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Subject[PATCH] memcg: remove PCG_CACHE page_cgroup flag
This patch is onto memcg-devel, can be applied to linux-next, too.

==
From 529653c266b0682894d64e4797fcaf6a3c35db25 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] 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 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 | 55 ++++++++++++++++++++++++++----------------
2 files changed, 35 insertions(+), 28 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 fb2dfc3..de7721d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -606,11 +606,16 @@ 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 not_rss, int nr_pages)
{
preempt_disable();

- if (file)
+ /*
+ * Here, RSS means 'mapped anon' and anon's SwapCache. Unlike LRU,
+ * Shmem is not included to Anon. It' counted as 'file cache'
+ * which tends to be shared between memcgs.
+ */
+ if (not_rss)
__this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_CACHE],
nr_pages);
else
@@ -2343,6 +2348,8 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
struct page_cgroup *pc,
enum charge_type ctype)
{
+ bool not_rss;
+
lock_page_cgroup(pc);
if (unlikely(PageCgroupUsed(pc))) {
unlock_page_cgroup(pc);
@@ -2362,21 +2369,15 @@ 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_CACHE) ||
+ (ctype == MEM_CGROUP_CHARGE_TYPE_SHMEM))
+ not_rss = true;
+ else
+ not_rss = false;
+
+ mem_cgroup_charge_statistics(memcg, not_rss, nr_pages);
unlock_page_cgroup(pc);
WARN_ON_ONCE(PageLRU(page));
/*
@@ -2441,6 +2442,7 @@ static int mem_cgroup_move_account(struct page *page,
{
unsigned long flags;
int ret;
+ bool not_rss = !PageAnon(page);

VM_BUG_ON(from == to);
VM_BUG_ON(PageLRU(page));
@@ -2469,14 +2471,14 @@ 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, not_rss, -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, not_rss, nr_pages);
/*
* We charges against "to" which may not have any tasks. Then, "to"
* can be under rmdir(). But in current implementation, caller of
@@ -2824,6 +2826,7 @@ __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 not_rss = false;

if (mem_cgroup_disabled())
return NULL;
@@ -2850,6 +2853,10 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
goto unlock_out;

switch (ctype) {
+ case MEM_CGROUP_CHARGE_TYPE_CACHE:
+ case MEM_CGROUP_CHARGE_TYPE_SHMEM:
+ not_rss = true;
+ break;
case MEM_CGROUP_CHARGE_TYPE_MAPPED:
case MEM_CGROUP_CHARGE_TYPE_DROP:
/* See mem_cgroup_prepare_migration() */
@@ -2867,7 +2874,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
break;
}

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

ClearPageCgroupUsed(pc);
/*
@@ -2908,9 +2915,15 @@ void mem_cgroup_uncharge_page(struct page *page)

void mem_cgroup_uncharge_cache_page(struct page *page)
{
+ int ctype;
+
VM_BUG_ON(page_mapped(page));
VM_BUG_ON(page->mapping);
- __mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_CACHE);
+ if (page_is_file_cache(page))
+ ctype = MEM_CGROUP_CHARGE_TYPE_CACHE;
+ else
+ ctype = MEM_CGROUP_CHARGE_TYPE_SHMEM;
+ __mem_cgroup_uncharge_common(page, ctype);
}

/*
@@ -3253,7 +3266,7 @@ 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, true, -1);
ClearPageCgroupUsed(pc);
unlock_page_cgroup(pc);

--
1.7.4.1



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