On 23-Jan 11:49, Peter Zijlstra wrote:

On Tue, Jan 15, 2019 at 10:15:06AM +0000, Patrick Bellasi wrote:

quoted

@@ -858,16 +859,23 @@ static inline void
 uclamp_effective_get(struct task_struct *p, unsigned int clamp_id,
 		     unsigned int *clamp_value, unsigned int *bucket_id)
 {
+	struct uclamp_se *default_clamp;
+
 	/* Task specific clamp value */
 	*clamp_value = p->uclamp[clamp_id].value;
 	*bucket_id = p->uclamp[clamp_id].bucket_id;
 
+	/* RT tasks have different default values */
+	default_clamp = task_has_rt_policy(p)
+		? uclamp_default_perf
+		: uclamp_default;
+
 	/* System default restriction */
-	if (unlikely(*clamp_value < uclamp_default[UCLAMP_MIN].value ||
-		     *clamp_value > uclamp_default[UCLAMP_MAX].value)) {
+	if (unlikely(*clamp_value < default_clamp[UCLAMP_MIN].value ||
+		     *clamp_value > default_clamp[UCLAMP_MAX].value)) {
 		/* Keep it simple: unconditionally enforce system defaults */
-		*clamp_value = uclamp_default[clamp_id].value;
-		*bucket_id = uclamp_default[clamp_id].bucket_id;
+		*clamp_value = default_clamp[clamp_id].value;
+		*bucket_id = default_clamp[clamp_id].bucket_id;
 	}
 }

So I still don't much like the whole effective thing;

:/

I find back-annotation useful in many cases since we have different
sources for possible clamp values:

 1. task specific
 2. cgroup defined
 3. system defaults
 4. system power default

I don't think we can avoid to somehow back annotate on which bucket a
task has been refcounted... it makes dequeue so much easier, it helps
in ensuring that the refcouning is consistent and enable lazy updates.

but I think you should use rt_task() instead of
task_has_rt_policy().

Right... will do.

-- 
#include <best/regards.h>

Patrick Bellasi