[PATCH v6 10/16] sched/core: Add uclamp_util_with()

[Patrick Bellasi]

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.bell...@arm.com>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Peter Zijlstra <pet...@infradead.org>
---
 kernel/sched/core.c  |  4 ++--
 kernel/sched/sched.h | 21 ++++++++++++++++++++-
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1ed01f381641..b41db1190d28 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -904,8 +904,8 @@ static inline unsigned int 
uclamp_effective_bucket_id(struct task_struct *p,
        return bucket_id;
 }
 
-static unsigned int uclamp_effective_value(struct task_struct *p,
-                                          unsigned int clamp_id)
+unsigned int uclamp_effective_value(struct task_struct *p,
+                                   unsigned int clamp_id)
 {
        unsigned int clamp_value, bucket_id;
 
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 95d62a2a0b44..b7ce3023d023 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2268,11 +2268,20 @@ static inline unsigned int uclamp_none(int clamp_id)
 }
 
 #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
@@ -2283,7 +2292,17 @@ 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;
-- 
2.19.2