Hello,
This change seems to be pretty logical. OTOH, it's just a micro-optimization.
So there is no hurry and we may wait till Con is back (Andrew, if you think it'd be better).
Logically-wise, this is similar to the changes I have sent earlier for the mainline.
There is no need to change TASK_PREEMPTS_CURR() here. All the infrastructure is already in place
(task_preempts_curr() already does the necessary checks). And nevertheless, set_user_nice() can be made
nicer. So that's what this patch is about.
---
Call for reschedule upon increasing a task's priority in set_user_nice() only
if the task may preempt the current one.
Signed-off-by: Dmitry Adamushko <[email protected]>
---
--- linux-2.6.21-rc6-mm1/kernel/sched-orig.c 2007-04-09 10:10:52.000000000 +0200
+++ linux-2.6.21-rc6-mm1/kernel/sched.c 2007-04-09 17:07:12.000000000 +0200
@@ -4022,14 +4022,14 @@ EXPORT_SYMBOL(sleep_on_timeout);
void rt_mutex_setprio(struct task_struct *p, int prio)
{
unsigned long flags;
- int queued, oldprio;
+ int queued, delta;
struct rq *rq;
BUG_ON(prio < 0 || prio > MAX_PRIO);
rq = task_rq_lock(p, &flags);
- oldprio = p->prio;
+ delta = prio - p->prio;
queued = task_queued(p);
if (queued)
dequeue_task(p, rq);
@@ -4043,7 +4043,7 @@ void rt_mutex_setprio(struct task_struct
* this runqueue and our priority is higher than the current's
*/
if (task_running(rq, p)) {
- if (p->prio > oldprio)
+ if (delta > 0)
resched_task(rq->curr);
} else
try_preempt(p, rq);
@@ -4055,7 +4055,7 @@ void rt_mutex_setprio(struct task_struct
void set_user_nice(struct task_struct *p, long nice)
{
- int queued, old_prio,delta;
+ int queued, old_prio, delta;
unsigned long flags;
struct rq *rq;
@@ -4096,8 +4096,11 @@ void set_user_nice(struct task_struct *p
* If the task increased its priority or is running and
* lowered its priority, then reschedule its CPU:
*/
- if (delta < 0 || (delta > 0 && task_running(rq, p)))
- resched_task(rq->curr);
+ if (task_running(rq, p)) {
+ if (delta > 0)
+ resched_task(rq->curr);
+ } else
+ try_preempt(p, rq);
}
out_unlock:
task_rq_unlock(rq, &flags);
-
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