Commit 39af1765 authored Jun 04, 2014 by Oleg Nesterov Committed by Linus Torvalds Jun 04, 2014

memcg: optimize the "Search everything else" loop in mm_update_next_owner()



for_each_process_thread() is sub-optimal. All threads share the same
->mm, we can swicth to the next process once we found a thread with
->mm != NULL and ->mm != mm.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Peter Chiang <pchiang@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent f87fb599

kernel/exit.c

+9 −3

Original line number	Diff line number	Diff line
		@@ -397,9 +397,15 @@ void mm_update_next_owner(struct mm_struct *mm)
		/*
		* Search through everything else, we should not get here often.
		*/
		for_each_process_thread(g, c) {
		if (!(c->flags & PF_KTHREAD) && c->mm == mm)
		for_each_process(g) {
		if (g->flags & PF_KTHREAD)
		continue;
		for_each_thread(g, c) {
		if (c->mm == mm)
		goto assign_new_owner;
		if (c->mm)
		break;
		}
		}
		read_unlock(&tasklist_lock);
		/*