From:   Alexey Makhalov <amakhalov@vmware.com>
To:     Michal Hocko <mhocko@suse.com>
CC:     David Hildenbrand <david@redhat.com>,
        Dennis Zhou <dennis@kernel.org>,
        Eric Dumazet <eric.dumazet@gmail.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Oscar Salvador <osalvador@suse.de>, Tejun Heo <tj@kernel.org>,
        Christoph Lameter <cl@linux.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH v3] mm: fix panic in __alloc_pages
Thread-Topic: [PATCH v3] mm: fix panic in __alloc_pages
Thread-Index: AQHX1N5+lqzX5/9/hUCR9L+z9tfLRKv6c74AgAD9U4CAAB7tAIAADZWAgAnMHQCAAIIHgIAAufyAgAJfDQCAHgMmAIAABAWAgAASAgCAAAQ5gIAADzyAgAAdyYCAAAWLgIAAAWYAgAAGEoCAAAPOAIAABOmAgAACrYCAAAckgA==
Date:   Tue, 7 Dec 2021 17:02:35 +0000
Message-ID: <2E174230-04F3-4798-86D5-1257859FFAD8@vmware.com>
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> On Dec 7, 2021, at 8:36 AM, Michal Hocko <mhocko@suse.com> wrote:
>=20
> On Tue 07-12-21 17:27:29, Michal Hocko wrote:
> [...]
>> So your proposal is to drop set_node_online from the patch and add it =
as
>> a separate one which handles
>> 	- sysfs part (i.e. do not register a node which doesn't span a
>> 	  physical address space)
>> 	- hotplug side of (drop the pgd allocation, register node lazily
>> 	  when a first memblocks are registered)
>=20
> In other words, the first stage
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index c5952749ad40..f9024ba09c53 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6382,7 +6382,11 @@ static void __build_all_zonelists(void *data)
> 	if (self && !node_online(self->node_id)) {
> 		build_zonelists(self);
> 	} else {
> -		for_each_online_node(nid) {
> +		/*
> +		 * All possible nodes have pgdat preallocated
> +		 * free_area_init
> +		 */
> +		for_each_node(nid) {
> 			pg_data_t *pgdat =3D NODE_DATA(nid);
>=20
> 			build_zonelists(pgdat);

Will it blow up memory usage for the nodes which might never be onlined?
I prefer the idea of init on demand.

Even now there is an existing problem.
In my experiments, I observed _huge_ memory consumption increase by =
increasing number
of possible numa nodes. I=E2=80=99m going to report it in separate mail =
thread.

Thanks,
=E2=80=94-Alexey


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