Re: cgroup oom regression introduced by 6a5ce1b94e1e5979f8db579f77d6e08a5f44c13b

[CAI Qian <caiqian@redhat.com>]

----- "Minchan Kim" <minchan.kim@gmail.com> wrote:

> On Sat, Sep 18, 2010 at 08:52:34AM -0400, caiqian@redhat.com wrote:
> > This test hung the kernel without triggering oom.
> > # mount -t cgroup -o memory none /cgroup/memory/
> > # mkdir /cgroup/memory/A
> > # echo $$ >/cgroup/memory/A/tasks
> > # echo 4096M >/cgroup/memory/A/memory.limit_in_bytes
> > # echo 4096M >/cgroup/memory/A/memory.memsw.limit_in_bytes
> > # use malloc to allocate more than 4G memory.
> > 
> > Sometimes, this had been thrown out of console,
> > localhost.localdomain login: INFO: task sm1:5065 blocked for more
> than 120 seconds.
> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this
> message.
> > sm1           D 00000000fffca130     0  5065   5051 0x00000080
> >  ffff880c5f419c38 0000000000000086 ffff880c5f419bc8
> ffffffff81034ca8
> >  ffff880100000000 0000000000015440 ffff880c608ab4e0
> 0000000000015440
> >  ffff880c608aba40 ffff880c5f419fd8 ffff880c608aba48
> ffff880c5f419fd8
> > Call Trace:
> >  [<ffffffff81034ca8>] ? pvclock_clocksource_read+0x58/0xd0
> >  [<ffffffff810f2c60>] ? sync_page+0x0/0x50
> >  [<ffffffff81492553>] io_schedule+0x73/0xc0
> >  [<ffffffff810f2c9d>] sync_page+0x3d/0x50
> >  [<ffffffff81492cba>] __wait_on_bit_lock+0x5a/0xc0
> >  [<ffffffff810f2c37>] __lock_page+0x67/0x70
> >  [<ffffffff8107cf90>] ? wake_bit_function+0x0/0x50
> >  [<ffffffff810f2a6e>] ? find_get_page+0x1e/0xa0
> >  [<ffffffff810f4a5c>] filemap_fault+0x33c/0x450
> >  [<ffffffff81110524>] __do_fault+0x54/0x550
> >  [<ffffffff8113f30a>] ? __mem_cgroup_commit_charge+0x5a/0xa0
> >  [<ffffffff811132a2>] handle_mm_fault+0x1c2/0xc70
> >  [<ffffffff8149809c>] do_page_fault+0x11c/0x320
> >  [<ffffffff81494cd5>] page_fault+0x25/0x30
> > 
> > Reverted the following commit from mmotm tree made the problem go
> away.
> > commit 6a5ce1b94e1e5979f8db579f77d6e08a5f44c13b
> > Author: Minchan Kim <minchan.kim@gmail.com>
> > Date:   Thu Sep 16 01:17:26 2010 +0200
> > 
> >     M.  Vefa Bicakci reported 2.6.35 kernel hang up when hibernation
> on his
> >     32bit 3GB mem machine.
> >     (https://bugzilla.kernel.org/show_bug.cgi?id=16771). Also he
> bisected
> >     the regression to
> >     
> >       commit bb21c7ce18eff8e6e7877ca1d06c6db719376e3c
> >       Author: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> >       Date:   Fri Jun 4 14:15:05 2010 -0700
> >     
> >          vmscan: fix do_try_to_free_pages() return value when
> priority==0 reclaim failure
> >     
> >     At first impression, this seemed very strange because the above
> commit
> >     only chenged function return value and
> hibernate_preallocate_memory()
> >     ignore return value of shrink_all_memory().  But it's related.
> >     
> >     Now, page allocation from hibernation code may enter infinite
> loop if the
> >     system has highmem.  The reasons are that vmscan don't care
> enough OOM
> >     case when oom_killer_disabled.
> >     
> >     The problem sequence is following as.
> >     
> >     1. hibernation
> >     2. oom_disable
> >     3. alloc_pages
> >     4. do_try_to_free_pages
> >            if (scanning_global_lru(sc) && !all_unreclaimable)
> >                    return 1;
> >     
> >     If kswapd is not freozen, it would set zone->all_unreclaimable
> to 1 and
> >     then shrink_zones maybe return true(ie, all_unreclaimable is
> true).  So at
> >     last, alloc_pages could go to _nopage_.  If it is, it should
> have no
> >     problem.
> >     
> >     This patch adds all_unreclaimable check to protect in direct
> reclaim path,
> >     too.  It can care of hibernation OOM case and help bailout
> >     all_unreclaimable case slightly.
> >     
> >     Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> >     Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
> >     Reported-by: M. Vefa Bicakci <bicave@superonline.com>
> >     Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
> >     Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
> >     Cc: Rik van Riel <riel@redhat.com>
> >     Cc: <stable@kernel.org>
> >     Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> > 
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 225a759..f56a8c3 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -1804,12 +1804,11 @@ static void shrink_zone(int priority, struct
> zone *zone,
> >   * If a zone is deemed to be full of pinned pages then just give it
> a light
> >   * scan then give up on it.
> >   */
> > -static bool shrink_zones(int priority, struct zonelist *zonelist,
> > +static void shrink_zones(int priority, struct zonelist *zonelist,
