linux-kernel - [PATCH] cpuidle: menu: Optimize bucket assignment when next_timer_ns equals KTIME

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Message-ID: <20250403092852.1072015-1-quic_zhonhan@quicinc.com>
Date: Thu, 3 Apr 2025 17:28:52 +0800
From: Zhongqiu Han <quic_zhonhan@...cinc.com>
To: <rafael@...nel.org>, <daniel.lezcano@...aro.org>,
        <christian.loehle@....com>
CC: <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <quic_zhonhan@...cinc.com>
Subject: [PATCH] cpuidle: menu: Optimize bucket assignment when next_timer_ns equals KTIME_MAX

Directly assign the last bucket value instead of calling which_bucket()
when next_timer_ns equals KTIME_MAX, the largest possible value that
always falls into the last bucket. This avoids unnecessary calculations
and enhances performance.

Signed-off-by: Zhongqiu Han <quic_zhonhan@...cinc.com>
---
 drivers/cpuidle/governors/menu.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 39aa0aea61c6..8fc7fbed0052 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -255,7 +255,12 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 		 */
 		data->next_timer_ns = KTIME_MAX;
 		delta_tick = TICK_NSEC / 2;
-		data->bucket = which_bucket(KTIME_MAX);
+		/*
+		 * Assign the last bucket value directly instead of calling
+		 * which_bucket(), since KTIME_MAX is the largest possible
+		 * value that always falls into the last bucket.
+		 */
+		data->bucket = BUCKETS - 1;
 	}
 
 	if (unlikely(drv->state_count <= 1 || latency_req == 0) ||
-- 
2.25.1