linux-kernel - [RFC PATCH v2 7/7] sched/uclamp: Simplify uclamp_eff

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Date: Thu,  1 Feb 2024 13:12:03 +0000
From: Hongyan Xia <hongyan.xia2@....com>
To: Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Juri Lelli <juri.lelli@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>,
	Mel Gorman <mgorman@...e.de>,
	Daniel Bristot de Oliveira <bristot@...hat.com>,
	Valentin Schneider <vschneid@...hat.com>
Cc: Qais Yousef <qyousef@...alina.io>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Lukasz Luba <lukasz.luba@....com>,
	Christian Loehle <christian.loehle@....com>,
	linux-kernel@...r.kernel.org,
	David Dai <davidai@...gle.com>,
	Saravana Kannan <saravanak@...gle.com>
Subject: [RFC PATCH v2 7/7] sched/uclamp: Simplify uclamp_eff_value()

The commit

sched: Remove all uclamp bucket logic

removes uclamp_rq_{inc/dec}() functions, so now p->uclamp contains the
correct values all the time after a uclamp_update_active() call, and
there's no need to toggle the boolean `active` after an update. As a
result, this function is fairly simple now and can live as a static
inline function.

Signed-off-by: Hongyan Xia <hongyan.xia2@....com>
---
 kernel/sched/core.c  | 13 ++++---------
 kernel/sched/sched.h | 14 ++++++++++++--
 2 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index a3b36adc4dcc..f5f5f056525c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1499,21 +1499,15 @@ uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id)
 	return uc_req;
 }
 
-unsigned long uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
-{
-	if (!uclamp_is_used() || !p->uclamp[clamp_id].active)
-		return uclamp_none(clamp_id);
-
-	return p->uclamp[clamp_id].value;
-}
-
 static inline void
 uclamp_update_active_nolock(struct task_struct *p)
 {
 	enum uclamp_id clamp_id;
 
-	for_each_clamp_id(clamp_id)
+	for_each_clamp_id(clamp_id) {
 		p->uclamp[clamp_id] = uclamp_eff_get(p, clamp_id);
+		p->uclamp[clamp_id].active = 1;
+	}
 }
 
 static inline void
@@ -1773,6 +1767,7 @@ static void uclamp_fork(struct task_struct *p)
 		for_each_clamp_id(clamp_id) {
 			uclamp_se_set(&p->uclamp_req[clamp_id],
 				      uclamp_none(clamp_id), false);
+			p->uclamp[clamp_id].active = 0;
 		}
 	}
 
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 81578410984c..2caefc3344bb 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2991,8 +2991,6 @@ static inline unsigned long cpu_util_rt(struct rq *rq)
 #endif
 
 #ifdef CONFIG_UCLAMP_TASK
-unsigned long uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id);
-
 /* Is the rq being capped/throttled by uclamp_max? */
 static inline bool uclamp_rq_is_capped(struct rq *rq)
 {
@@ -3022,6 +3020,18 @@ static inline bool uclamp_is_used(void)
 	return static_branch_likely(&sched_uclamp_used);
 }
 
+static inline unsigned long uclamp_eff_value(struct task_struct *p,
+					     enum uclamp_id clamp_id)
+{
+	if (uclamp_is_used() && p->uclamp[clamp_id].active)
+		return p->uclamp[clamp_id].value;
+
+	if (clamp_id == UCLAMP_MIN)
+		return 0;
+
+	return SCHED_CAPACITY_SCALE;
+}
+
 static inline unsigned long root_cfs_util(struct rq *rq)
 {
 	return READ_ONCE(rq->root_cfs_util_uclamp);
-- 
2.34.1