linux-kernel - Re: [PATCH 0/7] writeback: avoid touching dirtied

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Date:	Sat, 22 Oct 2011 15:46:07 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Jan Kara <jack@...e.cz>
Cc:	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	Dave Chinner <david@...morbit.com>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/7] writeback: avoid touching dirtied_when on blocked
 inodes

On Sat, Oct 22, 2011 at 01:38:51PM +0800, Wu Fengguang wrote:
> On Sat, Oct 22, 2011 at 11:11:35AM +0800, Wu Fengguang wrote:
> > > > btw, with the I_SYNC case converted, it's actually no longer necessary
> > > > to keep a standalone b_more_io_wait. It should still be better to keep
> > > > the list and the above error check for catching possible errors and
> > > > the flexibility of adding policies like "don't retry possible blocked
> > > > inodes in N seconds as long as there are other inodes to work with".
> > > > 
> > > > The below diff only intends to show the _possibility_ to remove
> > > > b_more_io_wait:
> > >   Good observation. So should we introduce b_more_io_wait in the end? We
> > > could always introduce it when the need for some more complicated policy
> > > comes...
> > > 
> > 
> > I have no problem removing it if you liked it more. Anyway, let me
> > test the idea out first (just kicked off the tests).
> 
> When removing b_more_io_wait, performance is slightly dropped
> comparing to the full more_io_wait patchset.
> 
> 3.1.0-rc9-ioless-full-more_io_wait-next-20111014+  3.1.0-rc9-ioless-full-more_io_wait-x-next-20111014+  
> ------------------------  ------------------------  
>                    45.30        +6.3%        48.14  thresh=1G/ext3-1dd-4k-8p-4096M-1024M:10-X
>                    48.23        -2.0%        47.27  thresh=1G/ext4-100dd-4k-8p-4096M-1024M:10-X
>                    54.21        -2.6%        52.80  thresh=1G/ext4-10dd-4k-8p-4096M-1024M:10-X
>                    56.07        -0.3%        55.91  thresh=1G/ext4-1dd-4k-8p-4096M-1024M:10-X
>                    45.12        -5.8%        42.49  thresh=1G/xfs-100dd-4k-8p-4096M-1024M:10-X
>                    53.94        -1.2%        53.27  thresh=1G/xfs-10dd-4k-8p-4096M-1024M:10-X
>                    55.66        -0.1%        55.63  thresh=1G/xfs-1dd-4k-8p-4096M-1024M:10-X
>                   358.53        -0.8%       355.51  TOTAL write_bw
> 
> I'll try to reduce the changes and retest.

Unfortunately, the reduced patches 1-4 + I_SYNC change + remove
requeue_more_io_wait combination still performances noticeably worse:

3.1.0-rc9-ioless-full-next-20111014+  3.1.0-rc9-ioless-full-more_io_wait-x2-next-20111014+  
------------------------  ------------------------  
                   49.84        -7.9%        45.91  thresh=1G/ext4-100dd-4k-8p-4096M-1024M:10-X
                   56.03        -7.2%        52.01  thresh=1G/ext4-10dd-4k-8p-4096M-1024M:10-X
                   57.42        -1.7%        56.45  thresh=1G/ext4-1dd-4k-8p-4096M-1024M:10-X
                   45.74        -2.8%        44.48  thresh=1G/xfs-100dd-4k-8p-4096M-1024M:10-X
                   54.19        -4.8%        51.57  thresh=1G/xfs-10dd-4k-8p-4096M-1024M:10-X
                   55.93        -2.2%        54.70  thresh=1G/xfs-1dd-4k-8p-4096M-1024M:10-X
                  319.14        -4.4%       305.12  TOTAL write_bw

Thanks,
Fengguang
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