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    SubjectRe: Kernel falls apart under light memory pressure (i.e. linking vmlinux)
    On Sun, May 22, 2011 at 7:12 PM, Minchan Kim <minchan.kim@gmail.com> wrote:
    > Could you test below patch based on vanilla 2.6.38.6?
    > The expect result is that system hang never should happen.
    > I hope this is last test about hang.
    >
    > Thanks.
    >
    > diff --git a/mm/vmscan.c b/mm/vmscan.c
    > index 292582c..1663d24 100644
    > --- a/mm/vmscan.c
    > +++ b/mm/vmscan.c
    > @@ -231,8 +231,11 @@ unsigned long shrink_slab(struct shrink_control *shrink,
    >       if (scanned == 0)
    >               scanned = SWAP_CLUSTER_MAX;
    >
    > -       if (!down_read_trylock(&shrinker_rwsem))
    > -               return 1;       /* Assume we'll be able to shrink next time */
    > +       if (!down_read_trylock(&shrinker_rwsem)) {
    > +               /* Assume we'll be able to shrink next time */
    > +               ret = 1;
    > +               goto out;
    > +       }
    >
    >       list_for_each_entry(shrinker, &shrinker_list, list) {
    >               unsigned long long delta;
    > @@ -286,6 +289,8 @@ unsigned long shrink_slab(struct shrink_control *shrink,
    >               shrinker->nr += total_scan;
    >       }
    >       up_read(&shrinker_rwsem);
    > +out:
    > +       cond_resched();
    >       return ret;
    >  }
    >
    > @@ -2331,7 +2336,7 @@ static bool sleeping_prematurely(pg_data_t
    > *pgdat, int order, long remaining,
    >        * must be balanced
    >        */
    >       if (order)
    > -               return pgdat_balanced(pgdat, balanced, classzone_idx);
    > +               return !pgdat_balanced(pgdat, balanced, classzone_idx);
    >       else
    >               return !all_zones_ok;
    >  }

    So far with this patch I can't reproduce the hang or the bogus OOM.

    To be completely clear, I have COMPACTION, MIGRATION, and THP off, I'm
    running 2.6.38.6, and I have exactly two patches applied. One is the
    attached patch and the other is a the fpu.ko/aesni_intel.ko merger
    which I need to get dracut to boot my box.

    For fun, I also upgraded to 8GB of RAM and it still works.

    --Andy

    >
    > --
    > Kind regards,
    > Minchan Kim
    >
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