Re: [PATCH 4/7] sched: Account rr and fifo tasks separately

[Peter Zijlstra]

On Fri, Nov 13, 2015 at 03:22:06PM +0100, Frederic Weisbecker wrote:
> In order to evaluate tick dependency, we need to account SCHED_RR and
> SCHED_FIFO tasks separately as those policies don't have the same
> preemption requirements.
> 
> We still keep rt_nr_running as a cache to avoid additions between nr_rr
> and nr_fifo all over the place.

In which case you only need one of nr_fifo/nr_rr. Less accounting is
better.

Pick the one you need for the nohz_full condition, and leave the other.
A quick look at sched_can_stop_tick() seems to suggest nr_rr is the
interesting one. nr_rr < 2 should allow stopping the tick.
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