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Date: Thu, 9 Sep 2010 00:45:27 +0900
From: Minchan Kim <minchan.kim@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Johannes Weiner <hannes@...xchg.org>
Cc: linux-mm <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Rik van Riel <riel@...hat.com>,
"Rafael J. Wysocki" <rjw@...k.pl>,
"M. Vefa Bicakci" <bicave@...eronline.com>, stable@...nel.org
Subject: Re: [PATCH] vmscan: check all_unreclaimable in direct reclaim path
On Wed, Sep 08, 2010 at 07:48:31AM +0200, Johannes Weiner wrote:
> On Sun, Sep 05, 2010 at 11:40:37PM +0900, Minchan Kim wrote:
> > 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 was bisected first bad commit is below
> >
> > commit bb21c7ce18eff8e6e7877ca1d06c6db719376e3c
> > Author: KOSAKI Motohiro <kosaki.motohiro@...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 freezed, 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.
> >
> > Cc: Johannes Weiner <hannes@...xchg.org>
> > Cc: Rik van Riel <riel@...hat.com>
> > Cc: "Rafael J. Wysocki" <rjw@...k.pl>
> > Cc: M. Vefa Bicakci <bicave@...eronline.com>
> > Cc: stable@...nel.org
> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> > Signed-off-by: Minchan Kim <minchan.kim@...il.com>
> > ---
> > mm/vmscan.c | 33 +++++++++++++++++++++++++++------
> > 1 files changed, 27 insertions(+), 6 deletions(-)
> >
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index f620ab3..53b23a7 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -1893,12 +1893,11 @@ 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) {
> > @@ -1916,8 +1915,31 @@ static bool shrink_zones(int priority, struct zonelist *zonelist,
> > }
> >
> > shrink_zone(priority, zone, sc);
> > - all_unreclaimable = false;
> > }
> > +}
> > +
> > +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->pages_scanned < (zone_reclaimable_pages(zone) * 6)) {
>
> Small nitpick: kswapd does the same check against the magic number,
> could you move it into a separate function? zone_reclaimable()?
Nice cleanup.
Thanks, Hannes.
>
> Otherwise,
> Reviewed-by: Johannes Weiner <hannes@...xchg.org>
>
== CUT HERE ==
Changelog
v2
* cleanup zone_reclaimable(suggested by Johannes)
* rebase on mmotm-08-27
>From 7b47ffbc9ce89daa44f16bdf447d63ce94dd5f9a Mon Sep 17 00:00:00 2001
From: Minchan Kim <minchan.kim@...il.com>
Date: Thu, 9 Sep 2010 00:37:52 +0900
Subject: [PATCH v2] vmscan: check all_unreclaimable in direct reclaim path
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 was bisected first bad commit is below
commit bb21c7ce18eff8e6e7877ca1d06c6db719376e3c
Author: KOSAKI Motohiro <kosaki.motohiro@...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 freezed, 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.
Cc: Rik van Riel <riel@...hat.com>
Cc: M. Vefa Bicakci <bicave@...eronline.com>
Cc: stable@...nel.org
Acked-by: Rafael J. Wysocki <rjw@...k.pl>
Reviewed-by: Johannes Weiner <hannes@...xchg.org>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Signed-off-by: Minchan Kim <minchan.kim@...il.com>
---
mm/vmscan.c | 41 +++++++++++++++++++++++++++++++++--------
1 files changed, 33 insertions(+), 8 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 7870893..9a45758 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1877,12 +1877,11 @@ 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) {
@@ -1900,8 +1899,36 @@ 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;
}
@@ -1925,7 +1952,6 @@ 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;
@@ -1942,7 +1968,7 @@ 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
@@ -2004,7 +2030,7 @@ 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;
@@ -2270,8 +2296,7 @@ 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
--
1.7.0.5
--
Kind regards,
Minchan Kim
--
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