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    Subject[tip:sched/core] sched: Optimize branch hint in context_switch()
    Commit-ID:  710390d90f143a9ebb87a475215140f426792efd
    Gitweb: http://git.kernel.org/tip/710390d90f143a9ebb87a475215140f426792efd
    Author: Tim Blechmann <tim@klingt.org>
    AuthorDate: Tue, 24 Nov 2009 11:55:27 +0100
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Tue, 24 Nov 2009 12:18:42 +0100

    sched: Optimize branch hint in context_switch()

    Branch hint profiling on my nehalem machine showed over 90%
    incorrect branch hints:

    10420275 170645395 94 context_switch sched.c
    3043
    10408421 171098521 94 context_switch sched.c
    3050

    Signed-off-by: Tim Blechmann <tim@klingt.org>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Mike Galbraith <efault@gmx.de>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    LKML-Reference: <4B0BBB9F.6080304@klingt.org>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    ---
    kernel/sched.c | 4 ++--
    1 files changed, 2 insertions(+), 2 deletions(-)

    diff --git a/kernel/sched.c b/kernel/sched.c
    index 93474a7..010d5e1 100644
    --- a/kernel/sched.c
    +++ b/kernel/sched.c
    @@ -2829,14 +2829,14 @@ context_switch(struct rq *rq, struct task_struct *prev,
    */
    arch_start_context_switch(prev);

    - if (unlikely(!mm)) {
    + if (likely(!mm)) {
    next->active_mm = oldmm;
    atomic_inc(&oldmm->mm_count);
    enter_lazy_tlb(oldmm, next);
    } else
    switch_mm(oldmm, mm, next);

    - if (unlikely(!prev->mm)) {
    + if (likely(!prev->mm)) {
    prev->active_mm = NULL;
    rq->prev_mm = oldmm;
    }

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