linux-kernel - [PATCH v6 5/5] sched/pelt: Remove shift of thermal clock

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Date: Tue, 26 Mar 2024 10:16:16 +0100
From: Vincent Guittot <vincent.guittot@...aro.org>
To: linux@...linux.org.uk,
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	will@...nel.org,
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Cc: Vincent Guittot <vincent.guittot@...aro.org>,
	Qais Yousef <qyousef@...alina.io>
Subject: [PATCH v6 5/5] sched/pelt: Remove shift of thermal clock

The optional shift of the clock used by thermal/hw load avg has been
introduced to handle case where the signal was not always a high frequency
hw signal. Now that cpufreq provides a signal for firmware and
SW pressure, we can remove this exception and always keep this PELT signal
aligned with other signals.
Mark sysctl_sched_migration_cost boot parameter as deprecated

Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
Reviewed-by: Qais Yousef <qyousef@...alina.io>
Reviewed-by: Lukasz Luba <lukasz.luba@....com>
Tested-by: Lukasz Luba <lukasz.luba@....com>
---
 .../admin-guide/kernel-parameters.txt          |  1 +
 kernel/sched/core.c                            |  2 +-
 kernel/sched/fair.c                            | 10 ++--------
 kernel/sched/sched.h                           | 18 ------------------
 4 files changed, 4 insertions(+), 27 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index bb884c14b2f6..3f390cc5f77e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5807,6 +5807,7 @@
 			but is useful for debugging and performance tuning.
 
 	sched_thermal_decay_shift=
+			[Deprecated]
 			[KNL, SMP] Set a decay shift for scheduler thermal
 			pressure signal. Thermal pressure signal follows the
 			default decay period of other scheduler pelt
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 67a8302c3131..1a914388144a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5680,7 +5680,7 @@ void sched_tick(void)
 
 	update_rq_clock(rq);
 	hw_pressure = arch_scale_hw_pressure(cpu_of(rq));
-	update_hw_load_avg(rq_clock_hw(rq), rq, hw_pressure);
+	update_hw_load_avg(rq_clock_task(rq), rq, hw_pressure);
 	curr->sched_class->task_tick(rq, curr, 0);
 	if (sched_feat(LATENCY_WARN))
 		resched_latency = cpu_resched_latency(rq);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 2cdc4c242afe..3ac17b20350a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -78,15 +78,9 @@ static unsigned int normalized_sysctl_sched_base_slice	= 750000ULL;
 
 const_debug unsigned int sysctl_sched_migration_cost	= 500000UL;
 
-int sched_hw_decay_shift;
 static int __init setup_sched_thermal_decay_shift(char *str)
 {
-	int _shift = 0;
-
-	if (kstrtoint(str, 0, &_shift))
-		pr_warn("Unable to set scheduler thermal pressure decay shift parameter\n");
-
-	sched_hw_decay_shift = clamp(_shift, 0, 10);
+	pr_warn("Ignoring the deprecated sched_thermal_decay_shift= option\n");
 	return 1;
 }
 __setup("sched_thermal_decay_shift=", setup_sched_thermal_decay_shift);
@@ -9371,7 +9365,7 @@ static bool __update_blocked_others(struct rq *rq, bool *done)
 
 	decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) |
 		  update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) |
-		  update_hw_load_avg(rq_clock_hw(rq), rq, hw_pressure) |
+		  update_hw_load_avg(now, rq, hw_pressure) |
 		  update_irq_load_avg(rq, 0);
 
 	if (others_have_blocked(rq))
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 5d73d4612e58..35a05f95af3a 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1543,24 +1543,6 @@ static inline u64 rq_clock_task(struct rq *rq)
 	return rq->clock_task;
 }
 
-/**
- * By default the decay is the default pelt decay period.
- * The decay shift can change the decay period in
- * multiples of 32.
- *  Decay shift		Decay period(ms)
- *	0			32
- *	1			64
- *	2			128
- *	3			256
- *	4			512
- */
-extern int sched_hw_decay_shift;
-
-static inline u64 rq_clock_hw(struct rq *rq)
-{
-	return rq_clock_task(rq) >> sched_hw_decay_shift;
-}
-
 static inline void rq_clock_skip_update(struct rq *rq)
 {
 	lockdep_assert_rq_held(rq);
-- 
2.34.1