This patch add power aware scheduling in fork/exec/wake. It try to
select cpu from the busiest while still has utilization group. That's
will save power since it leaves more groups idle in system.
The trade off is adding a power aware statistics collection in group
seeking. But since the collection just happened in power scheduling
eligible condition, the worst case of hackbench testing just drops
about 2% with powersaving policy. No clear change for performance
policy.
The main function in this patch is get_cpu_for_power_policy(), that
will try to get a idlest cpu from the busiest while still has
utilization group, if the system is using power aware policy and
has such group.
Signed-off-by: Alex Shi <alex....@intel.com>
---
kernel/sched/fair.c | 109 +++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 103 insertions(+), 6 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8ac021f..83b2c39 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3368,25 +3368,113 @@ static unsigned int max_rq_util(int cpu)
}
/*
- * sched_balance_self: balance the current task (running on cpu) in domains
+ * Try to collect the task running number and capacity of the group.
+ */
+static void get_sg_power_stats(struct sched_group *group,
+ struct sched_domain *sd, struct sg_lb_stats *sgs)
+{
+ int i;
+
+ for_each_cpu(i, sched_group_cpus(group))
+ sgs->group_util += max_rq_util(i);
+
+ sgs->group_weight = group->group_weight;
+}
+
+/*
+ * Is this domain full of utilization with the task?
+ */
+static int is_sd_full(struct sched_domain *sd,
+ struct task_struct *p, struct sd_lb_stats *sds)
+{
+ struct sched_group *group;
+ struct sg_lb_stats sgs;
+ long sd_min_delta = LONG_MAX;
+ unsigned int putil;
+
+ if (p->se.load.weight == p->se.avg.load_avg_contrib)
+ /* p maybe a new forked task */
+ putil = FULL_UTIL;
+ else
+ putil = (u64)(p->se.avg.runnable_avg_sum << SCHED_POWER_SHIFT)
+ / (p->se.avg.runnable_avg_period + 1);
+
+ /* Try to collect the domain's utilization */
+ group = sd->groups;
+ do {
+ long g_delta;
+
+ memset(&sgs, 0, sizeof(sgs));
+ get_sg_power_stats(group, sd, &sgs);
+
+ g_delta = sgs.group_weight * FULL_UTIL - sgs.group_util;
+
+ if (g_delta > 0 && g_delta < sd_min_delta) {
+ sd_min_delta = g_delta;
+ sds->group_leader = group;
+ }
+
+ sds->sd_util += sgs.group_util;
+ } while (group = group->next, group != sd->groups);
+
+ if (sds->sd_util + putil < sd->span_weight * FULL_UTIL)
+ return 0;
+
+ /* can not hold one more task in this domain */
+ return 1;
+}
+
+/*
+ * Execute power policy if this domain is not full.
+ */
+static inline int get_sd_sched_balance_policy(struct sched_domain *sd,
+ int cpu, struct task_struct *p, struct sd_lb_stats *sds)
+{
+ if (sched_balance_policy == SCHED_POLICY_PERFORMANCE)
+ return SCHED_POLICY_PERFORMANCE;
+
+ memset(sds, 0, sizeof(*sds));
+ if (is_sd_full(sd, p, sds))
+ return SCHED_POLICY_PERFORMANCE;
+ return sched_balance_policy;
+}
+
+/*
+ * 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)
+{
+ 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);
+
+ return new_cpu;
+}
+
+/*
+ * select_task_rq_fair: balance the current task (running on cpu) in domains
* that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
* SD_BALANCE_EXEC.
*
- * Balance, ie. select the least loaded group.
- *
* Returns the target CPU number, or the same CPU if no balancing is needed.
*
* preempt must be disabled.
*/
static int
-select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
+select_task_rq_fair(struct task_struct *p, int sd_flag, int flags)
{
struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
int cpu = smp_processor_id();
int prev_cpu = task_cpu(p);
int new_cpu = cpu;
int want_affine = 0;
- int sync = wake_flags & WF_SYNC;
+ int sync = flags & WF_SYNC;
+ struct sd_lb_stats sds;
if (p->nr_cpus_allowed == 1)
return prev_cpu;
@@ -3412,11 +3500,20 @@ select_task_rq_fair(struct task_struct *p, int sd_flag,
int wake_flags)
break;
}
- if (tmp->flags & sd_flag)
+ if (tmp->flags & sd_flag) {
sd = tmp;
+
+ new_cpu = get_cpu_for_power_policy(sd, cpu, p, &sds);
+ if (new_cpu != -1)
+ goto unlock;
+ }
}
if (affine_sd) {
+ new_cpu = get_cpu_for_power_policy(affine_sd, cpu, p, &sds);
+ if (new_cpu != -1)
+ goto unlock;
+
if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
prev_cpu = cpu;
--
1.7.12
--
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