Message-ID: <f9786109-518f-38d4-0270-a3e87a13c4ef@redhat.com>
Date:   Tue, 7 Dec 2021 19:03:28 +0100
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To:     Alexey Makhalov <amakhalov@vmware.com>
Cc:     Michal Hocko <mhocko@suse.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>
References: <1043a1a4-b7f2-8730-d192-7cab9f15ee24@redhat.com>
 <Ya9P5NxhcZDcyptT@dhcp22.suse.cz>
 <ab5cfba0-1d49-4e4d-e2c8-171e24473c1b@redhat.com>
 <Ya9gN3rZ1eQou3rc@dhcp22.suse.cz>
 <77e785e6-cf34-0cff-26a5-852d3786a9b8@redhat.com>
 <Ya992YvnZ3e3G6h0@dhcp22.suse.cz>
 <b7deaf90-8c3c-c22a-b8dc-e6d98bc93ae6@redhat.com>
 <Ya+EHUYgzo8GaCeq@dhcp22.suse.cz>
 <d01c20fe-86d2-1dc8-e56d-15c0da49afb3@redhat.com>
 <Ya+LbaD8mkvIdq+c@dhcp22.suse.cz> <Ya+Nq2fWrSgl79Bn@dhcp22.suse.cz>
 <2E174230-04F3-4798-86D5-1257859FFAD8@vmware.com>
 <21539fc8-15a8-1c8c-4a4f-8b85734d2a0e@redhat.com>
 <78E39A43-D094-4706-B4BD-18C0B18EB2C3@vmware.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
Subject: Re: [PATCH v3] mm: fix panic in __alloc_pages
In-Reply-To: <78E39A43-D094-4706-B4BD-18C0B18EB2C3@vmware.com>
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On 07.12.21 18:17, Alexey Makhalov wrote:
> 
> 
>> On Dec 7, 2021, at 9:13 AM, David Hildenbrand <david@redhat.com> wrote:
>>
>> On 07.12.21 18:02, Alexey Makhalov wrote:
>>>
>>>
>>>> On Dec 7, 2021, at 8:36 AM, Michal Hocko <mhocko@suse.com> wrote:
>>>>
>>>> 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)
>>>>
>>>> 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 = NODE_DATA(nid);
>>>>
>>>> 			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’m going to report it in separate mail thread.
>>
>> I already raised that PPC might be problematic in that regard. Which
>> architecture / setup do you have in mind that can have a lot of possible
>> nodes?
>>
> It is x86_64 VMware VM, not the regular one, but specially configured (1 vCPU per node,
> with hot-plug support, 128 possible nodes)  

I thought the pgdat would be smaller but I just gave it a test:

On my system, pgdata_t is 173824 bytes. So 128 nodes would correspond to
21 MiB, which is indeed a lot. I assume it's due to "struct zonelist",
which has MAX_ZONES_PER_ZONELIST == (MAX_NUMNODES * MAX_NR_ZONES) zone
references ...

-- 
Thanks,

David / dhildenb