Revert "sched/fair: Detect capacity inversion"

This reverts commit 30f04dd56d.

It breaks the Android kernel abi, so revert it.  If it needs to come
back later, it can do so in an abi-safe way.

Bug: 161946584
Cc: Qais Yousef <qyousef@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I576fa3894406ad6db3d4eafe5c08572d20c71902

kernel/sched/fair.c

@@ -8513,74 +8513,17 @@ static unsigned long scale_rt_capacity(int cpu)
 
 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
 {
-	unsigned long capacity_orig = arch_scale_cpu_capacity(cpu);
 	unsigned long capacity = scale_rt_capacity(cpu);
 	struct sched_group *sdg = sd->groups;
-	struct rq *rq = cpu_rq(cpu);
 
-	rq->cpu_capacity_orig = capacity_orig;
+	cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(cpu);
 
 	if (!capacity)
 		capacity = 1;
 
 	trace_android_rvh_update_cpu_capacity(cpu, &capacity);
-	rq->cpu_capacity = capacity;
+	cpu_rq(cpu)->cpu_capacity = capacity;
-
+	trace_sched_cpu_capacity_tp(cpu_rq(cpu));
-	/*
-	 * Detect if the performance domain is in capacity inversion state.
-	 *
-	 * Capacity inversion happens when another perf domain with equal or
-	 * lower capacity_orig_of() ends up having higher capacity than this
-	 * domain after subtracting thermal pressure.
-	 *
-	 * We only take into account thermal pressure in this detection as it's
-	 * the only metric that actually results in *real* reduction of
-	 * capacity due to performance points (OPPs) being dropped/become
-	 * unreachable due to thermal throttling.
-	 *
-	 * We assume:
-	 *   * That all cpus in a perf domain have the same capacity_orig
-	 *     (same uArch).
-	 *   * Thermal pressure will impact all cpus in this perf domain
-	 *     equally.
-	 */
-	if (static_branch_unlikely(&sched_asym_cpucapacity)) {
-		unsigned long inv_cap = capacity_orig - thermal_load_avg(rq);
-		struct perf_domain *pd = rcu_dereference(rq->rd->pd);
-
-		rq->cpu_capacity_inverted = 0;
-
-		for (; pd; pd = pd->next) {
-			struct cpumask *pd_span = perf_domain_span(pd);
-			unsigned long pd_cap_orig, pd_cap;
-
-			cpu = cpumask_any(pd_span);
-			pd_cap_orig = arch_scale_cpu_capacity(cpu);
-
-			if (capacity_orig < pd_cap_orig)
-				continue;
-
-			/*
-			 * handle the case of multiple perf domains have the
-			 * same capacity_orig but one of them is under higher
-			 * thermal pressure. We record it as capacity
-			 * inversion.
-			 */
-			if (capacity_orig == pd_cap_orig) {
-				pd_cap = pd_cap_orig - thermal_load_avg(cpu_rq(cpu));
-
-				if (pd_cap > inv_cap) {
-					rq->cpu_capacity_inverted = inv_cap;
-					break;
-				}
-			} else if (pd_cap_orig > inv_cap) {
-				rq->cpu_capacity_inverted = inv_cap;
-				break;
-			}
-		}
-	}
-
-	trace_sched_cpu_capacity_tp(rq);
 
 	sdg->sgc->capacity = capacity;
 	sdg->sgc->min_capacity = capacity;

kernel/sched/sched.h

@@ -993,7 +993,6 @@ struct rq {
 
 	unsigned long		cpu_capacity;
 	unsigned long		cpu_capacity_orig;
-	unsigned long		cpu_capacity_inverted;
 
 	struct callback_head	*balance_callback;
 
@@ -2625,24 +2624,6 @@ static inline unsigned long capacity_orig_of(int cpu)
 {
 	return cpu_rq(cpu)->cpu_capacity_orig;
 }
-
-/*
- * Returns inverted capacity if the CPU is in capacity inversion state.
- * 0 otherwise.
- *
- * Capacity inversion detection only considers thermal impact where actual
- * performance points (OPPs) gets dropped.
- *
- * Capacity inversion state happens when another performance domain that has
- * equal or lower capacity_orig_of() becomes effectively larger than the perf
- * domain this CPU belongs to due to thermal pressure throttling it hard.
- *
- * See comment in update_cpu_capacity().
- */
-static inline unsigned long cpu_in_capacity_inversion(int cpu)
-{
-	return cpu_rq(cpu)->cpu_capacity_inverted;
-}
 #endif
 
 /**