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sched: Try to deal with low capacity 

When the capacity drops low, we want to migrate load away.
Allow the load-balancer to remove all tasks when we hit rock
bottom.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Acked-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Acked-by: Gautham R Shenoy <ego@in.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
LKML-Reference: <20090901083826.342231003@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-09-01 10:34:38 +02:00 committed by Ingo Molnar
parent e9e9250bc7
commit bdb94aa5db
1 changed files with 28 additions and 5 deletions
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33
kernel/sched.c
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@ -3908,8 +3908,8 @@ static inline void update_sg_lb_stats(struct sched_domain *sd,
if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task)
sgs->group_imb = 1;
sgs->group_capacity = group->__cpu_power / SCHED_LOAD_SCALE;
sgs->group_capacity =
DIV_ROUND_CLOSEST(group->__cpu_power, SCHED_LOAD_SCALE);
}
/**
@ -3959,7 +3959,7 @@ static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu,
* and move all the excess tasks away.
*/
if (prefer_sibling)
sgs.group_capacity = 1;
sgs.group_capacity = min(sgs.group_capacity, 1UL);
if (local_group) {
sds->this_load = sgs.avg_load;
@ -4191,6 +4191,26 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
return NULL;
}
static struct sched_group *group_of(int cpu)
{
struct sched_domain *sd = rcu_dereference(cpu_rq(cpu)->sd);
if (!sd)
return NULL;
return sd->groups;
}
static unsigned long power_of(int cpu)
{
struct sched_group *group = group_of(cpu);
if (!group)
return SCHED_LOAD_SCALE;
return group->__cpu_power;
}
/*
* find_busiest_queue - find the busiest runqueue among the cpus in group.
*/
@ -4203,15 +4223,18 @@ find_busiest_queue(struct sched_group *group, enum cpu_idle_type idle,
int i;
for_each_cpu(i, sched_group_cpus(group)) {
unsigned long power = power_of(i);
unsigned long capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);
unsigned long wl;
if (!cpumask_test_cpu(i, cpus))
continue;
rq = cpu_rq(i);
wl = weighted_cpuload(i);
wl = weighted_cpuload(i) * SCHED_LOAD_SCALE;
wl /= power;
if (rq->nr_running == 1 && wl > imbalance)
if (capacity && rq->nr_running == 1 && wl > imbalance)
continue;
if (wl > max_load) {