Hi Patrick,

On Thu, 9 Aug 2018 at 17:34, Patrick Bellasi [off-list ref] wrote:

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

quoted

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

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?

Does the policy for (sched_feat(UCLAMP_SCHED_CLASS)== true) really
make sense as it is ?
I mean, uclamp_util doesn't make any difference between rt and cfs
tasks when clamping the utilization so why should be add twice the
returned value ?
IMHO, this policy would make sense if there were something like
uclamp_util_rt() and a uclamp_util_cfs()

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