linux-kernel - [patch 2/4] memcg: convert per-cpu stock from bytes to page granularity

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Date:	Wed,  9 Feb 2011 12:01:51 +0100
From:	Johannes Weiner <hannes@...xchg.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: [patch 2/4] memcg: convert per-cpu stock from bytes to page granularity

We never keep subpage quantities in the per-cpu stock.

Signed-off-by: Johannes Weiner <hannes@...xchg.org>
---
 mm/memcontrol.c |   24 +++++++++++++-----------
 1 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index cabf421..179fd74 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1624,14 +1624,14 @@ EXPORT_SYMBOL(mem_cgroup_update_page_stat);
 #define CHARGE_SIZE	(32 * PAGE_SIZE)
 struct memcg_stock_pcp {
 	struct mem_cgroup *cached; /* this never be root cgroup */
-	int charge;
+	unsigned int nr_pages;
 	struct work_struct work;
 };
 static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock);
 static atomic_t memcg_drain_count;
 
 /*
- * Try to consume stocked charge on this cpu. If success, PAGE_SIZE is consumed
+ * 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.
@@ -1642,8 +1642,8 @@ static bool consume_stock(struct mem_cgroup *mem)
 	bool ret = true;
 
 	stock = &get_cpu_var(memcg_stock);
-	if (mem == stock->cached && stock->charge)
-		stock->charge -= PAGE_SIZE;
+	if (mem == stock->cached && stock->nr_pages)
+		stock->nr_pages--;
 	else /* need to call res_counter_charge */
 		ret = false;
 	put_cpu_var(memcg_stock);
@@ -1657,13 +1657,15 @@ static void drain_stock(struct memcg_stock_pcp *stock)
 {
 	struct mem_cgroup *old = stock->cached;
 
-	if (stock->charge) {
-		res_counter_uncharge(&old->res, stock->charge);
+	if (stock->nr_pages) {
+		unsigned long bytes = stock->nr_pages * PAGE_SIZE;
+
+		res_counter_uncharge(&old->res, bytes);
 		if (do_swap_account)
-			res_counter_uncharge(&old->memsw, stock->charge);
+			res_counter_uncharge(&old->memsw, bytes);
+		stock->nr_pages = 0;
 	}
 	stock->cached = NULL;
-	stock->charge = 0;
 }
 
 /*
@@ -1680,7 +1682,7 @@ static void drain_local_stock(struct work_struct *dummy)
  * Cache charges(val) which is from res_counter, to local per_cpu area.
  * This will be consumed by consume_stock() function, later.
  */
-static void refill_stock(struct mem_cgroup *mem, int val)
+static void refill_stock(struct mem_cgroup *mem, unsigned int nr_pages)
 {
 	struct memcg_stock_pcp *stock = &get_cpu_var(memcg_stock);
 
@@ -1688,7 +1690,7 @@ static void refill_stock(struct mem_cgroup *mem, int val)
 		drain_stock(stock);
 		stock->cached = mem;
 	}
-	stock->charge += val;
+	stock->nr_pages += nr_pages;
 	put_cpu_var(memcg_stock);
 }
 
@@ -1986,7 +1988,7 @@ again:
 	} while (ret != CHARGE_OK);
 
 	if (csize > page_size)
-		refill_stock(mem, csize - page_size);
+		refill_stock(mem, (csize - page_size) >> PAGE_SHIFT);
 	css_put(&mem->css);
 done:
 	*memcg = mem;
-- 
1.7.4

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