lkml.org 
[lkml]   [2009]   [Jun]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: Found the commit that causes the OOMs
    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/

    \
     
     \ /
      Last update: 2009-06-27 17:43    [W:0.031 / U:0.080 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site