On 08/05/18 21:54, Joel Fernandes wrote:
[...]
> Just for discussion sake, is there any need for work_in_progress? If we can
> queue multiple work say kthread_queue_work can handle it, then just queuing
> works whenever they are available should be Ok and the kthread loop can
> handle them. __cpufreq_driver_target is also protected by the work lock if
> there is any concern that can have races... only thing is rate-limiting of
> the requests, but we are doing a rate limiting, just not for the "DL
> increased utilization" type requests (which I don't think we are doing at the
> moment for urgent DL requests anyway).
>
> Following is an untested diff to show the idea. What do you think?
>
> thanks,
>
> - Joel
>
> ----8<---
> diff --git a/kernel/sched/cpufreq_schedutil.c
> b/kernel/sched/cpufreq_schedutil.c
> index d2c6083304b4..862634ff4bf3 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -38,7 +38,6 @@ struct sugov_policy {
> struct mutex work_lock;
> struct kthread_worker worker;
> struct task_struct *thread;
> - bool work_in_progress;
>
> bool need_freq_update;
> };
> @@ -92,16 +91,8 @@ 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;
> - /*
> - * This happens when limits change, so forget the previous
> - * next_freq value and force an update.
> - */
> - sg_policy->next_freq = UINT_MAX;
> return true;
> }
>
> @@ -129,7 +120,6 @@ 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);
Isn't this potentially introducing unneeded irq pressure (and doing the
whole wakeup the kthread thing), while the already active kthread could
simply handle multiple back-to-back requests before going to sleep?
Best,
- Juri
