linux-kernel - [PATCH] cpufreq: intel_pstate: Use likely() optimization in intel_pstate

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Message-Id: <20250912073502.743735-1-tianyaxiong@kylinos.cn>
Date: Fri, 12 Sep 2025 15:35:02 +0800
From: Yaxiong Tian <tianyaxiong@...inos.cn>
To: srinivas.pandruvada@...ux.intel.com,
	lenb@...nel.org,
	rafael@...nel.org,
	viresh.kumar@...aro.org
Cc: linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Yaxiong Tian <tianyaxiong@...inos.cn>
Subject: [PATCH] cpufreq: intel_pstate: Use likely() optimization in intel_pstate_sample()

The comment above the condition `if (cpu->last_sample_time)` clearly
indicates that the branch is taken for the vast majority of invocations
after the first sample in a cycle. The first sample is a one-time
initialization case.

Add likely() hint to the condition to improve branch prediction for
this performance-critical path in intel_pstate_sample().

Signed-off-by: Yaxiong Tian <tianyaxiong@...inos.cn>
---
 drivers/cpufreq/intel_pstate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 2519eb527468..d540f2ab9a52 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -2531,7 +2531,7 @@ static inline bool intel_pstate_sample(struct cpudata *cpu, u64 time)
 	 * that sample.time will always be reset before setting the utilization
 	 * update hook and make the caller skip the sample then.
 	 */
-	if (cpu->last_sample_time) {
+	if (likely(cpu->last_sample_time)) {
 		intel_pstate_calc_avg_perf(cpu);
 		return true;
 	}
-- 
2.25.1