Messages in this thread | | | Date | Tue, 15 Apr 2014 15:03:01 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC PATCHC 3/3] sched/fair: use the idle state info to choose the idlest cpu |
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On Fri, Mar 28, 2014 at 01:29:56PM +0100, Daniel Lezcano wrote: > @@ -4336,20 +4337,53 @@ 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 idle_stamp, min_idle_stamp = ULONG_MAX; > + > + struct rq *rq; > + struct cpuidle_power *power; > + > + int cpu_idle = -1; > + int cpu_busy = -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)) { > + > + rq = cpu_rq(i); > + power = rq->power; > + idle_stamp = rq->idle_stamp; > + > + /* The cpu is idle since a shorter time */ > + if (idle_stamp < min_idle_stamp) { > + min_idle_stamp = idle_stamp; > + cpu_idle = i; > + continue; > + } > + > + /* The cpu is idle but the exit_latency is shorter */ > + if (power && power->exit_latency < min_exit_latency) { > + min_exit_latency = power->exit_latency; > + cpu_idle = i; > + continue; > + }
Aside from the arguments made by Nico (which I agree with), depending on the life time rules of the power object we might need smp_read_barrier_depends() between reading and using.
If all these objects are static and never change content we do not, if there's dynamic objects involved we probably should.
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