On Wed 20-06-12 23:36:47, Glauber Costa wrote:

On 06/20/2012 05:28 PM, Michal Hocko wrote:

quoted

On Mon 18-06-12 14:27:59, Glauber Costa wrote:

quoted

From: Suleiman Souhlal <redacted>

Signed-off-by: Suleiman Souhlal <redacted>
Signed-off-by: Glauber Costa <redacted>
Acked-by: Kamezawa Hiroyuki <redacted>

I am not sure the patch is good to merge on its own without the rest.
One comment bellow.

quoted

---
 mm/memcontrol.c |   18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ce15be4..00b9f1e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c

@@ -1998,19 +1998,19 @@ static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock);
 static DEFINE_MUTEX(percpu_charge_mutex);

 /*
- * Try to consume stocked charge on this cpu. If success, one page is consumed
- * from local stock and true is returned. If the stock is 0 or charges from a
- * cgroup which is not current target, returns false. This stock will be
- * refilled.
+ * Try to consume stocked charge on this cpu. If success, nr_pages pages are
+ * consumed from local stock and true is returned. If the stock is 0 or
+ * charges from a cgroup which is not current target, returns false.
+ * This stock will be refilled.
  */
-static bool consume_stock(struct mem_cgroup *memcg)
+static bool consume_stock(struct mem_cgroup *memcg, int nr_pages)
 {
 	struct memcg_stock_pcp *stock;
 	bool ret = true;

I guess you want:
if (nr_pages > CHARGE_BATCH)
	return false;

because you don't want to try to use stock for THP pages.

The code reads:

+       if (memcg == stock->cached && stock->nr_pages >= nr_pages)
+               stock->nr_pages -= nr_pages;

Isn't stock->nr_pages always <= CHARGE_BATCH by definition?

Yes it is, but why to disable preemption if we know this has no chance
to succeed at all?

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic