Re: 2.5.64-mm6, a new test case for scheduler interactivity problems

[Mike Galbraith <efault@gmx.de>]

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At 10:01 PM 3/13/2003 +0000, Charles Baylis wrote:

>Hi all
>
>I've just installed 2.5.64-mm6, and I've tried out the new improved
>scheduler and it's definately not there yet. I can easily cause ogg
>playback to skip (for example) by changing virtual desktop in windowmaker
>to busy konqueror window. X is not reniced (has a nice level of 0)
>
>It's several months since I last ran a 2.4 kernel on this machine, but as I
>remember it did not skip when changing desktops.
>
>My experience suggests that skips occur when more than one interactive task
>starts to become a CPU hog, for example X and konqueror can be idle for
>long periods, and so become interactive, but during an intensive redraw
>they briefly behave as CPU hogs but maintain their interactive bonus this
>means that ogg123 has to wait until the hogs complete their timeslice
>before being scheduled.
>
>My test case tries to reproduce this by creating a number of tasks which
>alternate between being 'interactive' and CPU hogs. On my Celery 333 laptop
>it can sometimes cause skips with only 1 child, and is pretty much
>guaranteed to cause skips with more child tasks.

Greetings,

Nice test case.  I don't have sound capability on my linux box, but your 
test case makes it fail the window wiggle test horribly.  I fiddled with it 
a bit, and convinced it to "stop doing that please".  Does the attached 
(experimental butchery) help your box's sp-sp-speach im-p-p-pediment?

         -Mike 

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--- linux-2.5.64-bk5/kernel/sched.c.org	Wed Mar 12 08:51:11 2003
+++ linux-2.5.64-bk5/kernel/sched.c	Fri Mar 14 15:27:12 2003
@@ -72,7 +72,7 @@
 #define PRIO_BONUS_RATIO	25
 #define INTERACTIVE_DELTA	2
 #define MAX_SLEEP_AVG		(10*HZ)
-#define STARVATION_LIMIT	(10*HZ)
+#define STARVATION_LIMIT	(1*HZ)
 #define NODE_THRESHOLD		125
 
 /*
@@ -356,6 +356,8 @@
 		 * spends sleeping, the higher the average gets - and the
 		 * higher the priority boost gets as well.
 		 */
+		if (sleep_time > MAX_TIMESLICE)
+			sleep_time = MAX_TIMESLICE;
 		sleep_avg = p->sleep_avg + sleep_time;
 
 		/*
@@ -397,6 +399,8 @@
 		rq->nr_uninterruptible++;
 	dequeue_task(p, p->array);
 	p->array = NULL;
+	if (p->sleep_avg)
+		p->sleep_avg--;
 }
 
 /*
@@ -1249,6 +1253,8 @@
 	if (!--p->time_slice) {
 		dequeue_task(p, rq->active);
 		set_tsk_need_resched(p);
+		if (TASK_INTERACTIVE(p) && p->sleep_avg > MIN_TIMESLICE)
+			p->sleep_avg -= MIN_TIMESLICE;
 		p->prio = effective_prio(p);
 		p->time_slice = task_timeslice(p);
 		p->first_time_slice = 0;