diff mbox series

mm: Only re-generate demotion targets when a numa node changes its N_CPU state

Message ID 20220309144644.4278-1-osalvador@suse.de (mailing list archive)
State New
Headers show
Series mm: Only re-generate demotion targets when a numa node changes its N_CPU state | expand

Commit Message

Oscar Salvador March 9, 2022, 2:46 p.m. UTC 
Abhishek reported that after patch [1], hotplug operations are
taking ~double the expected time. [2]

The reason behind is that the CPU callbacks that migrate_on_reclaim_init()
sets always call set_migration_target_nodes() whenever a CPU is brought
up/down.
But we only care about numa nodes going from having cpus to become
cpuless, and vice versa, as that influences the demotion_target order.

We do already have two CPU callbacks (vmstat_cpu_online() and vmstat_cpu_dead())
that check exactly that, so get rid of the CPU callbacks in
migrate_on_reclaim_init() and only call set_migration_target_nodes() from
vmstat_cpu_{dead,online}() whenever a numa node change its N_CPU state.

[1] https://lore.kernel.org/linux-mm/20210721063926.3024591-2-ying.huang@intel.com/
[2] https://lore.kernel.org/linux-mm/eb438ddd-2919-73d4-bd9f-b7eecdd9577a@linux.vnet.ibm.com/

Reported-by: Abhishek Goel <huntbag@linux.vnet.ibm.com>
Signed-off-by: Oscar Salvador <osalvador@suse.de>
---
I think there is further room for improvement like should we call in to
set_migration_target_nodes() when demotion is disabled via sysctl?
I will have a look into that, but let us go with this quick fix for now.
Also, I am not really strong about the Fixes tag, but it can be added
if you think it makes sense.
---
 include/linux/migrate.h |  5 +++++
 mm/migrate.c            | 36 +-----------------------------------
 mm/vmstat.c             | 10 +++++++++-
 3 files changed, 15 insertions(+), 36 deletions(-)

Comments

Andrew Morton March 9, 2022, 9:02 p.m. UTC | #1 
On Wed,  9 Mar 2022 15:46:44 +0100 Oscar Salvador <osalvador@suse.de> wrote:

> Abhishek reported that after patch [1], hotplug operations are
> taking ~double the expected time. [2]
> 
> The reason behind is that the CPU callbacks that migrate_on_reclaim_init()
> sets always call set_migration_target_nodes() whenever a CPU is brought
> up/down.
> But we only care about numa nodes going from having cpus to become
> cpuless, and vice versa, as that influences the demotion_target order.
> 
> We do already have two CPU callbacks (vmstat_cpu_online() and vmstat_cpu_dead())
> that check exactly that, so get rid of the CPU callbacks in
> migrate_on_reclaim_init() and only call set_migration_target_nodes() from
> vmstat_cpu_{dead,online}() whenever a numa node change its N_CPU state.
> 
> [1] https://lore.kernel.org/linux-mm/20210721063926.3024591-2-ying.huang@intel.com/
> [2] https://lore.kernel.org/linux-mm/eb438ddd-2919-73d4-bd9f-b7eecdd9577a@linux.vnet.ibm.com/
> 
> ...
>
>  extern bool numa_demotion_enabled;
> +#ifdef CONFIG_HOTPLUG_CPU
> +extern void set_migration_target_nodes(void);
> +#else
> +static inline void set_migration_target_nodes() {}

Compiler won't like that.  Please test (compile and runtime) with
CONFIG_HOTPLUG_CPU=n.

>
> ...
>
Oscar Salvador March 9, 2022, 9:55 p.m. UTC | #2 
On Wed, Mar 09, 2022 at 01:02:49PM -0800, Andrew Morton wrote:
> On Wed,  9 Mar 2022 15:46:44 +0100 Oscar Salvador <osalvador@suse.de> wrote:
> > +static inline void set_migration_target_nodes() {}
> 
> Compiler won't like that.  Please test (compile and runtime) with
> CONFIG_HOTPLUG_CPU=n.

