Re: [sched] [patch] activate-task-speedup-2.5.3-pre2-A0

[Ingo Molnar <mingo@elte.hu>]

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> the attached patch against 2.5.3-pre2 is an optimization of
> activate_task(), to not call effective_prio() if no jiffy passed since
> ->sleep_timestamp was updated. This optimizes high-frequency wakeups.

[attached for real this time.]

	Ingo

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--- linux/kernel/sched.c.orig	Sun Jan 20 11:37:04 2002
+++ linux/kernel/sched.c	Sun Jan 20 11:37:21 2002
@@ -126,9 +126,10 @@
 
 static inline void activate_task(task_t *p, runqueue_t *rq)
 {
+	unsigned long sleep_time = jiffies - p->sleep_timestamp;
 	prio_array_t *array = rq->active;
 
-	if (!rt_task(p)) {
+	if (!rt_task(p) && sleep_time) {
 		/*
 		 * This code gives a bonus to interactive tasks. We update
 		 * an 'average sleep time' value here, based on
@@ -136,7 +137,7 @@
 		 * the higher the average gets - and the higher the priority
 		 * boost gets as well.
 		 */
-		p->sleep_avg += jiffies - p->sleep_timestamp;
+		p->sleep_avg += sleep_time;
 		if (p->sleep_avg > MAX_SLEEP_AVG)
 			p->sleep_avg = MAX_SLEEP_AVG;
 		p->prio = effective_prio(p);