Re: [patch] sched: fix active load balance

[Nick Piggin <nickpiggin@yahoo.com.au>]

Siddha, Suresh B wrote:
> On Wed, Apr 13, 2005 at 10:08:28PM +0200, Ingo Molnar wrote:
>
> > * Siddha, Suresh B <suresh.b.siddha@intel.com> wrote:
> >
> >
> > > -	for_each_domain(target_cpu, sd) {
> > > +	for_each_domain(target_cpu, sd)
> > > 		if ((sd->flags & SD_LOAD_BALANCE) &&
> > > -			cpu_isset(busiest_cpu, sd->span)) {
> > > -				sd = tmp;
> > > +			cpu_isset(busiest_cpu, sd->span))
> > > 				break;
> > > -		}
> > > -	}

Yep that was broken :(
Thanks for picking that up Suresh.

> > hm, the right fix i think is to do:
> >
> > 	for_each_domain(target_cpu, tmp) {
> >  		if ((tmp->flags & SD_LOAD_BALANCE) &&
> > 			cpu_isset(busiest_cpu, tmp->span)) {
> > 				sd = tmp;
> >  				break;
> > 		}
> > 	}
>
>
> Your suggestion also looks similar to my patch. You are also breaking on the 
> first one.
>
>
> > because when balancing we want to match the widest-scope domain, not the 
> > first one.
>
>
> We want the first domain spanning both the cpu's. That is the domain where
> normal load balance failed and we restore to active load balance.

Yes, that's right.

--
SUSE Labs, Novell Inc.

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