sched/fair: Make EAS wakeup placement consider uclamp restrictions

task_fits_capacity() has just been made uclamp-aware, and
find_energy_efficient_cpu() needs to go through the same treatment.

Things are somewhat different here however - using the task max clamp isn't
sufficient. Consider the following setup:

  The target runqueue, rq:
    rq.cpu_capacity_orig = 512
    rq.cfs.avg.util_avg = 200
    rq.uclamp.max = 768 // the max p.uclamp.max of all enqueued p's is 768

  The waking task, p (not yet enqueued on rq):
    p.util_est = 600
    p.uclamp.max = 100

Now, consider the following code which doesn't use the rq clamps:

  util = uclamp_task_util(p);
  // Does the task fit in the spare CPU capacity?
  cpu = cpu_of(rq);
  fits_capacity(util, cpu_capacity(cpu) - cpu_util(cpu))

This would lead to:

  util = 100;
  fits_capacity(100, 512 - 200)

fits_capacity() would return true. However, enqueuing p on that CPU *will*
cause it to become overutilized since rq clamp values are max-aggregated,
so we'd remain with

  rq.uclamp.max = 768

which comes from the other tasks already enqueued on rq. Thus, we could
select a high enough frequency to reach beyond 0.8 * 512 utilization
(== overutilized) after enqueuing p on rq. What find_energy_efficient_cpu()
needs here is uclamp_rq_util_with() which lets us peek at the future
utilization landscape, including rq-wide uclamp values.

Make find_energy_efficient_cpu() use uclamp_rq_util_with() for its
fits_capacity() check. This is in line with what compute_energy() ends up
using for estimating utilization.

Tested-By: Dietmar Eggemann <[email protected]>
Suggested-by: Quentin Perret <[email protected]>
Signed-off-by: Valentin Schneider <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Vincent Guittot <[email protected]>
Reviewed-by: Dietmar Eggemann <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

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