diff options
| -rw-r--r-- | Documentation/scheduler/sched-hmp.txt | 7 | ||||
| -rw-r--r-- | kernel/sched/fair.c | 23 |
2 files changed, 28 insertions, 2 deletions
diff --git a/Documentation/scheduler/sched-hmp.txt b/Documentation/scheduler/sched-hmp.txt index 62c33b8b45fd..581a9f4d5159 100644 --- a/Documentation/scheduler/sched-hmp.txt +++ b/Documentation/scheduler/sched-hmp.txt @@ -819,9 +819,14 @@ in Sec 5. This is a per-cpu parameter. If non-zero for a cpu which is part of a cluster and cluster current frequency is less than this threshold, then scheduler will -poack all tasks on a single cpu in cluster. The cpu chosen is the first most +pack all tasks on a single cpu in cluster. The cpu chosen is the first most power-efficient cpu found while scanning cluster's online cpus. +- PF_WAKE_UP_IDLE + Any task that has this flag set in its 'task_struct.flags' field will be +always woken to idle cpu. Further any task woken by such tasks will be also +placed on idle cpu. + For some low band of frequency, spread of task on all available cpus can be groslly power-inefficient. As an example, consider two tasks that each need 500MHz. Packing them on one cpu could lead to 1GHz. In spread case, we incur diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index d9d4694d58da..4260cb552d9f 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3230,6 +3230,20 @@ static int select_packing_target(struct task_struct *p, int best_cpu) return target; } +/* + * Should task be woken to any available idle cpu? + * + * Waking tasks to idle cpu has mixed implications on both performance and + * power. In many cases, scheduler can't estimate correctly impact of using idle + * cpus on either performance or power. PF_WAKE_UP_IDLE allows external kernel + * module to pass a strong hint to scheduler that the task in question should be + * woken to idle cpu, generally to improve performance. + */ +static inline int wake_to_idle(struct task_struct *p) +{ + return (current->flags & PF_WAKE_UP_IDLE) || + (p->flags & PF_WAKE_UP_IDLE); +} /* return cheapest cpu that can fit this task */ static int select_best_cpu(struct task_struct *p, int target, int reason, @@ -3245,6 +3259,13 @@ static int select_best_cpu(struct task_struct *p, int target, int reason, int cstate, min_cstate = INT_MAX; int prefer_idle = reason ? 1 : sysctl_sched_prefer_idle; int curr_cpu = smp_processor_id(); + int prefer_idle_override = 0; + + if (wake_to_idle(p)) { + prefer_idle = 1; + prefer_idle_override = 1; + small_task = 0; + } trace_sched_task_load(p, small_task, boost, reason, sync, prefer_idle); @@ -3377,7 +3398,7 @@ done: best_cpu = fallback_idle_cpu; } - if (cpu_rq(best_cpu)->mostly_idle_freq) + if (cpu_rq(best_cpu)->mostly_idle_freq && !prefer_idle_override) best_cpu = select_packing_target(p, best_cpu); return best_cpu; |