linux-kernel - Re: [PATCH] mm: check zone->all_unreclaimable in all

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Date:	Tue, 3 May 2011 21:38:39 -0400 (EDT)
From:	CAI Qian <caiqian@...hat.com>
To:	avagin@...il.com
Cc:	Andrey Vagin <avagin@...nvz.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Minchan Kim <minchan.kim@...il.com>
Subject: Re: [PATCH] mm: check zone->all_unreclaimable in
 all_unreclaimable()



----- Original Message -----
> On 03/05/2011 06:20 PM, Minchan Kim wrote:
> > On Sat, Mar 05, 2011 at 02:44:16PM +0300, Andrey Vagin wrote:
> >> Check zone->all_unreclaimable in all_unreclaimable(), otherwise the
> >> kernel may hang up, because shrink_zones() will do nothing, but
> >> all_unreclaimable() will say, that zone has reclaimable pages.
> >>
> >> do_try_to_free_pages()
> >> 	shrink_zones()
> >> 		 for_each_zone
> >> 			if (zone->all_unreclaimable)
> >> 				continue
> >> 	if !all_unreclaimable(zonelist, sc)
> >> 		return 1
> >>
> >> __alloc_pages_slowpath()
> >> retry:
> >> 	did_some_progress = do_try_to_free_pages(page)
> >> 	...
> >> 	if (!page&& did_some_progress)
> >> 		retry;
> >>
> >> Signed-off-by: Andrey Vagin<avagin@...nvz.org>
> >> ---
> >>   mm/vmscan.c | 2 ++
> >>   1 files changed, 2 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/mm/vmscan.c b/mm/vmscan.c
> >> index 6771ea7..1c056f7 100644
> >> --- a/mm/vmscan.c
> >> +++ b/mm/vmscan.c
> >> @@ -2002,6 +2002,8 @@ static bool all_unreclaimable(struct zonelist
> >> *zonelist,
> >>
> >>   	for_each_zone_zonelist_nodemask(zone, z, zonelist,
> >>   			gfp_zone(sc->gfp_mask), sc->nodemask) {
> >> + if (zone->all_unreclaimable)
> >> + continue;
> >>   		if (!populated_zone(zone))
> >>   			continue;
> >>   		if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
> >
> > zone_reclaimable checks it. Isn't it enough?
> I sent one more patch [PATCH] mm: skip zombie in OOM-killer.
> This two patches are enough.
> > Does the hang up really happen or see it by code review?
> Yes. You can reproduce it for help the attached python program. It's
> not
> very clever:)
> It make the following actions in loop:
> 1. fork
> 2. mmap
> 3. touch memory
> 4. read memory
> 5. munmmap
> 
> >> --
> >> 1.7.1
I have tested this for the latest mainline kernel using the reproducer
attached, the system just hung or deadlock after oom. The whole oom
trace is here.
http://people.redhat.com/qcai/oom.log

Did I miss anything?
View attachment "memeater.py" of type "text/plain" (695 bytes)