On Fri, Jul 18, 2003 at 08:43:05PM +1000, Con Kolivas wrote:
> On Fri, 18 Jul 2003 20:31, Wiktor Wodecki wrote:
> > On Fri, Jul 18, 2003 at 12:18:33PM +0200, Mike Galbraith wrote:
> > > That _might_ (add salt) be priorities of kernel threads dropping too low.
> > >
> > > I'm also seeing occasional total stalls under heavy I/O in the order of
> > > 10-12 seconds (even the disk stops).  I have no idea if that's something
> > > in mm or the scheduler changes though, as I've yet to do any isolation
> > > and/or tinkering.  All I know at this point is that I haven't seen it in
> > > stock yet.
> >
> > I've seen this too while doing a huge nfs transfer from a 2.6 machine to
> > a 2.4 machine (sparc32). Thought it'd be something with the nfs changes
> > which were recently, might be the scheduler, tho. Ah, and it is fully
> > reproducable.
> 
> Well I didn't want to post this yet because I'm not sure if it's a good 
> workaround yet but it looks like a reasonable compromise, and since you have a 
> testcase it will be interesting to see if it addresses it. It's possible that 
> a task is being requeued every millisecond, and this is a little smarter. It 
> allows cpu hogs to run for 100ms before being round robinned, but shorter for 
> interactive tasks. Can you try this O7 which applies on top of O6.1 please:
> 
> available here:
> http://kernel.kolivas.org/2.5

sorry, the problem still persists. Aborting the cp takes less time, tho
(about 10 seconds now, before it was about 30 secs). I'm aborting during
a big file, FYI.

> 
> and here:
> 
> --- linux-2.6.0-test1-mm1/kernel/sched.c	2003-07-17 19:59:16.000000000 +1000
> +++ linux-2.6.0-testck1/kernel/sched.c	2003-07-18 00:10:55.000000000 +1000
> @@ -1310,10 +1310,12 @@ void scheduler_tick(int user_ticks, int 
>  			enqueue_task(p, rq->expired);
>  		} else
>  			enqueue_task(p, rq->active);
> -	} else if (p->prio < effective_prio(p)){
> +	} else if (!((task_timeslice(p) - p->time_slice) %
> +		 (MIN_TIMESLICE * (MAX_BONUS + 1 - p->sleep_avg * MAX_BONUS / MAX_SLEEP_AVG)))){
>  		/*
> -		 * Tasks that have lowered their priority are put to the end
> -		 * of the active array with their remaining timeslice
> +		 * Running tasks get requeued with their remaining timeslice
> +		 * after a period proportional to how cpu intensive they are to
> +		 * minimise the duration one interactive task can starve another
>  		 */
>  		dequeue_task(p, rq->active);
>  		set_tsk_need_resched(p);
> 
> -
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-- 
Regards,

Wiktor Wodecki