From: David Hildenbrand <david@redhat.com>
To: Mike Rapoport <rppt@kernel.org>
Cc: Wei Yang <richard.weiyang@gmail.com>,
Michal Hocko <mhocko@suse.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
Alexey Makhalov <amakhalov@vmware.com>,
Dennis Zhou <dennis@kernel.org>,
Eric Dumazet <eric.dumazet@gmail.com>,
Oscar Salvador <osalvador@suse.de>, Tejun Heo <tj@kernel.org>,
Christoph Lameter <cl@linux.com>, Nico Pache <npache@redhat.com>,
Rafael Aquini <raquini@redhat.com>
Subject: Re: [PATCH 2/6] mm: handle uninitialized numa nodes gracefully
Date: Thu, 3 Feb 2022 10:11:21 +0100 [thread overview]
Message-ID: <15ad305f-a147-4a9c-35e5-bb0a868499ad@redhat.com> (raw)
In-Reply-To: <YfubhocKKKWgKlEq@kernel.org>
On 03.02.22 10:08, Mike Rapoport wrote:
> On Thu, Feb 03, 2022 at 09:27:16AM +0100, David Hildenbrand wrote:
>> On 03.02.22 08:23, Mike Rapoport wrote:
>>> On Thu, Feb 03, 2022 at 12:21:16AM +0000, Wei Yang wrote:
>>>> On Tue, Feb 01, 2022 at 10:54:37AM +0100, Michal Hocko wrote:
>>>>> On Tue 01-02-22 02:41:19, Wei Yang wrote:
>>>>>> On Thu, Jan 27, 2022 at 03:47:40PM +0100, Michal Hocko wrote:
>>>>>> [...]
>>>>>>>>> + /*
>>>>>>>>> + * not marking this node online because we do not want to
>>>>>>>>> + * confuse userspace by sysfs files/directories for node
>>>>>>>>> + * without any memory attached to it (see topology_init)
>>>>>>>>> + * The pgdat will get fully initialized when a memory is
>>>>>>>>> + * hotpluged into it by hotadd_init_pgdat
>>>>>>>>> + */
>>>>>>
>>>>>> Hmm... which following step would mark the node online? On x86, the node is
>>>>>> onlined in alloc_node_date(). This is not onlined here.
>>>>>
>>>>> The comment tries to explain that this happens during the memory
>>>>> hotplug. Or maybe I have missed your question?
>>>>>
>>>>
>>>> I am not sure for others, while the comment confused me a little.
>>>>
>>>> Currently in kernel, there are two situations for node online:
>>>>
>>>> * during memory hotplug
>>>> * during sys-init
>>>>
>>>> For memory hotplug, we allocate pgdat and online node. And current hot-add
>>>> process has already put them in two steps:
>>>>
>>>> 1. __try_online_node()
>>>> 2. node_set_online()
>>>>
>>>> So emphasize "not online" node here, confuse me a little. It is a natural
>>>> thing to not online node until it has memory.
>>>>
>>>> But from another point of view, the comment here is reasonable. During
>>>> sys-init, we online node at the same time when creating pgdat. And even for
>>>> memory-less node on x86, we online them too.
>>>>
>>>> Well, this is all about the comment. I have tried to grab may head but not
>>>> come up with a better idea.
>>>>
>>>> Or maybe this is just my personal feeling, don't bother if no-one else feel
>>>> like this.
>>>
>>> I shuffled the words a bit, maybe this sounds better not only to me :)
>>>
>>> /*
>>> * We do not want to confuse userspace by sysfs files/directories for node
>>> * without any memory attached to it, so this node is not marked as
>>> * N_MEMORY and not marked online so that topology_init() won't create
>>> * sysfs hierarchy for this node. The pgdat will get fully initialized by
>>> * hotadd_init_pgdat() when memory is hotpluged into this node
>>> */
>>>
>>
>> Note that the topology_init() part might change soon [1] so maybe we
>> want to rephrase that to "so that no sysfs hierarchy will be created via
>> register_one_node() for this node." right away.
