From: Mel Gorman Date: Fri, 20 May 2022 10:35:17 +0000 (+0100) Subject: sched/numa: Do not swap tasks between nodes when spare capacity is available X-Git-Tag: v6.1-rc5~791^2~30 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=13ede33150877d44756171e33570076882b17b0b;p=platform%2Fkernel%2Flinux-starfive.git sched/numa: Do not swap tasks between nodes when spare capacity is available If a destination node has spare capacity but there is an imbalance then two tasks are selected for swapping. If the tasks have no numa group or are within the same NUMA group, it's simply shuffling tasks around without having any impact on the compute imbalance. Instead, it's just punishing one task to help another. Signed-off-by: Mel Gorman Signed-off-by: Peter Zijlstra (Intel) Tested-by: K Prateek Nayak Link: https://lore.kernel.org/r/20220520103519.1863-3-mgorman@techsingularity.net --- diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 51836ef..23da36c 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1790,6 +1790,15 @@ static bool task_numa_compare(struct task_numa_env *env, */ cur_ng = rcu_dereference(cur->numa_group); if (cur_ng == p_ng) { + /* + * Do not swap within a group or between tasks that have + * no group if there is spare capacity. Swapping does + * not address the load imbalance and helps one task at + * the cost of punishing another. + */ + if (env->dst_stats.node_type == node_has_spare) + goto unlock; + imp = taskimp + task_weight(cur, env->src_nid, dist) - task_weight(cur, env->dst_nid, dist); /*