[PATCH v10 10/16] sched/core: uclamp: Add uclamp_util_with()

Patrick Bellasi
2019-06-21T08:43:04Z

So far uclamp_util() allows to clamp a specified utilization considering
the clamp values requested by RUNNABLE tasks in a CPU. For the Energy
Aware Scheduler (EAS) it is interesting to test how clamp values will
change when a task is becoming RUNNABLE on a given CPU.
For example, EAS is interested in comparing the energy impact of
different scheduling decisions and the clamp values can play a role on
that.

Add uclamp_util_with() which allows to clamp a given utilization by
considering the possible impact on CPU clamp values of a specified task.

Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
---
kernel/sched/core.c | 13 +++++++++++++
kernel/sched/sched.h | 21 ++++++++++++++++++++-
2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ab75e874fdcc..2226ddd1de04 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -869,6 +869,19 @@ uclamp_eff_get(struct task_struct *p, unsigned int clamp_id)
return uc_req;
}

+unsigned int uclamp_eff_value(struct task_struct *p, unsigned int clamp_id)
+{
+ struct uclamp_se uc_eff;
+
+ /* Task currently refcounted: use back-annotated (effective) value */
+ if (p->uclamp[clamp_id].active)
+ return p->uclamp[clamp_id].value;
+
+ uc_eff = uclamp_eff_get(p, clamp_id);
+
+ return uc_eff.value;
+}
+
/*
* When a task is enqueued on a rq, the clamp bucket currently defined by the
* task's uclamp::bucket_id is refcounted on that rq. This also immediately
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index c33a57f14743..ce2da8b9ff8c 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2266,11 +2266,20 @@ static inline void cpufreq_update_util(struct rq *rq, unsigned int flags) {}
#endif /* CONFIG_CPU_FREQ */

#ifdef CONFIG_UCLAMP_TASK
-static inline unsigned int uclamp_util(struct rq *rq, unsigned int util)
+unsigned int uclamp_eff_value(struct task_struct *p, unsigned int clamp_id);
+
+static __always_inline
+unsigned int uclamp_util_with(struct rq *rq, unsigned int util,
+ struct task_struct *p)
{
unsigned int min_util = READ_ONCE(rq->uclamp[UCLAMP_MIN].value);
unsigned int max_util = READ_ONCE(rq->uclamp[UCLAMP_MAX].value);

+ if (p) {
+ min_util = max(min_util, uclamp_eff_value(p, UCLAMP_MIN));
+ max_util = max(max_util, uclamp_eff_value(p, UCLAMP_MAX));
+ }
+
/*
* Since CPU's {min,max}_util clamps are MAX aggregated considering
* RUNNABLE tasks with _different_ clamps, we can end up with an
@@ -2281,7 +2290,17 @@ static inline unsigned int uclamp_util(struct rq *rq, unsigned int util)

return clamp(util, min_util, max_util);
}
+
+static inline unsigned int uclamp_util(struct rq *rq, unsigned int util)
+{
+ return uclamp_util_with(rq, util, NULL);
+}
#else /* CONFIG_UCLAMP_TASK */
+static inline unsigned int uclamp_util_with(struct rq *rq, unsigned int util,
+ struct task_struct *p)
+{
+ return util;
+}
static inline unsigned int uclamp_util(struct rq *rq, unsigned int util)
{
return util;
--
2.21.0