From: Rik van Riel Date: Mon, 4 Aug 2014 17:23:27 +0000 (-0400) Subject: sched/numa: Fix off-by-one in capacity check X-Git-Tag: firefly_0821_release~176^2~3059^2~68 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=b932c03c34f3b03c7364c06aa8cae5b74609fc41;p=firefly-linux-kernel-4.4.55.git sched/numa: Fix off-by-one in capacity check Commit a43455a1d572daf7b730fe12eb747d1e17411365 ensures that task_numa_migrate will call task_numa_compare on the preferred node all the time, even when the preferred node has no free capacity. This could lead to a performance regression if nr_running == capacity on both the source and the destination node. This can be avoided by also checking for nr_running == capacity on the source node, which is one stricter than checking .has_free_capacity. Signed-off-by: Rik van Riel Signed-off-by: Peter Zijlstra Cc: mgorman@suse.de Cc: vincent.guittot@linaro.org Cc: Morten.Rasmussen@arm.com Cc: nicolas.pitre@linaro.org Cc: efault@gmx.de Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1407173008-9334-2-git-send-email-riel@redhat.com Signed-off-by: Ingo Molnar --- diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index df1ed176c7b7..e1cf419c3c7f 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1206,7 +1206,7 @@ static void task_numa_compare(struct task_numa_env *env, if (!cur) { /* Is there capacity at our destination? */ - if (env->src_stats.has_free_capacity && + if (env->src_stats.nr_running <= env->src_stats.task_capacity && !env->dst_stats.has_free_capacity) goto unlock;