linux-ext4 - Re: ext4 unlink performance

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Message-ID: <20081113204240.GF21652@mit.edu>
Date:	Thu, 13 Nov 2008 15:42:40 -0500
From:	Theodore Tso <tytso@....edu>
To:	linux-ext4@...r.kernel.org
Subject: Re: ext4 unlink performance

On Thu, Nov 13, 2008 at 01:10:00PM -0600, Bruce Guenter wrote:
> On Thu, Nov 13, 2008 at 12:57:12PM -0600, Bruce Guenter wrote:
> > Ouch.  Why is ext4 so much slower than ext3 here,
> 
> I forgot to mention one important detail.  I started running 'vmstat 5'
> during one of the unlink runs, and noticed that there were intervals of
> 15 or 20 seconds where no blocks were being read or written, and minimal
> CPU was being used.  I do not observe the same stalls when using ext3.

Hmm... how very strange.  Can you run the command:

       ps -eo pid,tid,class,rtprio,ni,pri,psr,pcpu,stat,wchan:16,comm

during one of the quiescent periods, and see what is in the WCHAN
field for the unlink command?

						- Ted
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