linux-kernel - [RFC PATCH] sched/feec: Simplify the traversal of pd'cpus

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Message-ID: <20250812093339.8895-1-xuewen.yan@unisoc.com>
Date: Tue, 12 Aug 2025 17:33:39 +0800
From: Xuewen Yan <xuewen.yan@...soc.com>
To: <dietmar.eggemann@....com>, <mingo@...hat.com>, <peterz@...radead.org>,
        <juri.lelli@...hat.com>, <vincent.guittot@...aro.org>
CC: <rostedt@...dmis.org>, <bsegall@...gle.com>, <mgorman@...e.de>,
        <vschneid@...hat.com>, <vdonnefort@...gle.com>, <ke.wang@...soc.com>,
        <xuewen.yan94@...il.com>, <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH] sched/feec: Simplify the traversal of pd'cpus

Now we use for_each_cpu() to traversal all pd's cpus,
it is in order to compute the pd_cap. This approach may
result in some unnecessary judgments.
We can simply calculate pd_cap as follows:

pd_cap = cpu_actual_cap * cpumask_weight(pd_cpus);

Then we can AND pd'scpus, sd's cpus and task's cpus_ptr
before traversing, which can save some unnecessary judgment.

Signed-off-by: Xuewen Yan <xuewen.yan@...soc.com>
---
 kernel/sched/fair.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b173a059315c..e47fe94d6889 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8330,18 +8330,12 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 		cpu_actual_cap = get_actual_cpu_capacity(cpu);
 
 		eenv.cpu_cap = cpu_actual_cap;
-		eenv.pd_cap = 0;
+		eenv.pd_cap = cpu_actual_cap * cpumask_weight(cpus);
 
-		for_each_cpu(cpu, cpus) {
-			struct rq *rq = cpu_rq(cpu);
-
-			eenv.pd_cap += cpu_actual_cap;
-
-			if (!cpumask_test_cpu(cpu, sched_domain_span(sd)))
-				continue;
+		cpumask_and(cpus, cpus, sched_domain_span(sd));
 
-			if (!cpumask_test_cpu(cpu, p->cpus_ptr))
-				continue;
+		for_each_cpu_and(cpu, cpus, p->cpus_ptr) {
+			struct rq *rq = cpu_rq(cpu);
 
 			util = cpu_util(cpu, p, cpu, 0);
 			cpu_cap = capacity_of(cpu);
-- 
2.25.1