ANDROID: sched: Initialize energy data structures

The sched_group_energy (sge) pointer of the first sched_group (sg) in
the sched_domain (sd) is initialized to point to the appropriate (in
terms of sd level and cpu) sge data defined in the arch and so to the
correct part of the Energy Model (EM).

Energy-aware scheduling allows that a system has only EM data up to a
certain sd level (so called highest energy aware balancing sd level).
A check in init_sched_energy() enforces that all sd's below this sd
level contain EM data.

The 'int cpu' parameter of sched_domain_energy_f requires that
check_sched_energy_data() makes sure that all cpus spanned by a sg
are provisioned with the same EM data.

This patch has also been tested with feature FORCE_SD_OVERLAP enabled.

cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Change-Id: Ic73adfee78a189576fb4ed8ad309424ee498dac1
Signed-off-by: Chris Redpath <chris.redpath@arm.com>

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 6798276d29af2e72ecc91351b34c9adbf2985099..a58f05e701c9aab4a28030393ffd619b60f52bed 100644 (file)
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -943,6 +943,73 @@ next:
        update_group_capacity(sd, cpu);
 }
 
+#define energy_eff(e, n) \
+    ((e->cap_states[n].cap << SCHED_CAPACITY_SHIFT)/e->cap_states[n].power)
+
+static void init_sched_groups_energy(int cpu, struct sched_domain *sd,
+                                    sched_domain_energy_f fn)
+{
+       struct sched_group *sg = sd->groups;
+       const struct sched_group_energy *sge;
+       int i;
+
+       if (!(fn && fn(cpu)))
+               return;
+
+       if (cpu != group_balance_cpu(sg))
+               return;
+
+       if (sd->flags & SD_OVERLAP) {
+               pr_err("BUG: EAS does not support overlapping sd spans\n");
+#ifdef CONFIG_SCHED_DEBUG
+               pr_err("     the %s domain has SD_OVERLAP set\n", sd->name);
+#endif
+               return;
+       }
+
+       if (sd->child && !sd->child->groups->sge) {
+               pr_err("BUG: EAS setup borken for CPU%d\n", cpu);
+#ifdef CONFIG_SCHED_DEBUG
+               pr_err("     energy data on %s but not on %s domain\n",
+                       sd->name, sd->child->name);
+#endif
+               return;
+       }
+
+       sge = fn(cpu);
+
+       /*
+        * Check that the per-cpu provided sd energy data is consistent for all
+        * cpus within the mask.
+        */
+       if (cpumask_weight(sched_group_span(sg)) > 1) {
+               struct cpumask mask;
+
+               cpumask_xor(&mask, sched_group_span(sg), get_cpu_mask(cpu));
+
+               for_each_cpu(i, &mask)
+                       BUG_ON(sge != fn(i));
+       }
+
+       /* Check that energy efficiency (capacity/power) is monotonically
+        * decreasing in the capacity state vector with higher indexes
+        */
+       for (i = 0; i < (sge->nr_cap_states - 1); i++) {
+               if (energy_eff(sge, i) > energy_eff(sge, i+1))
+                       continue;
+#ifdef CONFIG_SCHED_DEBUG
+               pr_warn("WARN: cpu=%d, domain=%s: incr. energy eff %lu[%d]->%lu[%d]\n",
+                       cpu, sd->name, energy_eff(sge, i), i,
+                       energy_eff(sge, i+1), i+1);
+#else
+               pr_warn("WARN: cpu=%d: incr. energy eff %lu[%d]->%lu[%d]\n",
+                       cpu, energy_eff(sge, i), i, energy_eff(sge, i+1), i+1);
+#endif
+       }
+
+       sd->groups->sge = fn(cpu);
+}
+
 /*
  * Initializers for schedule domains
  * Non-inlined to reduce accumulated stack pressure in build_sched_domains()
@@ -1671,10 +1738,13 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
 
        /* Calculate CPU capacity for physical packages and nodes */
        for (i = nr_cpumask_bits-1; i >= 0; i--) {
+               struct sched_domain_topology_level *tl = sched_domain_topology;
+
                if (!cpumask_test_cpu(i, cpu_map))
                        continue;
 
-               for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
+               for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent, tl++) {
+                       init_sched_groups_energy(i, sd, tl->energy);
                        claim_allocations(i, sd);
                        init_sched_groups_capacity(i, sd);
                }