Re: [PATCH] O3int interactivity for 2.5.74-mm2

[Con Kolivas <kernel@kolivas.org>]

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On Mon, 7 Jul 2003 04:36, Felipe Alfaro Solana wrote:
> On Sun, 2003-07-06 at 19:16, Con Kolivas wrote:
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA1
> >
> > 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.
>
> I'm seeing extreme X starvation with this patch under 2.5.74-mm2 when
> starting a CPU hogger:
>
> 1. Start a KDE session.
> 2. Launch a Konsole
> 3. Launch Konqueror
> 4. Launch XMMS
> 5. Make XMMS play an MP3 file
> 6. On the Konsole terminal, run "while true; do a=2; done"
>
> When the "while..." is run, X starves completely for ~5 seconds (e.g.
> the mouse cursor doesn't respond to my input events). After those 5
> seconds, the mouse cursor goes jerky for a while (~2 seconds) and then
> the system gets responsive.

Aha!

Thanks to Felipe who picked this up I was able to find the one bug causing me 
grief. The idle detection code was allowing the sleep_avg to get to 
ridiculously high levels. This is corrected in the following replacement 
O3int patch. Note this fixes the mozilla issue too. Kick arse!!

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 13:15:04.000000000 +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)
@@ -406,22 +407,19 @@ 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)
-			p->sleep_avg = runtime / 2;
+		if (sleep_time > MIN_SLEEP_AVG){
+			p->avg_start = jiffies - MIN_SLEEP_AVG;
+			p->sleep_avg = MIN_SLEEP_AVG / 2;
+		}
 
 		if (unlikely(p->avg_start > jiffies)){
 			p->avg_start = jiffies;