Re: Linux 2.4.17-pre5

[Davide Libenzi]

On Sun, 9 Dec 2001, Mike Kravetz wrote:

> On Sun, Dec 09, 2001 at 04:24:59PM +0000, Alan Cox wrote:
> > I'm currently using the following rule in wake up
> >
> > 	if(current->mm->runnable > 0)	/* One already running ? */
> > 		cpu = current->mm->last_cpu;
> > 	else
> > 		cpu = idle_cpu();
> > 	else
> > 		cpu = cpu_num[fast_fl1(runnable_set)]
> >
> > that is
> > 	If we are running threads with this mm on a cpu throw them at the
> > 		same core
> > 	If there is an idle CPU use it
> > 	Take the mask of currently executing priority levels, find the last
> > 	set bit (lowest pri) being executed, and look up a cpu running at
> > 	that priority
> >
> > Then the idle stealing code will do the rest of the balancing, but at least
> > it converges towards each mm living on one cpu core.
>
> This implies that the idle loop will poll looking for work to do.
> Is that correct?  Davide's scheduler also does this.  I believe
> the current default idle loop (at least for i386) does as little
> as possible and stops execting instructions.  Comments in the code
> mention power consumption.  Should we be concerned with this?

My idea is not to poll ( due energy issues ) but to wake up idles (
kernel/timer.c ) at every timer tick to let them monitor the overall
balancing status.

- Davide