mm: memcontrol: remove unnecessary PCG_USED pc->mem_cgroup valid flag
authorJohannes Weiner <hannes@cmpxchg.org>
Wed, 10 Dec 2014 23:44:02 +0000 (15:44 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 11 Dec 2014 01:41:07 +0000 (17:41 -0800)
commit2983331575bfb248abfb02efb5140b4a299e3f45
treeee76b29264683d8053007b2959c930edb1c27b13
parentf4aaa8b43d90294ca7546317997c452600e9a8a7
mm: memcontrol: remove unnecessary PCG_USED pc->mem_cgroup valid flag

pc->mem_cgroup had to be left intact after uncharge for the final LRU
removal, and !PCG_USED indicated whether the page was uncharged.  But
since commit 0a31bc97c80c ("mm: memcontrol: rewrite uncharge API") pages
are uncharged after the final LRU removal.  Uncharge can simply clear
the pointer and the PCG_USED/PageCgroupUsed sites can test that instead.

Because this is the last page_cgroup flag, this patch reduces the memcg
per-page overhead to a single pointer.

[akpm@linux-foundation.org: remove unneeded initialization of `memcg', per Michal]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
include/linux/page_cgroup.h
mm/memcontrol.c