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sched: update aggregate when holding the RQs
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>
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1 changed files with 20 additions and 0 deletions
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@ -1721,6 +1721,11 @@ aggregate_get_up(struct task_group *tg, int cpu, struct sched_domain *sd)
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aggregate_group_set_shares(tg, cpu, sd);
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}
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static void
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aggregate_get_nop(struct task_group *tg, int cpu, struct sched_domain *sd)
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{
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}
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static DEFINE_PER_CPU(spinlock_t, aggregate_lock);
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static void __init init_aggregate(void)
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@ -1740,6 +1745,11 @@ static int get_aggregate(int cpu, struct sched_domain *sd)
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return 1;
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}
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static void update_aggregate(int cpu, struct sched_domain *sd)
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{
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aggregate_walk_tree(aggregate_get_down, aggregate_get_nop, cpu, sd);
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}
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static void put_aggregate(int cpu, struct sched_domain *sd)
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{
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spin_unlock(&per_cpu(aggregate_lock, cpu));
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@ -1761,6 +1771,10 @@ static inline int get_aggregate(int cpu, struct sched_domain *sd)
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return 0;
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}
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static inline void update_aggregate(int cpu, struct sched_domain *sd)
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{
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}
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static inline void put_aggregate(int cpu, struct sched_domain *sd)
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{
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}
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@ -2192,6 +2206,12 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
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int load_idx = sd->forkexec_idx;
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int imbalance = 100 + (sd->imbalance_pct-100)/2;
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/*
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* now that we have both rqs locked the rq weight won't change
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* anymore - so update the stats.
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*/
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update_aggregate(this_cpu, sd);
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do {
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unsigned long load, avg_load;
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int local_group;
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