From: Rik van Riel <[email protected]> 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 having the group converge on a few nodes.
When placing a task in a pseudo-interleaved numa_group, it pays to examine all nodes, to see if it isn't better to move to eg. the #2 node, so the group locality can be improved. Signed-off-by: Rik van Riel <[email protected]> Tested-by: Chegu Vinod <[email protected]> --- 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 b973d77..00c1137 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1425,8 +1425,15 @@ 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; -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
