On Thu, Feb 11, 2016 at 7:52 PM, Steve Muckle [off-list ref] wrote:

On 02/11/2016 09:30 AM, Peter Zijlstra wrote:

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My concern above is that pokes are guaranteed to keep occurring when

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there is only RT or DL activity so nothing breaks.

The hook in their respective tick handler should ensure stuff is called
sporadically and isn't stalled.

But that's only true if the RT/DL tasks happen to be running when the
tick arrives right?

Couldn't we have RT/DL activity which doesn't overlap with the tick? And
if no CFS tasks happen to be executing on that CPU, we'll never trigger
the cpufreq update. This could go on for an arbitrarily long time
depending on the periodicity of the work.

I'm thinking that two additional hooks in enqueue_task_rt/dl() might
help here.  Then, we will hit either the tick or enqueue and that
should do the trick.

Peter, what do you think?

Rafael