From: Alex Shi alex.shi@intel.com
If the waked task is transitory enough, it will has a chance to be packed into a cpu which is busy but still has time to care it.
For powersaving policy, only the history util < 25% task has chance to be packed. If there is no cpu eligible to handle it, will use a idlest cpu in leader group.
Morten Rasmussen catch a type bug. And PeterZ reminder to consider rt_util. thanks you!
Inspired-by: Vincent Guittot vincent.guittot@linaro.org Signed-off-by: Alex Shi alex.shi@intel.com [Added CONFIG_SCHED_POWER switch to enable this patch] Signed-off-by: Preeti U Murthy preeti@linux.vnet.ibm.com ---
kernel/sched/fair.c | 56 +++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 49 insertions(+), 7 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 3db77e8..e7a677e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4693,24 +4693,65 @@ static inline int get_sd_sched_balance_policy(struct sched_domain *sd, }
/* + * find_leader_cpu - find the busiest but still has enough free time cpu + * among the cpus in group. + */ +static int +find_leader_cpu(struct sched_group *group, struct task_struct *p, int this_cpu, + int policy) +{ + int vacancy, min_vacancy = INT_MAX; + int leader_cpu = -1; + int i; + /* percentage of the task's util */ + unsigned putil = (u64)(p->se.avg.runnable_avg_sum << SCHED_CAPACITY_SHIFT) + / (p->se.avg.runnable_avg_period + 1); + + /* bias toward local cpu */ + if (cpumask_test_cpu(this_cpu, tsk_cpus_allowed(p)) && + FULL_UTIL - max_rq_util(this_cpu) - (putil << 2) > 0) + return this_cpu; + + /* Traverse only the allowed CPUs */ + for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) { + if (i == this_cpu) + continue; + + /* only light task allowed, putil < 25% */ + vacancy = FULL_UTIL - max_rq_util(i) - (putil << 2); + + if (vacancy > 0 && vacancy < min_vacancy) { + min_vacancy = vacancy; + leader_cpu = i; + } + } + return leader_cpu; +} + +/* * If power policy is eligible for this domain, and it has task allowed cpu. * we will select CPU from this domain. */ static int get_cpu_for_power_policy(struct sched_domain *sd, int cpu, - struct task_struct *p, struct sd_lb_stats *sds) + struct task_struct *p, struct sd_lb_stats *sds, int wakeup) { int policy; int new_cpu = -1;
policy = get_sd_sched_balance_policy(sd, cpu, p, sds); - if (policy != SCHED_POLICY_PERFORMANCE && sds->group_leader) - new_cpu = find_idlest_cpu(sds->group_leader, p, cpu); - + if (policy != SCHED_POLICY_PERFORMANCE && sds->group_leader) { + if (wakeup) + new_cpu = find_leader_cpu(sds->group_leader, + p, cpu, policy); + /* for fork balancing and a little busy task */ + if (new_cpu == -1) + new_cpu = find_idlest_cpu(sds->group_leader, p, cpu); + } return new_cpu; } #else static int get_cpu_for_power_policy(struct sched_domain *sd, int cpu, - struct task_struct *p, struct sd_lb_stats *sds) + struct task_struct *p, struct sd_lb_stats *sds, int wakeup) { return -1; } @@ -4768,13 +4809,14 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f if (tmp->flags & sd_flag) { sd = tmp;
- new_cpu = get_cpu_for_power_policy(sd, cpu, p, &sds); + new_cpu = get_cpu_for_power_policy(sd, cpu, p, &sds, + sd_flag & SD_BALANCE_WAKE); if (new_cpu != -1) goto unlock; } } if (affine_sd) { - new_cpu = get_cpu_for_power_policy(affine_sd, cpu, p, &sds); + new_cpu = get_cpu_for_power_policy(affine_sd, cpu, p, &sds, 1); if (new_cpu != -1) goto unlock;