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Subject[Patch v8 1/7] sched/pelt: Add support to track thermal pressure
Date
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 "delta" capacity and is not
binary(util_avg 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.

Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
---

v6->v7:
- Added CONFIG_HAVE_SCHED_THERMAL_PRESSURE to stub out
update_thermal_load_avg in unsupported architectures as per
review comments from Peter, Dietmar and Quentin.
- Updated comment for update_thermal_load_avg as per review
comments from Peter and Dietmar.
v7->v8:
- Fixed typo in defining update_thermal_load_avg which was
causing build errors (reported by kbuild test report)

include/trace/events/sched.h | 4 ++++
init/Kconfig | 4 ++++
kernel/sched/pelt.c | 31 +++++++++++++++++++++++++++++++
kernel/sched/pelt.h | 16 ++++++++++++++++
kernel/sched/sched.h | 1 +
5 files changed, 56 insertions(+)

diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index 420e80e..a8fb667 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -613,6 +613,10 @@ 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));
diff --git a/init/Kconfig b/init/Kconfig
index f6a4a91..c16ea88 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -450,6 +450,10 @@ config HAVE_SCHED_AVG_IRQ
depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
depends on SMP

+config HAVE_SCHED_THERMAL_PRESSURE
+ bool "Enable periodic averaging of thermal pressure"
+ depends on SMP
+
config BSD_PROCESS_ACCT
bool "BSD Process Accounting"
depends on MULTIUSER
diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c
index bd006b7..5d1fbf0 100644
--- a/kernel/sched/pelt.c
+++ b/kernel/sched/pelt.c
@@ -367,6 +367,37 @@ int update_dl_rq_load_avg(u64 now, struct rq *rq, int running)
return 0;
}

+#ifdef CONFIG_HAVE_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
+ * weighted "delta" capacity and is not binary(util_avg 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.
+ */
+
+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, 1);
+ trace_pelt_thermal_tp(rq);
+ return 1;
+ }
+
+ return 0;
+}
+#endif
+
#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
/*
* irq:
diff --git a/kernel/sched/pelt.h b/kernel/sched/pelt.h
index afff644..bf1e17b 100644
--- a/kernel/sched/pelt.h
+++ b/kernel/sched/pelt.h
@@ -7,6 +7,16 @@ 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_HAVE_SCHED_THERMAL_PRESSURE
+int update_thermal_load_avg(u64 now, struct rq *rq, u64 capacity);
+#else
+static inline int
+update_thermal_load_avg(u64 now, struct rq *rq, u64 capacity)
+{
+ return 0;
+}
+#endif
+
#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
int update_irq_load_avg(struct rq *rq, u64 running);
#else
@@ -159,6 +169,12 @@ update_dl_rq_load_avg(u64 now, struct rq *rq, int running)
}

static inline int
+update_thermal_load_avg(u64 now, struct rq *rq, u64 capacity)
+{
+ return 0;
+}
+
+static inline int
update_irq_load_avg(struct rq *rq, u64 running)
{
return 0;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 280a3c7..37bd7ef 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -944,6 +944,7 @@ struct rq {
#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
struct sched_avg avg_irq;
#endif
+ struct sched_avg avg_thermal;
u64 idle_stamp;
u64 avg_idle;

--
2.1.4
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