sched/fair: Refactor CPU utilization functions

There is a lot of code duplication in cpu_util_next() & cpu_util_cfs().

Remove this by allowing cpu_util_next() to be called with p = NULL.
Rename cpu_util_next() to cpu_util() since the '_next' suffix is no
longer necessary to distinct cpu utilization related functions.
Implement cpu_util_cfs(cpu) as cpu_util(cpu, p = NULL, -1).

This will allow to code future related cpu util changes only in one
place, namely in cpu_util().

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20230515115735.296329-2-dietmar.eggemann@arm.com

1 files changed, 1 insertions, 46 deletions

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index d8ba81c66579..aaf6fc2df6ff 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2955,53 +2955,8 @@ static inline unsigned long cpu_util_dl(struct rq *rq)
 	return READ_ONCE(rq->avg_dl.util_avg);
 }
 
-/**
- * cpu_util_cfs() - Estimates the amount of CPU capacity used by CFS tasks.
- * @cpu: the CPU to get the utilization for.
- *
- * The unit of the return value must be the same as the one of CPU capacity
- * so that CPU utilization can be compared with CPU capacity.
- *
- * CPU utilization is the sum of running time of runnable tasks plus the
- * recent utilization of currently non-runnable tasks on that CPU.
- * It represents the amount of CPU capacity currently used by CFS tasks in
- * the range [0..max CPU capacity] with max CPU capacity being the CPU
- * capacity at f_max.
- *
- * The estimated CPU utilization is defined as the maximum between CPU
- * utilization and sum of the estimated utilization of the currently
- * runnable tasks on that CPU. It preserves a utilization "snapshot" of
- * previously-executed tasks, which helps better deduce how busy a CPU will
- * be when a long-sleeping task wakes up. The contribution to CPU utilization
- * of such a task would be significantly decayed at this point of time.
- *
- * CPU utilization can be higher than the current CPU capacity
- * (f_curr/f_max * max CPU capacity) or even the max CPU capacity because
- * of rounding errors as well as task migrations or wakeups of new tasks.
- * CPU utilization has to be capped to fit into the [0..max CPU capacity]
- * range. Otherwise a group of CPUs (CPU0 util = 121% + CPU1 util = 80%)
- * could be seen as over-utilized even though CPU1 has 20% of spare CPU
- * capacity. CPU utilization is allowed to overshoot current CPU capacity
- * though since this is useful for predicting the CPU capacity required
- * after task migrations (scheduler-driven DVFS).
- *
- * Return: (Estimated) utilization for the specified CPU.
- */
-static inline unsigned long cpu_util_cfs(int cpu)
-{
-	struct cfs_rq *cfs_rq;
-	unsigned long util;
-
-	cfs_rq = &cpu_rq(cpu)->cfs;
-	util = READ_ONCE(cfs_rq->avg.util_avg);
 
-	if (sched_feat(UTIL_EST)) {
-		util = max_t(unsigned long, util,
-			     READ_ONCE(cfs_rq->avg.util_est.enqueued));
-	}
-
-	return min(util, capacity_orig_of(cpu));
-}
+extern unsigned long cpu_util_cfs(int cpu);
 
 static inline unsigned long cpu_util_rt(struct rq *rq)
 {