Messages in this thread | | | Date | Mon, 29 Jun 2009 01:53:32 +0900 | Subject | Re: Found the commit that causes the OOMs | From | Minchan Kim <> |
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On Sun, Jun 28, 2009 at 12:36 AM, Johannes Weiner<hannes@cmpxchg.org> wrote: > 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.
I agree. :) total_swap_pages is better than nr_swap_pages although it isn't related this problem.
>
-- Kinds regards, Minchan Kim -- 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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