[PATCH v7 09/15] sched/core: uclamp: Add uclamp_util_with()

Patrick Bellasi
2019-02-08T10:05:48Z

Currently uclamp_util() allows to clamp a specified utilization
considering the clamp values requested by RUNNABLE tasks in a CPU.
Sometimes however, it could be interesting to verify how clamp values
will change when a task is going to be running on a given CPU.
For example, the Energy Aware Scheduler (EAS) is interested in
evaluating and comparing the energy impact of different scheduling
decisions.

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/sched.h | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index f07048a0e845..de181b8a3a2a 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2278,11 +2278,20 @@ 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_effective_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_effective_value(p, UCLAMP_MIN));
+ max_util = max(max_util, uclamp_effective_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
@@ -2293,7 +2302,17 @@ 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;
--
2.20.1