From: Mel Gorman <mel@csn.ul.ie>
To: Wu Fengguang <fengguang.wu@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Dave Chinner <david@fromorbit.com>,
Christoph Hellwig <hch@infradead.org>,
Chris Mason <chris.mason@oracle.com>,
Jens Axboe <jens.axboe@oracle.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 5/6] writeback: try more writeback as long as something was written
Date: Mon, 26 Jul 2010 12:01:25 +0100 [thread overview]
Message-ID: <20100726110125.GN5300@csn.ul.ie> (raw)
In-Reply-To: <20100722061823.050523298@intel.com>
On Thu, Jul 22, 2010 at 01:09:33PM +0800, Wu Fengguang wrote:
> writeback_inodes_wb()/__writeback_inodes_sb() are not agressive in that
> they only populate b_io when necessary at entrance time. When the queued
> set of inodes are all synced, they just return, possibly with
> wbc.nr_to_write > 0.
>
> For kupdate and background writeback, there may be more eligible inodes
> sitting in b_dirty when the current set of b_io inodes are completed. So
> it is necessary to try another round of writeback as long as we made some
> progress in this round. When there are no more eligible inodes, no more
> inodes will be enqueued in queue_io(), hence nothing could/will be
> synced and we may safely bail.
>
> This will livelock sync when there are heavy dirtiers. However in that case
> sync will already be livelocked w/o this patch, as the current livelock
> avoidance code is virtually a no-op (for one thing, wb_time should be
> set statically at sync start time and be used in move_expired_inodes()).
> The sync livelock problem will be addressed in other patches.
>
There does seem to be a livelock issue. During iozone, I see messages in
the console log with this series applied that look like
[ 1687.132034] INFO: task iozone:21225 blocked for more than 120 seconds.
[ 1687.211425] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 1687.305204] iozone D ffff880001b13640 0 21225 21108 0x00000000
[ 1687.387677] ffff880037419d48 0000000000000082 0000000000000348 0000000000013640
[ 1687.476594] ffff880037419fd8 ffff880037419fd8 ffff880065892da0 0000000000013640
[ 1687.565512] 0000000000013640 0000000000013640 ffff880065892da0 ffff88007f411510
[ 1687.654431] Call Trace:
[ 1687.683663] [<ffffffff81002996>] ? ftrace_call+0x5/0x2b
[ 1687.747204] [<ffffffff812d8f67>] schedule_timeout+0x2d/0x214
[ 1687.815947] [<ffffffff81002996>] ? ftrace_call+0x5/0x2b
[ 1687.879489] [<ffffffff812d8527>] wait_for_common+0xd2/0x14a
[ 1687.947195] [<ffffffff8103ef1e>] ? default_wake_function+0x0/0x14
[ 1688.021132] [<ffffffff81002996>] ? ftrace_call+0x5/0x2b
[ 1688.084680] [<ffffffff811160f0>] ? sync_one_sb+0x0/0x22
[ 1688.148223] [<ffffffff812d8657>] wait_for_completion+0x1d/0x1f
[ 1688.219051] [<ffffffff811121c4>] sync_inodes_sb+0x92/0x14c
[ 1688.285710] [<ffffffff811160f0>] ? sync_one_sb+0x0/0x22
[ 1688.349249] [<ffffffff811160b9>] __sync_filesystem+0x4c/0x83
[ 1688.417995] [<ffffffff81116110>] sync_one_sb+0x20/0x22
[ 1688.480505] [<ffffffff810f6a23>] iterate_supers+0x66/0xa4
[ 1688.546124] [<ffffffff81116157>] sys_sync+0x45/0x5c
[ 1688.605509] [<ffffffff81002c72>] system_call_fastpath+0x16/0x1b
Similar messages do not appear without the patch. iozone does complete though
and the performance figures are not affected. Should I be worried?
