AcoSail/kernel_optimize_test
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sched: call resched_task() conditionally from new task wake up path

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- During wake up of a new task, task_new_fair() can do a resched_task()
  on the current task. Later in the code path, check_preempt_curr() also ends
  up doing the same, which can be avoided. Check if TIF_NEED_RESCHED is
  already set for the current task.

- task_new_fair() does a resched_task() on the current task unconditionally.
  This can be done only in case when child runs before the parent.

So this is a small speedup.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Bharata B Rao 2008-08-28 14:42:49 +05:30 committed by Ingo Molnar
parent 65eb3dc609
commit aec0a5142c
1 changed files with 8 additions and 1 deletions
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9
kernel/sched_fair.c
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@ -1348,6 +1348,13 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p)
if (unlikely(se == pse))
return;
/*
* We can come here with TIF_NEED_RESCHED already set from new task
* wake up path.
*/
if (test_tsk_need_resched(curr))
return;
cfs_rq_of(pse)->next = pse;
/*
@ -1620,10 +1627,10 @@ static void task_new_fair(struct rq *rq, struct task_struct *p)
* 'current' within the tree based on its new key value.
*/
swap(curr->vruntime, se->vruntime);
resched_task(rq->curr);
}
enqueue_task_fair(rq, p, 0);
resched_task(rq->curr);
}
/*