linux-kernel - Re: [PATCH] fs: sync: fixed performance regression

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Date:	Thu, 11 Jul 2013 12:00:12 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Paul Taysom <taysom@...omium.org>
Cc:	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	jack@...e.cz, sonnyrao@...omium.org
Subject: Re: [PATCH] fs: sync: fixed performance regression

On Wed, Jul 10, 2013 at 04:12:36PM -0700, Paul Taysom wrote:
> The following commit introduced a 10x regression for
> syncing inodes in ext4 with relatime enabled where just
> the atime had been modified.
> 
>     commit 4ea425b63a3dfeb7707fc7cc7161c11a51e871ed
>     Author: Jan Kara <jack@...e.cz>
>     Date:   Tue Jul 3 16:45:34 2012 +0200
>     vfs: Avoid unnecessary WB_SYNC_NONE writeback during sys_sync and reorder sync passes
> 
>     See also: http://www.kernelhub.org/?msg=93100&p=2
> 
> Fixed by putting back in the call to writeback_inodes_sb.
> 
> I'll attach the test in a reply to this e-mail.
> 
> The test starts by creating 512 files, syncing, reading one byte
> from each of those files, syncing, and then deleting each file
> and syncing. The time to do each sync is printed. The process
> is then repeated for 1024 files and then the next power of
> two up to 262144 files.
> 
> Note, when running the test, the slow down doesn't always happen
> but most of the tests will show a slow down.

Can you please check if the patch attached to this mail:

http://marc.info/?l=linux-kernel&m=137276874025813&w=2

Fixes your problem?

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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