From: Dave Chinner <david@fromorbit.com>
To: Wu Fengguang <fengguang.wu@intel.com>
Cc: Jan Kara <jack@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mel@linux.vnet.ibm.com>, Mel Gorman <mel@csn.ul.ie>,
Itaru Kitayama <kitayama@cl.bb4u.ne.jp>,
Minchan Kim <minchan.kim@gmail.com>,
Linux Memory Management List <linux-mm@kvack.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 6/6] writeback: refill b_io iff empty
Date: Tue, 10 May 2011 14:53:46 +1000 [thread overview]
Message-ID: <20110510045346.GC19446@dastard> (raw)
In-Reply-To: <20110510043104.GA14423@localhost>
On Tue, May 10, 2011 at 12:31:04PM +0800, Wu Fengguang wrote:
> On Fri, May 06, 2011 at 10:21:55PM +0800, Jan Kara wrote:
> > On Fri 06-05-11 13:29:55, Wu Fengguang wrote:
> > > On Fri, May 06, 2011 at 12:37:08AM +0800, Jan Kara wrote:
> > > > On Wed 04-05-11 15:39:31, Wu Fengguang wrote:
> > > > > To help understand the behavior change, I wrote the writeback_queue_io
> > > > > trace event, and found very different patterns between
> > > > > - vanilla kernel
> > > > > - this patchset plus the sync livelock fixes
> > > > >
> > > > > Basically the vanilla kernel each time pulls a random number of inodes
> > > > > from b_dirty, while the patched kernel tends to pull a fixed number of
> > > > > inodes (enqueue=1031) from b_dirty. The new behavior is very interesting...
> > > > This regularity is really strange. Did you have a chance to look more into
> > > > it? I find it highly unlikely that there would be exactly 1031 dirty inodes
> > > > in b_dirty list every time you call move_expired_inodes()...
> > >
> > > Jan, I got some results for ext4. The total dd+tar+sync time is
> > > decreased from 177s to 167s. The other numbers are either raised or
> > > dropped.
> > Nice, but what I was more curious about was to understand why you saw
> > enqueued=1031 all the time.
>
> Maybe some unknown interactions with XFS? Attached is another trace
> with both writeback_single_inode and writeback_queue_io.
Perhaps because write throttling is limiting the number of files
being dirtied to match the number of files being cleaned? hence they
age at roughly the same rate as writeback is cleaning them?
Especially as most file are only a single page in size?
Or perhaps that is the rate at which IO completions are occurring
and updating the inode size and redirtying the inode? After all,
there are lots of inodes that are only state=I_DIRTY_SYNC and
wrote=0 in the traces around when it starts going to ~1000 inodes
per queue_io call....
Or maybe a combination of both?
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
prev parent reply other threads:[~2011-05-10 4:53 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-20 8:03 [PATCH 0/6] writeback: moving expire targets for background/kupdate works v2 Wu Fengguang
2011-04-20 8:03 ` [PATCH 1/6] writeback: pass writeback_control down to move_expired_inodes() Wu Fengguang
2011-05-04 11:04 ` Christoph Hellwig
2011-05-04 11:13 ` Wu Fengguang
2011-04-20 8:03 ` [PATCH 2/6] writeback: introduce writeback_control.inodes_cleaned Wu Fengguang
2011-05-04 11:05 ` Christoph Hellwig
2011-05-04 11:11 ` Wu Fengguang
2011-05-04 11:16 ` Christoph Hellwig
2011-05-04 11:32 ` Wu Fengguang
2011-04-20 8:03 ` [PATCH 3/6] writeback: try more writeback as long as something was written Wu Fengguang
2011-04-20 8:03 ` [PATCH 4/6] writeback: the kupdate expire timestamp should be a moving target Wu Fengguang
2011-04-20 8:03 ` [PATCH 5/6] writeback: sync expired inodes first in background writeback Wu Fengguang
2011-04-20 23:40 ` Andrew Morton
2011-04-21 1:14 ` Wu Fengguang
2011-04-21 1:21 ` Wu Fengguang
2011-04-24 3:15 ` Wu Fengguang
2011-04-26 12:17 ` Jan Kara
2011-04-26 13:51 ` Wu Fengguang
2011-04-26 13:59 ` Wu Fengguang
2011-04-26 14:05 ` Wu Fengguang
2011-04-27 11:15 ` Wu Fengguang
2011-04-20 8:03 ` [PATCH 6/6] writeback: refill b_io iff empty Wu Fengguang
2011-05-04 7:39 ` Wu Fengguang
2011-05-05 16:37 ` Jan Kara
2011-05-05 16:47 ` Wu Fengguang
2011-05-06 5:29 ` Wu Fengguang
2011-05-06 8:42 ` [RFC][PATCH] writeback: limit number of moved inodes in queue_io() Wu Fengguang
2011-05-06 10:06 ` [RFC][PATCH v2] " Wu Fengguang
2011-05-06 23:06 ` Dave Chinner
2011-05-06 14:21 ` [PATCH 6/6] writeback: refill b_io iff empty Jan Kara
2011-05-10 4:31 ` Wu Fengguang
2011-05-10 4:53 ` Dave Chinner [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20110510045346.GC19446@dastard \
--to=david@fromorbit.com \
--cc=akpm@linux-foundation.org \
--cc=fengguang.wu@intel.com \
--cc=jack@suse.cz \
--cc=kitayama@cl.bb4u.ne.jp \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mel@csn.ul.ie \
--cc=mel@linux.vnet.ibm.com \
--cc=minchan.kim@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).