Commit 5a883813 authored by Minchan Kim's avatar Minchan Kim Committed by Linus Torvalds

memory-hotplug: fix zone stat mismatch

During memory-hotplug, I found NR_ISOLATED_[ANON|FILE] are increasing,
causing the kernel to hang.  When the system doesn't have enough free
pages, it enters reclaim but never reclaim any pages due to
too_many_isolated()==true and loops forever.

The cause is that when we do memory-hotadd after memory-remove,
__zone_pcp_update() clears a zone's ZONE_STAT_ITEMS in setup_pageset()
although the vm_stat_diff of all CPUs still have values.

In addtion, when we offline all pages of the zone, we reset them in
zone_pcp_reset without draining so we loss some zone stat item.
Reviewed-by: default avatarWen Congyang <>
Signed-off-by: default avatarMinchan Kim <>
Cc: Kamezawa Hiroyuki <>
Cc: Yasuaki Ishimatsu <>
Cc: KOSAKI Motohiro <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 08270807
......@@ -198,6 +198,8 @@ extern void __dec_zone_state(struct zone *, enum zone_stat_item);
void refresh_cpu_vm_stats(int);
void refresh_zone_stat_thresholds(void);
void drain_zonestat(struct zone *zone, struct per_cpu_pageset *);
int calculate_pressure_threshold(struct zone *zone);
int calculate_normal_threshold(struct zone *zone);
void set_pgdat_percpu_threshold(pg_data_t *pgdat,
......@@ -251,6 +253,8 @@ 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 drain_zonestat(struct zone *zone,
struct per_cpu_pageset *pset) { }
#endif /* CONFIG_SMP */
static inline void __mod_zone_freepage_state(struct zone *zone, int nr_pages,
......@@ -5916,6 +5916,7 @@ static int __meminit __zone_pcp_update(void *data)
if (pcp->count > 0)
free_pcppages_bulk(zone, pcp->count, pcp);
drain_zonestat(zone, pset);
setup_pageset(pset, batch);
......@@ -5932,10 +5933,16 @@ void __meminit zone_pcp_update(struct zone *zone)
void zone_pcp_reset(struct zone *zone)
unsigned long flags;
int cpu;
struct per_cpu_pageset *pset;
/* avoid races with drain_pages() */
if (zone->pageset != &boot_pageset) {
for_each_online_cpu(cpu) {
pset = per_cpu_ptr(zone->pageset, cpu);
drain_zonestat(zone, pset);
zone->pageset = &boot_pageset;
......@@ -495,6 +495,18 @@ void refresh_cpu_vm_stats(int cpu)
atomic_long_add(global_diff[i], &vm_stat[i]);
void drain_zonestat(struct zone *zone, struct per_cpu_pageset *pset)
int i;
for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
if (pset->vm_stat_diff[i]) {
int v = pset->vm_stat_diff[i];
pset->vm_stat_diff[i] = 0;
atomic_long_add(v, &zone->vm_stat[i]);
atomic_long_add(v, &vm_stat[i]);
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