From: Jan Kara <jack@suse.cz>
To: Wu Fengguang <fengguang.wu@intel.com>
Cc: Jan Kara <jack@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Christoph Hellwig <hch@lst.de>,
Trond Myklebust <Trond.Myklebust@netapp.com>,
Dave Chinner <david@fromorbit.com>, Theodore Ts'o <tytso@mit.edu>,
Chris Mason <chris.mason@oracle.com>, 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 02/35] writeback: safety margin for bdi stat error
Date: Thu, 13 Jan 2011 11:38:34 +0100 [thread overview]
Message-ID: <20110113103834.GA5008@quack.suse.cz> (raw)
In-Reply-To: <20110113041440.GC7840@localhost>
On Thu 13-01-11 12:14:40, Wu Fengguang wrote:
> On Thu, Jan 13, 2011 at 05:59:49AM +0800, Jan Kara wrote:
> > > So the root cause is, the bdi_dirty is well under the global nr_dirty
> > > due to accounting errors. This can be fixed by using bdi_stat_sum(),
> > So which statistic had the big error? I'd just like to understand
> > this (and how come your patch improves the situation)...
>
> bdi_stat_error() = nr_cpu_ids * BDI_STAT_BATCH
> = 8 * (8*(1+ilog2(8)))
> = 8 * 8 * 4
> = 256 pages
> = 1MB
Yes, my question was more aiming at on which statistics the error happens
so that it causes problems for you. Thinking about it now I suppose you
observe that bdi_nr_writeback + bdi_nr_reclaimable < bdi_thresh but in fact
the number of pages is higher than bdi_thresh because of accounting errors.
And thus we are able to reach global dirty limit and the tasks get
throttled heavily. Am I right?
Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR
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next prev parent reply other threads:[~2011-01-13 10:38 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 [this message]
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
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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