sched: Deal with low-load in wake_affine()
wake_affine() would always fail under low-load situations where both prev and this were idle, because adding a single task will always be a significant imbalance, even if there's nothing around that could balance it. Deal with this by allowing imbalance when there's nothing you can do about it. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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@ -1262,7 +1262,17 @@ wake_affine(struct sched_domain *this_sd, struct rq *this_rq,
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tg = task_group(p);
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tg = task_group(p);
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weight = p->se.load.weight;
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weight = p->se.load.weight;
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balanced = 100*(tl + effective_load(tg, this_cpu, weight, weight)) <=
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/*
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* In low-load situations, where prev_cpu is idle and this_cpu is idle
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* due to the sync cause above having dropped tl to 0, we'll always have
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* an imbalance, but there's really nothing you can do about that, so
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* that's good too.
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*
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* Otherwise check if either cpus are near enough in load to allow this
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* task to be woken on this_cpu.
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*/
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balanced = !tl ||
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100*(tl + effective_load(tg, this_cpu, weight, weight)) <=
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imbalance*(load + effective_load(tg, prev_cpu, 0, weight));
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imbalance*(load + effective_load(tg, prev_cpu, 0, weight));
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/*
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/*
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