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| author | Jupyung Lee <jupyung@gmail.com> | 2009-11-17 18:51:40 +0900 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-12-09 10:03:06 +0100 |
| commit | a65ac745e47e91f9d98dbf07f22ed0492e34d998 (patch) | |
| tree | 246b0953cbf4e2d890d71d01cbfb070f8e4b1811 /kernel/sched_fair.c | |
| parent | cd29fe6f2637cc2ccbda5ac65f5332d6bf5fa3c6 (diff) | |
| download | lwn-a65ac745e47e91f9d98dbf07f22ed0492e34d998.tar.gz lwn-a65ac745e47e91f9d98dbf07f22ed0492e34d998.zip | |
sched: Move update_curr() in check_preempt_wakeup() to avoid redundant call
If a RT task is woken up while a non-RT task is running,
check_preempt_wakeup() is called to check whether the new task can
preempt the old task. The function returns quickly without going deeper
because it is apparent that a RT task can always preempt a non-RT task.
In this situation, check_preempt_wakeup() always calls update_curr() to
update vruntime value of the currently running task. However, the
function call is unnecessary and redundant at that moment because (1) a
non-RT task can always be preempted by a RT task regardless of its
vruntime value, and (2) update_curr() will be called shortly when the
context switch between two occurs.
By moving update_curr() in check_preempt_wakeup(), we can avoid
redundant call to update_curr(), slightly reducing the time taken to
wake up RT tasks.
Signed-off-by: Jupyung Lee <jupyung@gmail.com>
[ Place update_curr() right before the wake_preempt_entity() call, which
is the only thing that relies on the updated vruntime ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1258451500-6714-1-git-send-email-jupyung@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched_fair.c')
| -rw-r--r-- | kernel/sched_fair.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 44ec80ccfa85..4dec18579c9a 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1651,8 +1651,6 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ int sync = wake_flags & WF_SYNC; int scale = cfs_rq->nr_running >= sched_nr_latency; - update_curr(cfs_rq); - if (unlikely(rt_prio(p->prio))) { resched_task(curr); return; @@ -1710,6 +1708,8 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ BUG_ON(!pse); + update_curr(cfs_rq); + if (wakeup_preempt_entity(se, pse) == 1) { resched_task(curr); /* |