Sorry, fat fingers. This on top:

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index c64fe2923fb0..b82b4a9a0136 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -51,7 +51,7 @@ extern bool numa_demotion_enabled;
 #ifdef CONFIG_HOTPLUG_CPU
 extern void set_migration_target_nodes(void);
 #else
-static inline void set_migration_target_nodes() {}
+static inline void set_migration_target_nodes(void) {}
 #endif
 #else

I will wait for some feedback before sending a v2.

thanks Andrew!
Huang, Ying March 10, 2022, 12:39 a.m. UTC | #3 
Oscar Salvador <osalvador@suse.de> writes:

> Abhishek reported that after patch [1], hotplug operations are
> taking ~double the expected time. [2]
>
> The reason behind is that the CPU callbacks that migrate_on_reclaim_init()
> sets always call set_migration_target_nodes() whenever a CPU is brought
> up/down.
> But we only care about numa nodes going from having cpus to become
> cpuless, and vice versa, as that influences the demotion_target order.
>
> We do already have two CPU callbacks (vmstat_cpu_online() and vmstat_cpu_dead())
> that check exactly that, so get rid of the CPU callbacks in
> migrate_on_reclaim_init() and only call set_migration_target_nodes() from
> vmstat_cpu_{dead,online}() whenever a numa node change its N_CPU state.
>
> [1] https://lore.kernel.org/linux-mm/20210721063926.3024591-2-ying.huang@intel.com/
> [2] https://lore.kernel.org/linux-mm/eb438ddd-2919-73d4-bd9f-b7eecdd9577a@linux.vnet.ibm.com/
>
> Reported-by: Abhishek Goel <huntbag@linux.vnet.ibm.com>
> Signed-off-by: Oscar Salvador <osalvador@suse.de>
> ---
> I think there is further room for improvement like should we call in to
> set_migration_target_nodes() when demotion is disabled via sysctl?
> I will have a look into that, but let us go with this quick fix for now.
> Also, I am not really strong about the Fixes tag, but it can be added
> if you think it makes sense.
> ---
>  include/linux/migrate.h |  5 +++++
>  mm/migrate.c            | 36 +-----------------------------------
>  mm/vmstat.c             | 10 +++++++++-
>  3 files changed, 15 insertions(+), 36 deletions(-)
>
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index db96e10eb8da..c64fe2923fb0 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -48,6 +48,11 @@ int folio_migrate_mapping(struct address_space *mapping,
>  		struct folio *newfolio, struct folio *folio, int extra_count);
>  
>  extern bool numa_demotion_enabled;
> +#ifdef CONFIG_HOTPLUG_CPU
> +extern void set_migration_target_nodes(void);
> +#else
> +static inline void set_migration_target_nodes() {}
> +#endif
>  #else
>  
>  static inline void putback_movable_pages(struct list_head *l) {}
> diff --git a/mm/migrate.c b/mm/migrate.c
> index c7da064b4781..7847e4de01d7 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -3190,7 +3190,7 @@ static void __set_migration_target_nodes(void)
>  /*
>   * For callers that do not hold get_online_mems() already.
>   */
> -static void set_migration_target_nodes(void)
> +void set_migration_target_nodes(void)
>  {
>  	get_online_mems();
>  	__set_migration_target_nodes();
> @@ -3254,47 +3254,13 @@ static int __meminit migrate_on_reclaim_callback(struct notifier_block *self,
>  	return notifier_from_errno(0);
>  }
>  
> -/*
> - * React to hotplug events that might affect the migration targets
> - * like events that online or offline NUMA nodes.
> - *
> - * The ordering is also currently dependent on which nodes have
> - * CPUs.  That means we need CPU on/offline notification too.
> - */
> -static int migration_online_cpu(unsigned int cpu)
> -{
> -	set_migration_target_nodes();
> -	return 0;
> -}
> -
> -static int migration_offline_cpu(unsigned int cpu)
> -{
> -	set_migration_target_nodes();
> -	return 0;
> -}
> -
>  static int __init migrate_on_reclaim_init(void)
>  {
> -	int ret;
> -
>  	node_demotion = kmalloc_array(nr_node_ids,
>  				      sizeof(struct demotion_nodes),
>  				      GFP_KERNEL);
>  	WARN_ON(!node_demotion);
>  
> -	ret = cpuhp_setup_state_nocalls(CPUHP_MM_DEMOTION_DEAD, "mm/demotion:offline",
> -					NULL, migration_offline_cpu);
> -	/*
> -	 * In the unlikely case that this fails, the automatic
> -	 * migration targets may become suboptimal for nodes
> -	 * where N_CPU changes.  With such a small impact in a
> -	 * rare case, do not bother trying to do anything special.
> -	 */
> -	WARN_ON(ret < 0);
> -	ret = cpuhp_setup_state(CPUHP_AP_MM_DEMOTION_ONLINE, "mm/demotion:online",
> -				migration_online_cpu, NULL);
> -	WARN_ON(ret < 0);
> -

