[PATCH] O3int interactivity for 2.5.74-mm2

[Con Kolivas <kernel@kolivas.org>]

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Attached is an incremental patch against 2.5.74-mm2 with more interactivity 
work. Audio should be quite resistant to skips with this, and it should not 
induce further unfairness.

Changes:
The sleep_avg buffer was not needed with the improved semantics in O2int so it 
has been removed entirely as it created regressions in O2int.

A small change to the idle detection code to only make tasks with enough 
accumulated sleep_avg become idle.

Minor cleanups and clarified code.


Other issues:
Jerky mouse with heavy page rendering in web browsers remains. This is a 
different issue to the audio and will need some more thought.

The patch is also available for download here:
http://kernel.kolivas.org/2.5

Note for those who wish to get smooth X desktop feel now for their own use, 
the granularity patch on that website will do wonders on top of O3int, but a 
different approach will be needed for mainstream consumption.

Con
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--- linux-2.5.74/kernel/sched.c	2003-07-07 02:13:57.000000000 +1000
+++ linux-2.5.74-test/kernel/sched.c	2003-07-07 02:58:47.000000000 +1000
@@ -77,6 +77,7 @@
 #define MAX_SLEEP_AVG		(10*HZ)
 #define STARVATION_LIMIT	(10*HZ)
 #define NODE_THRESHOLD		125
+#define MAX_BONUS		((MAX_USER_PRIO - MAX_RT_PRIO) * PRIO_BONUS_RATIO / 100)
 
 /*
  * If a task is 'interactive' then we reinsert it in the active
@@ -306,7 +307,7 @@ static inline void normalise_sleep(task_
 {
 	unsigned long old_avg_time = jiffies - p->avg_start;
 
-	if (old_avg_time < MIN_SLEEP_AVG)
+	if (unlikely(old_avg_time < MIN_SLEEP_AVG))
 		return;
 
 	if (p->sleep_avg > MAX_SLEEP_AVG)
@@ -406,21 +407,16 @@ static inline void activate_task(task_t 
 		 */
 		if (runtime < MAX_SLEEP_AVG)
 			p->sleep_avg += (runtime - p->sleep_avg) * (MAX_SLEEP_AVG - runtime) *
-				(10 - INTERACTIVE_DELTA) / 10 / MAX_SLEEP_AVG;
+				(MAX_BONUS - INTERACTIVE_DELTA) / MAX_BONUS / MAX_SLEEP_AVG;
 
-		/*
-		 * Keep a buffer of 10% sleep_avg
-		 * to prevent short bursts of cpu activity from making
-		 * interactive tasks lose their bonus
-		 */
-		if (p->sleep_avg > MAX_SLEEP_AVG * 11/10)
-			p->sleep_avg = MAX_SLEEP_AVG * 11/10;
+		if (p->sleep_avg > MAX_SLEEP_AVG)
+			p->sleep_avg = MAX_SLEEP_AVG;
 
 		/*
 		 * Tasks that sleep a long time are categorised as idle and
 		 * get their static priority only
 		 */
-		if (sleep_time > MIN_SLEEP_AVG)
+		if ((sleep_time > MIN_SLEEP_AVG) && (p->sleep_avg > runtime / 2))
 			p->sleep_avg = runtime / 2;
 
 		if (unlikely(p->avg_start > jiffies)){