[PATCH v3 2/2] memcg: use native word page statistics counters

[Greg Thelen <gthelen@google.com>]

From: Johannes Weiner <hannes@cmpxchg.org>

The statistic counters are in units of pages, there is no reason to
make them 64-bit wide on 32-bit machines.

Make them native words.  Since they are signed, this leaves 31 bit on
32-bit machines, which can represent roughly 8TB assuming a page size
of 4k.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Greg Thelen <gthelen@google.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
---
 mm/memcontrol.c |   29 ++++++++++++++---------------
 1 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a11ff1e..1c2704a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -107,7 +107,7 @@ enum mem_cgroup_events_index {
 };
 
 struct mem_cgroup_stat_cpu {
-	s64 count[MEM_CGROUP_STAT_NSTATS];
+	long count[MEM_CGROUP_STAT_NSTATS];
 	unsigned long events[MEM_CGROUP_EVENTS_NSTATS];
 };
 
@@ -546,11 +546,11 @@ mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz)
  * common workload, threashold and synchonization as vmstat[] should be
  * implemented.
  */
-static s64 mem_cgroup_read_stat(struct mem_cgroup *mem,
-		enum mem_cgroup_stat_index idx)
+static long mem_cgroup_read_stat(struct mem_cgroup *mem,
+				 enum mem_cgroup_stat_index idx)
 {
+	long val = 0;
 	int cpu;
-	s64 val = 0;
 
 	get_online_cpus();
 	for_each_online_cpu(cpu)
@@ -564,9 +564,9 @@ static s64 mem_cgroup_read_stat(struct mem_cgroup *mem,
 	return val;
 }
 
-static s64 mem_cgroup_local_usage(struct mem_cgroup *mem)
+static long mem_cgroup_local_usage(struct mem_cgroup *mem)
 {
-	s64 ret;
+	long ret;
 
 	ret = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_RSS);
 	ret += mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_CACHE);
@@ -1761,7 +1761,7 @@ static void mem_cgroup_drain_pcp_counter(struct mem_cgroup *mem, int cpu)
 
 	spin_lock(&mem->pcp_counter_lock);
 	for (i = 0; i < MEM_CGROUP_STAT_DATA; i++) {
-		s64 x = per_cpu(mem->stat->count[i], cpu);
+		long x = per_cpu(mem->stat->count[i], cpu);
 
 		per_cpu(mem->stat->count[i], cpu) = 0;
 		mem->nocpu_base.count[i] += x;
@@ -3473,13 +3473,13 @@ static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
 }
 
 
-static u64 mem_cgroup_get_recursive_idx_stat(struct mem_cgroup *mem,
-				enum mem_cgroup_stat_index idx)
+static unsigned long mem_cgroup_recursive_stat(struct mem_cgroup *mem,
+					       enum mem_cgroup_stat_index idx)
 {
 	struct mem_cgroup *iter;
-	s64 val = 0;
+	long val = 0;
 
-	/* each per cpu's value can be minus.Then, use s64 */
+	/* Per-cpu values can be negative, use a signed accumulator */
 	for_each_mem_cgroup_tree(iter, mem)
 		val += mem_cgroup_read_stat(iter, idx);
 
@@ -3499,12 +3499,11 @@ static inline u64 mem_cgroup_usage(struct mem_cgroup *mem, bool swap)
 			return res_counter_read_u64(&mem->memsw, RES_USAGE);
 	}
 
-	val = mem_cgroup_get_recursive_idx_stat(mem, MEM_CGROUP_STAT_CACHE);
-	val += mem_cgroup_get_recursive_idx_stat(mem, MEM_CGROUP_STAT_RSS);
+	val = mem_cgroup_recursive_stat(mem, MEM_CGROUP_STAT_CACHE);
+	val += mem_cgroup_recursive_stat(mem, MEM_CGROUP_STAT_RSS);
 
 	if (swap)
-		val += mem_cgroup_get_recursive_idx_stat(mem,
-				MEM_CGROUP_STAT_SWAPOUT);
+		val += mem_cgroup_recursive_stat(mem, MEM_CGROUP_STAT_SWAPOUT);
 
 	return val << PAGE_SHIFT;
 }
-- 
1.7.3.1

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