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SubjectRe: [PATCH RFC] schedutil: Allow cpufreq requests to be made even when kthread kicked
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".

> + 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 ?

> 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.

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

LGTM.

--
viresh

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