linux-kernel - [PATCH 5/5] memcg : use spinlock in pcg instad of bit

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Message-Id: <20100729184927.9a3e214d.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 29 Jul 2010 18:49:27 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	vgoyal@...hat.com, m-ikeda@...jp.nec.com, gthelen@...gle.com,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH 5/5] memcg : use spinlock in pcg instad of bit_spinlock

From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...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_locked().

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
--
---
 include/linux/page_cgroup.h |   35 +++++++++++++++++++++++++++++++++--
 mm/page_cgroup.c            |    3 +++
 2 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 */
@@ -60,7 +68,7 @@ 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)
@@ -90,6 +98,22 @@ 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_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);
@@ -100,6 +124,13 @@ static inline void unlock_page_cgroup(st
 	bit_spin_unlock(PCG_LOCK, &pc->flags);
 }
 
+static inline bool page_cgroup_locked(struct page_cgroup *pc)
+{
+	return test_bit(PCG_LOCK, &pc->flags);
+}
+
+#endif
+
 static inline void SetPCGFileFlag(struct page_cgroup *pc, int idx)
 {
 	set_bit(PCG_FILE_FLAGS + idx, &pc->flags);
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;
 

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