[RFC v3 5/5] sched/{core,cpufreq_schedutil}: add capacity clamping for RT/DL tasks

[Patrick Bellasi]

Currently schedutil enforce a maximum OPP when RT/DL tasks are RUNNABLE.
Such a mandatory policy can be made more tunable from userspace thus
allowing for example to define a reasonable max capacity (i.e.
frequency) which is required for the execution of a specific RT/DL
workload. This will contribute to make the RT class more "friendly" for
power/energy sensible applications.

This patch extends the usage of capacity_{min,max} to the RT/DL classes.
Whenever a task in these classes is RUNNABLE, the capacity required is
defined by the constraints of the control group that task belongs to.

Signed-off-by: Patrick Bellasi <patrick.bell...@arm.com>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux...@vger.kernel.org
---
 kernel/sched/cpufreq_schedutil.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 51484f7..18abd62 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -256,7 +256,9 @@ static void sugov_update_single(struct update_util_data 
*hook, u64 time,
                return;
 
        if (flags & SCHED_CPUFREQ_RT_DL) {
-               next_f = policy->cpuinfo.max_freq;
+               util = cap_clamp_cpu_util(smp_processor_id(),
+                                         SCHED_CAPACITY_SCALE);
+               next_f = get_next_freq(sg_cpu, util, policy->cpuinfo.max_freq);
        } else {
                sugov_get_util(&util, &max);
                sugov_iowait_boost(sg_cpu, &util, &max);
@@ -272,15 +274,11 @@ static unsigned int sugov_next_freq_shared(struct 
sugov_cpu *sg_cpu,
 {
        struct sugov_policy *sg_policy = sg_cpu->sg_policy;
        struct cpufreq_policy *policy = sg_policy->policy;
-       unsigned int max_f = policy->cpuinfo.max_freq;
        u64 last_freq_update_time = sg_policy->last_freq_update_time;
        unsigned int cap_max = SCHED_CAPACITY_SCALE;
        unsigned int cap_min = 0;
        unsigned int j;
 
-       if (flags & SCHED_CPUFREQ_RT_DL)
-               return max_f;
-
        sugov_iowait_boost(sg_cpu, &util, &max);
 
        /* Initialize clamping range based on caller CPU constraints */
@@ -308,10 +306,11 @@ static unsigned int sugov_next_freq_shared(struct 
sugov_cpu *sg_cpu,
                        j_sg_cpu->iowait_boost = 0;
                        continue;
                }
-               if (j_sg_cpu->flags & SCHED_CPUFREQ_RT_DL)
-                       return max_f;
 
-               j_util = j_sg_cpu->util;
+               if (j_sg_cpu->flags & SCHED_CPUFREQ_RT_DL)
+                       j_util = cap_clamp_cpu_util(j, SCHED_CAPACITY_SCALE);
+               else
+                       j_util = j_sg_cpu->util;
                j_max = j_sg_cpu->max;
                if (j_util * max > j_max * util) {
                        util = j_util;
-- 
2.7.4