Re: [RFCv5 PATCH 22/46] sched: Calculate energy consumption of sched_group

Morten Rasmussen
2015-08-14T10:25:10Z

On Thu, Aug 13, 2015 at 05:34:17PM +0200, Peter Zijlstra wrote:
> On Tue, Jul 07, 2015 at 07:24:05PM +0100, Morten Rasmussen wrote:
> > +static unsigned int sched_group_energy(struct sched_group *sg_top)
> > +{
> > + struct sched_domain *sd;
> > + int cpu, total_energy = 0;
> > + struct cpumask visit_cpus;
> > + struct sched_group *sg;
> > +
> > + WARN_ON(!sg_top->sge);
> > +
> > + cpumask_copy(&visit_cpus, sched_group_cpus(sg_top));
> > +
> > + while (!cpumask_empty(&visit_cpus)) {
> > + struct sched_group *sg_shared_cap = NULL;
> > +
> > + cpu = cpumask_first(&visit_cpus);
> > +
> > + /*
> > + * Is the group utilization affected by cpus outside this
> > + * sched_group?
> > + */
> > + sd = highest_flag_domain(cpu, SD_SHARE_CAP_STATES);
> > + if (sd && sd->parent)
> > + sg_shared_cap = sd->parent->groups;
> > +
> > + for_each_domain(cpu, sd) {
> > + sg = sd->groups;
> > +
> > + /* Has this sched_domain already been visited? */
> > + if (sd->child && group_first_cpu(sg) != cpu)
> > + break;
> > +
> > + do {
> > + struct sched_group *sg_cap_util;
> > + unsigned long group_util;
> > + int sg_busy_energy, sg_idle_energy, cap_idx;
> > +
> > + if (sg_shared_cap && sg_shared_cap->group_weight >= sg->group_weight)
> > + sg_cap_util = sg_shared_cap;
> > + else
> > + sg_cap_util = sg;
> > +
> > + cap_idx = find_new_capacity(sg_cap_util, sg->sge);
>
> So here its not really 'new' capacity is it, most like the current
> capacity?

Yes, sort of. It is what the current capacity (P-state) should be to
accommodate the current utilization. Using a sane cpufreq governor it is
most likely not far off.

I could rename it to find_capacity() instead. It is extended in a
subsequent patch to figure out the 'new' capacity in cases were we
consider putting more utilization into the group.

> So in the case of coupled P states, you look for the CPU with highest
> utilization, as that is the on that determines the required P state.

Yes. That is why we need the SD_SHARE_CAP_STATES flag and we use
group_max_usage() in find_new_capacity().