memcg: remove PCG_CACHE page_cgroup flag
We record 'the page is cache' with the PCG_CACHE bit in page_cgroup.
Here, "CACHE" means anonymous user pages (and SwapCache). This doesn't
include shmem.
Considering callers, at charge/uncharge, the caller should know what the
page is and we don't need to record it by using one bit per page.
This patch removes PCG_CACHE bit and make callers of
mem_cgroup_charge_statistics() to specify what the page is.
About page migration: Mapping of the used page is not touched during migra
tion (see page_remove_rmap) so we can rely on it and push the correct
charge type down to __mem_cgroup_uncharge_common from end_migration for
unused page. The force flag was misleading was abused for skipping the
needless page_mapped() / PageCgroupMigration() check, as we know the
unused page is no longer mapped and cleared the migration flag just a few
lines up. But doing the checks is no biggie and it's not worth adding
another flag just to skip them.
[akpm@linux-foundation.org: checkpatch fixes]
[hughd@google.com: fix PageAnon uncharging]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ying Han <yinghan@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h
index a2d1177..1060292 100644
--- a/include/linux/page_cgroup.h
+++ b/include/linux/page_cgroup.h
@@ -4,7 +4,6 @@
enum {
/* flags for mem_cgroup */
PCG_LOCK, /* Lock for pc->mem_cgroup and following bits. */
- PCG_CACHE, /* charged as cache */
PCG_USED, /* this object is in use. */
PCG_MIGRATION, /* under page migration */
/* flags for mem_cgroup and file and I/O status */
@@ -64,11 +63,6 @@
static inline int TestClearPageCgroup##uname(struct page_cgroup *pc) \
{ return test_and_clear_bit(PCG_##lname, &pc->flags); }
-/* Cache flag is set only once (at allocation) */
-TESTPCGFLAG(Cache, CACHE)
-CLEARPCGFLAG(Cache, CACHE)
-SETPCGFLAG(Cache, CACHE)
-
TESTPCGFLAG(Used, USED)
CLEARPCGFLAG(Used, USED)
SETPCGFLAG(Used, USED)
@@ -85,7 +79,7 @@
{
/*
* Don't take this lock in IRQ context.
- * This lock is for pc->mem_cgroup, USED, CACHE, MIGRATION
+ * This lock is for pc->mem_cgroup, USED, MIGRATION
*/
bit_spin_lock(PCG_LOCK, &pc->flags);
}