linux-kernel - Re: [PATCH 3/3] mm: page allocator: Drain per-cpu lists after direct reclaim allocation fails

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Message-ID: <20100904081414.GF705@dastard>
Date:	Sat, 4 Sep 2010 18:14:14 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Mel Gorman <mel@....ul.ie>,
	Linux Kernel List <linux-kernel@...r.kernel.org>,
	linux-mm@...ck.org, Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Minchan Kim <minchan.kim@...il.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH 3/3] mm: page allocator: Drain per-cpu lists after
 direct reclaim allocation fails

On Sat, Sep 04, 2010 at 05:58:40PM +1000, Dave Chinner wrote:
> On Fri, Sep 03, 2010 at 08:21:01PM -0700, Andrew Morton wrote:
> > On Sat, 4 Sep 2010 12:25:45 +1000 Dave Chinner <david@...morbit.com> wrote:
> > 
> > > Still, given the improvements in performance from this patchset,
> > > I'd say inclusion is a no-braniner....
> > 
> > OK, thanks.
> > 
> > It'd be interesting to check the IPI frequency with and without -
> > /proc/interrupts "CAL" field.  Presumably it went down a lot.
> 
> Maybe I suspected you would ask for this. I happened to dump
> /proc/interrupts after the livelock run finished, so you're in
> luck :)
....
> 
> livelock:  59458 58367 58559 59493 59614 57970 59060 58207
> 
> So the livelock case tends to indicate roughly 40,000 more IPI
> interrupts per CPU occurred.  The livelock occurred for close to 5
> minutes, so that's roughly 130 IPIs per second per CPU....

And just to confuse the issue further, I just had a livelock on a
vanilla kernel that did *not* cause the CAL counts to increase.
Hence it appears that the IPI storms are not the cause of the
livelocks І'm triggering....

Cheers,

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