On Thu, Jun 21, 2018 at 08:45:24PM +0200, Peter Zijlstra wrote:
> On Fri, Jun 08, 2018 at 02:09:47PM +0200, Vincent Guittot wrote:
> > static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu)
> > {
> > struct rq *rq = cpu_rq(sg_cpu->cpu);
> > + unsigned long util;
> >
> > if (rq->rt.rt_nr_running)
> > return sg_cpu->max;
> >
> > + util = sg_cpu->util_dl;
> > + util += sg_cpu->util_cfs;
> > + util += sg_cpu->util_rt;
> > +
> > /*
> > * Utilization required by DEADLINE must always be granted while, for
> > * FAIR, we use blocked utilization of IDLE CPUs as a mechanism to
> > @@ -197,7 +204,7 @@ static unsigned long sugov_aggregate_util(struct
> > sugov_cpu *sg_cpu)
> > * util_cfs + util_dl as requested freq. However, cpufreq is not yet
> > * ready for such an interface. So, we only do the latter for now.
> > */
> > - return min(sg_cpu->max, (sg_cpu->util_dl + sg_cpu->util_cfs));
> > + return min(sg_cpu->max, util);
> > }
>
> So this (and the dl etc. equivalents) result in exactly the problems
> complained about last time, no?
>
> What I proposed was something along the lines of:
>
> util = 1024 * sg_cpu->util_cfs;
> util /= (1024 - (sg_cpu->util_rt + sg_cpu->util_dl + ...));
>
> return min(sg_cpu->max, util + sg_cpu->bw_dl);
>
> Where we, instead of directly adding the various util signals.
That looks unfinished; I think that wants to include: "we renormalize
the CFS signal".
> I now see an email from Quentin asking if these things are not in fact
> the same, but no, they are not. The difference is that the above only
> affects the CFS signal and will re-normalize the utilization of an
> 'always' running task back to 1 by compensating for the stolen capacity.
>
> But it will not, like these here patches, affect the OPP selection of
> other classes. If there is no CFS utilization (or very little), then the
> renormalization will not matter, and the existing DL bandwidth
> compuation will be unaffected.
>
