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    SubjectRe: [PATCH] Performance regression in 2.6.7-rc3

    * Con Kolivas <kernel@kolivas.org> wrote:

    > with a little bit of detective work and help from Wli we tracked down that
    > this patch caused it:
    > [PATCH] sched: improve wakeup-affinity

    > A massive increase in idle time was observed and the throughput
    > dropped by 40% Reversing this patch gave these results:

    > backsched1: http://khack.osdl.org/stp/293865/
    > Composite Query Processing Power Throughput Numerical Quantity
    > 193.93 145.95 257.67
    >
    > It may be best to reverse this patch until the regression is better
    > understood.

    agreed. It is weird because Nick said that pgsql was tested with the
    patch - and we applied the patch based on those good results. Nick?

    Anyway, does the patch below fix the pgsql problem? It reverts to the
    more agressive idle-balancing variant (which isnt strictly necessary for
    the bw_pipe problem).

    Ingo

    Signed-off-by: Ingo Molnar <mingo@elte.hu>

    --- linux/kernel/sched.c
    +++ linux/kernel/sched.c
    @@ -1625,8 +1626,7 @@
    return busiest;

    out_balanced:
    - if (busiest && idle != NOT_IDLE && max_load > SCHED_LOAD_SCALE) {
    + if (busiest && (idle == NEWLY_IDLE ||
    + (idle == IDLE && max_load > SCHED_LOAD_SCALE)) ) {
    *imbalance = 1;
    return busiest;
    }
    -
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