[patch] mm: memcontrol: use per-cpu caches for uncharging

[Johannes Weiner]

---
 mm/memcontrol.c | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ec4dcf1b9562..cb79ecff399d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2365,6 +2365,7 @@ static void drain_stock(struct memcg_stock_pcp *stock)
 		res_counter_uncharge(&old->res, bytes);
 		if (do_swap_account)
 			res_counter_uncharge(&old->memsw, bytes);
+		memcg_oom_recover(old);
 		stock->nr_pages = 0;
 	}
 	stock->cached = NULL;
@@ -2405,6 +2406,13 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
 		stock->cached = memcg;
 	}
 	stock->nr_pages += nr_pages;
+	if (stock->nr_pages > CHARGE_BATCH * 4) {
+		res_counter_uncharge(&memcg->res, CHARGE_BATCH);
+		if (do_swap_account)
+			res_counter_uncharge(&memcg->memsw, CHARGE_BATCH);
+		memcg_oom_recover(memcg);
+		stock->nr_pages -= CHARGE_BATCH;
+	}
 	put_cpu_var(memcg_stock);
 }
 
@@ -6509,12 +6517,20 @@ static void uncharge_batch(struct mem_cgroup *memcg, unsigned long pgpgout,
 {
 	unsigned long flags;
 
-	if (nr_mem)
-		res_counter_uncharge(&memcg->res, nr_mem * PAGE_SIZE);
-	if (nr_memsw)
-		res_counter_uncharge(&memcg->memsw, nr_memsw * PAGE_SIZE);
-
-	memcg_oom_recover(memcg);
+	/*
+	 * The percpu caches count both memory and memsw charges in a
+	 * single conuter, but there might be less memsw charges when
+	 * some of the pages have been swapped out.
+	 */
+	if (nr_mem == nr_memsw)
+		refill_stock(memcg, nr_mem);
+	else {
+		if (nr_mem)
+			res_counter_uncharge(&memcg->res, nr_mem * PAGE_SIZE);
+		if (nr_memsw)
+			res_counter_uncharge(&memcg->memsw, nr_memsw * PAGE_SIZE);
+		memcg_oom_recover(memcg);
+	}
 
 	local_irq_save(flags);
 	__this_cpu_sub(memcg->stat->count[MEM_CGROUP_STAT_RSS], nr_anon);
-- 
2.0.4

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