---
 mm/vmstat.c |   69 +++++++++++++++++++++++++++++++++---------------------------
 1 file changed, 38 insertions(+), 31 deletions(-)

Index: linux-2.6/mm/vmstat.c
===================================================================
--- linux-2.6.orig/mm/vmstat.c	2007-11-08 20:19:59.013637624 -0800
+++ linux-2.6/mm/vmstat.c	2007-11-08 20:25:40.018137624 -0800
@@ -211,6 +211,33 @@ EXPORT_SYMBOL(mod_zone_page_state);
  * in between and therefore the atomicity vs. interrupt cannot be exploited
  * in a useful way here.
  */
+static s8 inc_diff(s8 *p)
+{
+	__asm__ __volatile__(
+		"incb %0;"
+			: "=m" (p)
+			: "m" (p));
+	return *p;
+}
+
+static s8 dec_diff(s8 *p)
+{
+	__asm__ __volatile__(
+		"decb %0;"
+			: "=m" (p)
+			: "m" (p));
+	return *p;
+}
+
+static inline void sync_diff(struct zone *zone, s8 *p,
+		int i, int offset)
+{
+	/*
+	 * xchg_local() would be useful here but that does not exist.
+	 */
+	zone_page_state_add(xchg(p, offset) - offset, zone, i);
+}
+
 void __inc_zone_state(struct zone *zone, enum zone_stat_item item)
 {
 	struct per_cpu_pageset *pcp = THIS_CPU(zone->pageset);
@@ -218,15 +245,10 @@ void __inc_zone_state(struct zone *zone,
 	s8 new;
 	s8 t = pcp->stat_threshold;
 
-	new = *p + 1;
+	new = inc_diff(p);
 
-	if (unlikely(new > t)) {
-		int overstep = t / 2;
-
-		zone_page_state_add(new + overstep, zone, item);
-		new = -overstep;
-	}
-	*p = new;
+	if (unlikely(new > t))
+		sync_diff(zone, p, item, t / 2);
 }
 
 void __inc_zone_page_state(struct page *page, enum zone_stat_item item)
@@ -242,15 +264,10 @@ void __dec_zone_state(struct zone *zone,
 	s8 new;
 	s8 t = -pcp->stat_threshold;
 
-	new = *p - 1;
+	new = dec_diff(p);
 
-	if (unlikely(new < t)) {
-		int overstep = t / 2;
-
-		zone_page_state_add(new + overstep, zone, item);
-		new = -overstep;
-	}
-	*p = new;
+	if (unlikely(new < t))
+		sync_diff(zone, p, item, t / 2);
 }
 
 void __dec_zone_page_state(struct page *page, enum zone_stat_item item)
@@ -261,32 +278,22 @@ EXPORT_SYMBOL(__dec_zone_page_state);
 
 void inc_zone_state(struct zone *zone, enum zone_stat_item item)
 {
-	unsigned long flags;
-
-	local_irq_save(flags);
+	preempt_disable();
 	__inc_zone_state(zone, item);
-	local_irq_restore(flags);
+	preempt_enable();
 }
 
 void inc_zone_page_state(struct page *page, enum zone_stat_item item)
 {
-	unsigned long flags;
-	struct zone *zone;
-
-	zone = page_zone(page);
-	local_irq_save(flags);
-	__inc_zone_state(zone, item);
-	local_irq_restore(flags);
+	inc_zone_state(page_zone(page), item);
 }
 EXPORT_SYMBOL(inc_zone_page_state);
 
 void dec_zone_page_state(struct page *page, enum zone_stat_item item)
 {
-	unsigned long flags;
-
-	local_irq_save(flags);
+	preempt_disable();
 	__dec_zone_page_state(page, item);
-	local_irq_restore(flags);
+	preempt_enable();
 }
 EXPORT_SYMBOL(dec_zone_page_state);