linux-kernel - Re: long sleep_on_page delays writing to slow storage

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Message-ID: <20111121091818.GC1771@redhat.com>
Date:	Mon, 21 Nov 2011 10:18:18 +0100
From:	Johannes Weiner <jweiner@...hat.com>
To:	Dave Jones <davej@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Jan Kara <jack@...e.cz>, Andy Isaacson <adi@...apodia.org>,
	linux-kernel@...r.kernel.org, linux-mm@...r.kernel.org,
	kernel-team@...oraproject.org
Subject: Re: long sleep_on_page delays writing to slow storage

On Thu, Nov 17, 2011 at 02:47:20PM -0500, Dave Jones wrote:
> On Tue, Nov 15, 2011 at 10:13:13AM +0000, Mel Gorman wrote:
>  
>  > If they are still experiencing major stalls, I have an experimental
>  > script that may be able to capture stack traces of processes stalled
>  > for more than 1 second. I've had some success with it locally so
>  > maybe they could try it out to identify if it's THP or something else.
>  
> I'm not sure if it's the same problem, but I'd be interested in trying
> that script.
> 
> When I build a kernel on my laptop, when it gets to the final link stage,
> and there's a ton of IO, my entire X session wedges for a few seconds.
> This may be unrelated, because this is on an SSD, which shouldn't suffer
> from the slow IO of the USB devices mentioned in this thread.
> 
> (This is even with that patch applied btw, perhaps adding further fuel to
> the idea that it's unrelated).

We still have the problem that individual zones may fill up
unproportionately with dirty pages and reclaim can take a while to
make progress in such zones.

Would you mind trying the per-zone dirty limits patch set?  You can
find it here:

	http://cmpxchg.org/~hannes/kernel/mm-per-zone-dirty-limits/

git am pzd.mbox should work on 3.2-rc1.
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