We need to call set_migration_target_nodes() during system boot
somewhere, either here or in init_mm_internals().

Best Regards,
Huang, Ying


>  	hotplug_memory_notifier(migrate_on_reclaim_callback, 100);
>  	return 0;
>  }
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 4057372745d0..0529a83c8f89 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -28,6 +28,7 @@
>  #include <linux/mm_inline.h>
>  #include <linux/page_ext.h>
>  #include <linux/page_owner.h>
> +#include <linux/migrate.h>
>  
>  #include "internal.h"
>  
> @@ -2043,7 +2044,12 @@ static void __init init_cpu_node_state(void)
>  static int vmstat_cpu_online(unsigned int cpu)
>  {
>  	refresh_zone_stat_thresholds();
> -	node_set_state(cpu_to_node(cpu), N_CPU);
> +
> +	if (!node_state(cpu_to_node(cpu), N_CPU)) {
> +		node_set_state(cpu_to_node(cpu), N_CPU);
> +		set_migration_target_nodes();
> +	}
> +
>  	return 0;
>  }
>  
> @@ -2066,6 +2072,8 @@ static int vmstat_cpu_dead(unsigned int cpu)
>  		return 0;
>  
>  	node_clear_state(node, N_CPU);
> +	set_migration_target_nodes();
> +
>  	return 0;
>  }
kernel test robot March 10, 2022, 12:56 a.m. UTC | #4 
Hi Oscar,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on hnaz-mm/master]

