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    SubjectRe: [PATCH 1/3] lockdep: Move lock events under lockdep recursion protection
    On Tue, Mar 09, 2010 at 09:34:10AM +0100, Jens Axboe wrote:
    > I went to try this on 2.6.34-rc1 to see how much it would improve things
    > here. With 2.6.34-rc1, a
    >
    > $ time sudo perf lock record ls /dev/shm
    >
    > essentially hangs the box, it ends up crashing hard (not just live
    > locked like before). With the patch in place, it does eventually finish:
    >
    > real 0m21.301s
    > user 0m0.030s
    > sys 0m21.040s
    >
    > The directory is empty.


    Hehe :-)

    That said you are probably missing a part of the puzzle.
    This patch avoids the scary recursions we had. But there
    is another separate patch that fixes the buffers multiplexing
    dependency we had. Buffering is now done per cpu.

    You need this patch:

    commit b67577dfb45580c498bfdb1bc76c00c3b2ad6310
    Author: Frederic Weisbecker <fweisbec@gmail.com>
    Date: Wed Feb 3 09:09:33 2010 +0100

    perf lock: Drop the buffers multiplexing dependency

    But this is not in -rc1, you need to checkout tip/perf/core

    Well, the best would be you actually pull this on top of -rc1:

    git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing.git
    perf/core

    so that you get the buffers multiplexing dependency that is in -tip,
    and you also get the recursions fixes, not yet in -tip (but should make
    it soon).

    I bet you still won't have magic results after that, but still it should
    be better.

    We still have further projects in mind to improve the scalability,
    like the events injection thing (that avoids the string copy)

    Again, you are my eyes on this, I'm still blind with my poor dual
    laptop or my atom testbox.

    Thanks for your testing.



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