From 9de05d48711cd5314920ed05f873d84eaf66ccf1 Mon Sep 17 00:00:00 2001 From: Rik van Riel Date: Thu, 9 Oct 2014 17:27:47 -0400 Subject: [PATCH] sched/numa: Check all nodes when placing a pseudo-interleaved group In pseudo-interleaved numa_groups, all tasks try to relocate to the group's preferred_nid. When a group is spread across multiple NUMA nodes, this can lead to tasks swapping their location with other tasks inside the same group, instead of swapping location with tasks from other NUMA groups. This can keep NUMA groups from converging. Examining all nodes, when dealing with a task in a pseudo-interleaved NUMA group, avoids this problem. Note that only CPUs in nodes that improve the task or group score are examined, so the loop isn't too bad. Tested-by: Vinod Chegu Signed-off-by: Rik van Riel Signed-off-by: Peter Zijlstra (Intel) Cc: "Vinod Chegu" Cc: mgorman@suse.de Cc: Linus Torvalds Link: http://lkml.kernel.org/r/20141009172747.0d97c38c@annuminas.surriel.com Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 7760c2ad3162..ec32c26d7fb6 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1436,8 +1436,15 @@ static int task_numa_migrate(struct task_struct *p) /* Try to find a spot on the preferred nid. */ task_numa_find_cpu(&env, taskimp, groupimp); - /* No space available on the preferred nid. Look elsewhere. */ - if (env.best_cpu == -1) { + /* + * Look at other nodes in these cases: + * - there is no space available on the preferred_nid + * - the task is part of a numa_group that is interleaved across + * multiple NUMA nodes; in order to better consolidate the group, + * we need to check other locations. + */ + if (env.best_cpu == -1 || (p->numa_group && + nodes_weight(p->numa_group->active_nodes) > 1)) { for_each_online_node(nid) { if (nid == env.src_nid || nid == p->numa_preferred_nid) continue; -- 2.20.1