Messages in this thread | | | Date | Thu, 11 Feb 2016 12:59:59 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks |
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On Tue, Feb 09, 2016 at 05:02:33PM -0800, Steve Muckle wrote: > > Index: linux-pm/kernel/sched/deadline.c > > =================================================================== > > --- linux-pm.orig/kernel/sched/deadline.c > > +++ linux-pm/kernel/sched/deadline.c > > @@ -1197,6 +1197,9 @@ static void task_tick_dl(struct rq *rq, > > { > > update_curr_dl(rq); > > > > + /* Kick cpufreq to prevent it from stalling. */ > > + cpufreq_kick(); > > + > > /* > > * Even when we have runtime, update_curr_dl() might have resulted in us > > * not being the leftmost task anymore. In that case NEED_RESCHED will > > 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.
No, for RT (RR/FIFO) we do not have enough information to do anything useful. Basically RR/FIFO should result in running 100% whenever we schedule such a task.
That means RR/FIFO want a hook in pick_next_task_rt() to bump the freq to 100% and leave it there until something else gets to run.
For DL it basically wants to set a minimum freq based on reserved utilization, so that is __setparam_dl() or somewhere around there.
And we should either use CPPC hints for min freq or manually ensure that the CFS callback will not select something less than this.
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