On Thu, Jul 16, 2015 at 05:10:52PM -0700, Sai Gurrappadi wrote: > Hi Morten, > > On 07/07/2015 11:24 AM, Morten Rasmussen wrote: > > --- > > > +static int energy_aware_wake_cpu(struct task_struct *p, int target) > > +{ > > + struct sched_domain *sd; > > + struct sched_group *sg, *sg_target; > > + int target_max_cap = INT_MAX; > > + int target_cpu = task_cpu(p); > > + int i; > > + > > + sd = rcu_dereference(per_cpu(sd_ea, task_cpu(p))); > > + > > + if (!sd) > > + return target; > > + > > + sg = sd->groups; > > + sg_target = sg; > > + > > + /* > > + * Find group with sufficient capacity. We only get here if no cpu is > > + * overutilized. We may end up overutilizing a cpu by adding the task, > > + * but that should not be any worse than select_idle_sibling(). > > + * load_balance() should sort it out later as we get above the tipping > > + * point. > > + */ > > + do { > > + /* Assuming all cpus are the same in group */ > > + int max_cap_cpu = group_first_cpu(sg); > > + > > + /* > > + * Assume smaller max capacity means more energy-efficient. > > + * Ideally we should query the energy model for the right > > + * answer but it easily ends up in an exhaustive search. > > + */ > > + if (capacity_of(max_cap_cpu) < target_max_cap && > > + task_fits_capacity(p, max_cap_cpu)) { > > + sg_target = sg; > > + target_max_cap = capacity_of(max_cap_cpu); > > + } > > + } while (sg = sg->next, sg != sd->groups); > > Should be capacity_orig_of(max_cap_cpu) right? Might select a suboptimal > sg_target if max_cap_cpu has a significant amount of IRQ/RT activity.
Right, this heuristic isn't as good as I had hoped for. task_fits_capacity() is using capacity_of() to check if we have available capacity after subtracting RT/IRQ activity which should be right but I only check the first cpu. So I might discard a group due to RT/IRQ activity on cpu the first cpu while one the sibling cpus could be fine. Then going for lowest capacity_of() means preferring group with most RT/IRQ activity that still has enough capacity to fit the task. Using capacity_orig_of() we would ignore RT/IRQ activity but is likely to be better as we can try to avoid RQ/IRQ activity later. I will use capacity_orig_of() here instead. Thanks. > > + > > + /* Find cpu with sufficient capacity */ > > + for_each_cpu_and(i, tsk_cpus_allowed(p), sched_group_cpus(sg_target)) { > > + /* > > + * p's blocked utilization is still accounted for on prev_cpu > > + * so prev_cpu will receive a negative bias due the double > > + * accouting. However, the blocked utilization may be zero. > > + */ > > + int new_usage = get_cpu_usage(i) + task_utilization(p); > > + > > + if (new_usage > capacity_orig_of(i)) > > + continue; > > Is this supposed to be capacity_of(i) instead? Yes, we should skip cpus with too much RT/IRQ activity here. Thanks. Morten -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/