On 07-Aug 15:26, Juri Lelli wrote:

Hi,

On 06/08/18 17:39, Patrick Bellasi wrote:

[...]

quoted

@@ -223,13 +224,25 @@ static unsigned long sugov_get_util(struct sugov_cpu *sg_cpu)
 	 * utilization (PELT windows are synchronized) we can directly add them
 	 * to obtain the CPU's actual utilization.
 	 *
-	 * CFS utilization can be boosted or capped, depending on utilization
-	 * clamp constraints configured for currently RUNNABLE tasks.
+	 * CFS and RT utilizations can be boosted or capped, depending on
+	 * utilization constraints enforce by currently RUNNABLE tasks.
+	 * They are individually clamped to ensure fairness across classes,
+	 * meaning that CFS always gets (if possible) the (minimum) required
+	 * bandwidth on top of that required by higher priority classes.

Is this a stale comment written before UCLAMP_SCHED_CLASS was
introduced? It seems to apply to the below if branch only.

Yes, you right... I'll update the comment.

quoted

 	 */
-	util = cpu_util_cfs(rq);
-	if (util)
-		util = uclamp_util(cpu_of(rq), util);
-	util += cpu_util_rt(rq);
+	util_cfs = cpu_util_cfs(rq);
+	util_rt  = cpu_util_rt(rq);
+	if (sched_feat(UCLAMP_SCHED_CLASS)) {
+		util = 0;
+		if (util_cfs)
+			util += uclamp_util(cpu_of(rq), util_cfs);
+		if (util_rt)
+			util += uclamp_util(cpu_of(rq), util_rt);
+	} else {
+		util  = cpu_util_cfs(rq);
+		util += cpu_util_rt(rq);
+		util  = uclamp_util(cpu_of(rq), util);
+	}

Regarding the two policies, do you have any comment?

We had an internal discussion and we found pro/cons for both... but
I'm not sure keeping the sched_feat is a good solution on the long
run, i.e. mainline merge ;)

-- 
#include <best/regards.h>

Patrick Bellasi