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sched: update aggregate when holding the RQs

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It was observed that in __update_group_shares_cpu()

  rq_weight > aggregate()->rq_weight

This is caused by forks/wakeups in between the initial aggregate pass and
locking of the RQs for load balance. To avoid this situation partially re-do
the aggregation once we have the RQs locked (which avoids new tasks from
appearing).

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2008-06-27 13:41:19 +02:00 • committed by Ingo Molnar
parent b6a86c746f
commit 4d8d595dfa
1 changed files with 20 additions and 0 deletions
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20
kernel/sched.c
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@ -1721,6 +1721,11 @@ aggregate_get_up(struct task_group *tg, int cpu, struct sched_domain *sd)
aggregate_group_set_shares(tg, cpu, sd); aggregate_group_set_shares(tg, cpu, sd);
} }
static void
aggregate_get_nop(struct task_group *tg, int cpu, struct sched_domain *sd)
{
}
static DEFINE_PER_CPU(spinlock_t, aggregate_lock); static DEFINE_PER_CPU(spinlock_t, aggregate_lock);
static void __init init_aggregate(void) static void __init init_aggregate(void)
@ -1740,6 +1745,11 @@ static int get_aggregate(int cpu, struct sched_domain *sd)
return 1; return 1;
} }
static void update_aggregate(int cpu, struct sched_domain *sd)
{
aggregate_walk_tree(aggregate_get_down, aggregate_get_nop, cpu, sd);
}
static void put_aggregate(int cpu, struct sched_domain *sd) static void put_aggregate(int cpu, struct sched_domain *sd)
{ {
spin_unlock(&per_cpu(aggregate_lock, cpu)); spin_unlock(&per_cpu(aggregate_lock, cpu));
@ -1761,6 +1771,10 @@ static inline int get_aggregate(int cpu, struct sched_domain *sd)
return 0; return 0;
} }
static inline void update_aggregate(int cpu, struct sched_domain *sd)
{
}
static inline void put_aggregate(int cpu, struct sched_domain *sd) static inline void put_aggregate(int cpu, struct sched_domain *sd)
{ {
} }
@ -2192,6 +2206,12 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
int load_idx = sd->forkexec_idx; int load_idx = sd->forkexec_idx;
int imbalance = 100 + (sd->imbalance_pct-100)/2; int imbalance = 100 + (sd->imbalance_pct-100)/2;
/*
* now that we have both rqs locked the rq weight won't change
* anymore - so update the stats.
*/
update_aggregate(this_cpu, sd);
do { do {
unsigned long load, avg_load; unsigned long load, avg_load;
int local_group; int local_group;