The patch titled vmscan: all_unreclaimable() use zone->all_unreclaimable as a name has been added to the -mm tree. Its filename is vmscan-all_unreclaimable-use-zone-all_unreclaimable-as-a-name.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: vmscan: all_unreclaimable() use zone->all_unreclaimable as a name From: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> all_unreclaimable check in direct reclaim has been introduced at 2.6.19 by following commit. 2006 Sep 25; commit 408d8544; oom: use unreclaimable info And it went through strange history. firstly, following commit broke the logic unintentionally. 2008 Apr 29; commit a41f24ea; page allocator: smarter retry of costly-order allocations Two years later, I've found obvious meaningless code fragment and restored original intention by following commit. 2010 Jun 04; commit bb21c7ce; vmscan: fix do_try_to_free_pages() return value when priority==0 But, the logic didn't works when 32bit highmem system goes hibernation and Minchan slightly changed the algorithm and fixed it . 2010 Sep 22: commit d1908362: vmscan: check all_unreclaimable in direct reclaim path But, recently, Andrey Vagin found the new corner case. Look, struct zone { .. int all_unreclaimable; .. unsigned long pages_scanned; .. } zone->all_unreclaimable and zone->pages_scanned are neigher atomic variables nor protected by lock. Therefore zones can become a state of zone->page_scanned=0 and zone->all_unreclaimable=1. In this case, current all_unreclaimable() return false even though zone->all_unreclaimabe=1. Is this ignorable minor issue? No. Unfortunately, x86 has very small dma zone and it become zone->all_unreclamble=1 easily. and if it become all_unreclaimable=1, it never restore all_unreclaimable=0. Why? if all_unreclaimable=1, vmscan only try DEF_PRIORITY reclaim and a-few-lru-pages>>DEF_PRIORITY always makes 0. that mean no page scan at all! Eventually, oom-killer never works on such systems. That said, we can't use zone->pages_scanned for this purpose. This patch restore all_unreclaimable() use zone->all_unreclaimable as old. and in addition, to add oom_killer_disabled check to avoid reintroduce the issue of commit d1908362 ("vmscan: check all_unreclaimable in direct reclaim path"). Reported-by: Andrey Vagin <avagin@xxxxxxxxxx> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> Cc: Nick Piggin <npiggin@xxxxxxxxx> Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/vmscan.c | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-) diff -puN mm/vmscan.c~vmscan-all_unreclaimable-use-zone-all_unreclaimable-as-a-name mm/vmscan.c --- a/mm/vmscan.c~vmscan-all_unreclaimable-use-zone-all_unreclaimable-as-a-name +++ a/mm/vmscan.c @@ -41,6 +41,7 @@ #include <linux/memcontrol.h> #include <linux/delayacct.h> #include <linux/sysctl.h> +#include <linux/oom.h> #include <asm/tlbflush.h> #include <asm/div64.h> @@ -1988,17 +1989,12 @@ static bool zone_reclaimable(struct zone return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; } -/* - * As hibernation is going on, kswapd is freezed so that it can't mark - * the zone into all_unreclaimable. It can't handle OOM during hibernation. - * So let's check zone's unreclaimable in direct reclaim as well as kswapd. - */ +/* All zones in zonelist are unreclaimable? */ static bool all_unreclaimable(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) { @@ -2006,13 +2002,11 @@ static bool all_unreclaimable(struct zon continue; if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) continue; - if (zone_reclaimable(zone)) { - all_unreclaimable = false; - break; - } + if (!zone->all_unreclaimable) + return false; } - return all_unreclaimable; + return true; } /* @@ -2108,6 +2102,14 @@ out: if (sc->nr_reclaimed) return sc->nr_reclaimed; + /* + * As hibernation is going on, kswapd is freezed so that it can't mark + * the zone into all_unreclaimable. Thus bypassing all_unreclaimable + * check. + */ + if (oom_killer_disabled) + return 0; + /* top priority shrink_zones still had more to do? don't OOM, then */ if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc)) return 1; _ Patches currently in -mm which might be from kosaki.motohiro@xxxxxxxxxxxxxx are memcg-fix-mem_cgroup_rotate_reclaimable_page.patch mm-per-node-vmstat-show-proper-vmstats.patch mm-per-node-vmstat-show-proper-vmstats-fix.patch mm-increase-reclaim_distance-to-30.patch vmscan-all_unreclaimable-use-zone-all_unreclaimable-as-a-name.patch oom-kill-remove-boost_dying_task_prio.patch mm-introduce-wait_on_page_locked_killable.patch x86mm-make-pagefault-killable.patch mm-mem-hotplug-fix-section-mismatch-setup_per_zone_inactive_ratio-should-be-__meminit.patch mm-mem-hotplug-recalculate-lowmem_reserve-when-memory-hotplug-occur.patch mm-mem-hotplug-update-pcp-stat_threshold-when-memory-hotplug-occur.patch mm-batch-activate_page-to-reduce-lock-contention.patch mm-move-enum-vm_event_item-into-a-standalone-header-file.patch memcg-count-the-soft_limit-reclaim-in-global-background-reclaim.patch memcg-add-stats-to-monitor-soft_limit-reclaim.patch add-the-pagefault-count-into-memcg-stats.patch add-the-pagefault-count-into-memcg-stats-fix.patch kexec-remove-kmsg_dump_kexec.patch kexec-remove-kmsg_dump_kexec-fix.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html