Messages in this thread | | | Date | Fri, 15 Jun 2012 11:45:51 +0100 | From | Mel Gorman <> | Subject | Re: [resend][PATCH] mm, vmscan: fix do_try_to_free_pages() livelock |
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On Thu, Jun 14, 2012 at 04:13:12AM -0400, 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>
Acked-by: Mel Gorman <mel@csn.ul.ie>
-- Mel Gorman SUSE Labs
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