On Wed, Feb 10, 2016 at 8:47 PM, Steve Muckle <[email protected]> wrote: > On 02/09/2016 07:09 PM, Rafael J. Wysocki wrote: >>>> >> I think additional hooks such as enqueue/dequeue would be needed in >>>> >> RT/DL. The task tick callbacks will only run if a task in that class is >>>> >> executing at the time of the tick. There could be intermittent RT/DL >>>> >> task activity in a frequency domain (the only task activity there, no >>>> >> CFS tasks) that doesn't happen to overlap the tick. Worst case the task >>>> >> activity could be periodic in such a way that it never overlaps the tick >>>> >> and the update is never made. >>> > >>> > So if I'm reading this correctly, it would be better to put the hooks >>> > into update_curr_rt/dl()? > > That should AFAICS be sufficient to avoid stalling. It may be more than > is required as that covers more than just enqueue/dequeue but I'm not > sure offhand. > >> >> If done this way, I guess we may pass rq_clock_task(rq) as the time >> arg to cpufreq_update_util() from there and then the cpu_lock() call >> I've added to this prototype won't be necessary any more. > > Is it rq_clock_task() or rq_clock()? The former can omit irq time so may > gradually fall behind wall clock time, delaying callbacks in cpufreq.
What matters to us is the difference between the current time and the time we previously took a sample and there shouldn't be too much difference between the two in that respect. Both are good enough IMO, but I can update the patch to use rq_clock() if that's preferred. Thanks, Rafael
