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    SubjectRe: [PATCH] slub: reduce overhead of slub_debug
    On Thu, Jul 7, 2011 at 10:21 PM, David Miller <> wrote:
    > From: Christoph Lameter <>
    > Date: Thu, 7 Jul 2011 14:12:37 -0500 (CDT)
    >> On Thu, 7 Jul 2011, Pekka Enberg wrote:
    >>> On Thu, 7 Jul 2011, Pekka Enberg wrote:
    >>> > > Looks good to me. Christoph, David, ?
    >>> On Thu, 2011-07-07 at 13:17 -0500, Christoph Lameter wrote:
    >>> > The reason debug code is there is because it is useless overhead typically
    >>> > not needed. There is no point in optimizing the code that is not run in
    >>> > production environments unless there are gross performance issues that
    >>> > make debugging difficult. A performance patch for debugging would have to
    >>> > cause significant performance improvements. This patch does not do that
    >>> > nor was there such an issue to be addressed in the first place.
    >>> Is there something technically wrong with the patch? Quoting the patch
    >>> email:
    >>>   (Compiling some project with different options)
    >>>                                  make -j12    make clean
    >>>   slub_debug disabled:             1m 27s       1.2 s
    >>>   slub_debug enabled:              1m 46s       7.6 s
    >>>   slub_debug enabled + this patch: 1m 33s       3.2 s
    >>>   check_bytes still shows up high, but not always at the top.
    >>> That's significant enough speedup for me!
    >> Ok. I had a different set of numbers in mind from earlier posts.
    >> The benefit here comes from accessing memory in larger (word) chunks
    >> instead of byte wise. This is a form of memscan() with inverse matching.
    >> Isnt there an asm optimized version that can do this much better (there is
    >> one for memscan())? Optimizing this in core code by codeing something as
    >> generic as that is not that good since the arch code can deliver better
    >> performance and it seems that this is functionality that could be useful
    >> elsewhere.
    > You're being so unreasonable, just let the optimization in, refine it
    > with follow-on patches.

    I applied the patch. I think a follow up patch that moves the function
    to lib/string.c with proper generic name would be in order. Thanks!
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      Last update: 2011-07-07 21:51    [W:0.038 / U:15.536 seconds]
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