url:    https://github.com/0day-ci/linux/commits/Oscar-Salvador/mm-Only-re-generate-demotion-targets-when-a-numa-node-changes-its-N_CPU-state/20220309-224707
base:   https://github.com/hnaz/linux-mm master
config: sparc-randconfig-r001-20220309 (https://download.01.org/0day-ci/archive/20220310/202203100830.iDtoMHKt-lkp@intel.com/config)
compiler: sparc64-linux-gcc (GCC) 11.2.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/8af0c9ff9475c64e31963a5810b127875081c5ff
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Oscar-Salvador/mm-Only-re-generate-demotion-targets-when-a-numa-node-changes-its-N_CPU-state/20220309-224707
        git checkout 8af0c9ff9475c64e31963a5810b127875081c5ff
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=sparc SHELL=/bin/bash kernel/sched/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   In file included from kernel/sched/sched.h:53,
                    from kernel/sched/core.c:13:
   include/linux/migrate.h:54:20: error: function declaration isn't a prototype [-Werror=strict-prototypes]
      54 | static inline void set_migration_target_nodes() {}
         |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/migrate.h: In function 'set_migration_target_nodes':
>> include/linux/migrate.h:54:20: warning: old-style function definition [-Wold-style-definition]
   kernel/sched/core.c: At top level:
   kernel/sched/core.c:3442:6: warning: no previous prototype for 'sched_set_stop_task' [-Wmissing-prototypes]
    3442 | void sched_set_stop_task(int cpu, struct task_struct *stop)
         |      ^~~~~~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors
--
   In file included from kernel/sched/sched.h:53,
                    from kernel/sched/loadavg.c:9:
   include/linux/migrate.h:54:20: error: function declaration isn't a prototype [-Werror=strict-prototypes]
      54 | static inline void set_migration_target_nodes() {}
         |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/migrate.h: In function 'set_migration_target_nodes':
>> include/linux/migrate.h:54:20: warning: old-style function definition [-Wold-style-definition]
   cc1: some warnings being treated as errors
--
   In file included from kernel/sched/sched.h:53,
                    from kernel/sched/fair.c:23:
   include/linux/migrate.h:54:20: error: function declaration isn't a prototype [-Werror=strict-prototypes]
      54 | static inline void set_migration_target_nodes() {}
         |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/migrate.h: In function 'set_migration_target_nodes':
>> include/linux/migrate.h:54:20: warning: old-style function definition [-Wold-style-definition]
   kernel/sched/fair.c: At top level:
   kernel/sched/fair.c:11135:6: warning: no previous prototype for 'task_vruntime_update' [-Wmissing-prototypes]
   11135 | void task_vruntime_update(struct rq *rq, struct task_struct *p, bool in_fi)
         |      ^~~~~~~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors
--
   In file included from kernel/sched/sched.h:53,
                    from kernel/sched/rt.c:6:
   include/linux/migrate.h:54:20: error: function declaration isn't a prototype [-Werror=strict-prototypes]
      54 | static inline void set_migration_target_nodes() {}
         |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/migrate.h: In function 'set_migration_target_nodes':
>> include/linux/migrate.h:54:20: warning: old-style function definition [-Wold-style-definition]
   kernel/sched/rt.c: At top level:
   kernel/sched/rt.c:730:6: warning: no previous prototype for 'sched_rt_bandwidth_account' [-Wmissing-prototypes]
     730 | bool sched_rt_bandwidth_account(struct rt_rq *rt_rq)
         |      ^~~~~~~~~~~~~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors


vim +54 include/linux/migrate.h

    36	
    37	extern void migrate_page_states(struct page *newpage, struct page *page);
    38	extern void migrate_page_copy(struct page *newpage, struct page *page);
    39	extern int migrate_huge_page_move_mapping(struct address_space *mapping,
    40					  struct page *newpage, struct page *page);
    41	extern int migrate_page_move_mapping(struct address_space *mapping,
    42			struct page *newpage, struct page *page, int extra_count);
    43	void migration_entry_wait_on_locked(swp_entry_t entry, pte_t *ptep,
    44					spinlock_t *ptl);
    45	void folio_migrate_flags(struct folio *newfolio, struct folio *folio);
    46	void folio_migrate_copy(struct folio *newfolio, struct folio *folio);
    47	int folio_migrate_mapping(struct address_space *mapping,
    48			struct folio *newfolio, struct folio *folio, int extra_count);
    49	
    50	extern bool numa_demotion_enabled;
    51	#ifdef CONFIG_HOTPLUG_CPU
    52	extern void set_migration_target_nodes(void);
    53	#else
  > 54	static inline void set_migration_target_nodes() {}
    55	#endif
    56	#else
    57	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
kernel test robot March 10, 2022, 1:17 a.m. UTC | #5 
Hi Oscar,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on hnaz-mm/master]

