Messages in this thread | | | From | KOSAKI Motohiro <> | Date | Thu, 14 Jun 2012 11:46:47 -0400 | Subject | Re: [resend][PATCH] mm, vmscan: fix do_try_to_free_pages() livelock |
| |
On Thu, Jun 14, 2012 at 11:25 AM, Michal Hocko <mhocko@suse.cz> wrote: > On Thu 14-06-12 04:13:12, kosaki.motohiro@gmail.com wrote: >> From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> >> >> Currently, do_try_to_free_pages() can enter livelock. Because of, >> now vmscan has two conflicted policies. >> >> 1) kswapd sleep when it couldn't reclaim any page when reaching >> priority 0. This is because to avoid kswapd() infinite >> loop. That said, kswapd assume direct reclaim makes enough >> free pages to use either regular page reclaim or oom-killer. >> This logic makes kswapd -> direct-reclaim dependency. >> 2) direct reclaim continue to reclaim without oom-killer until >> kswapd turn on zone->all_unreclaimble. This is because >> to avoid too early oom-kill. >> This logic makes direct-reclaim -> kswapd dependency. >> >> In worst case, direct-reclaim may continue to page reclaim forever >> when kswapd sleeps forever. >> >> We can't turn on zone->all_unreclaimable from direct reclaim path >> because direct reclaim path don't take any lock and this way is racy. >> >> Thus this patch removes zone->all_unreclaimable field completely and >> recalculates zone reclaimable state every time. >> >> Note: we can't take the idea that direct-reclaim see zone->pages_scanned >> directly and kswapd continue to use zone->all_unreclaimable. Because, it >> is racy. commit 929bea7c71 (vmscan: all_unreclaimable() use >> zone->all_unreclaimable as a name) describes the detail. >> >> Reported-by: Aaditya Kumar <aaditya.kumar.30@gmail.com> >> Reported-by: Ying Han <yinghan@google.com> >> Cc: Nick Piggin <npiggin@gmail.com> >> Acked-by: Rik van Riel <riel@redhat.com> >> Cc: Michal Hocko <mhocko@suse.cz> >> Cc: Johannes Weiner <hannes@cmpxchg.org> >> Cc: Mel Gorman <mel@csn.ul.ie> >> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> >> Cc: Minchan Kim <minchan.kim@gmail.com> >> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> > > Looks good, just one comment bellow: > > Reviewed-by: Michal Hocko <mhocko@suse.cz> > > [...] >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index eeb3bc9..033671c 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c > [...] >> @@ -1936,8 +1936,8 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc) >> if (global_reclaim(sc)) { >> if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) >> continue; >> - if (zone->all_unreclaimable && >> - sc->priority != DEF_PRIORITY) >> + if (!zone_reclaimable(zone) && >> + sc->priority != DEF_PRIORITY) > > Not exactly a hot path but still would be nice to test the priority > first as the test is cheaper (maybe compiler is clever enough to reorder > this, as both expressions are independent and without any side-effects > but...).
ok, will fix. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |