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    SubjectRe: Delete scheduler SD_WAKE_AFFINE and SD_WAKE_BALANCE flags

    * Nick Piggin <nickpiggin@yahoo.com.au> wrote:

    > Well, you can easily see suboptimal scheduling decisions on many
    > programs with lots of interprocess communication. For example, tbench
    > on a dual Xeon:
    >
    > processes 1 2 3 4
    >
    > 2.6.13-rc4: 187, 183, 179 260, 259, 256 340, 320, 349 504, 496, 500
    > no wake-bal: 180, 180, 177 254, 254, 253 268, 270, 348 345, 290, 500
    >
    > Numbers are MB/s, higher is better.

    i cannot see any difference with/without wake-balancing in this
    workload, on a dual Xeon. Could you try the quick hack below and do:

    echo 1 > /proc/sys/kernel/panic # turn on wake-balancing
    echo 0 > /proc/sys/kernel/panic # turn off wake-balancing

    does the runtime switching show any effects on the throughput numbers
    tbench is showing? I'm using dbench-3.03. (i only checked the status
    numbers, didnt do full runs)

    (did you have SCHED_SMT enabled?)

    Ingo

    kernel/sched.c | 2 ++
    1 files changed, 2 insertions(+)

    Index: linux-prefetch-task/kernel/sched.c
    ===================================================================
    --- linux-prefetch-task.orig/kernel/sched.c
    +++ linux-prefetch-task/kernel/sched.c
    @@ -1155,6 +1155,8 @@ static int try_to_wake_up(task_t * p, un
    goto out_activate;

    new_cpu = cpu;
    + if (!panic_timeout)
    + goto out_set_cpu;

    schedstat_inc(rq, ttwu_cnt);
    if (cpu == this_cpu) {
    -
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