url:    https://github.com/0day-ci/linux/commits/Oscar-Salvador/mm-Only-re-generate-demotion-targets-when-a-numa-node-changes-its-N_CPU-state/20220309-224707
base:   https://github.com/hnaz/linux-mm master
config: riscv-randconfig-s032-20220309 (https://download.01.org/0day-ci/archive/20220310/202203100900.4UKi7486-lkp@intel.com/config)
compiler: riscv32-linux-gcc (GCC) 11.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # apt-get install sparse
        # sparse version: v0.6.4-dirty
        # https://github.com/0day-ci/linux/commit/8af0c9ff9475c64e31963a5810b127875081c5ff
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Oscar-Salvador/mm-Only-re-generate-demotion-targets-when-a-numa-node-changes-its-N_CPU-state/20220309-224707
        git checkout 8af0c9ff9475c64e31963a5810b127875081c5ff
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=riscv SHELL=/bin/bash

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   mm/vmstat.c: In function 'vmstat_cpu_online':
>> mm/vmstat.c:2056:17: error: implicit declaration of function 'set_migration_target_nodes' [-Werror=implicit-function-declaration]
    2056 |                 set_migration_target_nodes();
         |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors


vim +/set_migration_target_nodes +2056 mm/vmstat.c

  2049	
  2050	static int vmstat_cpu_online(unsigned int cpu)
  2051	{
  2052		refresh_zone_stat_thresholds();
  2053	
  2054		if (!node_state(cpu_to_node(cpu), N_CPU)) {
  2055			node_set_state(cpu_to_node(cpu), N_CPU);
> 2056			set_migration_target_nodes();
  2057		}
  2058	
  2059		return 0;
  2060	}
  2061	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
Oscar Salvador March 10, 2022, 5:48 a.m. UTC | #6 
On Thu, Mar 10, 2022 at 08:39:53AM +0800, Huang, Ying wrote:
> We need to call set_migration_target_nodes() during system boot
> somewhere, either here or in init_mm_internals().

Hi Huang Ying,

vmstat_cpu_online() already gets called during boot:

static struct cpuhp_step cpuhp_hp_states[] = {
...
	#ifdef CONFIG_SMP
	[CPUHP_CREATE_THREADS]= {
		.name			= "threads:prepare",
		.startup.single		= smpboot_create_threads,
		.teardown.single	= NULL,
		.cant_stop		= true,
	},
...

smpboot_create_threads
 __smpboot_create_thread
  smpboot_thread_fn
   ht->thread_fn() 
    cpuhp_thread_fun
     cpuhp_invoke_callback
      vmstat_cpu_online

That for every CPU that is brought up during boot.

So unless I am missing something, I would say we are already covered
there, right?
Baolin Wang March 10, 2022, 6:24 a.m. UTC | #7 
Hi Oscar,

On 3/10/2022 1:48 PM, Oscar Salvador wrote:
> On Thu, Mar 10, 2022 at 08:39:53AM +0800, Huang, Ying wrote:
>> We need to call set_migration_target_nodes() during system boot
>> somewhere, either here or in init_mm_internals().
> 
> Hi Huang Ying,
> 
> vmstat_cpu_online() already gets called during boot:
> 
> static struct cpuhp_step cpuhp_hp_states[] = {
> ...
> 	#ifdef CONFIG_SMP
> 	[CPUHP_CREATE_THREADS]= {
> 		.name			= "threads:prepare",
> 		.startup.single		= smpboot_create_threads,
> 		.teardown.single	= NULL,
> 		.cant_stop		= true,
> 	},
> ...
> 
> smpboot_create_threads
>   __smpboot_create_thread
>    smpboot_thread_fn
>     ht->thread_fn()
>      cpuhp_thread_fun
>       cpuhp_invoke_callback
>        vmstat_cpu_online
> 
> That for every CPU that is brought up during boot.
> 
> So unless I am missing something, I would say we are already covered
> there, right?

I've tested your patch, unfortunately it can not work. It already set 
the node with N_CPU state in init_cpu_node_state() earlier, so in 
vmstat_cpu_online() ,the sentence 'if(!node_state(cpu_to_node(cpu), 
N_CPU))' is always false, which means it will not call 
set_migration_target_nodes().

