Re: [patch 01/11] mm: memcg: consolidate hierarchy iteration primitives

On Tue 13-09-11 01:37:46, Kirill A. Shutemov wrote:

On Mon, Sep 12, 2011 at 12:57:18PM +0200, Johannes Weiner wrote:

[...]

quoted

 	while (1) {
-		victim = mem_cgroup_select_victim(root_memcg);
-		if (victim == root_memcg) {
+		victim = mem_cgroup_iter(root_memcg, victim, true);
+		if (!victim) {
 			loop++;
 			/*
 			 * We are not draining per cpu cached charges during

@@ -1689,10 +1644,8 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_memcg,
 				 * anything, it might because there are
 				 * no reclaimable pages under this hierarchy
 				 */
-				if (!check_soft || !total) {
-					css_put(&victim->css);
+				if (!check_soft || !total)
 					break;
-				}
 				/*
 				 * We want to do more targeted reclaim.
 				 * excess >> 2 is not to excessive so as to

@@ -1700,15 +1653,13 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_memcg,
 				 * coming back to reclaim from this cgroup
 				 */
 				if (total >= (excess >> 2) ||
-					(loop > MEM_CGROUP_MAX_RECLAIM_LOOPS)) {
-					css_put(&victim->css);
+					(loop > MEM_CGROUP_MAX_RECLAIM_LOOPS))
 					break;
-				}
 			}
+			continue;

Souldn't we do

victim = root_memcg;

instead?

You want to save mem_cgroup_iter call?
Yes it will work... I am not sure it is really an improvement. If we
just continue we can rely on mem_cgroup_iter doing the right thing.
Assignment might be not that obvious. But I dunno. 
-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>