FROMLIST: sched: use pelt for scale_rt_capacity()

The utilization of the CPU by rt, dl and interrupts are now tracked with
PELT so we can use these metrics instead of rt_avg to evaluate the remaining
capacity available for cfs class.

scale_rt_capacity() behavior has been changed and now returns the remaining
capacity available for cfs instead of a scaling factor because rt, dl and
interrupt provide now absolute utilization value.

The same formula as schedutil is used:
  irq util_avg + (1 - irq util_avg / max capacity ) * /Sum rq util_avg
but the implementation is different because it doesn't return the same value
and doesn't benefit of the same optimization

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
[ - Fixed issue with the max freq capping in update_cpu_capacity()
  - Fixed compile warning for !CONFIG_IRQ_TIME_ACCOUNTING ]
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
Change-Id: I4a25191bba3b7b19d075f5a95845caebdbcb9c24

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 1a49ad9..a201105 100644 (file)
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1180,8 +1180,6 @@ static void update_curr_dl(struct rq *rq)
        curr->se.exec_start = now;
        cgroup_account_cputime(curr, delta_exec);
 
-       sched_rt_avg_update(rq, delta_exec);
-
        if (dl_entity_is_special(dl_se))
                return;
 

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c5db839..cbe909b 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8276,28 +8276,27 @@ static inline int get_sd_load_idx(struct sched_domain *sd,
 static unsigned long scale_rt_capacity(int cpu)
 {
        struct rq *rq = cpu_rq(cpu);
-       u64 total, used, age_stamp, avg;
-       s64 delta;
-
-       /*
-        * Since we're reading these variables without serialization make sure
-        * we read them once before doing sanity checks on them.
-        */
-       age_stamp = READ_ONCE(rq->age_stamp);
-       avg = READ_ONCE(rq->rt_avg);
-       delta = __rq_clock_broken(rq) - age_stamp;
-
-       if (unlikely(delta < 0))
-               delta = 0;
+       unsigned long max = arch_scale_cpu_capacity(NULL, cpu);
+       unsigned long used, free;
+#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
+       unsigned long irq = READ_ONCE(rq->avg_irq.util_avg);
 
-       total = sched_avg_period() + delta;
+       if (unlikely(irq >= max))
+               return 1;
+#endif
 
-       used = div_u64(avg, total);
+       used = READ_ONCE(rq->avg_rt.util_avg);
+       used += READ_ONCE(rq->avg_dl.util_avg);
 
-       if (likely(used < SCHED_CAPACITY_SCALE))
-               return SCHED_CAPACITY_SCALE - used;
+       if (unlikely(used >= max))
+               return 1;
 
-       return 1;
+       free = max - used;
+#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
+       free *= (max - irq);
+       free /= max;
+#endif
+       return free;
 }
 
 void init_max_cpu_capacity(struct max_cpu_capacity *mcc) {
@@ -8340,7 +8339,7 @@ static void update_cpu_capacity(struct sched_domain *sd, int cpu)
 
 skip_unlock: __attribute__ ((unused));
        capacity *= scale_rt_capacity(cpu);
-       capacity >>= SCHED_CAPACITY_SHIFT;
+       capacity /= arch_scale_cpu_capacity(sd, cpu);
 
        if (!capacity)
                capacity = 1;

diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c
index ead6d8b..35475c0 100644 (file)
--- a/kernel/sched/pelt.c
+++ b/kernel/sched/pelt.c
@@ -237,7 +237,7 @@ ___update_load_avg(struct sched_avg *sa, unsigned long load, unsigned long runna
         */
        sa->load_avg = div_u64(load * sa->load_sum, divider);
        sa->runnable_load_avg = div_u64(runnable * sa->runnable_load_sum, divider);
-       sa->util_avg = sa->util_sum / divider;
+       WRITE_ONCE(sa->util_avg, sa->util_sum / divider);
 }
 
 /*

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index a43c6ec..0be707d 100644 (file)
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -975,8 +975,6 @@ static void update_curr_rt(struct rq *rq)
        curr->se.exec_start = now;
        cgroup_account_cputime(curr, delta_exec);
 
-       sched_rt_avg_update(rq, delta_exec);
-
        if (!rt_bandwidth_enabled())
                return;