linux-kernel - [PATCH v4 3/4] sched/fair: Rework sched_use_asym_prio() and sched_asym

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Message-ID: <20240207034704.935774-3-alexs@kernel.org>
Date: Wed,  7 Feb 2024 11:47:03 +0800
From: alexs@...nel.org
To: Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>,
	Daniel Bristot de Oliveira <bristot@...hat.com>,
	Valentin Schneider <vschneid@...hat.com>,
	linux-kernel@...r.kernel.org,
	ricardo.neri-calderon@...ux.intel.com,
	yangyicong@...ilicon.com
Cc: Alex Shi <alexs@...nel.org>
Subject: [PATCH v4 3/4] sched/fair: Rework sched_use_asym_prio() and sched_asym_prefer()

From: Alex Shi <alexs@...nel.org>

sched_use_asym_prio() sched_asym_prefer() are used together in various
places. Consolidate them into a single function sched_asym().

The existing sched_group_asym() is only used when collecting statistics
of a scheduling group. Rename it as sched_group_asym().
This makes the code easier to read. No functional changes.

Signed-off-by: Alex Shi <alexs@...nel.org>
To: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To: Valentin Schneider <vschneid@...hat.com>
To: Vincent Guittot <vincent.guittot@...aro.org>
To: Peter Zijlstra <peterz@...radead.org>
To: Ingo Molnar <mingo@...hat.com>
---
 kernel/sched/fair.c | 37 ++++++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 17 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 607dc310b355..942b6358f683 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9746,8 +9746,18 @@ static bool sched_use_asym_prio(struct sched_domain *sd, int cpu)
 	return sd->flags & SD_SHARE_CPUCAPACITY || is_core_idle(cpu);
 }
 
+static inline bool sched_asym(struct sched_domain *sd, int dst_cpu, int src_cpu)
+{
+	/*
+	 * First check if @dst_cpu can do asym_packing load balance. Only do it
+	 * if it has higher priority than @src_cpu.
+	 */
+	return sched_use_asym_prio(sd, dst_cpu) &&
+		sched_asym_prefer(dst_cpu, src_cpu);
+}
+
 /**
- * sched_asym - Check if the destination CPU can do asym_packing load balance
+ * sched_group_asym - Check if the destination CPU can do asym_packing balance
  * @env:	The load balancing environment
  * @sgs:	Load-balancing statistics of the candidate busiest group
  * @group:	The candidate busiest group
@@ -9767,22 +9777,17 @@ static bool sched_use_asym_prio(struct sched_domain *sd, int cpu)
  * otherwise.
  */
 static inline bool
-sched_asym(struct lb_env *env, struct sg_lb_stats *sgs, struct sched_group *group)
+sched_group_asym(struct lb_env *env, struct sg_lb_stats *sgs, struct sched_group *group)
 {
-	/* Ensure that the whole local core is idle, if applicable. */
-	if (!sched_use_asym_prio(env->sd, env->dst_cpu))
-		return false;
-
 	/*
-	 * CPU priorities does not make sense for SMT cores with more than one
+	 * CPU priorities do not make sense for SMT cores with more than one
 	 * busy sibling.
 	 */
-	if (group->flags & SD_SHARE_CPUCAPACITY) {
-		if (sgs->group_weight - sgs->idle_cpus != 1)
-			return false;
-	}
+	if ((group->flags & SD_SHARE_CPUCAPACITY) &&
+	    (sgs->group_weight - sgs->idle_cpus != 1))
+		return false;
 
-	return sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu);
+	return sched_asym(env->sd, env->dst_cpu, group->asym_prefer_cpu);
 }
 
 /* One group has more than one SMT CPU while the other group does not */
@@ -9938,7 +9943,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
 	/* Check if dst CPU is idle and preferred to this group */
 	if (!local_group && env->sd->flags & SD_ASYM_PACKING &&
 	    env->idle != CPU_NOT_IDLE && sgs->sum_h_nr_running &&
-	    sched_asym(env, sgs, group)) {
+	    sched_group_asym(env, sgs, group)) {
 		sgs->group_asym_packing = 1;
 	}
 
@@ -11037,8 +11042,7 @@ static struct rq *find_busiest_queue(struct lb_env *env,
 		 * SMT cores with more than one busy sibling.
 		 */
 		if ((env->sd->flags & SD_ASYM_PACKING) &&
-		    sched_use_asym_prio(env->sd, i) &&
-		    sched_asym_prefer(i, env->dst_cpu) &&
+		    sched_asym(env->sd, i, env->dst_cpu) &&
 		    nr_running == 1)
 			continue;
 
@@ -11908,8 +11912,7 @@ static void nohz_balancer_kick(struct rq *rq)
 		 * preferred CPU must be idle.
 		 */
 		for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) {
-			if (sched_use_asym_prio(sd, i) &&
-			    sched_asym_prefer(i, cpu)) {
+			if (sched_asym(sd, i, cpu)) {
 				flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK;
 				goto unlock;
 			}
-- 
2.43.0