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From:   brookxu <brookxu.cn@gmail.com>
To:     mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
        vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
        rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
        bristot@redhat.com
Cc:     linux-kernel@vger.kernel.org
Subject: [RFC PATCH] sched/fair: use max_spare_cap_cpu if it is more energy efficient
Date:   Thu, 21 Oct 2021 16:23:14 +0800
Message-Id: <1634804594-4163-1-git-send-email-brookxu.cn@gmail.com>
Precedence: bulk

From: Chunguang Xu <brookxu@tencent.com>

When debugging EAS, I found that if the task is migrated to
max_spare_cap_cpu, even if the power consumption of pd is lower,
we still put the task on prev_cpu. Maybe we should fix it.

Signed-off-by: Chunguang Xu <brookxu@tencent.com>
---
 kernel/sched/fair.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ff69f245b939..2ae7e03de6d2 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6867,8 +6867,10 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 		/* Evaluate the energy impact of using max_spare_cap_cpu. */
 		if (max_spare_cap_cpu >= 0) {
 			cur_delta = compute_energy(p, max_spare_cap_cpu, pd);
-			if (cur_delta < base_energy_pd)
+			if (cur_delta < base_energy_pd) {
+				target = max_spare_cap_cpu;
 				goto unlock;
+			}
 			cur_delta -= base_energy_pd;
 			if (cur_delta < best_delta) {
 				best_delta = cur_delta;
-- 
2.30.0