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Date:	Thu, 9 Sep 2010 09:32:52 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Mel Gorman <mel@....ul.ie>
cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	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>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH 3/3] mm: page allocator: Drain per-cpu lists after direct
 reclaim allocation fails

On Thu, 9 Sep 2010, Mel Gorman wrote:

> > This will have the effect of never sending IPIs for slab allocations since
> > they do not do allocations for orders > PAGE_ALLOC_COSTLY_ORDER.
> >
>
> The question is how severe is that? There is somewhat of an expectation
> that the lower orders free naturally so it the IPI justified? That said,
> our historical behaviour would have looked like
>
> if (!page && !drained && order) {
> 	drain_all_pages();
> 	draiained = true;
> 	goto retry;
> }
>
> Play it safe for now and go with that?

I am fine with no IPIs for order <= COSTLY. Just be aware that this is
a change that may have some side effects. Lets run some tests and see
how it affect the issues that we are seeing.
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