Commit 9de05d48 authored Oct 09, 2014 by Rik van Riel Committed by Ingo Molnar Oct 28, 2014

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 <chegu_vinod@hp.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: "Vinod Chegu" <chegu_vinod@hp.com>
Cc: mgorman@suse.de
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20141009172747.0d97c38c@annuminas.surriel.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 54009416

kernel/sched/fair.c

+9 −2

Original line number	Diff line number	Diff line
		@@ -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;

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