From: Dave Chinner <david@fromorbit.com>
To: Brian Foster <bfoster@redhat.com>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH v3] xfs: re-enable xfsaild idle mode and fix associated races
Date: Mon, 2 Jul 2012 10:07:12 +1000 [thread overview]
Message-ID: <20120702000712.GN19223@dastard> (raw)
In-Reply-To: <1340880776-45730-1-git-send-email-bfoster@redhat.com>
On Thu, Jun 28, 2012 at 06:52:56AM -0400, Brian Foster wrote:
> xfsaild idle mode logic currently leads to a couple hangs:
>
> 1.) If xfsaild is rescheduled in during an incremental scan
> (i.e., tout != 0) and the target has been updated since
> the previous run, we can hit the new target and go into
> idle mode with a still populated ail.
> 2.) A wake up is only issued when the target is pushed forward.
> The wake up can race with xfsaild if it is currently in the
> process of entering idle mode, causing future wake up
> events to be lost.
>
> These hangs have been reproduced and verified as fixed by
> running xfstests 273 in a loop on a slightly modified upstream
> kernel. The kernel is modified to re-enable idle mode as
> previously implemented (when count == 0) and with a revert of
> commit 670ce93f, which includes performance improvements that
> make this harder to reproduce.
>
> The solution, the algorithm for which has been outlined by
> Dave Chinner, is to modify xfsaild to enter idle mode only when
> the ail is empty and the push target has not been moved forward
> since the last push.
>
> Signed-off-by: Brian Foster <bfoster@redhat.com>
Looks OK to me, and hasn't caused any problems here.
Final question - did you confirm with powertop that the xfsaild is
no longer causing wakeups a minute or two after you stop writing to
the filesystem? (I haven't yet)
Reviewed-by: Dave Chinner <dchinner@redhat.com>
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2012-07-02 0:07 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-28 10:52 [PATCH v3] xfs: re-enable xfsaild idle mode and fix associated races Brian Foster
2012-07-02 0:07 ` Dave Chinner [this message]
2012-07-02 13:33 ` Brian Foster
2012-07-02 23:51 ` Dave Chinner
2012-07-03 13:13 ` Brian Foster
2012-07-03 16:07 ` Christoph Hellwig
2012-07-02 7:05 ` Christoph Hellwig
2012-07-02 8:29 ` Dave Chinner
2012-07-02 13:51 ` Brian Foster
2012-07-17 7:00 ` Christoph Hellwig
2012-07-24 13:22 ` Christoph Hellwig
2012-07-24 14:54 ` Ben Myers
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