[RFC PATCH v1 1/8] sched/cpufreq_schedutil: make use of DEADLINE utilization signal

Juri Lelli
2017-07-05T09:00:29Z

SCHED_DEADLINE tracks active utilization signal with a per dl_rq
variable named running_bw.

Make use of that to drive cpu frequency selection: add up FAIR and
DEADLINE contribution to get the required CPU capacity to handle both
requirements (while RT still selects max frequency).

Co-authored-by: Claudio Scordino <claudio@evidence.eu.com>
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Luca Abeni <luca.abeni@santannapisa.it>
---
Changes from RFCv0:

- use BW_SHIFT (Peter)
- add comment about guaranteed and requested freq (Peter)
- modify comment about go to max behaviour (Claudio)
---
include/linux/sched/cpufreq.h | 2 --
kernel/sched/cpufreq_schedutil.c | 25 +++++++++++++++----------
2 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/include/linux/sched/cpufreq.h b/include/linux/sched/cpufreq.h
index d2be2ccbb372..39640bb3a8ee 100644
--- a/include/linux/sched/cpufreq.h
+++ b/include/linux/sched/cpufreq.h
@@ -11,8 +11,6 @@
#define SCHED_CPUFREQ_DL (1U << 1)
#define SCHED_CPUFREQ_IOWAIT (1U << 2)

-#define SCHED_CPUFREQ_RT_DL (SCHED_CPUFREQ_RT | SCHED_CPUFREQ_DL)
-
#ifdef CONFIG_CPU_FREQ
struct update_util_data {
void (*func)(struct update_util_data *data, u64 time, unsigned int flags);
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 076a2e31951c..f2494d1fc8ef 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -157,12 +157,17 @@ static unsigned int get_next_freq(struct sugov_policy *sg_policy,
static void sugov_get_util(unsigned long *util, unsigned long *max)
{
struct rq *rq = this_rq();
- unsigned long cfs_max;
+ unsigned long dl_util = (rq->dl.running_bw * SCHED_CAPACITY_SCALE)
+ >> BW_SHIFT;

- cfs_max = arch_scale_cpu_capacity(NULL, smp_processor_id());
+ *max = arch_scale_cpu_capacity(NULL, smp_processor_id());

- *util = min(rq->cfs.avg.util_avg, cfs_max);
- *max = cfs_max;
+ /*
+ * Ideally we would like to set util_dl as min/guaranteed freq and
+ * util_cfs + util_dl as requested freq. However, cpufreq is not yet
+ * ready for such an interface. So, we only do the latter for now.
+ */
+ *util = min(rq->cfs.avg.util_avg + dl_util, *max);
}

static void sugov_set_iowait_boost(struct sugov_cpu *sg_cpu, u64 time,
@@ -226,7 +231,7 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,

busy = sugov_cpu_is_busy(sg_cpu);

- if (flags & SCHED_CPUFREQ_RT_DL) {
+ if (flags & SCHED_CPUFREQ_RT) {
next_f = policy->cpuinfo.max_freq;
} else {
sugov_get_util(&util, &max);
@@ -266,7 +271,7 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time)
j_sg_cpu->iowait_boost = 0;
continue;
}
- if (j_sg_cpu->flags & SCHED_CPUFREQ_RT_DL)
+ if (j_sg_cpu->flags & SCHED_CPUFREQ_RT)
return policy->cpuinfo.max_freq;

j_util = j_sg_cpu->util;
@@ -302,7 +307,7 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
sg_cpu->last_update = time;

if (sugov_should_update_freq(sg_policy, time)) {
- if (flags & SCHED_CPUFREQ_RT_DL)
+ if (flags & SCHED_CPUFREQ_RT)
next_f = sg_policy->policy->cpuinfo.max_freq;
else
next_f = sugov_next_freq_shared(sg_cpu, time);
@@ -332,9 +337,9 @@ static void sugov_irq_work(struct irq_work *irq_work)
sg_policy = container_of(irq_work, struct sugov_policy, irq_work);

/*
- * For RT and deadline tasks, the schedutil governor shoots the
- * frequency to maximum. Special care must be taken to ensure that this
- * kthread doesn't result in the same behavior.
+ * For RT tasks, the schedutil governor shoots the frequency to maximum.
+ * Special care must be taken to ensure that this kthread doesn't result
+ * in the same behavior.
*
* This is (mostly) guaranteed by the work_in_progress flag. The flag is
* updated only at the end of the sugov_work() function and before that
--
2.11.0