Hi!
On 18.9.2021 5.58, Huang Ying wrote:
The node demotion order needs to be updated during CPU hotplug.
Because whether a NUMA node has CPU may influence the demotion order.
The update function should be called during CPU online/offline after
the node_states[N_CPU] has been updated. That is done in
CPUHP_AP_ONLINE_DYN during CPU online and in CPUHP_MM_VMSTAT_DEAD
during CPU offline. But in commit 884a6e5d1f93 ("mm/migrate: update
node demotion order on hotplug events"), the function to update node
demotion order is called in CPUHP_AP_ONLINE_DYN during CPU
online/offline. This doesn't satisfy the order requirement. So in
this patch, we added CPUHP_AP_MM_DEMOTION_ONLINE and
CPUHP_MM_DEMOTION_OFFLINE to be called after CPUHP_AP_ONLINE_DYN and
CPUHP_MM_VMSTAT_DEAD during CPU online/offline, and register the
update function on them.
Fixes: 884a6e5d1f93 ("mm/migrate: update node demotion order on hotplug events")
Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Wei Xu <weixugc@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Greg Thelen <gthelen@xxxxxxxxxx>
Cc: Keith Busch <kbusch@xxxxxxxxxx>
---
include/linux/cpuhotplug.h | 2 ++
mm/migrate.c | 8 +++++---
2 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 832d8a74fa59..5a92ea56f21b 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -72,6 +72,7 @@ enum cpuhp_state {
CPUHP_SLUB_DEAD,
CPUHP_DEBUG_OBJ_DEAD,
CPUHP_MM_WRITEBACK_DEAD,
+ CPUHP_MM_DEMOTION_OFFLINE,
CPUHP_MM_VMSTAT_DEAD,
CPUHP_SOFTIRQ_DEAD,
CPUHP_NET_MVNETA_DEAD,
@@ -240,6 +241,7 @@ enum cpuhp_state {
CPUHP_AP_BASE_CACHEINFO_ONLINE,
CPUHP_AP_ONLINE_DYN,
CPUHP_AP_ONLINE_DYN_END = CPUHP_AP_ONLINE_DYN + 30,
+ CPUHP_AP_MM_DEMOTION_ONLINE,
CPUHP_AP_X86_HPET_ONLINE,
CPUHP_AP_X86_KVM_CLK_ONLINE,
CPUHP_AP_DTPM_CPU_ONLINE,
diff --git a/mm/migrate.c b/mm/migrate.c
index a6a7743ee98f..77d107a4577f 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -3278,9 +3278,8 @@ static int __init migrate_on_reclaim_init(void)
{
int ret;
- ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "migrate on reclaim",
- migration_online_cpu,
- migration_offline_cpu);
+ ret = cpuhp_setup_state_nocalls(CPUHP_MM_DEMOTION_OFFLINE, "mm/demotion:offline",
+ NULL, migration_offline_cpu);
/*
* In the unlikely case that this fails, the automatic
* migration targets may become suboptimal for nodes
@@ -3288,6 +3287,9 @@ static int __init migrate_on_reclaim_init(void)
* rare case, do not bother trying to do anything special.
*/
WARN_ON(ret < 0);
+ ret = cpuhp_setup_state_nocalls(CPUHP_AP_MM_DEMOTION_ONLINE, "mm/demotion:online",
+ migration_online_cpu, NULL);
You changed to _nocalls variant, how does this handle initialization for
cpus present at boot?
Thanks,
Mika
