mm/memcg: fix last_dead_count memory wastage

Shorten mem_cgroup_reclaim_iter.last_dead_count from unsigned long to
int: it's assigned from an int and compared with an int, and adjacent to
an unsigned int: so there's no point to it being unsigned long, which
wasted 104 bytes in every mem_cgroup_per_zone.

Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -149,7 +149,7 @@ struct mem_cgroup_reclaim_iter {
 	 * matches memcg->dead_count of the hierarchy root group.
 	 */
 	struct mem_cgroup *last_visited;
-	unsigned long last_dead_count;
+	int last_dead_count;
 
 	/* scan generation, increased every round-trip */
 	unsigned int generation;