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[2003:cb:c73d:2400:3be1:a856:724c:fd29]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-441b8a288f0sm128698705e9.27.2025.05.05.03.36.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 05 May 2025 03:36:22 -0700 (PDT) Message-ID: Date: Mon, 5 May 2025 12:36:21 +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> <0e568e33-34fa-40f6-a20d-ebf653de123d@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: vl9Pzyu1Psj_eY565zYB2CP3XI6A6_f9LIQc7b9HvLE_1746441384 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: E3633140004 X-Stat-Signature: 15tsdqqhwgkz1sxgttodo1fgsnbnhtg4 X-HE-Tag: 1746441386-595960 X-HE-Meta: U2FsdGVkX19rQvwWCviRO4MdNh/fQHOu0IOgRN3lm/lBV4zR4slo1kpeovyCPlyB4/eu7a9F4Gk+3/FpxEZIcTJo9MvB6jIW+U+GPxVOFpE0l8IXb6phQdBNnOyH7KHtfvK8oy/fr8vJS2PWxtvAf9GGo9WZfTBK5StM/CzqrmYO8fAhoMx34KpCeuuVuhzz3XK5E1+xriQ9LrKwir8D7/71i+cvFnYzWn34+lUDBl9uTD72IJJaZXZcbQryqggFVZI1wtD4WBXPH2pwq6v0adOwtpSTTlovsW35c/F/nV9pMHG/AXuH5M+9sJi1hy7U3uDirnKyzgxwdD5zmo8NHmIZTgDUjM/7vRKjQzhtKyk0HN0GRJFfIc2+xF/IIhrxAzlMHcazjawfOafzthGxrnbuKayYutwf02z4tN2TazkDxdV44Ka/8130D5UVmXNhMiHVdn/JNzdJCJknXoKXqie3eikp0jRfdDNuY1Kk/GHZ/BpgYaas5RLsq65f47aozDvgZIo66rNw2/wNjmzwJxOTc9aBLboEE/oTSDWVuUrfFY1qLaDvqKys+g7lO97JdgmWpkogfOQjM5grZ5pf2jkLVs45k9Gb68bHi1rswvOQlTkFJTuWgcQONtaBtKCVHoLfqF/T/bFYxJ86iMNBZC/PC2YY2UpqhxWQtS2jmyYZJzebqWThNmNgY0E6+hyeYRKD31iHL6V7W/X2Kmg+7DgraCkyhj+gWqUO+YI687iZt9VwZiciLiDPIZlsVXNOiOGpX9X596dmOD7dhnj3hU0ammuxQNC5RFO8+z+JpQAjQxpSLpwKeNLZLgnliA8bygf012wsb6doc7wgyY06Tl1otrpAcH7yTWh6IiymfGEZOkR75hCfeQXK9BkrGXT9g2wto+AGltFQzXl1iGXIoa9/3HipCW3ywrr75jUyTBvO33YiwxdzXReFOVSsYmqOGBEDaUAXR9OFxOsywYW 4yhV8Hnc 0gc7pABvtgSYVcaV/T+P8dLh5ofFix+5zp5fexE1CPMGJp0q+eK5PYkmPF8trB6q3vK30pBWmVEWXXK7hYhMY5ZJX1rj9GH7BxRTzZHqJ1TYSidS3rUlw+l182BPz0c3UIrz6RyutSsO99arXwt9H4CaLZTgSUL28/BjbKdJYxt00pnPXr41xLgVGG/6rhyEI5p2/LlRdWhTezAYBhPY+1c6kiZ3HlQZVZIEytRLlzBzsxWEP+z+g/uLbp5QR2aEluhAiuIcp7/qf5sYbX8eWSIpXkfTTF/MKfTqFGtNWbHHtjCDUgn0SSv1RTOXBAC+ByahiRklR1ob//g3Lm0ghnrBVdp7350yt8lhVhALo4zhaGZQ2NNnTU2W1JZl+lSvyuznmPOiuBeubthdGfRRERH+Vr7EBCXPdXBQm2FG5D/hIdzQyrhB0syiPmbDzLGAo7gZpfx2KyGDy00J6d8OTJXozGD12oVa9jcwU 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 11:36, Oscar Salvador wrote: > On Mon, May 05, 2025 at 10:12:48AM +0200, David Hildenbrand wrote: >> 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. > > So, I think this is the sequence of events: > > - hotplug cpu: > acpi_processor_hotadd_init > register_cpu > register_cpu_under_node > > online_store > device_online()->dev_bus_online() > cpu_subsys->online() > cpu_subsys_online > cpu_device_up > cpu_up > try_online_node <- brings node online > ... > register_one_node <- registers cpu under node > _cpu_up My thinking was, whether we can simply move the register_cpu_under_node() after the try_online_node(). See below regarding early. And then, remove the !node_online check from register_cpu_under_node(). But it's all complicated, because for memory, we link a memory block to the node (+set the node online) when it gets added, not when it gets onlined. For CPUs, we seem to be creating the link + set the node online when the CPU gets onlined. > > The first time we hotplug a cpu to the node, note that > register_cpu()->register_cpu_under_node() will bail out as node is still > offline, so only cpu's sysfs will be created but they will not be linked > to the node. > Later, online_store()->...->cpu_subsys_online()->..->cpu_up() will take> care of 1) onlining the node and 2) register the cpu to the node (so, > link the sysfs). And only if it actually gets onlined I assume. > > The second time we hotplug a cpu, > register_cpu()->register_cpu_under_node() will do its job as the node is > already onlined. > And we will not be calling register_one_node() from __try_online_node() > because of the same reason. > > The thing that bothers me is having register_cpu_under_node() spread > around. Right. > I think that ideally, we should only be calling register_cpu_under_node() > from register_cpu(), but we have this kinda of (sort of weird?) relation > that even if we hotplug the cpu, but we do not online it, the numa node > will remain online, and so we cannot do the linking part (cpu <-> node), > so we could not really only have register_cpu_under_node() in > register_cpu(), which is the hot-add part, but we also need it in the > cpu_up()->try_online_node() which is the online part. Maybe one could handle CPUs similar to how we handle it with memory: node gets onlined + link created as soon as we add the CPU, not when we online it. But likely there is a reason why we do it like that today ... > > And we cannot also remove the register_cpu_under_node() from > register_cpu() because it is used in other paths (e.g: at boot time ). Ah, so in that case we don't call cpu_up ... hm. Of course, we can always detect the context (early vs. hotplug). Maybe, we should split the early vs. hotplug case up much earlier. register_cpu_early() / register_cpu_hotplug() ... maybe -- Cheers, David / dhildenb