[PATCH 1/4] mm, memcg: reduce size of struct mem_cgroup by using bit field

[Yafang Shao <laoar.shao@gmail.com>]

There are some members in struct mem_group can be either 0(false) or
1(true), so we can define them using bit field to reduce size. With this
patch, the size of struct mem_cgroup can be reduced by 64 bytes in theory,
but as there're some MEMCG_PADDING()s, the real number may be different,
which is relate with the cacheline size. Anyway, this patch could reduce
the size of struct mem_cgroup more or less.

Cc: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 include/linux/memcontrol.h | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index a7a0a1a5..612a457 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -229,20 +229,26 @@ struct mem_cgroup {
 	/*
 	 * Should the accounting and control be hierarchical, per subtree?
 	 */
-	bool use_hierarchy;
+	unsigned int use_hierarchy : 1;
 
 	/*
 	 * Should the OOM killer kill all belonging tasks, had it kill one?
 	 */
-	bool oom_group;
+	unsigned int  oom_group : 1;
 
 	/* protected by memcg_oom_lock */
-	bool		oom_lock;
-	int		under_oom;
+	unsigned int oom_lock : 1;
 
-	int	swappiness;
 	/* OOM-Killer disable */
-	int		oom_kill_disable;
+	unsigned int oom_kill_disable : 1;
+
+	/* Legacy tcp memory accounting */
+	unsigned int tcpmem_active : 1;
+	unsigned int tcpmem_pressure : 1;
+
+	int under_oom;
+
+	int	swappiness;
 
 	/* memory.events and memory.events.local */
 	struct cgroup_file events_file;
@@ -297,9 +303,6 @@ struct mem_cgroup {
 
 	unsigned long		socket_pressure;
 
-	/* Legacy tcp memory accounting */
-	bool			tcpmem_active;
-	int			tcpmem_pressure;
 
 #ifdef CONFIG_MEMCG_KMEM
         /* Index in the kmem_cache->memcg_params.memcg_caches array */
-- 
1.8.3.1