Messages in this thread | | | Date | Fri, 19 Sep 2014 02:05:45 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2 2/2] sched/fair: leverage the idle state info when choosing the "idlest" cpu |
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On Thu, Sep 04, 2014 at 11:32:10AM -0400, Nicolas Pitre wrote: > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index bfa3c86d0d..416329e1a6 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -23,6 +23,7 @@ > #include <linux/latencytop.h> > #include <linux/sched.h> > #include <linux/cpumask.h> > +#include <linux/cpuidle.h> > #include <linux/slab.h> > #include <linux/profile.h> > #include <linux/interrupt.h> > @@ -4428,20 +4429,48 @@ static int > find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) > { > unsigned long load, min_load = ULONG_MAX; > - int idlest = -1; > + unsigned int min_exit_latency = UINT_MAX; > + u64 latest_idle_timestamp = 0; > + int least_loaded_cpu = this_cpu; > + int shallowest_idle_cpu = -1; > int i; > > /* Traverse only the allowed CPUs */ > for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) { > - load = weighted_cpuload(i); > - > - if (load < min_load || (load == min_load && i == this_cpu)) { > - min_load = load; > - idlest = i; > + if (idle_cpu(i)) { > + struct rq *rq = cpu_rq(i); > + struct cpuidle_state *idle = idle_get_state(rq); > + if (idle && idle->exit_latency < min_exit_latency) { > + /* > + * We give priority to a CPU whose idle state > + * has the smallest exit latency irrespective > + * of any idle timestamp. > + */ > + min_exit_latency = idle->exit_latency; > + latest_idle_timestamp = rq->idle_stamp; > + shallowest_idle_cpu = i; > + } else if ((!idle || idle->exit_latency == min_exit_latency) && > + rq->idle_stamp > latest_idle_timestamp) { > + /* > + * If equal or no active idle state, then > + * the most recently idled CPU might have > + * a warmer cache. > + */ > + latest_idle_timestamp = rq->idle_stamp; > + shallowest_idle_cpu = i; > + } > + cpuidle_put_state(rq);
Right, matching the other changes, I killed that line. The rest looks ok.
> + } else { > + load = weighted_cpuload(i); > + if (load < min_load || > + (load == min_load && i == this_cpu)) { > + min_load = load; > + least_loaded_cpu = i; > + } > } > } > > - return idlest; > + return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu; > }
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