sched/cpufreq: Rework schedutil governor performance estimation

The current method to take into account uclamp hints when estimating the
target frequency can end in a situation where the selected target
frequency is finally higher than uclamp hints, whereas there are no real
needs. Such cases mainly happen because we are currently mixing the
traditional scheduler utilization signal with the uclamp performance
hints. By adding these 2 metrics, we loose an important information when
it comes to select the target frequency, and we have to make some
assumptions which can't fit all cases.

Rework the interface between the scheduler and schedutil governor in order
to propagate all information down to the cpufreq governor.

effective_cpu_util() interface changes and now returns the actual
utilization of the CPU with 2 optional inputs:

- The minimum performance for this CPU; typically the capacity to handle
  the deadline task and the interrupt pressure. But also uclamp_min
  request when available.

- The maximum targeting performance for this CPU which reflects the
  maximum level that we would like to not exceed. By default it will be
  the CPU capacity but can be reduced because of some performance hints
  set with uclamp. The value can be lower than actual utilization and/or
  min performance level.

A new sugov_effective_cpu_perf() interface is also available to compute
the final performance level that is targeted for the CPU, after applying
some cpufreq headroom and taking into account all inputs.

With these 2 functions, schedutil is now able to decide when it must go
above uclamp hints. It now also has a generic way to get the min
performance level.

The dependency between energy model and cpufreq governor and its headroom
policy doesn't exist anymore.

eenv_pd_max_util() asks schedutil for the targeted performance after
applying the impact of the waking task.

[ mingo: Refined the changelog & C comments. ]

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/r/20231122133904.446032-2-vincent.guittot@linaro.org

1 files changed, 7 insertions, 17 deletions

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 8a70d51ffa33..c1574cd388e7 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2994,24 +2994,14 @@ static inline void cpufreq_update_util(struct rq *rq, unsigned int flags) {}
 #endif
 
 #ifdef CONFIG_SMP
-/**
- * enum cpu_util_type - CPU utilization type
- * @FREQUENCY_UTIL:	Utilization used to select frequency
- * @ENERGY_UTIL:	Utilization used during energy calculation
- *
- * The utilization signals of all scheduling classes (CFS/RT/DL) and IRQ time
- * need to be aggregated differently depending on the usage made of them. This
- * enum is used within effective_cpu_util() to differentiate the types of
- * utilization expected by the callers, and adjust the aggregation accordingly.
- */
-enum cpu_util_type {
-	FREQUENCY_UTIL,
-	ENERGY_UTIL,
-};
-
 unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
-				 enum cpu_util_type type,
-				 struct task_struct *p);
+				 unsigned long *min,
+				 unsigned long *max);
+
+unsigned long sugov_effective_cpu_perf(int cpu, unsigned long actual,
+				 unsigned long min,
+				 unsigned long max);
+
 
 /*
  * Verify the fitness of task @p to run on @cpu taking into account the