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Date: Tue, 19 Oct 2010 16:29:40 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Mel Gorman <mel@csn.ul.ie>, LKML <linux-kernel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>,
        Christoph Lameter <cl@linux-foundation.org>
Subject: Re: [resend][PATCH 2/2] mm, mem-hotplug: update pcp->stat_threshold
 when memory hotplug occur
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On Tue, 19 Oct 2010 12:11:09 -0700 (PDT)
David Rientjes <rientjes@google.com> wrote:

> On Tue, 19 Oct 2010, KOSAKI Motohiro wrote:
> 
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 14ee899..222d8cc 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -51,6 +51,7 @@
> >  #include <linux/kmemleak.h>
> >  #include <linux/memory.h>
> >  #include <linux/compaction.h>
> > +#include <linux/vmstat.h>
> >  #include <trace/events/kmem.h>
> >  #include <linux/ftrace_event.h>
> >  
> > @@ -5013,6 +5014,8 @@ int __meminit init_per_zone_wmark_min(void)
> >  		min_free_kbytes = 128;
> >  	if (min_free_kbytes > 65536)
> >  		min_free_kbytes = 65536;
> > +
> > +	refresh_zone_stat_thresholds();
> >  	setup_per_zone_wmarks();
> >  	setup_per_zone_lowmem_reserve();
> >  	setup_per_zone_inactive_ratio();
> 
> setup_per_zone_wmarks() could change the min and low watermarks for a zone 
> when refresh_zone_stat_thresholds() would have used the old value.

Indeed.

I could make the obvious fix, but then what I'd have wouldn't be
sufficiently tested.