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Subject[RFC PATCH 07/16] sched: Introduce system-wide sched_energy
Date
From: Dietmar Eggemann <dietmar.eggemann@arm.com>

The Energy-aware algorithm needs system wide sched energy information on
certain platforms (e.g. a one socket system with multiple cpus).

In such a system, the sched energy data is only attached to the sched
groups for the individual cpus in the sched domain MC level.

For those systems, this patch adds a _hack_ to provide system-wide sched
energy data via the sched_domain_topology_level table.

The problem is that the sched_domain_topology_level table is not an
interface to provide system-wide data but we want to keep the
configuration of all sched energy related data in one place.

The sched_domain_energy_f of the last entry (the one which is
initialized with {NULL, }) of the sched_domain_topology_level table is
set to cpu_sys_energy(). Since the sched_domain_mask_f of this entry
stays NULL it is still not considered for the existing scheduler set-up
code (see for_each_sd_topology()).

A second call to init_sched_energy() with a struct sched_domain pointer
equal NULL as an argument will initialize the system-wide sched energy
structure sse.

For the example platform (ARM TC2 (MC and DIE sd level)), the
system-wide sched_domain_energy_f returns NULL, so struct sched_energy
*sse stays NULL.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
---
arch/arm/kernel/topology.c | 8 +++++++-
kernel/sched/core.c | 26 ++++++++++++++++++++++----
kernel/sched/sched.h | 2 ++
3 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
index 4050348..0b9c1e0 100644
--- a/arch/arm/kernel/topology.c
+++ b/arch/arm/kernel/topology.c
@@ -374,6 +374,11 @@ static inline const struct sched_energy *cpu_core_energy(int cpu)
return cpu_topology[cpu].socket_id ? &energy_core_a7 :
&energy_core_a15;
}
+
+static inline const struct sched_energy *cpu_sys_energy(int cpu)
+{
+ return NULL;
+}
#endif /* CONFIG_SCHED_ENERGY */

static inline const int cpu_corepower_flags(void)
@@ -392,10 +397,11 @@ static struct sched_domain_topology_level arm_topology[] = {
#endif
#ifdef CONFIG_SCHED_ENERGY
{ cpu_cpu_mask, 0, cpu_cluster_energy, SD_INIT_NAME(DIE) },
+ { NULL, 0, cpu_sys_energy},
#else
{ cpu_cpu_mask, SD_INIT_NAME(DIE) },
+ { NULL, },
#endif
- { NULL, },
};

/*
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 096fa55..530a348 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5866,20 +5866,35 @@ static void init_sched_groups_power(int cpu, struct sched_domain *sd)
}

#ifdef CONFIG_SCHED_ENERGY
+/* System-wide energy information. */
+struct sched_energy *sse;
+
static void init_sched_energy(int cpu, struct sched_domain *sd,
struct sched_domain_topology_level *tl)
{
- struct sched_group *sg = sd->groups;
- struct sched_energy *energy = &sg->sge->data;
+ struct sched_group *sg = sd ? sd->groups : NULL;
+ struct sched_energy *energy = sd ? &sg->sge->data : sse;
sched_domain_energy_f fn = tl->energy;
- struct cpumask *mask = sched_group_cpus(sg);
+ const struct cpumask *mask = sd ? sched_group_cpus(sg) :
+ cpu_cpu_mask(cpu);

- if (!fn || !fn(cpu))
+ if (!fn || !fn(cpu) || (!sd && energy))
return;

if (cpumask_weight(mask) > 1)
check_sched_energy_data(cpu, fn, mask);

+ if (!sd) {
+ energy = sse = kzalloc_node(sizeof(struct sched_energy) +
+ fn(cpu)->nr_cap_states*
+ sizeof(struct capacity_state),
+ GFP_KERNEL, cpu_to_node(cpu));
+ BUG_ON(!energy);
+
+ energy->cap_states = (struct capacity_state *)((void *)energy +
+ sizeof(struct sched_energy));
+ }
+
energy->max_capacity = fn(cpu)->max_capacity;
energy->idle_power = fn(cpu)->idle_power;
energy->wakeup_energy = fn(cpu)->wakeup_energy;
@@ -6579,6 +6594,9 @@ static int build_sched_domains(const struct cpumask *cpu_map,
claim_allocations(i, sd);
init_sched_groups_power(i, sd);
}
+#ifdef CONFIG_SCHED_ENERGY
+ init_sched_energy(i, NULL, tl);
+#endif
}

/* Attach the domains */
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 6726437..9ff67a7 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -760,6 +760,8 @@ struct sched_group_energy {
atomic_t ref;
struct sched_energy data;
};
+
+extern struct sched_energy *sse;
#endif

struct sched_group {
--
1.7.9.5



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