Commit-ID: 4ad4e481bd02c80c4b9c64e563d16d1c4442ea13 Gitweb: https://git.kernel.org/tip/4ad4e481bd02c80c4b9c64e563d16d1c4442ea13 Author: Vincent Guittot <vincent.guittot@xxxxxxxxxx> AuthorDate: Fri, 14 Dec 2018 17:01:55 +0100 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Sun, 27 Jan 2019 12:29:37 +0100 sched/fair: Fix rounding bug for asym packing When check_asym_packing() is triggered, the imbalance is set to: busiest_stat.avg_load * busiest_stat.group_capacity / SCHED_CAPACITY_SCALE But busiest_stat.avg_load equals: sgs->group_load * SCHED_CAPACITY_SCALE / sgs->group_capacity These divisions can generate a rounding that will make imbalance slightly lower than the weighted load of the cfs_rq. But this is enough to skip the rq in find_busiest_queue() and prevents asym migration from happening. Directly set imbalance to busiest's sgs->group_load to remove the rounding. Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: valentin.schneider@xxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- kernel/sched/fair.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 9693cf2ea954..30450901200e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8453,9 +8453,7 @@ static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds) if (sched_asym_prefer(busiest_cpu, env->dst_cpu)) return 0; - env->imbalance = DIV_ROUND_CLOSEST( - sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity, - SCHED_CAPACITY_SCALE); + env->imbalance = sds->busiest_stat.group_load; return 1; }
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