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Message-ID: <20090919035835.GA9921@localhost>
Date: Sat, 19 Sep 2009 11:58:35 +0800
From: Wu Fengguang <fengguang.wu@...el.com>
To: Theodore Tso <tytso@....edu>, Jens Axboe <jens.axboe@...cle.com>,
Christoph Hellwig <hch@...radead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
"chris.mason@...cle.com" <chris.mason@...cle.com>,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
"jack@...e.cz" <jack@...e.cz>
Subject: Re: [PATCH 0/7] Per-bdi writeback flusher threads v20
On Sat, Sep 19, 2009 at 01:52:52AM +0800, Theodore Tso wrote:
> On Fri, Sep 11, 2009 at 10:39:29PM +0800, Wu Fengguang wrote:
> >
> > That would be good. Sorry for the late work. I'll allocate some time
> > in mid next week to help review and benchmark recent writeback works,
> > and hope to get things done in this merge window.
>
> Did you have some chance to get more work done on the your writeback
> patches?
Sorry for the delay, I'm now testing the patches with commands
cp /dev/zero /mnt/test/zero0 &
dd if=/dev/zero of=/mnt/test/zero1 &
and the attached debug patch.
One problem I found with ext3/4 is, redirty_tail() is called repeatedly
in the traces, which could slow down the inode writeback significantly.
Ideal is to call requeue_[partial_]io() instead of redirty_tail().
[ 131.963885] fs/fs-writeback.c +809 wb_writeback(): comm=flush-8:0 pid=2816 n=0
[ 131.966171] global dirty=4105 writeback=18793 nfs=0 flags=__ towrite=32768 skipped=0 file=0 written=0
[ 132.780826] fs/fs-writeback.c +809 wb_writeback(): comm=flush-0:15 pid=1150 n=0
[ 132.783097] global dirty=4105 writeback=16623 nfs=0 flags=__ towrite=32768 skipped=0 file=0 written=0
[ 134.307094] redirty_tail() +542: inode=12
[ 134.815776] redirty_tail() +542: inode=13
[ 134.817709] fs/fs-writeback.c +809 wb_writeback(): comm=flush-8:0 pid=2816 n=11493
[ 134.821242] global dirty=4192 writeback=16203 nfs=0 flags=__ towrite=21275 skipped=0 file=13 written=4430
[ 135.599954] redirty_tail() +542: inode=12
[ 136.372523] redirty_tail() +542: inode=13
[ 136.386748] fs/fs-writeback.c +809 wb_writeback(): comm=flush-8:0 pid=2816 n=11570
[ 136.432168] global dirty=4308 writeback=15752 nfs=0 flags=__ towrite=21198 skipped=0 file=13 written=4650
[ 137.789115] fs/fs-writeback.c +809 wb_writeback(): comm=flush-0:15 pid=1150 n=0
[ 138.587178] global dirty=9551 writeback=10755 nfs=0 flags=__ towrite=32768 skipped=0 file=0 written=0
[ 138.962743] redirty_tail() +542: inode=12
[ 139.395024] redirty_tail() +542: inode=13
[ 139.403194] fs/fs-writeback.c +809 wb_writeback(): comm=flush-8:0 pid=2816 n=11893
[ 139.413026] global dirty=4101 writeback=16630 nfs=0 flags=__ towrite=20875 skipped=0 file=0 written=2
[ 139.426074] fs/fs-writeback.c +809 wb_writeback(): comm=flush-8:0 pid=2816 n=0
[ 139.435190] global dirty=4101 writeback=16378 nfs=0 flags=__ towrite=32768 skipped=0 file=0 written=0
[ 140.266713] redirty_tail() +542: inode=12
[ 140.449304] redirty_tail() +542: inode=13
[ 140.496241] fs/fs-writeback.c +809 wb_writeback(): comm=flush-8:0 pid=2816 n=11678
[ 140.508339] global dirty=4203 writeback=19220 nfs=0 flags=__ towrite=21090 skipped=0 file=13 written=4254
[ 141.649192] redirty_tail() +542: inode=12
[ 141.971276] redirty_tail() +542: inode=13
[ 141.988572] fs/fs-writeback.c +809 wb_writeback(): comm=flush-8:0 pid=2816 n=11304
[ 142.000107] global dirty=4112 writeback=18362 nfs=0 flags=__ towrite=21464 skipped=0 file=13 written=4541
btrfs pattern is almost the same, but with an extra (metadata) inode 1.
[ 464.443873] fs/fs-writeback.c +809 wb_writeback(): comm=flush-btrfs-1 pid=2865 n=0
[ 464.450458] global dirty=163 writeback=4375 nfs=0 flags=__ towrite=32768 skipped=0 file=0 written=0
[ 464.655999] fs/fs-writeback.c +809 wb_writeback(): comm=flush-8:0 pid=2816 n=0
[ 464.664478] global dirty=3873 writeback=1175 nfs=0 flags=__ towrite=32768 skipped=0 file=0 written=0
[ 465.291059] redirty_tail() +542: inode=257
[ 465.331584] redirty_tail() +542: inode=258
[ 465.346433] redirty_tail() +560: inode=1
[ 465.352016] fs/fs-writeback.c +809 wb_writeback(): comm=flush-btrfs-1 pid=2865 n=14480
[ 465.355797] global dirty=337 writeback=3980 nfs=0 flags=__ towrite=18288 skipped=0 file=1 written=0
[ 466.226489] redirty_tail() +542: inode=257
[ 466.280894] redirty_tail() +542: inode=258
[ 466.282270] redirty_tail() +560: inode=1
[ 466.288079] fs/fs-writeback.c +809 wb_writeback(): comm=flush-btrfs-1 pid=2865 n=14300
[ 466.291738] global dirty=666 writeback=3807 nfs=0 flags=__ towrite=18468 skipped=0 file=1 written=0
[ 467.101730] redirty_tail() +542: inode=257
[ 467.134303] redirty_tail() +542: inode=258
[ 467.135675] redirty_tail() +560: inode=1
[ 467.144120] fs/fs-writeback.c +809 wb_writeback(): comm=flush-btrfs-1 pid=2865 n=14032
[ 467.147302] global dirty=331 writeback=3665 nfs=0 flags=__ towrite=18736 skipped=0 file=1 written=0
[ 467.964652] redirty_tail() +542: inode=257
[ 468.002423] redirty_tail() +542: inode=258
[ 468.003795] redirty_tail() +560: inode=1
I'm looking into it.
Thanks,
Fengguang
View attachment "writeback-debug.patch" of type "text/x-diff" (2334 bytes)
View attachment "requeue_io-debug.patch" of type "text/x-diff" (2800 bytes)
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