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    SubjectRe: [PATCH 3/5] sched: remove unlikely in pre_schedule_rt


    On Wed, 25 Mar 2009, Steven Rostedt wrote:

    > From: Steven Rostedt <rostedt@goodmis.org>
    >
    > Impact: clean up
    >
    > The annotated branch profiler shows that the unlikely used by
    > pre_schedule_rt is always incorrect. This makes sense because in
    > sched.c we have:
    >
    > if (prev->sched_class->pre_schedule)
    > prev->sched_class->pre_schedule(rq, prev);
    >
    > And we are saying that prev is unlikely to be an rt task. This looks
    > more like a likely candidate to me.

    I forgot to add the profiler output:

    correct incorrect % Function File Line
    ------- --------- - -------- ---- ----
    0 2248 100 pre_schedule_rt sched_rt.c 1263


    -- Steve

    >
    > Signed-off-by: Steven Rostedt <srostedt@redhat.com>
    > ---
    > kernel/sched_rt.c | 2 +-
    > 1 files changed, 1 insertions(+), 1 deletions(-)
    >
    > diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
    > index bac1061..537af77 100644
    > --- a/kernel/sched_rt.c
    > +++ b/kernel/sched_rt.c
    > @@ -1260,7 +1260,7 @@ static int pull_rt_task(struct rq *this_rq)
    > static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
    > {
    > /* Try to pull RT tasks here if we lower this rq's prio */
    > - if (unlikely(rt_task(prev)) && rq->rt.highest_prio > prev->prio)
    > + if (rt_task(prev) && rq->rt.highest_prio > prev->prio)
    > pull_rt_task(rq);
    > }
    >
    > --
    > 1.6.2
    >
    > --
    >


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