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sched: Estimate energy impact of scheduling decisions

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Adds a generic energy-aware helper function, energy_diff(), that
calculates energy impact of adding, removing, and migrating utilization
in the system.

cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
This commit is contained in:
Morten Rasmussen
2015-01-06 17:34:05 +00:00
committed by Leo Yan
parent df2030c841
commit 2c6a8a48a7
1 changed files with 52 additions and 0 deletions
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52
kernel/sched/fair.c
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@@ -4893,6 +4893,58 @@ next_cpu:
return 0;
}
static inline bool cpu_in_sg(struct sched_group *sg, int cpu)
{
return cpu != -1 && cpumask_test_cpu(cpu, sched_group_cpus(sg));
}
/*
* energy_diff(): Estimate the energy impact of changing the utilization
* distribution. eenv specifies the change: utilisation amount, source, and
* destination cpu. Source or destination cpu may be -1 in which case the
* utilization is removed from or added to the system (e.g. task wake-up). If
* both are specified, the utilization is migrated.
*/
static int energy_diff(struct energy_env *eenv)
{
struct sched_domain *sd;
struct sched_group *sg;
int sd_cpu = -1, energy_before = 0, energy_after = 0;
struct energy_env eenv_before = {
.util_delta = 0,
.src_cpu = eenv->src_cpu,
.dst_cpu = eenv->dst_cpu,
};
if (eenv->src_cpu == eenv->dst_cpu)
return 0;
sd_cpu = (eenv->src_cpu != -1) ? eenv->src_cpu : eenv->dst_cpu;
sd = rcu_dereference(per_cpu(sd_ea, sd_cpu));
if (!sd)
return 0; /* Error */
sg = sd->groups;
do {
if (cpu_in_sg(sg, eenv->src_cpu) || cpu_in_sg(sg, eenv->dst_cpu)) {
eenv_before.sg_top = eenv->sg_top = sg;
if (sched_group_energy(&eenv_before))
return 0; /* Invalid result abort */
energy_before += eenv_before.energy;
if (sched_group_energy(eenv))
return 0; /* Invalid result abort */
energy_after += eenv->energy;
}
} while (sg = sg->next, sg != sd->groups);
return energy_after-energy_before;
}
/*
* Detect M:N waker/wakee relationships via a switching-frequency heuristic.
* A waker of many should wake a different task than the one last awakened