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    SubjectRe: [RFC PATCH] mm: handle simple case in free_pcppages_bulk()
    On Thu, Feb 10, 2011 at 10:38:59PM +0900, Minchan Kim wrote:
    > On Thu, Feb 10, 2011 at 10:18 PM, Namhyung Kim <namhyung@gmail.com> wrote:
    > > 2011-02-10 (???), 22:10 +0900, Minchan Kim:
    > >> Hello Namhyung,
    > >>
    > >
    > > Hi Minchan,
    > >
    > >
    > >> On Thu, Feb 10, 2011 at 8:46 PM, Namhyung Kim <namhyung@gmail.com> wrote:
    > >> > Now I'm seeing that there are some cases to free all pages in a
    > >> > pcp lists. In that case, just frees all pages in the lists instead
    > >> > of being bothered with round-robin lists traversal.
    > >>
    > >> I though about that but I didn't send the patch.
    > >> That's because many cases which calls free_pcppages_bulk(,
    > >> pcp->count,..) are slow path so it adds comparison overhead on fast
    > >> path while it loses the effectiveness in slow path.
    > >>
    > >
    > > Hmm.. How about adding unlikely() then? Doesn't it help much here?
    >
    > Yes. It would help but I am not sure how much it is.
    > AFAIR, when Mel submit the patch, he tried to prove the effectiveness
    > with some experiment and profiler.

    Yep. Principally I *think* used netperf running UDP_STREAM for different
    buffer sizes and compared oprofile output but I also ran a battery of
    benchmarks to check for any other unexpected regression without profiling.

    --
    Mel Gorman
    SUSE Labs


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