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b=WlD8MKaUgx0yamc8h91fzZpUq+67Jj9i2OaP2jc0DoDFTbLwN9NDh1giPE8DcEJAz 8QWzyr2rLUvwsXjaUtU6g7x2xqFukPXEX5DFPVrrWpAp8KVHpLmXAfibyQaYG0DoHu X2n7EiLG27ZV6U4BpIQotcFuxlULVn6OWfchYpZncZeDU2n2fXWOiiDF+NvyfxOdLu ZMxE6Bl8h5EHVZd78B1q8CztRTwFAtCeqaT28dtbKsRpowV0rEIATOCZYAw14xPuo8 3Q0h0CLxLrJbKw1Fi34UpGfNSNU02cwvUYxH+xXZJUoUr4mYQ+0YEVE3GZkw5TFyzW lwkbI4TJnWnjg== Message-ID: <462b217c-a422-4818-bac1-7f204f32fa29@kernel.org> Date: Tue, 22 Sep 2026 15:55:13 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 0/2] mm/memory_hotplug: optimize zone contiguous check when changing pfn range To: Yuan Liu , Oscar Salvador , Mike Rapoport , Wei Yang Cc: linux-mm@kvack.org, Nanhai Zou , Chen Zhang , Jason Zeng , Chen Yu , Pan Deng , Tianyou Li , linux-kernel@vger.kernel.org References: <20260920084946.3266279-1-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: <20260920084946.3266279-1-yuan1.liu@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: zgd4zke84uucqneq77cfp8qj9u5tjyby X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 8769C40007 X-HE-Tag: 1790085322-748949 X-HE-Meta: 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 YDcW986V lonPaKUutop1jEf/v0c+9g44++DK6NfjZvXR22XHw82PkNKMsbPcivixLVoZKAu7dX9x7TtJ+7h574+MNmYWsO3otvpz0aoWvB998gizGZDfm5vaUzqDx+gmRGkrhs5WsfJq63VpFbFy+O8CeMNsBKywAJGvevHLdTK2PxE9Zg7v6oZKElTHyhUw9tyQqQHTwQF5lcuAOZSSRrOzW8r1NpYUbHIztvvvsteZnVF4GwVRwB6fZjW8FRix1JZ6RRUlMVyxp4Y72jyFigjDD3rAZ7EfdPPtdPlpBTRRS6VsVb1XBK32zWvJHXAsOYI4xEYDMMUuMktlh5WhjadJCeWmJ/ICi+sOJiopfIghhOIzUPkGHACadPntPORSb+AiCq62c+qRw80bwu4yAlTSqasvTF1VWXA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/20/26 10:49, Yuan Liu wrote: > This series introduces a pages_with_online_memmap member into struct > zone to avoid pageblock-by-pageblock scans across the entire zone and > improve memory hotplug performance. > > Approach > ======== > Add a new zone member, pages_with_online_memmap, that tracks the > number of pages within the zone span that have an online memory map, > including present pages and memory holes whose memory map has been > initialized and for which pfn_to_online_page() succeeds. > > For early boot memory, pages_with_online_memmap is calculated in > memmap_init_zone_range(). PFNs initialized by memmap_init_range() are > included in pages_with_online_memmap, and hole PFNs for which > pfn_to_online_page() succeeds are also counted in > init_unavailable_range(). For hotplugged memory, > pages_with_online_memmap is updated through adjust_present_page_count(), > which is called during memory online and offline operations. When > spanned_pages == pages_with_online_memmap, every PFN in the zone span > has a valid memmap entry, so pfn_to_page() can be called for any PFN > within the zone span without an additional pfn_valid() check. > > Note: this counter may temporarily undercount when pages with an > online memory map exist outside the current zone span. Such pages > are only created during boot, when initializing the memory map of > pages that do not fall into any zone span. The undercount itself > can only happen after boot, during memory hotplug, when growing > the zone to cover such pages and later shrinking it back, which > may result in a "too small" value. This is safe: it merely > prevents detecting a contiguous zone. > > The contiguity check using pages_with_online_memmap is stricter than > the old pageblock-by-pageblock scan. The old set_zone_contiguous() > iterated at pageblock granularity via pageblock_pfn_to_page(), so a > zone could be marked contiguous even if a subsection-sized hole > existed within a pageblock. The new check requires > spanned_pages == pages_with_online_memmap, meaning every PFN in the > zone span must satisfy pfn_to_online_page(). > > Performance > =========== > 1. For VM hotplug performance data, please refer to Patch 2. > 2. This series also benefits CXL hotplug. Performance results are > as follows > https://lore.kernel.org/all/20260409023552.GA2807@AE/ > > Tested cases > ============ > 1. Hotplug/unplug correctness with both online_movable and online > policies, including partial unplug, middle-block offline gaps, and > edge-block span shrink. > 2. Large scale (256G/512G) plug/unplug performance. > 3. Boot-time subsection holes (aligned/unaligned, in-zone and > cross-zone) with correct pages_with_online_memmap accounting. > 4. kernelcore=mirror: verified no overcounting. > > Patch overview > ============== > Patch 1 makes shrink_zone_span() more robust when memory/hole boundary > falls within a subsection. It checks the full subsection range to avoid > incorrectly shrinking the zone span during memory unplug. > > Patch 2 introduces pages_with_online_memmap to replace > pageblock-by-pageblock scans across the entire zone for zone contiguity > checks. > > v10 changes: > 1. Rebased onto v7.3-rc3. > 2. Added Acked-by: Mike Rapoport (Microsoft) on patch 2 and reworded > the init_unavailable_range() comment as suggested. Thanks, I'm planning on queuing this tomorrow. -- Cheers, David