The following commit has been merged into the sched/core branch of tip: Commit-ID: 2208cdaa56c957e20d8e16f28819aeb47851cb1e Gitweb: https://git.kernel.org/tip/2208cdaa56c957e20d8e16f28819aeb47851cb1e Author: Vincent Guittot <vincent.guittot@xxxxxxxxxx> AuthorDate: Mon, 21 Sep 2020 09:24:22 +02:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Fri, 25 Sep 2020 14:23:26 +02:00 sched/fair: Reduce minimal imbalance threshold The 25% default imbalance threshold for DIE and NUMA domain is large enough to generate significant unfairness between threads. A typical example is the case of 11 threads running on 2x4 CPUs. The imbalance of 20% between the 2 groups of 4 cores is just low enough to not trigger the load balance between the 2 groups. We will have always the same 6 threads on one group of 4 CPUs and the other 5 threads on the other group of CPUS. With a fair time sharing in each group, we ends up with +20% running time for the group of 5 threads. Consider decreasing the imbalance threshold for overloaded case where we use the load to balance task and to ensure fair time sharing. Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Phil Auld <pauld@xxxxxxxxxx> Acked-by: Hillf Danton <hdanton@xxxxxxxx> Link: https://lkml.kernel.org/r/20200921072424.14813-3-vincent.guittot@xxxxxxxxxx --- kernel/sched/topology.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 249bec7..41df628 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -1349,7 +1349,7 @@ sd_init(struct sched_domain_topology_level *tl, .min_interval = sd_weight, .max_interval = 2*sd_weight, .busy_factor = 32, - .imbalance_pct = 125, + .imbalance_pct = 117, .cache_nice_tries = 0,
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