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b=UsCwLrRV/K35zxbIA/hIc4Id6aozHPhPLOrJUiwPAl7OYQh1taZ1K0yNEOwgg/SUt nYUi3Hdf40wr/zFLSUOd6i/TOIIK06CsD7c76CpQ+3D1YmCqljd8DdsVwbaROCzkoN bENSolqCbH0aTMxV0Uodq/7fc051LdApcEbUX5xvVe+cCt1M8fnsy4r4oEb3MGJB7Q qX5rvlwvW6KxieSCMpPyqv8bCjsxXbYmszXW7B/c4r8xxSanuHoPI9dDZ4o+A2i+7T g0mDdl8HXlxn1gl3V37kQt9jiNDzGue/0Wkgo9odCMX7acV9lcZ2eca4XgFmgikc8T J2E591DIchXmA== Message-ID: Date: Thu, 20 Aug 2026 19:46:17 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 2/2] 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" , Chen Zhang , "Zeng, Jason" , "Chen, Yu C" , "Deng, Pan" , "Li, Tianyou" , "linux-kernel@vger.kernel.org" References: <20260818085702.3395529-1-yuan1.liu@intel.com> <20260818085702.3395529-3-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: 7bit X-Stat-Signature: rg5m4db3ckamqujwrsssj4i8ngp48wpq X-Rspamd-Queue-Id: A3C761C0005 X-Rspamd-Server: rspam03 X-Rspam-User: X-HE-Tag: 1787247983-274710 X-HE-Meta: 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 hUj+0qUL 0leWuDMWnW9usV7uAzo2yJEktVtJFll6QT3CIfg6uSoQIWMNgRdjeqSZr+zdv7hb4NUZZSKOUhaftVW7zq5NdcrMYGPlNGup1AO3x5eXlK5wOWxHvJlxZ2aQWl2ZqrJetntc40Ce5bGFGtzZi/Wz9o7cOq7vL4McaT3n4ZkV1gZPiuTptpo2yCTDeI6wEBOpYrkor44I2N4OdggS2nn4fGWQyrik6wA7ybXkEHUFfTr7n1/DMQZbmn1wceM2q6xLJhWWwZ7gIl+tR4PAhg6Lwdo6nUKNAq5uEsFOfahPfogV/+TE/6KqcFTRewr2ZwwTpdr4A8J7upSac1my7bETZNyKORp7MaCtuw0kuVlJPL+03pSOFvz9b6XlH8eJPefIxzx8bA7Ct09afde24OX4prchXF2CQpfihpJqJQgDRDMSCvU8= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: >>> + online_pgcnt++; >> >> Can we avoid these helpers? >> >> const unsigned long subsection = pfn & PAGE_SUBSECTION_MASK; >> >> /* We can have section-sized online holes with VMEMMAP. */ >> if (IS_ENMABLED(CONFIG_SPARSEMEM_VMEMMAP) && >> subsection != last_subsection) { >> is_online = pfn_to_online_page(pfn); >> last_subsection = subsection; >> } >> if (is_online) >> online_pgcnt++; > > I think there may be an issue here: PAGE_SUBSECTION_MASK is not > defined when CONFIG_FLATMEM is enabled, which would result in a > build failure. Ah, yeah. > >> An alternative is an inner loop that just walks in SUBSECTION chunks until >> epfn. >> That would probably be even cleaner and faster. >> >> I remember !vmemmap always only has early sections when they are actually >> online. We could extent the comment to clarify that. > > Hi David > > What about the following approach? It removes the helper and changes > the per-PFN online check to a per-chunk check. > > + u64 pgcnt = 0, online_pgcnt = 0; > +#ifdef CONFIG_SPARSEMEM_VMEMMAP > + const unsigned long chunk = PAGES_PER_SUBSECTION; > +#else > + const unsigned long chunk = epfn - spfn; > +#endif > > - for_each_valid_pfn(pfn, spfn, epfn) { > - __init_single_page(pfn_to_page(pfn), pfn, zone, node); > - __SetPageReserved(pfn_to_page(pfn)); > - pgcnt++; > + /* > + * With VMEMMAP, subsection-sized holes can exist, and PFNs within > + * these holes can fail pfn_to_online_page(). Without VMEMMAP, we > + * always only have early sections when they are actually online. > + */ > + for (pfn = spfn; pfn < epfn; pfn += chunk) { > + const unsigned long chunk_epfn = min(pfn + chunk, epfn); > + const bool is_online = !IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) || > + pfn_to_online_page(pfn); > + unsigned long p; > + > + for_each_valid_pfn(p, pfn, chunk_epfn) { > + __init_single_page(pfn_to_page(p), p, zone, node); > + __SetPageReserved(pfn_to_page(p)); > + if (is_online) > + online_pgcnt++; > + pgcnt++; > + } I'd keep the for_each_valid_pfn() the outer loop. -- Cheers, David