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b=jVDnwyuVrbu8xmITUkewRJXdiCkGi85k5+li2u7HyhGmXFfz4BbFRkDNfIpL9WDUE qlumkyj9GRy1Veh3uHqgNq7tR11Wo/u3XjPYkfzgxfUtNu0bnAiV6iW//9ag6tvjKp TlVD6Cc+Wp9RFTvCWcKfBTsqC+A2BDLHrJAqfWtlU5qspp8st7bIyUYhqAW4ocpYkv Ov+DIl+0w0ZJRyZViZbYl1GTB5pm0tWNipd2etEMHnoI7Hn7qT7Itdq0ydoIfAsjYe ywiicx4HXX1lfD/IPg2IPGHEAFxgXJhYzgBeJvhpKNNtosjydaGxeo8ID0D/n3LV2g nVMFd4bckyYGQ== Message-ID: <2cbd42e1-b5bb-474c-b0e7-ce3f46541891@kernel.org> Date: Thu, 6 Aug 2026 10:45:36 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 1/2] mm/memory_hotplug: optimize zone contiguous check when changing pfn range To: "Liu, Yuan1" , Oscar Salvador , Mike Rapoport , Wei Yang Cc: "linux-mm@kvack.org" , "Zou, Nanhai" , "Deng, Pan" , "Li, Tianyou" , Chen Zhang , "Zeng, Jason" , "linux-kernel@vger.kernel.org" References: <20260723084946.189392-1-yuan1.liu@intel.com> <20260723084946.189392-2-yuan1.liu@intel.com> 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: cdmoz8yanxaxefuqbixq88nh1t4cakjy X-Rspamd-Queue-Id: AD6971C000E X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1786005942-791274 X-HE-Meta: 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 sbV1M1CI tR4pfjWJFckKvbJVIpkjnxcyhVd1576eTb+sOEpNxb6pm8f1X+3fmBjzR1XWwF8TgmEaQyskucr99hKXbP695yyhhtNWEdhAkj1C6ZCeSwSl8ny41iiGuscClaKB50tuBQ5UT5JilLLw1bv/sH8FwSDvV37t1uGWMxuxl7jgITp4Xy2yXd9E0QEAC17/dI/LclQXkhSSWLwaij9xYiEA+rjvmaudy5SWlO9T9vmgHxhLEclcO1/vKnWVFMuScq/dqjmTSalMEbtsddqd3wUuOgMqAgRnvlSMCHggCqj6LhSsFS3x6c4hIBnBuE/bFP5AEmt7jdhY+8QOcT0sTRoD0MrQVjmdufZgsioz04d5+/jPu5hSq4yMqQ6bwqC4BKuXtTYscwVEo1rxCPAoiLCuFS64tAt1Yf6VgGvgpYB/37rzuc+EURaMmd35nZ0j47NxkKHBz Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: >>> +static void __init update_zone_online_memmap_pages(struct zone *zone, >>> + unsigned long start_pfn, >>> + unsigned long end_pfn, >>> + unsigned long *hole_pfn) >>> +{ >>> +#ifdef CONFIG_SPARSEMEM_VMEMMAP >>> + unsigned long zone_start_pfn = zone->zone_start_pfn; >>> + unsigned long zone_end_pfn = zone_start_pfn + zone->spanned_pages; >> >> These two can be const. > > Will do. > >>> + unsigned long sub_start, sub_end; >>> + >>> + sub_start = max(ALIGN_DOWN(start_pfn, PAGES_PER_SUBSECTION), >>> + zone_start_pfn); >>> + sub_end = min(ALIGN(end_pfn, PAGES_PER_SUBSECTION), zone_end_pfn); >> >> Hm, I don't immediately understand why we do the PAGES_PER_SUBSECTION >> thing >> here. Why is that required? > > pages_with_online_memmap counts all PFNs where pfn_to_online_page() is > valid. With CONFIG_SPARSEMEM_VMEMMAP, pfn_section_valid() operates at > PAGES_PER_SUBSECTION granularity — when any page in a subsection has > memory, the entire subsection is valid/online. So we align to subsection > boundaries to include hole pages within partially-populated subsections. But we must never account exceeding the zone range. So I don't understand why we would have to care about PAGES_PER_SUBSECTION here at all? -- Cheers, David