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/[email protected]/
[2] https://lore.kernel.org/linux-mm/[email protected]/
Reported-by: Abhishek Goel <[email protected]>
Signed-off-by: Oscar Salvador <[email protected]>
---
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);
-
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;
}
--
2.34.1
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/[email protected]/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 <[email protected]>
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/[email protected]
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?
--
Oscar Salvador
SUSE Labs
Oscar Salvador <[email protected]> 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/[email protected]/
> [2] https://lore.kernel.org/linux-mm/[email protected]/
>
> Reported-by: Abhishek Goel <[email protected]>
> Signed-off-by: Oscar Salvador <[email protected]>
> ---
> 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;
> }
On Wed, Mar 09, 2022 at 01:02:49PM -0800, Andrew Morton wrote:
> On Wed, 9 Mar 2022 15:46:44 +0100 Oscar Salvador <[email protected]> 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!
--
Oscar Salvador
SUSE Labs
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/[email protected]/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 <[email protected]>
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/[email protected]
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().
On Wed, 9 Mar 2022 15:46:44 +0100 Oscar Salvador <[email protected]> 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/[email protected]/
> [2] https://lore.kernel.org/linux-mm/[email protected]/
>
> ...
>
> 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.
>
> ...
>