Messages in this thread | | | Date | Wed, 9 May 2018 14:10:01 +0530 | From | Viresh Kumar <> | Subject | Re: [RFC PATCH] sched/cpufreq/schedutil: handling urgent frequency requests |
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On 09-05-18, 10:30, Rafael J. Wysocki wrote: > On Wed, May 9, 2018 at 10:06 AM, Joel Fernandes <joel@joelfernandes.org> wrote: > > How about this? Will use the latest request, and also doesn't do unnecessary > > irq_work_queue:
I almost wrote the same stuff before I went for lunch :)
> > (untested) > > -----8<-------- > > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c > > index d2c6083304b4..6a3e42b01f52 100644 > > --- a/kernel/sched/cpufreq_schedutil.c > > +++ b/kernel/sched/cpufreq_schedutil.c > > @@ -38,7 +38,7 @@ struct sugov_policy { > > struct mutex work_lock; > > struct kthread_worker worker; > > struct task_struct *thread; > > - bool work_in_progress; > > + bool work_in_progress; /* Has kthread been kicked */ > > > > bool need_freq_update; > > }; > > @@ -92,9 +92,6 @@ static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time) > > !cpufreq_can_do_remote_dvfs(sg_policy->policy)) > > return false; > > > > - if (sg_policy->work_in_progress) > > - return false; > > - > > Why this change? > > Doing the below is rather pointless if work_in_progress is set, isn't it? > > You'll drop the results of it on the floor going forward anyway then AFAICS. > > > if (unlikely(sg_policy->need_freq_update)) { > > sg_policy->need_freq_update = false; > > /* > > @@ -129,8 +126,11 @@ static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time, > > policy->cur = next_freq; > > trace_cpu_frequency(next_freq, smp_processor_id()); > > } else { > > - sg_policy->work_in_progress = true; > > - irq_work_queue(&sg_policy->irq_work); > > + /* work_in_progress helps us not queue unnecessarily */ > > + if (!sg_policy->work_in_progress) { > > + sg_policy->work_in_progress = true; > > + irq_work_queue(&sg_policy->irq_work); > > + } > > } > > }
Right, none of the above changes are required now.
> > @@ -381,13 +381,23 @@ sugov_update_shared(struct update_util_data *hook, u64 time, unsigned int flags) > > static void sugov_work(struct kthread_work *work) > > { > > struct sugov_policy *sg_policy = container_of(work, struct sugov_policy, work); > > + unsigned int freq; > > + > > + /* > > + * Hold sg_policy->update_lock just enough to handle the case where: > > + * if sg_policy->next_freq is updated before work_in_progress is set to > > + * false, we may miss queueing the new update request since > > + * work_in_progress would appear to be true. > > + */ > > + raw_spin_lock(&sg_policy->update_lock); > > + freq = sg_policy->next_freq; > > + sg_policy->work_in_progress = false; > > + raw_spin_unlock(&sg_policy->update_lock);
One problem we still have is that sg_policy->update_lock is only used in the shared policy case and not in the single CPU per policy case, so the race isn't solved there yet.
> > mutex_lock(&sg_policy->work_lock); > > - __cpufreq_driver_target(sg_policy->policy, sg_policy->next_freq, > > + __cpufreq_driver_target(sg_policy->policy, freq, > > CPUFREQ_RELATION_L); > > mutex_unlock(&sg_policy->work_lock); > > - > > - sg_policy->work_in_progress = false; > > } > > > > static void sugov_irq_work(struct irq_work *irq_work)
-- viresh
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