPGBNvS9@mail.gmail.com>
2010-12-14 4:59 ` [PATCH 00/35] IO-less dirty throttling v4 Wu Fengguang
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