[PATCH 3/3] memcg: change mm_update_next_owner() to search in sub-threads first

[Oleg Nesterov <oleg@redhat.com>]

mm_update_next_owner() checks the children and siblings to avoid
the "global" for_each_process() loop. Not sure this makes any sense,
but certainly it makes sense to check our sub-threads before anything
else.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 kernel/exit.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index 1d1810d..b1f7135 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -340,6 +340,12 @@ void mm_update_next_owner(struct mm_struct *mm)
 
 	read_lock(&tasklist_lock);
 	/*
+	 * Search in the sub-threads
+	 */
+	if (assign_new_owner(mm, p))
+		goto done;
+
+	/*
 	 * Search in the children
 	 */
 	list_for_each_entry(g, &p->children, sibling) {
@@ -359,7 +365,7 @@ void mm_update_next_owner(struct mm_struct *mm)
 	 * Search through everything else, we should not get here often.
 	 */
 	for_each_process(g) {
-		if (g->flags & PF_KTHREAD)
+		if (g == p || g->flags & PF_KTHREAD)
 			continue;
 		if (assign_new_owner(mm, g))
 			goto done;
-- 
1.5.5.1


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