[PATCH v5 08/10] cpufreq/schedutil: take into account interrupt

Vincent Guittot
2018-05-25T13:13:42Z

The time spent under interrupt can be significant but it is not reflected
in the utilization of CPU when deciding to choose an OPP. Now that we have
access to this metric, schedutil can take it into account when selecting
the OPP for a CPU.
The CPU utilization is :
irq util_avg + (1 - irq util_avg / max capacity ) * /Sum rq util_avg

A test with iperf on hikey (octo arm64) gives:
iperf -c server_address -r -t 5

w/o patch w/ patch
Tx 276 Mbits/sec 304 Mbits/sec +10%
Rx 299 Mbits/sec 328 Mbits/sec +09%

8 iterations
stdev is lower than 1%
Only WFI idle state is enable (shallowest diel state)

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
kernel/sched/cpufreq_schedutil.c | 10 ++++++++++
kernel/sched/sched.h | 5 +++++
2 files changed, 15 insertions(+)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index a84b5a5..06f2080 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -57,6 +57,7 @@ struct sugov_cpu {
unsigned long util_cfs;
unsigned long util_dl;
unsigned long util_rt;
+ unsigned long util_irq;
unsigned long max;

/* The field below is for single-CPU policies only: */
@@ -180,6 +181,7 @@ static void sugov_get_util(struct sugov_cpu *sg_cpu)
sg_cpu->util_cfs = cpu_util_cfs(rq);
sg_cpu->util_dl = cpu_util_dl(rq);
sg_cpu->util_rt = cpu_util_rt(rq);
+ sg_cpu->util_irq = cpu_util_irq(rq);
}

static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu)
@@ -190,9 +192,17 @@ static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu)
if (rq->rt.rt_nr_running) {
util = sg_cpu->max;
} else {
+ /* Sum rq utilization*/
util = sg_cpu->util_dl;
util += sg_cpu->util_cfs;
util += sg_cpu->util_rt;
+
+ /* Weight rq's utilization to the normal context */
+ util *= (sg_cpu->max - sg_cpu->util_irq);
+ util /= sg_cpu->max;
+
+ /* Add interrupt utilization */
+ util += sg_cpu->util_irq;
}

/*
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index f7e8d5b..718c55d 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2218,4 +2218,9 @@ static inline unsigned long cpu_util_rt(struct rq *rq)
{
return rq->avg_rt.util_avg;
}
+
+static inline unsigned long cpu_util_irq(struct rq *rq)
+{
+ return rq->avg_irq.util_avg;
+}
#endif
--
2.7.4