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@xxxxxxxxxxxxxx> > > 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@xxxxxxxxxxx> > > Cc: Rik van Riel <riel@xxxxxxxxxx> > > Cc: "Rafael J. Wysocki" <rjw@xxxxxxx> > > Cc: M. Vefa Bicakci <bicave@xxxxxxxxxxxxxxx> > > Cc: stable@xxxxxxxxxx > > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> > > Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx> > > --- > > 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@xxxxxxxxxxx> > == 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@xxxxxxxxx> 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@xxxxxxxxxxxxxx> 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@xxxxxxxxxx> Cc: M. Vefa Bicakci <bicave@xxxxxxxxxxxxxxx> Cc: stable@xxxxxxxxxx Acked-by: Rafael J. Wysocki <rjw@xxxxxxx> Reviewed-by: Johannes Weiner <hannes@xxxxxxxxxxx> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx> --- 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . 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