Messages in this thread |  | | | Date | Sat, 27 Jun 2009 17:36:30 +0200 | | From | Johannes Weiner <> | | Subject | Re: Found the commit that causes the OOMs |
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On Sat, Jun 27, 2009 at 10:50:25PM +0900, Minchan Kim wrote: > Hi, Hannes. > > On Sat, Jun 27, 2009 at 9:54 PM, Johannes Weiner<hannes@cmpxchg.org> wrote: > > On Sat, Jun 27, 2009 at 08:12:49AM +0100, David Howells wrote: > >> > >> I've managed to bisect things to find the commit that causes the OOMs. It's: > >> > >> commit 69c854817566db82c362797b4a6521d0b00fe1d8 > >> Author: MinChan Kim <minchan.kim@gmail.com> > >> Date: Tue Jun 16 15:32:44 2009 -0700 > >> > >> vmscan: prevent shrinking of active anon lru list in case of no swap space V3 > >> > >> shrink_zone() can deactivate active anon pages even if we don't have a > >> swap device. Many embedded products don't have a swap device. So the > >> deactivation of anon pages is unnecessary. > >> > >> This patch prevents unnecessary deactivation of anon lru pages. But, it > >> don't prevent aging of anon pages to swap out. > >> > >> Signed-off-by: Minchan Kim <minchan.kim@gmail.com> > >> Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> > >> Cc: Johannes Weiner <hannes@cmpxchg.org> > >> Acked-by: Rik van Riel <riel@redhat.com> > >> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > >> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> > >> > >> This exhibits the problem. The previous commit: > >> > >> commit 35282a2de4e5e4e173ab61aa9d7015886021a821 > >> Author: Brice Goglin <Brice.Goglin@ens-lyon.org> > >> Date: Tue Jun 16 15:32:43 2009 -0700 > >> > >> migration: only migrate_prep() once per move_pages() > >> > >> survives 16 iterations of the LTP syscall testsuite without exhibiting the > >> problem. > > > > Here is the patch in question: > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index 7592d8e..879d034 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -1570,7 +1570,7 @@ static void shrink_zone(int priority, struct zone *zone, > > * Even if we did not try to evict anon pages at all, we want to > > * rebalance the anon lru active/inactive ratio. > > */ > > - if (inactive_anon_is_low(zone, sc)) > > + if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0) > > shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0); > > > > throttle_vm_writeout(sc->gfp_mask); > > > > When this was discussed, I think we missed that nr_swap_pages can > > actually get zero on swap systems as well and this should have been > > total_swap_pages - otherwise we also stop balancing the two anon lists > > when swap is _full_ which was not the intention of this change at all. > > At that time we considered it so that we didn't prevent anon list > aging for background reclaim. > Do you think it is not enough ?
With a heavy multiprocess anon load, direct reclaimers will likely reuse the reclaimed pages for anon mappings, so you have a handful of processes shuffling pages on the active list and only one thread that tries to balance. I can imagine that it can not keep up for long. -- 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/
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