Like Huang Ying said, we should call set_migration_target_nodes() in 
migrate_on_reclaim_init() or init_mm_internals().
diff mbox series

Patch

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index db96e10eb8da..c64fe2923fb0 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -48,6 +48,11 @@  int folio_migrate_mapping(struct address_space *mapping,
 		struct folio *newfolio, struct folio *folio, int extra_count);
 
 extern bool numa_demotion_enabled;
+#ifdef CONFIG_HOTPLUG_CPU
+extern void set_migration_target_nodes(void);
+#else
+static inline void set_migration_target_nodes() {}
+#endif
 #else
 
 static inline void putback_movable_pages(struct list_head *l) {}
diff --git a/mm/migrate.c b/mm/migrate.c
index c7da064b4781..7847e4de01d7 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -3190,7 +3190,7 @@  static void __set_migration_target_nodes(void)
 /*
  * For callers that do not hold get_online_mems() already.
  */
-static void set_migration_target_nodes(void)
+void set_migration_target_nodes(void)
 {
 	get_online_mems();
 	__set_migration_target_nodes();
@@ -3254,47 +3254,13 @@  static int __meminit migrate_on_reclaim_callback(struct notifier_block *self,
 	return notifier_from_errno(0);
 }
 
-/*
- * React to hotplug events that might affect the migration targets
- * like events that online or offline NUMA nodes.
- *
- * The ordering is also currently dependent on which nodes have
- * CPUs.  That means we need CPU on/offline notification too.
- */
-static int migration_online_cpu(unsigned int cpu)
-{
-	set_migration_target_nodes();
-	return 0;
-}
-
-static int migration_offline_cpu(unsigned int cpu)
-{
-	set_migration_target_nodes();
-	return 0;
-}
-
 static int __init migrate_on_reclaim_init(void)
 {
-	int ret;
-
 	node_demotion = kmalloc_array(nr_node_ids,
 				      sizeof(struct demotion_nodes),
 				      GFP_KERNEL);
 	WARN_ON(!node_demotion);
 
-	ret = cpuhp_setup_state_nocalls(CPUHP_MM_DEMOTION_DEAD, "mm/demotion:offline",
-					NULL, migration_offline_cpu);
-	/*
-	 * In the unlikely case that this fails, the automatic
-	 * migration targets may become suboptimal for nodes
-	 * where N_CPU changes.  With such a small impact in a
-	 * rare case, do not bother trying to do anything special.
-	 */
-	WARN_ON(ret < 0);
-	ret = cpuhp_setup_state(CPUHP_AP_MM_DEMOTION_ONLINE, "mm/demotion:online",
-				migration_online_cpu, NULL);
-	WARN_ON(ret < 0);
-
 	hotplug_memory_notifier(migrate_on_reclaim_callback, 100);
 	return 0;
 }
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 4057372745d0..0529a83c8f89 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -28,6 +28,7 @@ 
 #include <linux/mm_inline.h>
 #include <linux/page_ext.h>
 #include <linux/page_owner.h>
+#include <linux/migrate.h>
 
 #include "internal.h"
 
@@ -2043,7 +2044,12 @@  static void __init init_cpu_node_state(void)
 static int vmstat_cpu_online(unsigned int cpu)
 {
 	refresh_zone_stat_thresholds();
-	node_set_state(cpu_to_node(cpu), N_CPU);
+
+	if (!node_state(cpu_to_node(cpu), N_CPU)) {
+		node_set_state(cpu_to_node(cpu), N_CPU);
+		set_migration_target_nodes();
+	}
+
 	return 0;
 }
 
@@ -2066,6 +2072,8 @@  static int vmstat_cpu_dead(unsigned int cpu)
 		return 0;
 
 	node_clear_state(node, N_CPU);
+	set_migration_target_nodes();
+
 	return 0;
 }