linux-kernel - [PATCH 3/4] sched: cpufreq: Move apply_dvfs

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Message-Id: <20230820210640.585311-4-qyousef@layalina.io>
Date:   Sun, 20 Aug 2023 22:06:39 +0100
From:   Qais Yousef <qyousef@...alina.io>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Lukasz Luba <lukasz.luba@....com>,
        Qais Yousef <qyousef@...alina.io>
Subject: [PATCH 3/4] sched: cpufreq: Move apply_dvfs_headroom() to sched.h

This function relies on updating util signal appropriately to give
a headroom to grow. This is more of a scheduler functionality than
cpufreq. Move it to sched.h where all the other util handling code
belongs.

Signed-off-by: Qais Yousef (Google) <qyousef@...alina.io>
---
 include/linux/sched/cpufreq.h | 30 ------------------------------
 kernel/sched/sched.h          | 24 ++++++++++++++++++++++++
 2 files changed, 24 insertions(+), 30 deletions(-)

diff --git a/include/linux/sched/cpufreq.h b/include/linux/sched/cpufreq.h
index f0069b354ac8..d01755d3142f 100644
--- a/include/linux/sched/cpufreq.h
+++ b/include/linux/sched/cpufreq.h
@@ -28,36 +28,6 @@ static inline unsigned long map_util_freq(unsigned long util,
 {
 	return freq * util / cap;
 }
-
-/*
- * DVFS decision are made at discrete points. If CPU stays busy, the util will
- * continue to grow, which means it could need to run at a higher frequency
- * before the next decision point was reached. IOW, we can't follow the util as
- * it grows immediately, but there's a delay before we issue a request to go to
- * higher frequency. The headroom caters for this delay so the system continues
- * to run at adequate performance point.
- *
- * This function provides enough headroom to provide adequate performance
- * assuming the CPU continues to be busy.
- *
- * At the moment it is a constant multiplication with 1.25.
- *
- * TODO: The headroom should be a function of the delay. 25% is too high
- * especially on powerful systems. For example, if the delay is 500us, it makes
- * more sense to give a small headroom as the next decision point is not far
- * away and will follow the util if it continues to rise. On the other hand if
- * the delay is 10ms, then we need a bigger headroom so the CPU won't struggle
- * at a lower frequency if it never goes to idle until then.
- */
-static inline unsigned long apply_dvfs_headroom(unsigned long util)
-{
-	return util + (util >> 2);
-}
-#else
-static inline unsigned long apply_dvfs_headroom(unsigned long util)
-{
-	return util;
-}
 #endif /* CONFIG_CPU_FREQ */
 
 #endif /* _LINUX_SCHED_CPUFREQ_H */
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 3a01b7a2bf66..56eeb5b05b50 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2997,6 +2997,30 @@ enum cpu_util_type {
 unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
 				 enum cpu_util_type type,
 				 struct task_struct *p);
+/*
+ * DVFS decision are made at discrete points. If CPU stays busy, the util will
+ * continue to grow, which means it could need to run at a higher frequency
+ * before the next decision point was reached. IOW, we can't follow the util as
+ * it grows immediately, but there's a delay before we issue a request to go to
+ * higher frequency. The headroom caters for this delay so the system continues
+ * to run at adequate performance point.
+ *
+ * This function provides enough headroom to provide adequate performance
+ * assuming the CPU continues to be busy.
+ *
+ * At the moment it is a constant multiplication with 1.25.
+ *
+ * TODO: The headroom should be a function of the delay. 25% is too high
+ * especially on powerful systems. For example, if the delay is 500us, it makes
+ * more sense to give a small headroom as the next decision point is not far
+ * away and will follow the util if it continues to rise. On the other hand if
+ * the delay is 10ms, then we need a bigger headroom so the CPU won't struggle
+ * at a lower frequency if it never goes to idle until then.
+ */
+static inline unsigned long apply_dvfs_headroom(unsigned long util)
+{
+	return util + (util >> 2);
+}
 
 /*
  * Verify the fitness of task @p to run on @cpu taking into account the
-- 
2.34.1