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[2003:cb:c73d:2400:3be1:a856:724c:fd29]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-441b8a31695sm126153245e9.40.2025.05.05.01.12.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 05 May 2025 01:12:51 -0700 (PDT) Message-ID: <0e568e33-34fa-40f6-a20d-ebf653de123d@redhat.com> Date: Mon, 5 May 2025 10:12:48 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/3] driver/base: Optimize memory block registration to reduce boot time To: Oscar Salvador Cc: Donet Tom , Mike Rapoport , Zi Yan , Greg Kroah-Hartman , Andrew Morton , rafael@kernel.org, Danilo Krummrich , Ritesh Harjani , Jonathan Cameron , Alison Schofield , Yury Norov , Dave Jiang , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <188fbfba-afb4-4db7-bbba-7689a96be931@redhat.com> <74c500dd-8d1c-4177-96c7-ddd51ca77306@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: -JpHEBTpnOMGruOkLGUddvvnU1gACXlo4NY3g7WeIOE_1746432772 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: abdfgpm1e4t7hicx3s9yzp51cgkto7n1 X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: D795BA0009 X-Rspam-User: X-HE-Tag: 1746432776-410672 X-HE-Meta: U2FsdGVkX1/tcLi7tbIvgLfA34cBj8kkWk8Jztiaq0YZddp3e0ZgMROGTFcph2KSVhrEDNJNY2SaO09fCE99o4JOiTzHKix3qTfnfKtKPSl3/ioyU56Y1tfx1itJ0x6zGkCIuavzuxeK6BlzbU1+zb9MjUROjVX6Ys6JiToRdWRBRCrIE0M2LNLMGYQWGMi6LdOc+hjaq120khNfjSBwXG2T8H7NLHTZnXcyToPYeoM7wZkIueckyjr0II720qzDw3ntrAB/46opynYhgAZfbMXCCwn8uhYjZYgcEzzBe1F5vz/cL7jMPHmibM+lH8Djes8zFgpFZZrCHwjUyjOzSjxM5MEqmdvSwHSqC9Nqd5r37JWlhnm18y6gFn5vnveXtZcT+5hjurzFIRN1rvKWMZs4KZV/vXtoMlzq8h3KIOk9GVCyqzf7+fuPHn+UMVJmRARy4jQ5b1THXMFFSELEsDN7QMWlnSyR2WctpqAX3+73QstTeGT9Urjbctxc8SjgF6rWWu6eaGppPdKYVm7hkmi8rg1/pMbgwl/x64lpDmChq+vFovThc0R8/Z1hBQ05RN3fARyEvsgWLwvh6e3lku2QqHQPxIrRXY5MCUFkWCbY6lx8clTzURjDDrjjHSZmL5Avs5cHeM13bG+/hyYFdvQtTXEJppG1lWeuY1M2Ib4BDbxrhwS9MT5l4T2Vz83ytouLknLQoz89tbUP+8Y7W4dxq1oetK5ABdlKsm95k50xKX0AJeB7B4u2508gNEf+4DVz8PL2HdiDBOKkfhMMw6rV2fOtyN1Hpz7ntZs6jtewj6YSgCP2nJ+ZtdJPd6x+vA49XspYKqRSfytRDeR3mvj0ecBwCOnKAQrLD9TIefg3rL5D8cY88fgusWVdVGz1lNPaLppogy3BOn2pvzY2NXSJuno+d+ITxHqV3LXdQUUABFGKyYrR8sOLRpdmY3HHlwy6/t8AHz25rs3dSLY mbEjh5OQ SE9exmxQ4AZxiJXif7xr3O6rBn6npjDmecKlZ4tt9JvWdHvJ+8yUps+LpmiZM+bfTz3wIxYtyvvFwbmjlXu6bns6r+kfimlvAVIlV3NK3AKE5bIY8+hpTom1VTPgM6xPG39bIOWeJRkesRgu5T0CR/umM9g== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 05.05.25 09:57, Oscar Salvador wrote: > On Mon, May 05, 2025 at 09:38:43AM +0200, David Hildenbrand wrote: >> On 05.05.25 09:28, Oscar Salvador wrote: >>> On Mon, May 05, 2025 at 09:16:48AM +0200, David Hildenbrand wrote: >>>> memory hotplug code never calls register_one_node(), unless I am missing >>>> something. >>>> >>>> During add_memory_resource(), we call __try_online_node(nid, false), meaning >>>> we skip register_one_node(). >>>> >>>> The only caller of __try_online_node(nid, true) is try_online_node(), called >>>> from CPU hotplug code, and I *guess* that is not required. >>> >>> Well, I guess this is because we need to link the cpus to the node. >>> register_one_node() has two jobs: 1) register cpus belonging to the node >>> and 2) register memory-blocks belonging to the node (if any). >> >> Ah, via __register_one_node() ... >> >> I would assume that an offline node >> >> (1) has no memory >> (2) has no CPUs > > That is right. > >> When we *hotplug* either memory or CPUs, and we first online the node, there >> is nothing to register. Because if there would be something, the node would >> already be online. > > I think I do not understand this, but let us imagine the following > scenario: > > - You craft a VM with qemu that has a numa node which is memoryless and cpuless. > This node will be allocated in free_area_init()->alloc_offline_node_data() but > it will not be marked online because it does not have any resources. > > Then if you create a cpu device and hotplug in there, this will > trigger try_online_node() from the cpu callback and go all the way to > __register_one_node() to link the hotplugged cpu to the corresponding node. Assume you hotplug the second CPU. The node is already registered/online, so who does the register_cpu_under_node() call? It's register_cpu() I guess? But no idea in which order that is called with node onlining. The code has to be cleaned up such that onlining a node does not traverse any cpus / memory. Whoever adds a CPU / memory *after onlining the node* must register the device manually under the *now online* node. Maybe we have to adjust CPU hotplug code if the existing register_cpu_under_node() is misplaced. register_cpu_under_node() has this weird !node_online check in there ... ... it's a mess > > Now, I do not see an issue with that. > The only think that makes me go "meh", is that register_one_node() > calls register_memory_blocks_under_node() blindly when there might not > be any memory block to register (I am sure we bail out if we see that > somewhere, but still feels kinda of "wrong"? Yes -- Cheers, David / dhildenb