On 17-05-18, 09:00, Juri Lelli wrote:
> Hi Joel,
>
> On 16/05/18 15:45, Joel Fernandes (Google) wrote:
>
> [...]
>
> > @@ -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);
>
> OK, we queue the new request up, but still we need to let this kthread
> activation complete and then wake it up again to service the request
> already queued, right? Wasn't what Claudio proposed (service back to
> back requests all in the same kthread activation) better from an
> overhead pow?
We would need more locking stuff in the work handler in that case and
I think there maybe a chance of missing the request in that solution
if the request happens right at the end of when sugov_work returns.
--
viresh
