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@linaro.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Lukasz Luba <lukasz.luba@arm.com>
Reviewed-by: Qais Yousef <qyousef@layalina.io>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://lore.kernel.org/r/20240326091616.3696851-6-vincent.guittot@linaro.org

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

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);

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;
+	pr_warn("Ignoring the deprecated sched_thermal_decay_shift= option\n");
-
-	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);
 	return 1;
 }
 __setup("sched_thermal_decay_shift=", setup_sched_thermal_decay_shift);
@@ -9367,7 +9361,7 @@ 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))

kernel/sched/sched.h

@@ -1550,24 +1550,6 @@ 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);