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sched/core: Warn if ENERGY_AWARE is enabled but data is missing

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If the EAS energy model is missing or incomplete, i.e. sd_scs is NULL, then
sched_group_energy will return -EINVAL on the assumption that it raced with a
CPU hotplug event. In that case, energy_diff will return 0 and the energy-aware
wake path will silently fail to trigger any migrations.

This case can be triggered by disabling CONFIG_SCHED_MC on existing platforms,
so that there are no sched_groups with the SD_SHARE_CAP_STATES flag, so that
sd_scs is NULL.

Add checks so that a warning is printed if EAS is ever enabled while the
necessary data is not present.

Change-Id: Id233a510b5ad8b7fcecac0b1d789e730bbfc7c4a
Signed-off-by: Brendan Jackman <brendan.jackman@arm.com>
This commit is contained in:
Brendan Jackman 2016-09-22 12:25:56 +01:00 committed by Amit Pundir
parent 43c509a309
commit 3dcbf5e447
1 changed files with 22 additions and 0 deletions
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22
kernel/sched/core.c
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@ -91,6 +91,8 @@
#include <trace/events/sched.h>
#include "walt.h"
static bool have_sched_energy_data(void);
DEFINE_MUTEX(sched_domains_mutex);
DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
@ -193,6 +195,10 @@ static int sched_feat_set(char *cmp)
sysctl_sched_features &= ~(1UL << i);
sched_feat_disable(i);
} else {
if (i == __SCHED_FEAT_ENERGY_AWARE)
WARN(!have_sched_energy_data(),
"Missing sched energy data\n");
sysctl_sched_features |= (1UL << i);
sched_feat_enable(i);
}
@ -6649,6 +6655,19 @@ static void init_sched_groups_capacity(int cpu, struct sched_domain *sd)
atomic_set(&sg->sgc->nr_busy_cpus, sg->group_weight);
}
static bool have_sched_energy_data(void)
{
int cpu;
for_each_possible_cpu(cpu) {
if (!rcu_dereference(per_cpu(sd_scs, cpu)) ||
!rcu_dereference(per_cpu(sd_ea, cpu)))
return false;
}
return true;
}
/*
* Check that the per-cpu provided sd energy data is consistent for all cpus
* within the mask.
@ -7461,6 +7480,9 @@ static int build_sched_domains(const struct cpumask *cpu_map,
}
rcu_read_unlock();
WARN(sched_feat(ENERGY_AWARE) && !have_sched_energy_data(),
"Missing data for energy aware scheduling\n");
ret = 0;
error:
__free_domain_allocs(&d, alloc_state, cpu_map);