> >  					struct scan_control *sc)
> >  {
> >  	struct zoneref *z;
> >  	struct zone *zone;
> > -	bool all_unreclaimable = true;
> >  
> >  	for_each_zone_zonelist_nodemask(zone, z, zonelist,
> >  					gfp_zone(sc->gfp_mask), sc->nodemask) {
> > @@ -1827,8 +1826,36 @@ static bool shrink_zones(int priority, struct
> zonelist *zonelist,
> >  		}
> >  
> >  		shrink_zone(priority, zone, sc);
> > -		all_unreclaimable = false;
> >  	}
> > +}
> > +
> > +static inline bool zone_reclaimable(struct zone *zone)
> > +{
> > +	return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
> > +}
> > +
> > +static inline bool all_unreclaimable(struct zonelist *zonelist,
> > +		struct scan_control *sc)
> > +{
> > +	struct zoneref *z;
> > +	struct zone *zone;
> > +	bool all_unreclaimable = true;
> > +
> > +	if (!scanning_global_lru(sc))
> > +		return false;
> > +
> > +	for_each_zone_zonelist_nodemask(zone, z, zonelist,
> > +			gfp_zone(sc->gfp_mask), sc->nodemask) {
> > +		if (!populated_zone(zone))
> > +			continue;
> > +		if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
> > +			continue;
> > +		if (zone_reclaimable(zone)) {
> > +			all_unreclaimable = false;
> > +			break;
> > +		}
> > +	}
> > +
> >  	return all_unreclaimable;
> >  }
> >  
> > @@ -1852,7 +1879,6 @@ static unsigned long
> do_try_to_free_pages(struct zonelist *zonelist,
> >  					struct scan_control *sc)
> >  {
> >  	int priority;
> > -	bool all_unreclaimable;
> >  	unsigned long total_scanned = 0;
> >  	struct reclaim_state *reclaim_state = current->reclaim_state;
> >  	struct zoneref *z;
> > @@ -1869,7 +1895,7 @@ static unsigned long
> do_try_to_free_pages(struct zonelist *zonelist,
> >  		sc->nr_scanned = 0;
> >  		if (!priority)
> >  			disable_swap_token();
> > -		all_unreclaimable = shrink_zones(priority, zonelist, sc);
> > +		shrink_zones(priority, zonelist, sc);
> >  		/*
> >  		 * Don't shrink slabs when reclaiming memory from
> >  		 * over limit cgroups
> > @@ -1931,7 +1957,7 @@ out:
> >  		return sc->nr_reclaimed;
> >  
> >  	/* top priority shrink_zones still had more to do? don't OOM, then
> */
> > -	if (scanning_global_lru(sc) && !all_unreclaimable)
> > +	if (!all_unreclaimable(zonelist, sc))
> >  		return 1;
> >  
> >  	return 0;
> > @@ -2197,8 +2223,7 @@ loop_again:
> >  			total_scanned += sc.nr_scanned;
> >  			if (zone->all_unreclaimable)
> >  				continue;
> > -			if (nr_slab == 0 &&
> > -			    zone->pages_scanned >= (zone_reclaimable_pages(zone) * 6))
> > +			if (nr_slab == 0 && !zone_reclaimable(zone))
> >  				zone->all_unreclaimable = 1;
> >  			/*
> >  			 * If we've done a decent amount of scanning and
> 
> Thanks for the reporting. 
> Could you test below patch?
The problem went away after applied this patch.
> 
> From 666a10163dcc2366a3cce64140487e5956f7f659 Mon Sep 17 00:00:00
> 2001
> From: Minchan Kim <minchan.kim@gmail.com>
> Date: Sat, 18 Sep 2010 23:16:14 +0900
> Subject: [PATCH] Fix all_unreclaimable in memcg.
> 
> vmscan-check-all_unreclaimable-in-direct-reclaim-path.patch
> has a problem. It changed old behavior of memcg.
> 
> When memory pressure in memcg is high, do_try_to_free_pages returns
> 0. It causes mem_cgroup_out_of_memory so that any process in mem
> group
> would be killed. 
> But vmscan-check-all_unreclaimable-in-direct-reclaim-path.patch
> changed
> the old behavior. It returns 1 unconditionally regardless of
> considering 
> global reclaim or memcg relcaim. It causes hang without triggering OOM
> 
> in case of memcg direct reclaim. 
> 
> This patch fixes it.
> 
> It's reported by caiqian@redhat.com. 
> (Thanks. Totally, it's my fault.)
> 
> Reported-by: caiqian@redhat.com
> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Cc: Balbir Singh <balbir@in.ibm.com>
> Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
> ---
>  mm/vmscan.c |    5 +----
>  1 files changed, 1 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index ecae0ef..0119d0d 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1919,9 +1919,6 @@ static bool all_unreclaimable(struct zonelist
> *zonelist,
>  	struct zone *zone;
>  	bool all_unreclaimable = true;
>  
> -	if (!scanning_global_lru(sc))
> -		return false;
> -
>  	for_each_zone_zonelist_nodemask(zone, z, zonelist,
>  			gfp_zone(sc->gfp_mask), sc->nodemask) {
>  		if (!populated_zone(zone))
> @@ -2035,7 +2032,7 @@ out:
>  		return sc->nr_reclaimed;
>  
>  	/* top priority shrink_zones still had more to do? don't OOM, then
> */
> -	if (!all_unreclaimable(zonelist, sc))
> +	if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc))
>  		return 1;
>  
>  	return 0;
> -- 
> 1.7.0.5
> 
> 
> -- 
> Kind regards,
> Minchan Kim
> 
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