From: Wu Fengguang <fengguang.wu@intel.com>
To: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>,
Andreas Dilger <adilger@dilger.ca>,
"aziro.linux.adm" <aziro.linux.adm@gmail.com>,
Eric Whitney <eric.whitney@hp.com>,
Ext4 Developers List <linux-ext4@vger.kernel.org>,
linux-fsdevel@vger.kernel.org
Subject: Re: 3.2 and 3.1 filesystem scalability measurements
Date: Tue, 31 Jan 2012 20:55:18 +0800 [thread overview]
Message-ID: <20120131125518.GA15622@localhost> (raw)
In-Reply-To: <20120131105353.GA1278@quack.suse.cz>
On Tue, Jan 31, 2012 at 11:53:53AM +0100, Jan Kara wrote:
> On Tue 31-01-12 11:14:15, Dave Chinner wrote:
> > I also found this oddity on both XFS and ext4:
> >
> > flush-253:32-3400 [001] 1936151.384563: writeback_start: bdi 253:32: sb_dev 0:0 nr_pages=-898403 sync_mode=0 kupdate=0 range_cyclic=1 background=1 reason=background
> > flush-253:32-3400 [005] 1936151.455845: writeback_start: bdi 253:32: sb_dev 0:0 nr_pages=-911663 sync_mode=0 kupdate=0 range_cyclic=1 background=1 reason=background
> > flush-253:32-3400 [006] 1936151.596298: writeback_start: bdi 253:32: sb_dev 0:0 nr_pages=-931332 sync_mode=0 kupdate=0 range_cyclic=1 background=1 reason=background
> > flush-253:32-3400 [006] 1936151.719074: writeback_start: bdi 253:32: sb_dev 0:0 nr_pages=-951001 sync_mode=0 kupdate=0 range_cyclic=1 background=1 reason=background
> >
> > That's indicating the work->nr_pages is starting extremely negative,
> > which should not be the case. The highest I saw was around -2m.
> > Something is not working right there, as writeback is supposed to
> > terminate if work->nr_pages < 0....
> Ugh, what kernel is this? The tracepoint is just a couple of lines after
> if (work->nr_pages <= 0)
> break;
> so I really don't see how that could happen.
It should be a recent kernel judging from the "reason=background"
field.
I cannot find such "writeback_start.*nr_pages=-" pattern at all in my
huge pile of saved tracing logs. Since the background work is only
started by wb_check_background_flush() with .nr_pages = LONG_MAX,
I can only find such patterns:
flush-0:27-5216 [005] .... 472.119012: writeback_start: bdi 0:27: sb_dev 0:0 nr_pages=9223372036854775807 sync_mode=0 kupdate=0 range_cyclic=1 background=1 reason=background
flush-0:27-5216 [005] .... 472.119076: writeback_start: bdi 0:27: sb_dev 0:0 nr_pages=9223372036854775803 sync_mode=0 kupdate=0 range_cyclic=1 background=1 reason=background
flush-9:0-5176 [025] .... 475.578426: writeback_start: bdi 9:0: sb_dev 0:0 nr_pages=361160 sync_mode=0 kupdate=1 range_cyclic=1 background=0 reason=periodic
flush-9:0-5176 [025] .... 475.710138: writeback_start: bdi 9:0: sb_dev 0:0 nr_pages=328392 sync_mode=0 kupdate=1 range_cyclic=1 background=0 reason=periodic
Thanks,
Fengguang
next prev parent reply other threads:[~2012-01-31 12:55 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-30 4:09 3.2 and 3.1 filesystem scalability measurements Eric Whitney
2012-01-30 15:13 ` aziro.linux.adm
2012-01-30 20:30 ` Andreas Dilger
2012-01-31 0:14 ` Dave Chinner
2012-01-31 10:53 ` Jan Kara
2012-01-31 12:55 ` Wu Fengguang [this message]
2012-01-31 20:27 ` Dave Chinner
[not found] ` <20120131112726.GC3867@localhost>
2012-01-31 20:40 ` Dave Chinner
2012-01-30 15:36 ` Cédric Villemain
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