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Subject[PATCH v3] memcg: remove PCG_CACHE page_cgroup flag
I think this version is much simplified.

==
From 5700a4fe9c581e1ebaa021ba6119dc8d921b024f Mon Sep 17 00:00:00 2001
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Date: Thu, 19 Jan 2012 17:09:41 +0900
Subject: [PATCH v3] memcg: remove PCG_CACHE

We record 'the page is cache' by PCG_CACHE bit to page_cgroup.
Here, "CACHE" means anonymous user pages (and SwapCache). This
doesn't include shmem.

Consdering callers, at charge/uncharge, the caller should know
what the page is and we don't need to record it by using 1bit
per page.

This patch removes PCG_CACHE bit and make callers of
mem_cgroup_charge_statistics() to specify what the page is.

Changelog since v2
- removed 'not_rss', added 'anon'
- changed a meaning of arguments to mem_cgroup_charge_statisitcs()
- removed a patch to mem_cgroup_uncharge_cache
- simplified comment.

Changelog since RFC.
- rebased onto memcg-devel
- rename 'file' to 'not_rss'
- some cleanup and added comment.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
include/linux/page_cgroup.h | 8 +------
mm/memcontrol.c | 48 +++++++++++++++++++++++-------------------
2 files changed, 27 insertions(+), 29 deletions(-)
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 void ClearPageCgroup##uname(struct page_cgroup *pc) \
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 @@ static inline void lock_page_cgroup(struct page_cgroup *pc)
{
/*
* 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);
}
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ff24520..f000c82 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -672,15 +672,19 @@ static unsigned long mem_cgroup_read_events(struct mem_cgroup *memcg,
}

static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
- bool file, int nr_pages)
+ bool rss, int nr_pages)
{
preempt_disable();

- if (file)
- __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_CACHE],
+ /*
+ * Here, RSS means 'mapped anon' and anon's SwapCache. Shmem/tmpfs is
+ * counted as CACHE even if it's on ANON LRU.
+ */
+ if (rss)
+ __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_RSS],
nr_pages);
else
- __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_RSS],
+ __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_CACHE],
nr_pages);

/* pagein of a big page is an event. So, ignore page size */
@@ -2409,6 +2413,8 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
struct page_cgroup *pc,
enum charge_type ctype)
{
+ bool anon;
+
lock_page_cgroup(pc);
if (unlikely(PageCgroupUsed(pc))) {
unlock_page_cgroup(pc);
@@ -2428,21 +2434,14 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
* See mem_cgroup_add_lru_list(), etc.
*/
smp_wmb();
- switch (ctype) {
- case MEM_CGROUP_CHARGE_TYPE_CACHE:
- case MEM_CGROUP_CHARGE_TYPE_SHMEM:
- SetPageCgroupCache(pc);
- SetPageCgroupUsed(pc);
- break;
- case MEM_CGROUP_CHARGE_TYPE_MAPPED:
- ClearPageCgroupCache(pc);
- SetPageCgroupUsed(pc);
- break;
- default:
- break;
- }

- mem_cgroup_charge_statistics(memcg, PageCgroupCache(pc), nr_pages);
+ SetPageCgroupUsed(pc);
+ if (ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED)
+ anon = true;
+ else
+ anon = false;
+
+ mem_cgroup_charge_statistics(memcg, anon, nr_pages);
unlock_page_cgroup(pc);
WARN_ON_ONCE(PageLRU(page));
/*
@@ -2507,6 +2506,7 @@ static int mem_cgroup_move_account(struct page *page,
{
unsigned long flags;
int ret;
+ bool anon = PageAnon(page);

VM_BUG_ON(from == to);
VM_BUG_ON(PageLRU(page));
@@ -2535,14 +2535,14 @@ static int mem_cgroup_move_account(struct page *page,
__this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
preempt_enable();
}
- mem_cgroup_charge_statistics(from, PageCgroupCache(pc), -nr_pages);
+ mem_cgroup_charge_statistics(from, anon, -nr_pages);
if (uncharge)
/* This is not "cancel", but cancel_charge does all we need. */
__mem_cgroup_cancel_charge(from, nr_pages);

/* caller should have done css_get */
pc->mem_cgroup = to;
- mem_cgroup_charge_statistics(to, PageCgroupCache(pc), nr_pages);
+ mem_cgroup_charge_statistics(to, anon, nr_pages);
/*
* We charges against "to" which may not have any tasks. Then, "to"
* can be under rmdir(). But in current implementation, caller of
@@ -2890,6 +2890,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
struct mem_cgroup *memcg = NULL;
unsigned int nr_pages = 1;
struct page_cgroup *pc;
+ bool anon;

if (mem_cgroup_disabled())
return NULL;
@@ -2921,6 +2922,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
/* See mem_cgroup_prepare_migration() */
if (page_mapped(page) || PageCgroupMigration(pc))
goto unlock_out;
+ anon = true;
break;
case MEM_CGROUP_CHARGE_TYPE_SWAPOUT:
if (!PageAnon(page)) { /* Shared memory */
@@ -2928,12 +2930,14 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
goto unlock_out;
} else if (page_mapped(page)) /* Anon */
goto unlock_out;
+ anon = true;
break;
default:
+ anon = false;
break;
}

- mem_cgroup_charge_statistics(memcg, PageCgroupCache(pc), -nr_pages);
+ mem_cgroup_charge_statistics(memcg, anon, -nr_pages);

ClearPageCgroupUsed(pc);
/*
@@ -3319,7 +3323,7 @@ void mem_cgroup_replace_page_cache(struct page *oldpage,
/* fix accounting on old pages */
lock_page_cgroup(pc);
memcg = pc->mem_cgroup;
- mem_cgroup_charge_statistics(memcg, PageCgroupCache(pc), -1);
+ mem_cgroup_charge_statistics(memcg, false, -1);
ClearPageCgroupUsed(pc);
unlock_page_cgroup(pc);

--
1.7.4.1



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