linux-kernel - [PATCH v2] cpuidle: menu: Optimize bucket assignment when next_timer_ns equals KTIME

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Message-ID: <20250405135308.1854342-1-quic_zhonhan@quicinc.com>
Date: Sat, 5 Apr 2025 21:53:08 +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 v2] 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.

Reviewed-by: Christian Loehle <christian.loehle@....com>
Signed-off-by: Zhongqiu Han <quic_zhonhan@...cinc.com>
---
v1 -> v2:
- Rebased on top of current next.
- Following Christian's review suggestions, remove unnecessary code comments.
- Link to v1: https://lore.kernel.org/all/20250403092852.1072015-1-quic_zhonhan@quicinc.com/

 drivers/cpuidle/governors/menu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 39aa0aea61c6..52d5d26fc7c6 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -255,7 +255,7 @@ 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);
+		data->bucket = BUCKETS - 1;
 	}
 
 	if (unlikely(drv->state_count <= 1 || latency_req == 0) ||
-- 
2.25.1