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sched: Optimize branch hint in context_switch()

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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>
This commit is contained in:
Tim Blechmann 2009-11-24 11:55:27 +01:00 • committed by Ingo Molnar
commit 710390d90f
1 changed files with 2 additions and 2 deletions
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4
kernel/sched.c
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@ -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;
}