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sched/fair: Make calculate_imbalance() independent 

Rik noticed that calculate_imbalance() relies on
update_sd_pick_busiest() to guarantee that busiest->sum_nr_running >
busiest->group_capacity_factor.

Break this implicit assumption (with the intent of not providing it
anymore) by having calculat_imbalance() verify it and not rely on
others.

Reported-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/20140729152631.GW12054@laptop.lan
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2014-07-29 17:00:21 +02:00 committed by Ingo Molnar
parent 98a96f2022
commit 743cb1ff19
1 changed files with 1 additions and 1 deletions
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2
kernel/sched/fair.c
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@ -6248,7 +6248,7 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
return fix_small_imbalance(env, sds);
}
if (!busiest->group_imb) {
if (busiest->sum_nr_running > busiest->group_capacity_factor) {
/*
* Don't want to pull so many tasks that a group would go idle.
* Except of course for the group_imb case, since then we might