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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next prev parent reply other threads:[~2010-07-26 11:01 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-22 5:09 [PATCH 0/6] [RFC] writeback: try to write older pages first Wu Fengguang
2010-07-22 5:09 ` [PATCH 1/6] writeback: pass writeback_control down to move_expired_inodes() Wu Fengguang
2010-07-23 18:16 ` Jan Kara
2010-07-26 10:44 ` Mel Gorman
2010-08-01 15:23 ` Minchan Kim
2010-07-22 5:09 ` [PATCH 2/6] writeback: the kupdate expire timestamp should be a moving target Wu Fengguang
2010-07-23 18:17 ` Jan Kara
2010-07-26 10:52 ` Mel Gorman
2010-07-26 11:32 ` Wu Fengguang
2010-08-01 15:29 ` Minchan Kim
2010-07-22 5:09 ` [PATCH 3/6] writeback: kill writeback_control.more_io Wu Fengguang
2010-07-23 18:24 ` Jan Kara
2010-07-26 10:53 ` Mel Gorman
2010-08-01 15:34 ` Minchan Kim
2010-08-05 14:50 ` Wu Fengguang
2010-08-05 14:55 ` Wu Fengguang
2010-08-05 14:56 ` Minchan Kim
2010-08-05 15:26 ` Wu Fengguang
2010-07-22 5:09 ` [PATCH 4/6] writeback: sync expired inodes first in background writeback Wu Fengguang
2010-07-23 18:15 ` Jan Kara
2010-07-26 11:51 ` Wu Fengguang
2010-07-26 12:12 ` Jan Kara
2010-07-26 12:29 ` Wu Fengguang
2010-07-26 10:57 ` Mel Gorman
2010-07-26 12:00 ` Wu Fengguang
2010-07-26 12:20 ` Jan Kara
2010-07-26 12:31 ` Wu Fengguang
2010-07-26 12:39 ` Jan Kara
2010-07-26 12:47 ` Wu Fengguang
2010-07-26 12:56 ` Wu Fengguang
2010-07-26 12:59 ` Mel Gorman
2010-07-26 13:11 ` Wu Fengguang
2010-07-27 9:45 ` Mel Gorman
2010-08-01 15:15 ` Minchan Kim
2010-07-22 5:09 ` [PATCH 5/6] writeback: try more writeback as long as something was written Wu Fengguang
2010-07-23 17:39 ` Jan Kara
2010-07-26 12:39 ` Wu Fengguang
2010-07-26 11:01 ` Mel Gorman [this message]
2010-07-26 11:39 ` Wu Fengguang
2010-07-22 5:09 ` [PATCH 6/6] writeback: introduce writeback_control.inodes_written Wu Fengguang
2010-07-26 11:04 ` Mel Gorman
2010-07-23 10:24 ` [PATCH 0/6] [RFC] writeback: try to write older pages first Mel Gorman
2010-07-26 7:18 ` Wu Fengguang
2010-07-26 10:42 ` Mel Gorman
2010-07-26 10:28 ` Itaru Kitayama
2010-07-26 11:47 ` Wu Fengguang
2011-04-19 3:00 [PATCH 0/6] writeback: moving expire targets for background/kupdate works Wu Fengguang
2011-04-19 3:00 ` [PATCH 5/6] writeback: try more writeback as long as something was written Wu Fengguang
2011-04-19 10:20 ` Jan Kara
2011-04-19 11:16 ` Wu Fengguang
2011-04-19 21:10 ` Jan Kara
2011-04-20 7:50 ` Wu Fengguang
2011-04-20 15:22 ` Jan Kara
2011-04-21 3:33 ` Wu Fengguang
2011-04-21 4:39 ` Christoph Hellwig
2011-04-21 6:05 ` Wu Fengguang
2011-04-21 16:41 ` Jan Kara
2011-04-22 2:32 ` Wu Fengguang
2011-04-22 21:23 ` Jan Kara
2011-04-21 7:09 ` Dave Chinner
2011-04-21 7:14 ` Christoph Hellwig
2011-04-21 7:52 ` Dave Chinner
2011-04-21 8:00 ` Christoph Hellwig
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