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b=c82kjq0W39pptBHRiBS4ArSRK6/Fh/0s2rmqjCc9WlbqLGE75f6ygPHNtm4qaButl 0tqYtmDERj0U778/Bf1Nv4fv6QNGup9boc/EtF5hR6AWa8aYdaUlw36792pmYjaC6B YY0h9uttKA4vHNbtz66eFXFdo7Tlow1i0N9cosx6axD29kFid7nuU/Z0vmbZ5dkaEE AJjLBrk3V1X1dHg1MQd99ZAZ+q0QhiE6a7D004X40vcKNf02ETMxyU9xpu3Qr1lnaH U+42K7HpnwVkS1cZs+bkd2mK4lcgSymsOBCLk/sx8TrIRDX/+hSkZR1wFslA+wNUVZ DwXE7pU/Qvs7Q== Message-ID: Date: Fri, 27 Mar 2026 16:22:52 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug To: "Vlastimil Babka (SUSE)" , Joshua Hahn , Hao Li Cc: osalvador@suse.de, akpm@linux-foundation.org, vbabka@suse.cz, harry.yoo@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org References: <20260327143823.3063541-1-joshua.hahnjy@gmail.com> <2356614e-d9b8-4639-8e2a-96c5e4eaef61@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <2356614e-d9b8-4639-8e2a-96c5e4eaef61@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: z9pc7tmac73qm538g78pq3oue5k8ui3o X-Rspamd-Queue-Id: D9983C0012 X-Rspamd-Server: rspam09 X-HE-Tag: 1774624980-645922 X-HE-Meta: U2FsdGVkX1+QlAe3ekfjVK4piO+FCSK4tVNl1Uq4yw3F3TEStTYhnxNPrXaD5RQ7TMBVzQzcK8UL0qN63DWrS64cjrquNnQydKojsWLWlUmpK/VZKzvd8ruXwz3SMBv6DYKR8TRfbDaWFsm9bTOqV7vKMwK4ygvPylh6MO68/o9FalcMCmE4g1lfF00KDeVx2+3cMEGHZ7gZZF2lf1sel7A+DhVbo1ru2gJJ+de4b+A6aBzqNfitH5YzeWUVMuM1W5UIBOdQDkoZJY3Nh5TRMsS1jMVggobD2P1Rj8hmzD6rW/R3eYoHRi/jeIc5QIeRYqGd2JmuFmqF1wArLpfLOJEtBSePBbEa6D4QrPZm0yLWoqNFAgCycqEH+teSOhCiSCidb7nMN8zPKiHwANj7wgBbUzH0GKuXvtkpUwcPdgBZDPaB3TbQACDLzOgxKqJdjVFQQ5Nq7gMz8CF+eWekwTzZP9Ia2eD6PkMIpX7XdoVL4FjJt0HOExS2kkBv5EGz4LLRKb8xMe9q6qLo7PwcD2UEXZmmY5LyI3e7NOkNHoiGtqNLXpoZPiCk0hcCw9jzzWGVw8Eq2WuUwT8rDu7GQMQxyxrwYRQIYNr8jL+d5YaMWxd+mA1wBfSfs89Jy8ebHgsUiGOrVMw+QaC67lyV39pDAKcznDy3uJ5mqS6Gz+xkWAa5JPLCR823E8PGkE/7OTH5UINUvdrL+QlgbSaJOewivvpPyGYkB1DNLbuvIOSsDwFxvTJHf4Oo3CSKyBaGN8lK+PbIHZ9LDyZ1oR2bfnhELX4nVagQchzNqeUQtahQX04sEk9nF7q0ipThVMbTZLPSt8pdqicP/i+F12+m7rTUpN5w1UwIoV8WQTcwoN91CHp18I/UiGwdPR8xj8xs/SUY28wttUad8i2md4dAoIgkxrbFqfXX/7o739ahmf4wE1qZFd7Au8aNUO4/T20g6VDMPWcn2zesWFfciAY Fh13pQxL soKfw/Mu8qoQtaymZSq3Utmu26Ncxf51MPK1X7xKz+NqLOKL/F8HbefBv7P3QXl7hLYAyLGeBoyz3RwnvTMekOqhzWJVoYvWNOj2YKAjQ3HUqGrDzp9zd0R9lLz8nvxdoaom8o/qNxiMlFull3Noez7tFOR6BPAE4RR/KgcidSu1EjbBlq8vCrimT5mW57/Pmmzj9RS7d2MS8wLaOa+b5VFromUsX2ha7mN0L5CRXj9nxZpoB2LCKLW0ye9PQjB9QE1C3EFQEFtLVr/WHhVr3ngF30kyXVvbTKQR6Vuzei17PJp7bDFYJHkvynQC9ip+S92JHIdsgTwVHnzFYrt/1MQEVw2vLEGLJ/4SWYVjMeBqggEcjN2WGZN4w6g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/27/26 15:44, Vlastimil Babka (SUSE) wrote: > On 3/27/26 15:38, Joshua Hahn wrote: >> On Fri, 27 Mar 2026 20:42:47 +0800 Hao Li wrote: >> >> Hello Hao, >> >> I hope you are doing well, thank you for the patch! >> >>> N_NORMAL_MEMORY is initialized from zone population at boot, but memory >>> hotplug currently only updates N_MEMORY. As a result, a node that gains >>> normal memory via hotplug can remain invisible to users iterating over >>> N_NORMAL_MEMORY, while a node that loses its last normal memory can stay >>> incorrectly marked as such. >> >> The second part feels more important than the second part, doing a quick >> glance through the code I can see a few N_NORMAL_MEMORY iterators that > > Note in practice it's unlikely that a node would hotplug normal memory, > start using it, and then manage to successfully hotremove it, due to > unmovable allocations. Most likely only ZONE_MOVABLE memory can get hotremoved. Yes, hotunplug of all normal memory of a node is unlikely. Possible, but nothing to optimize for. -- Cheers, David