diff options
| author | Morten Rasmussen <morten.rasmussen@arm.com> | 2013-03-22 15:03:30 +0000 |
|---|---|---|
| committer | Vincent Guittot <vincent.guittot@linaro.org> | 2013-05-16 13:46:36 +0200 |
| commit | c3f4db779c0b09e4ea795166946209512f441883 (patch) | |
| tree | 5595b7e93a906b18ac422e67bd182425bb357dbe | |
| parent | a575e19bf6fb52986d28361058af4e34bab6dfdb (diff) | |
sched: Pull tasks from cpus with multiple tasks when idleupstream-task-placement-on-mixed-cpu-power-systems-v1
If a cpu is idle and another cpu has more than one runnable task,
pull one of them without considering cpu_power source or target.
This allows low cpu_power cpus to offload potentially oversubscribed
high cpu_power cpus.
In heterogeneous systems containing cpus with different cpu_power,
the load-balancer will put more tasks on sched_domains with high
(above default) cpu_power cpus and fewer on sched_domains with low
cpu_power cpus. Hence, if the number of running tasks is equal to
the number of cpus, the load-balancer may decide to leave low
cpu_power idle and placing more than one task on each high cpu_power
cpu. This is not optimal use of the available compute resources.
Placing one task on each cpu before adding more to any of the high
cpu_power cpus should generally give a better overall throughput
regardless of the cpu_power of the cpus.
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
| -rw-r--r-- | kernel/sched/fair.c | 21 |
1 files changed, 18 insertions, 3 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index fd0ed9119d4..f39509ea5fa 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4033,7 +4033,8 @@ static int move_tasks(struct lb_env *env) if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed) goto next; - if ((load / 2) > env->imbalance) + if ((load / 2) > env->imbalance && + (env->idle != CPU_IDLE && env->idle != CPU_NEWLY_IDLE)) goto next; move_task(p, env); @@ -4530,6 +4531,15 @@ static inline void update_sg_lb_stats(struct lb_env *env, if (overloaded_cpu) sgs->group_imb = 1; + /* + * When idle balancing pull tasks if more than one task per cpu + * in group + */ + if (env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) { + if (group->group_weight < sgs->sum_nr_running) + sgs->group_imb = 1; + } + sgs->group_capacity = DIV_ROUND_CLOSEST(group->sgp->power, SCHED_POWER_SCALE); if (!sgs->group_capacity) @@ -4757,8 +4767,13 @@ void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds) min(sds->this_load_per_task, sds->this_load + tmp); pwr_move /= SCHED_POWER_SCALE; - /* Move if we gain throughput */ - if (pwr_move > pwr_now) + /* + * Move if we gain throughput, or if we have cpus idling while others + * are running more than one task. + */ + if ((pwr_move > pwr_now) || + (sds->busiest_group_weight < sds->busiest_nr_running && + (env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE))) env->imbalance = sds->busiest_load_per_task; } |