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Subject[PATCH -mm 5/5] memcg: use spinlock in page_cgroup instead of bit_spinlock
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

This patch replaces bit_spinlock with spinlock. In general,
spinlock has good functinality than bit_spin_lock and we should use
it if we have a room for it. In 64bit arch, we have extra 4bytes.
Let's use it.
expected effects:
- use better codes.
- ticket lock on x86-64
- para-vitualization aware lock
etc..

Chagelog: 20090729
- fixed page_cgroup_is_locked().

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
--
---
include/linux/page_cgroup.h | 33 ++++++++++++++++++++++++++++++++-
mm/memcontrol.c | 2 +-
mm/page_cgroup.c | 3 +++
3 files changed, 36 insertions(+), 2 deletions(-)
Index: mmotm-0727/include/linux/page_cgroup.h
===================================================================
--- mmotm-0727.orig/include/linux/page_cgroup.h
+++ mmotm-0727/include/linux/page_cgroup.h
@@ -10,8 +10,14 @@
* All page cgroups are allocated at boot or memory hotplug event,
* then the page cgroup for pfn always exists.
*/
+#ifdef CONFIG_64BIT
+#define PCG_HAS_SPINLOCK
+#endif
struct page_cgroup {
unsigned long flags;
+#ifdef PCG_HAS_SPINLOCK
+ spinlock_t lock;
+#endif
unsigned short mem_cgroup; /* ID of assigned memory cgroup */
unsigned short blk_cgroup; /* Not Used..but will be. */
struct page *page;
@@ -36,7 +42,9 @@ struct page_cgroup *lookup_page_cgroup(s

enum {
/* flags for mem_cgroup */
- PCG_LOCK, /* page cgroup is locked */
+#ifndef PCG_HAS_SPINLOCK
+ PCG_LOCK, /* page cgroup is locked (see below also.)*/
+#endif
PCG_CACHE, /* charged as cache */
PCG_USED, /* this object is in use. */
PCG_ACCT_LRU, /* page has been accounted for */
@@ -65,8 +73,6 @@ static inline void ClearPageCgroup##unam
static inline int TestClearPageCgroup##uname(struct page_cgroup *pc) \
{ return test_and_clear_bit(PCG_##lname, &pc->flags); }

-TESTPCGFLAG(Locked, LOCK)
-
/* Cache flag is set only once (at allocation) */
TESTPCGFLAG(Cache, CACHE)
CLEARPCGFLAG(Cache, CACHE)
@@ -95,6 +101,22 @@ static inline enum zone_type page_cgroup
return page_zonenum(pc->page);
}

+#ifdef PCG_HAS_SPINLOCK
+static inline void lock_page_cgroup(struct page_cgroup *pc)
+{
+ spin_lock(&pc->lock);
+}
+static inline void unlock_page_cgroup(struct page_cgroup *pc)
+{
+ spin_unlock(&pc->lock);
+}
+
+static inline bool page_cgroup_is_locked(struct page_cgroup *pc)
+{
+ return spin_is_locked(&pc->lock);
+}
+
+#else
static inline void lock_page_cgroup(struct page_cgroup *pc)
{
bit_spin_lock(PCG_LOCK, &pc->flags);
@@ -105,6 +127,14 @@ static inline void unlock_page_cgroup(st
bit_spin_unlock(PCG_LOCK, &pc->flags);
}

+static inline void page_cgroup_is_locked(struct page_cgrou *pc)
+{
+ bit_spin_is_locked(PCG_LOCK, &pc->flags);
+}
+TESTPCGFLAG(Locked, LOCK)
+
+#endif
+
#else /* CONFIG_CGROUP_MEM_RES_CTLR */
struct page_cgroup;

Index: mmotm-0727/mm/page_cgroup.c
===================================================================
--- mmotm-0727.orig/mm/page_cgroup.c
+++ mmotm-0727/mm/page_cgroup.c
@@ -18,6 +18,9 @@ __init_page_cgroup(struct page_cgroup *p
pc->mem_cgroup = 0;
pc->page = pfn_to_page(pfn);
INIT_LIST_HEAD(&pc->lru);
+#ifdef PCG_HAS_SPINLOCK
+ spin_lock_init(&pc->lock);
+#endif
}
static unsigned long total_usage;

Index: mmotm-0727/mm/memcontrol.c
===================================================================
--- mmotm-0727.orig/mm/memcontrol.c
+++ mmotm-0727/mm/memcontrol.c
@@ -1999,7 +1999,7 @@ static void __mem_cgroup_move_account(st
int i;
VM_BUG_ON(from == to);
VM_BUG_ON(PageLRU(pc->page));
- VM_BUG_ON(!PageCgroupLocked(pc));
+ VM_BUG_ON(!page_cgroup_is_locked(pc));
VM_BUG_ON(!PageCgroupUsed(pc));
VM_BUG_ON(id_to_memcg(pc->mem_cgroup) != from);



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