3 files changed, 37 insertions, 8 deletions

diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index c586679b6fef..502767f4e4d4 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -198,7 +198,7 @@ extern void __inc_zone_state(struct zone *, enum zone_stat_item);
 extern void dec_zone_state(struct zone *, enum zone_stat_item);
 extern void __dec_zone_state(struct zone *, enum zone_stat_item);
 
-void refresh_cpu_vm_stats(int);
+void cpu_vm_stats_fold(int cpu);
 void refresh_zone_stat_thresholds(void);
 
 void drain_zonestat(struct zone *zone, struct per_cpu_pageset *);
@@ -255,6 +255,7 @@ static inline void __dec_zone_page_state(struct page *page,
 
 static inline void refresh_cpu_vm_stats(int cpu) { }
 static inline void refresh_zone_stat_thresholds(void) { }
+static inline void cpu_vm_stats_fold(int cpu) { }
 
 static inline void drain_zonestat(struct zone *zone,
                         struct per_cpu_pageset *pset) { }
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 42c59300bacd..f885eb827159 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5435,7 +5435,7 @@ static int page_alloc_cpu_notify(struct notifier_block *self,
                  * This is only okay since the processor is dead and cannot
                  * race with what we are doing.
                  */
-                refresh_cpu_vm_stats(cpu);
+                cpu_vm_stats_fold(cpu);
         }
         return NOTIFY_OK;
 }
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 8a8da1f9b044..aaee66330e01 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -415,11 +415,7 @@ EXPORT_SYMBOL(dec_zone_page_state);
 #endif
 
 /*
- * Update the zone counters for one cpu.
- *
- * The cpu specified must be either the current cpu or a processor that
- * is not online. If it is the current cpu then the execution thread must
- * be pinned to the current cpu.
+ * Update the zone counters for the current cpu.
  *
  * Note that refresh_cpu_vm_stats strives to only access
  * node local memory. The per cpu pagesets on remote zones are placed
@@ -432,7 +428,7 @@ EXPORT_SYMBOL(dec_zone_page_state);
  * with the global counters. These could cause remote node cache line
  * bouncing and will have to be only done when necessary.
  */
-void refresh_cpu_vm_stats(int cpu)
+static void refresh_cpu_vm_stats(int cpu)
 {
         struct zone *zone;
         int i;
@@ -494,6 +490,38 @@ void refresh_cpu_vm_stats(int cpu)
 }
 
 /*
+ * Fold the data for an offline cpu into the global array.
+ * There cannot be any access by the offline cpu and therefore
+ * synchronization is simplified.
+ */
+void cpu_vm_stats_fold(int cpu)
+{
+        struct zone *zone;
+        int i;
+        int global_diff[NR_VM_ZONE_STAT_ITEMS] = { 0, };
+
+        for_each_populated_zone(zone) {
+                struct per_cpu_pageset *p;
+
+                p = per_cpu_ptr(zone->pageset, cpu);
+
+                for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
+                        if (p->vm_stat_diff[i]) {
+                                int v;
+
+                                v = p->vm_stat_diff[i];
+                                p->vm_stat_diff[i] = 0;
+                                atomic_long_add(v, &zone->vm_stat[i]);
+                                global_diff[i] += v;
+                        }
+        }
+
+        for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
+                if (global_diff[i])
+                        atomic_long_add(global_diff[i], &vm_stat[i]);
+}
+
+/*
  * this is only called if !populated_zone(zone), which implies no other users of
  * pset->vm_stat_diff[] exsist.
  */