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SubjectRe: [PATCH RFC] schedutil: Allow cpufreq requests to be made even when kthread kicked
On Thu, May 17, 2018 at 10:36:11AM +0530, Viresh Kumar wrote:
> On 16-05-18, 15:45, Joel Fernandes (Google) wrote:
> > kernel/sched/cpufreq_schedutil.c | 36 +++++++++++++++++++++++++-------
> > 1 file changed, 28 insertions(+), 8 deletions(-)
> >
> > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> > index e13df951aca7..a87fc281893d 100644
> > --- a/kernel/sched/cpufreq_schedutil.c
> > +++ b/kernel/sched/cpufreq_schedutil.c
> > @@ -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;
> > -
> > 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);
> > + /* Don't queue request if one was already queued */
> > + if (!sg_policy->work_in_progress) {
>
> Merge it above to make it "else if".

Sure.

> > + sg_policy->work_in_progress = true;
> > + irq_work_queue(&sg_policy->irq_work);
> > + }
> > }
> > }
> >
> > @@ -291,6 +291,15 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
> >
> > ignore_dl_rate_limit(sg_cpu, sg_policy);
> >
> > + /*
> > + * For slow-switch systems, single policy requests can't run at the
> > + * moment if the governor thread is already processing a pending
> > + * frequency switch request, this can be fixed by acquiring update_lock
> > + * while updating next_freq and work_in_progress but we prefer not to.
> > + */
> > + if (sg_policy->work_in_progress)
> > + return;
> > +
>
> @Rafael: Do you think its worth start using the lock now for unshared
> policies ?

Will wait for confirmation before next revision.

> > if (!sugov_should_update_freq(sg_policy, time))
> > return;
> >
> > @@ -382,13 +391,24 @@ 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;
> > + unsigned long flags;
> > +
> > + /*
> > + * Hold sg_policy->update_lock shortly to handle the case where:
> > + * incase sg_policy->next_freq is read here, and then updated by
> > + * sugov_update_shared just before work_in_progress is set to false
> > + * here, we may miss queueing the new update.
> > + */
> > + raw_spin_lock_irqsave(&sg_policy->update_lock, flags);
> > + freq = sg_policy->next_freq;
> > + sg_policy->work_in_progress = false;
> > + raw_spin_unlock_irqrestore(&sg_policy->update_lock, flags);
> >
> > 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);
>
> No need of line break anymore.

Yes, will fix.

> > mutex_unlock(&sg_policy->work_lock);
> > -
> > - sg_policy->work_in_progress = false;
> > }
> >
> > static void sugov_irq_work(struct irq_work *irq_work)
>
> LGTM.

Cool, thanks.

- Joel

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