The patch titled
sched: redundant reschedule when set_user_nice() boosts a prio of a task from the "expired" array
has been added to the -mm tree. Its filename is
sched-redundant-reschedule-when-set_user_nice-boosts-a-prio-of-a-task-from-the-expired-array.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: sched: redundant reschedule when set_user_nice() boosts a prio of a task from the "expired" array
From: "Dmitry Adamushko" <dmitry.adamushko@xxxxxxxxx>
- Make TASK_PREEMPTS_CURR(task, rq) return "true" only if the task's prio
is higher than the current's one and the task is in the "active" array.
This ensures we don't make redundant resched_task() calls when the task
is in the "expired" array (as may happen now in set_user_prio(),
rt_mutex_setprio() and pull_task() ) ;
- generalise conditions for a call to resched_task() in set_user_nice(),
rt_mutex_setprio() and sched_setscheduler()
Signed-off-by: Dmitry Adamushko <dmitry.adamushko@xxxxxxxxx>
Cc: Con Kolivas <kernel@xxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/sched.c | 31 +++++++++++++------------------
1 file changed, 13 insertions(+), 18 deletions(-)
diff -puN kernel/sched.c~sched-redundant-reschedule-when-set_user_nice-boosts-a-prio-of-a-task-from-the-expired-array kernel/sched.c
--- a/kernel/sched.c~sched-redundant-reschedule-when-set_user_nice-boosts-a-prio-of-a-task-from-the-expired-array
+++ a/kernel/sched.c
@@ -169,7 +169,7 @@ unsigned long long __attribute__((weak))
(MAX_BONUS / 2 + DELTA((p)) + 1) / MAX_BONUS - 1))
#define TASK_PREEMPTS_CURR(p, rq) \
- ((p)->prio < (rq)->curr->prio)
+ (((p)->prio < (rq)->curr->prio) && ((p)->array == (rq)->active))
#define SCALE_PRIO(x, prio) \
max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO / 2), MIN_TIMESLICE)
@@ -4077,13 +4077,13 @@ void rt_mutex_setprio(struct task_struct
struct prio_array *array;
unsigned long flags;
struct rq *rq;
- int oldprio;
+ int delta;
BUG_ON(prio < 0 || prio > MAX_PRIO);
rq = task_rq_lock(p, &flags);
- oldprio = p->prio;
+ delta = prio - p->prio;
array = p->array;
if (array)
dequeue_task(p, array);
@@ -4099,13 +4099,10 @@ void rt_mutex_setprio(struct task_struct
enqueue_task(p, array);
/*
* Reschedule if we are currently running on this runqueue and
- * our priority decreased, or if we are not currently running on
- * this runqueue and our priority is higher than the current's
+ * our priority decreased, or if our priority became higher
+ * than the current's.
*/
- if (task_running(rq, p)) {
- if (p->prio > oldprio)
- resched_task(rq->curr);
- } else if (TASK_PREEMPTS_CURR(p, rq))
+ if (TASK_PREEMPTS_CURR(p, rq) || (delta > 0 && task_running(rq, p)))
resched_task(rq->curr);
}
task_rq_unlock(rq, &flags);
@@ -4153,10 +4150,11 @@ void set_user_nice(struct task_struct *p
enqueue_task(p, array);
inc_raw_weighted_load(rq, p);
/*
- * If the task increased its priority or is running and
- * lowered its priority, then reschedule its CPU:
+ * Reschedule if we are currently running on this runqueue and
+ * our priority decreased, or if our priority became higher
+ * than the current's.
*/
- if (delta < 0 || (delta > 0 && task_running(rq, p)))
+ if (TASK_PREEMPTS_CURR(p, rq) || (delta > 0 && task_running(rq, p)))
resched_task(rq->curr);
}
out_unlock:
@@ -4383,13 +4381,10 @@ recheck:
__activate_task(p, rq);
/*
* Reschedule if we are currently running on this runqueue and
- * our priority decreased, or if we are not currently running on
- * this runqueue and our priority is higher than the current's
+ * our priority decreased, or our priority became higher
+ * than the current's.
*/
- if (task_running(rq, p)) {
- if (p->prio > oldprio)
- resched_task(rq->curr);
- } else if (TASK_PREEMPTS_CURR(p, rq))
+ if (TASK_PREEMPTS_CURR(p, rq) || (task_running(rq, p) && p->prio > oldprio))
resched_task(rq->curr);
}
__task_rq_unlock(rq);
_
Patches currently in -mm which might be from dmitry.adamushko@xxxxxxxxx are
kernel-irq-procc-unprotected-iteration-over-the-irq-action-list-in-name_unique.patch
sched-redundant-reschedule-when-set_user_nice-boosts-a-prio-of-a-task-from-the-expired-array.patch
sched-implement-staircase-deadline-cpu-scheduler-staircase-improvements.patch
sched-implement-staircase-deadline-cpu-scheduler-improvements-fix.patch
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