lkml.org 
[lkml]   [2018]   [May]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH RFC] schedutil: Allow cpufreq requests to be made even when kthread kicked
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

\
 
 \ /
  Last update: 2018-05-17 12:20    [W:0.096 / U:0.060 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site