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Message-ID: <ccf79d4d-4dd6-14c3-bab6-4fac034d8e22@nextfour.com>
Date: Sat, 18 Sep 2021 07:04:41 +0300
From: Mika Penttilä <mika.penttila@...tfour.com>
To: Huang Ying <ying.huang@...el.com>,
Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Dave Hansen <dave.hansen@...ux.intel.com>,
Yang Shi <shy828301@...il.com>, Zi Yan <ziy@...dia.com>,
Michal Hocko <mhocko@...e.com>, Wei Xu <weixugc@...gle.com>,
Oscar Salvador <osalvador@...e.de>,
David Rientjes <rientjes@...gle.com>,
Dan Williams <dan.j.williams@...el.com>,
David Hildenbrand <david@...hat.com>,
Greg Thelen <gthelen@...gle.com>,
Keith Busch <kbusch@...nel.org>
Subject: Re: [PATCH] mm/migrate: fix CPUHP state to update node demotion order
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@...el.com>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: Yang Shi <shy828301@...il.com>
> Cc: Zi Yan <ziy@...dia.com>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Wei Xu <weixugc@...gle.com>
> Cc: Oscar Salvador <osalvador@...e.de>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Greg Thelen <gthelen@...gle.com>
> Cc: Keith Busch <kbusch@...nel.org>
> ---
> 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
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