>
> Heh, this will be your responsibility to update the comment here when you
> post non-RFC version ;-)
I'm usually sending patches against Linus' tree. And I'll post non-RFC
most probably today (after testing on aarch64) ;)
So I'd appreciate if we could just phrase it more generically, as I
tried. But of course, we can try making my life harder ;)
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2022-02-03 9:11 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-27 8:52 [PATCH 0/6] mm, memory_hotplug: handle unitialized numa node gracefully Michal Hocko
2022-01-27 8:53 ` [PATCH 1/6] mm, memory_hotplug: make arch_alloc_nodedata independent on CONFIG_MEMORY_HOTPLUG Michal Hocko
2022-01-27 12:27 ` David Hildenbrand
2022-01-27 13:36 ` Mike Rapoport
2022-01-28 6:18 ` Oscar Salvador
2022-02-01 2:13 ` Wei Yang
2022-01-27 8:53 ` [PATCH 2/6] mm: handle uninitialized numa nodes gracefully Michal Hocko
2022-01-27 12:41 ` David Hildenbrand
2022-01-27 14:50 ` Michal Hocko
2022-01-27 13:37 ` Mike Rapoport
2022-01-27 14:47 ` Michal Hocko
2022-01-27 15:04 ` Mike Rapoport
2022-02-01 2:41 ` Wei Yang
2022-02-01 9:54 ` Michal Hocko
2022-02-03 0:21 ` Wei Yang
2022-02-03 7:23 ` Mike Rapoport
2022-02-03 8:27 ` David Hildenbrand
2022-02-03 9:08 ` Mike Rapoport
2022-02-03 9:11 ` David Hildenbrand [this message]
2022-02-03 9:19 ` Michal Hocko
2022-02-03 9:21 ` David Hildenbrand
2022-02-03 8:39 ` Michal Hocko
2022-02-04 22:54 ` Andrew Morton
2022-01-28 6:27 ` Oscar Salvador
2022-01-31 10:34 ` Michal Hocko
2022-01-27 8:53 ` [PATCH 3/6] mm, memory_hotplug: drop arch_free_nodedata Michal Hocko
2022-01-27 12:42 ` David Hildenbrand
2022-01-27 13:37 ` Mike Rapoport
2022-01-28 6:29 ` Oscar Salvador
2022-02-01 2:41 ` Wei Yang
2022-01-27 8:53 ` [PATCH 4/6] mm, memory_hotplug: reorganize new pgdat initialization Michal Hocko
2022-01-27 12:46 ` David Hildenbrand
2022-01-27 14:44 ` Michal Hocko
2022-02-17 10:40 ` Oscar Salvador
2022-01-27 13:39 ` Mike Rapoport
2022-01-27 14:45 ` Michal Hocko
2022-01-28 10:51 ` Oscar Salvador
2022-02-01 2:42 ` Wei Yang
2022-01-27 8:53 ` [PATCH 5/6] mm: make free_area_init_node aware of memory less nodes Michal Hocko
2022-01-27 12:47 ` David Hildenbrand
2022-01-27 13:34 ` Mike Rapoport
2022-01-28 10:59 ` Oscar Salvador
2022-02-01 2:43 ` Wei Yang
2022-01-27 8:53 ` [PATCH 6/6] memcg: do not tweak node in alloc_mem_cgroup_per_node_info Michal Hocko
2022-01-27 12:50 ` David Hildenbrand
2022-01-28 11:01 ` Oscar Salvador
2022-02-01 2:45 ` Wei Yang
2022-02-01 9:51 ` Michal Hocko
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=15ad305f-a147-4a9c-35e5-bb0a868499ad@redhat.com \
--to=david@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=amakhalov@vmware.com \
--cc=cl@linux.com \
--cc=dennis@kernel.org \
--cc=eric.dumazet@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@suse.com \
--cc=npache@redhat.com \
--cc=osalvador@suse.de \
--cc=raquini@redhat.com \
--cc=richard.weiyang@gmail.com \
--cc=rppt@kernel.org \
--cc=tj@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).