Attempt to pick most energy efficient wakeup in find_idlest_{group,
cpu}(). Finding the optimum target requires an exhaustive search
through all cpus in the groups. Instead, the target group is determined
based on load and probing the energy cost on a single cpu in each group.
The target cpu is the cpu with the lowest energy cost.Signed-off-by: Morten Rasmussen <[email protected]> --- kernel/sched/fair.c | 71 +++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 57 insertions(+), 14 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index a32d6eb..2acd45a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4662,25 +4662,27 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) } /* - * find_idlest_group finds and returns the least busy CPU group within the - * domain. + * find_target_group finds and returns the least busy/most energy-efficient + * CPU group within the domain. */ static struct sched_group * -find_idlest_group(struct sched_domain *sd, struct task_struct *p, +find_target_group(struct sched_domain *sd, struct task_struct *p, int this_cpu, int sd_flag) { - struct sched_group *idlest = NULL, *group = sd->groups; + struct sched_group *idlest = NULL, *group = sd->groups, *energy = NULL; unsigned long min_load = ULONG_MAX, this_load = 0; int load_idx = sd->forkexec_idx; int imbalance = 100 + (sd->imbalance_pct-100)/2; + int local_nrg = 0, min_nrg = INT_MAX; if (sd_flag & SD_BALANCE_WAKE) load_idx = sd->wake_idx; do { - unsigned long load, avg_load; + unsigned long load, avg_load, util, probe_util = UINT_MAX; int local_group; int i; + int probe_cpu, nrg_diff; /* Skip over this group if it has no CPUs allowed */ if (!cpumask_intersects(sched_group_cpus(group), @@ -4692,53 +4694,94 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p, /* Tally up the load of all CPUs in the group */ avg_load = 0; + probe_cpu = cpumask_first(sched_group_cpus(group)); for_each_cpu(i, sched_group_cpus(group)) { /* Bias balancing toward cpus of our domain */ - if (local_group) + if (local_group) { load = source_load(i, load_idx, 0); - else + util = source_load(i, load_idx, 1); + } else { load = target_load(i, load_idx, 0); + util = target_load(i, load_idx, 1); + } avg_load += load; + + if (util < probe_util) { + probe_util = util; + probe_cpu = i; + } } /* Adjust by relative CPU capacity of the group */ avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity; + /* + * Sample energy diff on probe_cpu. + * Finding the optimum cpu requires testing all cpus which is + * expensive. + */ + + nrg_diff = energy_diff_task(probe_cpu, p); + if (local_group) { this_load = avg_load; - } else if (avg_load < min_load) { - min_load = avg_load; - idlest = group; + local_nrg = nrg_diff; + } else { + if (avg_load < min_load) { + min_load = avg_load; + idlest = group; + } + + if (nrg_diff < min_nrg) { + min_nrg = nrg_diff; + energy = group; + } } } while (group = group->next, group != sd->groups); + if (energy_aware()) { + if (energy && min_nrg < local_nrg) + return energy; + return NULL; + } + if (!idlest || 100*this_load < imbalance*min_load) return NULL; return idlest; } /* - * find_idlest_cpu - find the idlest cpu among the cpus in group. + * find_target_cpu - find the target cpu among the cpus in group. */ static int -find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) +find_target_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) { unsigned long load, min_load = ULONG_MAX; + int min_nrg = INT_MAX, nrg, least_nrg = -1; int idlest = -1; int i; /* Traverse only the allowed CPUs */ for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) { load = cpu_load(i, 0); + nrg = energy_diff_task(i, p); if (load < min_load || (load == min_load && i == this_cpu)) { min_load = load; idlest = i; } + + if (nrg < min_nrg) { + min_nrg = nrg; + least_nrg = i; + } } + if (least_nrg >= 0) + return least_nrg; + return idlest; } @@ -4886,13 +4929,13 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f continue; } - group = find_idlest_group(sd, p, cpu, sd_flag); + group = find_target_group(sd, p, cpu, sd_flag); if (!group) { sd = sd->child; continue; } - new_cpu = find_idlest_cpu(group, p, cpu); + new_cpu = find_target_cpu(group, p, cpu); if (new_cpu == -1 || new_cpu == cpu) { /* Now try balancing at a lower domain level of cpu */ sd = sd->child; -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
