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sched/fair: Fix imbalance overflow 

[ Upstream commit 91dcf1e806 ]

When local group is fully busy but its average load is above system load,
computing the imbalance will overflow and local group is not the best
target for pulling this load.

Fixes: 0b0695f2b3 ("sched/fair: Rework load_balance()")
Reported-by: Tingjia Cao <tjcao980311@gmail.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Tingjia Cao <tjcao980311@gmail.com>
Link: https://lore.kernel.org/lkml/CABcWv9_DAhVBOq2=W=2ypKE9dKM5s2DvoV8-U0+GDwwuKZ89jQ@mail.gmail.com/T/
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Vincent Guittot 2023-04-11 11:06:11 +02:00 committed by Greg Kroah-Hartman
parent 68387ae3b6
commit ba4a2f6d99
1 changed files with 10 additions and 0 deletions
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10
kernel/sched/fair.c
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@ -9353,6 +9353,16 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
sds->avg_load = (sds->total_load * SCHED_CAPACITY_SCALE) /
sds->total_capacity;
/*
* If the local group is more loaded than the average system
* load, don't try to pull any tasks.
*/
if (local->avg_load >= sds->avg_load) {
env->imbalance = 0;
return;
}
}
/*