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    SubjectRe: [PATCH] x86: Use asm-goto to implement mutex fast path on x86-64
    On Sat, Jun 29, 2013 at 04:56:30PM -0700, Wedson Almeida Filho wrote:
    > On Fri, Jun 28, 2013 at 7:09 AM, Borislav Petkov <bp@alien8.de> wrote:
    >
    > > Btw, do we have any perf data showing any improvements from this patch?
    >
    > I wrote a simple test the measures the time it takes to acquire and
    > release an uncontended mutex (i.e., we always take the fast path)
    > 100k times. I ran it a few times, the original code averages
    > 2.743436ms, and the new code averages 2.101098ms, so it's about 23% improvement.

    Microbenchmark results tend to be misleading in such situations. Rather,
    it would be much closer to reality if you traced a real workload like a
    simple kernel build, for example, with and without your patch.

    I.e., something like

    perf stat --repeat 5 ./build-kernel.sh

    and take a look at what the perfcouters are saying in both cases.

    > I also think the code looks cleaner this way.

    No doubt.

    --
    Regards/Gruss,
    Boris.

    Sent from a fat crate under my desk. Formatting is fine.
    --


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