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    Subject[RFC PATCH] sched: Kill WAKEUP_PREEMPT
    On Fri, Jul 29, 2011 at 09:56:58AM +0200, Peter Zijlstra wrote:
    > I've queued Lin's patch as I don't see the point of this thing either,
    > normally WAKEUP_PREEMPT is enabled so it says || 0 which is kinda
    > useless :-)
    >
    > And I'm starting to think we should just kill all of WAKEUP_PREEMPT I
    > don't think we ever want to disable it anyway..

    Someting like this?

    ---
    From: Yong Zhang <yong.zhang0@gmail.com>
    Subject: [RFC PATCH] sched: Kill WAKEUP_PREEMPT

    Per Peter Zijlstra:
    > And I'm starting to think we should just kill all of WAKEUP_PREEMPT I
    > don't think we ever want to disable it anyway..

    Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
    ---
    kernel/sched_fair.c | 8 +-------
    kernel/sched_features.h | 5 -----
    2 files changed, 1 insertions(+), 12 deletions(-)

    diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
    index 46b7855..3c58042 100644
    --- a/kernel/sched_fair.c
    +++ b/kernel/sched_fair.c
    @@ -1114,9 +1114,6 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
    * narrow margin doesn't have to wait for a full slice.
    * This also mitigates buddy induced latencies under load.
    */
    - if (!sched_feat(WAKEUP_PREEMPT))
    - return;
    -
    if (delta_exec < sysctl_sched_min_granularity)
    return;

    @@ -1252,7 +1249,7 @@ entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
    return;
    #endif

    - if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))
    + if (cfs_rq->nr_running > 1)
    check_preempt_tick(cfs_rq, curr);
    }

    @@ -1918,9 +1915,6 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
    return;


    - if (!sched_feat(WAKEUP_PREEMPT))
    - return;
    -
    update_curr(cfs_rq);
    find_matching_se(&se, &pse);
    BUG_ON(!pse);
    diff --git a/kernel/sched_features.h b/kernel/sched_features.h
    index 1e7066d..878a5f9 100644
    --- a/kernel/sched_features.h
    +++ b/kernel/sched_features.h
    @@ -12,11 +12,6 @@ SCHED_FEAT(GENTLE_FAIR_SLEEPERS, 1)
    SCHED_FEAT(START_DEBIT, 1)

    /*
    - * Should wakeups try to preempt running tasks.
    - */
    -SCHED_FEAT(WAKEUP_PREEMPT, 1)
    -
    -/*
    * Based on load and program behaviour, see if it makes sense to place
    * a newly woken task on the same cpu as the task that woke it --
    * improve cache locality. Typically used with SYNC wakeups as
    --
    1.7.4.1

    --
    Only stand for myself


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