linux-kernel - [PATCH 13/13] sched/balancing: Rename find_idlest_cpu() => sched_balance_find_dst

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Message-Id: <20240308111819.1101550-14-mingo@kernel.org>
Date: Fri,  8 Mar 2024 12:18:19 +0100
From: Ingo Molnar <mingo@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Dietmar Eggemann <dietmar.eggemann@....com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Shrikanth Hegde <sshegde@...ux.ibm.com>,
	Valentin Schneider <vschneid@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>
Subject: [PATCH 13/13] sched/balancing: Rename find_idlest_cpu() => sched_balance_find_dst_cpu()

Standardize scheduler load-balancing function names on the
sched_balance_() prefix.

Also use 'dst' instead of 'idlest', because it's not really
true that we return the 'idlest' group or CPU, we sort by
idle-exit latency and only return the idlest CPUs from the
lowest-latency set of CPUs.

The true 'idlest' CPUs often remain idle for a long time
and are never returned as long as the system is under-loaded.

Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: Dietmar Eggemann <dietmar.eggemann@....com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Shrikanth Hegde <sshegde@...ux.ibm.com>
Cc: Valentin Schneider <vschneid@...hat.com>
Cc: Vincent Guittot <vincent.guittot@...aro.org>
---
 kernel/sched/fair.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d0c3a091d7d1..4b3c4a181a91 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7160,7 +7160,7 @@ sched_balance_find_dst_group_cpu(struct sched_group *group, struct task_struct *
 	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
 }
 
-static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,
+static inline int sched_balance_find_dst_cpu(struct sched_domain *sd, struct task_struct *p,
 				  int cpu, int prev_cpu, int sd_flag)
 {
 	int new_cpu = cpu;
@@ -7936,7 +7936,7 @@ compute_energy(struct energy_env *eenv, struct perf_domain *pd,
  * NOTE: Forkees are not accepted in the energy-aware wake-up path because
  * they don't have any useful utilization data yet and it's not possible to
  * forecast their impact on energy consumption. Consequently, they will be
- * placed by find_idlest_cpu() on the least loaded CPU, which might turn out
+ * placed by sched_balance_find_dst_cpu() on the least loaded CPU, which might turn out
  * to be energy-inefficient in some use-cases. The alternative would be to
  * bias new tasks towards specific types of CPUs first, or to try to infer
  * their util_avg from the parent task, but those heuristics could hurt
@@ -8201,7 +8201,7 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
 
 	if (unlikely(sd)) {
 		/* Slow path */
-		new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
+		new_cpu = sched_balance_find_dst_cpu(sd, p, cpu, prev_cpu, sd_flag);
 	} else if (wake_flags & WF_TTWU) { /* XXX always ? */
 		/* Fast path */
 		new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
-- 
2.40.1