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    SubjectRe: Kernel falls apart under light memory pressure (i.e. linking vmlinux)
    On Tue, May 17, 2011 at 2:00 AM, Wu Fengguang <fengguang.wu@intel.com> wrote:
    > On Sun, May 15, 2011 at 12:12:36PM -0400, Andrew Lutomirski wrote:
    >> On Sun, May 15, 2011 at 11:27 AM, Wu Fengguang <fengguang.wu@intel.com> wrote:
    >>
    >> That was probably because one of my testcases creates a 1.4GB file on
    >> ramfs.  (I can provoke the problem without doing evil things like
    >> that, but the test script is rather reliable at killing my system and
    >> it works fine on my other machines.)
    >
    > Ah I didn't read your first email.. I'm now running
    >
    > ./test_mempressure.sh 1500 1400 1
    >
    > with mem=2G and no swap, but cannot reproduce OOM.

    Do you have a Sandy Bridge laptop? There was a recent thread on lkml
    suggesting that only Sandy Bridge laptops saw this problem. Although
    there's something else needed to trigger it, because I can't do it
    from an initramfs I made that tried to show this problem.

    >
    > What's your kconfig?

    Attached. This is 2.6.38.6.

    >
    >> If you want, I can try to generate a trace that isn't polluted with
    >> the evil ramfs file.
    >
    > No, thanks. However it would be valuable if you can retry with this
    > patch _alone_ (without the "if (need_resched()) return false;" change,
    > as I don't see how it helps your case).
    >
    > @@ -2286,7 +2290,7 @@ 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;
    >  }

    Done.

    I logged in, added swap, and ran a program that allocated 1900MB of
    RAM and memset it. The system lagged a bit but survived. kswapd
    showed 10% CPU (which is odd, IMO, since I'm using aesni-intel and I
    think that all the crypt happens in kworker when aesni-intel is in
    use).

    Then I started Firefox, loaded gmail, and ran test_mempressure.sh.
    Kaboom! (I.e. system was hung) SysRq-F saved the system and produced
    the attached dump. I had 6GB swap available, so there shouldn't have
    been any OOM.

    --Andy
    [unhandled content-type:application/x-xz][unhandled content-type:application/octet-stream]
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