Commit 76504793 authored by Thara Gopinath's avatar Thara Gopinath Committed by Ingo Molnar
Browse files

sched/pelt: Add support to track thermal pressure 



Extrapolating on the existing framework to track rt/dl utilization using
pelt signals, add a similar mechanism to track thermal pressure. The
difference here from rt/dl utilization tracking is that, instead of
tracking time spent by a CPU running a RT/DL task through util_avg, the
average thermal pressure is tracked through load_avg. This is because
thermal pressure signal is weighted time "delta" capacity unlike util_avg
which is binary. "delta capacity" here means delta between the actual
capacity of a CPU and the decreased capacity a CPU due to a thermal event.

In order to track average thermal pressure, a new sched_avg variable
avg_thermal is introduced. Function update_thermal_load_avg can be called
to do the periodic bookkeeping (accumulate, decay and average) of the
thermal pressure.

Reviewed-by: default avatarVincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: default avatarThara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200222005213.3873-2-thara.gopinath@linaro.org
parent f1dfdab6

include/trace/events/sched.h

+4 −0
Original line number Diff line number Diff line
@@ -618,6 +618,10 @@ DECLARE_TRACE(pelt_dl_tp, 
	TP_PROTO(struct rq *rq),

	TP_ARGS(rq));



DECLARE_TRACE(pelt_thermal_tp,

	TP_PROTO(struct rq *rq),

	TP_ARGS(rq));



DECLARE_TRACE(pelt_irq_tp,

	TP_PROTO(struct rq *rq),

	TP_ARGS(rq));

init/Kconfig

+4 −0
Original line number Diff line number Diff line
@@ -451,6 +451,10 @@ config HAVE_SCHED_AVG_IRQ 
	depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING

	depends on SMP



config SCHED_THERMAL_PRESSURE

	bool "Enable periodic averaging of thermal pressure"

	depends on SMP



config BSD_PROCESS_ACCT

	bool "BSD Process Accounting"

	depends on MULTIUSER

kernel/sched/pelt.c

+31 −0
Original line number Diff line number Diff line
@@ -368,6 +368,37 @@ int update_dl_rq_load_avg(u64 now, struct rq *rq, int running) 
	return 0;

}



#ifdef CONFIG_SCHED_THERMAL_PRESSURE

/*

 * thermal:

 *

 *   load_sum = \Sum se->avg.load_sum but se->avg.load_sum is not tracked

 *

 *   util_avg and runnable_load_avg are not supported and meaningless.

 *

 * Unlike rt/dl utilization tracking that track time spent by a cpu

 * running a rt/dl task through util_avg, the average thermal pressure is

 * tracked through load_avg. This is because thermal pressure signal is

 * time weighted "delta" capacity unlike util_avg which is binary.

 * "delta capacity" =  actual capacity  -

 *			capped capacity a cpu due to a thermal event.

 */



int update_thermal_load_avg(u64 now, struct rq *rq, u64 capacity)

{

	if (___update_load_sum(now, &rq->avg_thermal,

			       capacity,

			       capacity,

			       capacity)) {

		___update_load_avg(&rq->avg_thermal, 1);

		trace_pelt_thermal_tp(rq);

		return 1;

	}



	return 0;

}

#endif



#ifdef CONFIG_HAVE_SCHED_AVG_IRQ

/*

 * irq:

kernel/sched/pelt.h

+31 −0
Original line number Diff line number Diff line
@@ -7,6 +7,26 @@ int __update_load_avg_cfs_rq(u64 now, struct cfs_rq *cfs_rq); 
int update_rt_rq_load_avg(u64 now, struct rq *rq, int running);

int update_dl_rq_load_avg(u64 now, struct rq *rq, int running);



#ifdef CONFIG_SCHED_THERMAL_PRESSURE

int update_thermal_load_avg(u64 now, struct rq *rq, u64 capacity);



static inline u64 thermal_load_avg(struct rq *rq)

{

	return READ_ONCE(rq->avg_thermal.load_avg);

}

#else

static inline int

update_thermal_load_avg(u64 now, struct rq *rq, u64 capacity)

{

	return 0;

}



static inline u64 thermal_load_avg(struct rq *rq)

{

	return 0;

}

#endif



#ifdef CONFIG_HAVE_SCHED_AVG_IRQ

int update_irq_load_avg(struct rq *rq, u64 running);

#else
@@ -158,6 +178,17 @@ update_dl_rq_load_avg(u64 now, struct rq *rq, int running) 
	return 0;

}



static inline int

update_thermal_load_avg(u64 now, struct rq *rq, u64 capacity)

{

	return 0;

}



static inline u64 thermal_load_avg(struct rq *rq)

{

	return 0;

}



static inline int

update_irq_load_avg(struct rq *rq, u64 running)

{

kernel/sched/sched.h

+3 −0
Original line number Diff line number Diff line
@@ -960,6 +960,9 @@ struct rq { 
	struct sched_avg	avg_dl;

#ifdef CONFIG_HAVE_SCHED_AVG_IRQ

	struct sched_avg	avg_irq;

#endif

#ifdef CONFIG_SCHED_THERMAL_PRESSURE

	struct sched_avg	avg_thermal;

#endif

	u64			idle_stamp;

	u64			avg_idle;

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