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b=O9I8PGtLJWa9DIBRghbCyKURocY6wNLozHNI/XwJoO+Xy5sbuUqV/kQiwg3c0Bny7 av+b7ToiQqQRoTZ/M2y1p68hSq6A7m/00VGRElsa8U2FGTmEO/qcFYcG9cDCBlRn4+ VWXe07l3Rem4dHGPLf3c5jILT9FIAmwpX8woztHMk6RfMRIkGYaaiLPczGrd73+HHp iewAeyIJObVirsAPI180O76zM208vcADCEHutE9u0ofLI0/iYA/YbH76Tzm8qDqvVL DE9IAyBY6MHrhw5UuIJ9rQU4fFVIwtUdLGGd5SuqqirzqXQnHvpb+TiY8cMJvoUJOv 8UhJQMiYEQPBQ== Message-ID: Date: Wed, 14 Jan 2026 12:13:14 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 2/2] mm/memory hotplug/unplug: Optimize zone->contiguous update when changes pfn range To: "Li, Tianyou" , Oscar Salvador , Mike Rapoport , Wei Yang Cc: linux-mm@kvack.org, Yong Hu , Nanhai Zou , Yuan Liu , Tim Chen , Qiuxu Zhuo , Yu C Chen , Pan Deng , Chen Zhang , linux-kernel@vger.kernel.org References: <20251222145807.11351-1-tianyou.li@intel.com> <20251222145807.11351-3-tianyou.li@intel.com> <2786022e-91ba-4ac3-98ef-bf7daad0467a@kernel.org> From: "David Hildenbrand (Red Hat)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: CF1C6180010 X-Stat-Signature: 5yw46zwgzn3h3tkfg1p7razq1c33wuz1 X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1768389200-761045 X-HE-Meta: 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 gefINFMw ojCXc3dSkwO4s6W0d4bwCPxWjn97D3dSFlzG1bYjb8YamNfiLZVIUsQqabhCK2hmXsHQlmYmcXXsx3gesnkdSQH85ubPoGm668akzLbzJsrfOeIJQLN178NwwpRMJL2nT9eSLF1XSO+Su/iMk95fUmmGeXUGvFDv+DPcbodcWzhXQAQQhX1zNmQ1OwM/dpjoH6udlYcZJTg9LbBDFAG4aCPB5upaChTFFMOwxGjfQWXbSAXvDzxCIWgtn/PKa7PmI0V+QBCWaEQmV0LDk/ED2gWdFsVJuUP9yAWhSPgXKJ2jYfkAl6P+zmmIolfpyKUNhPfvI6/fJaOvkySQ= 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: >> >> This is nasty. I would wish we could just leave that code path alone. >> >> In particular: I am 99% sure that we never ever run into this case in >> practice. >> >> E.g., on x86, we can have up to 2 GiB memory blocks. But the memmap of >> that is 64/4096*2GiB == 32 MB ... and a memory section is 128 MiB. >> >> >> As commented on patch #1, we should drop the set_zone_contiguous() in >> this function either way and let online_pages() deal with it. >> >> We just have to make sure that we don't create some inconsistencies by >> doing that. >> >> Can you double-check? I thought about this some more, and it's all a bit nasty. We have to get this right. Losing the optimization for memmap_on_memory users indicates that we are doing the wrong thing. You could introduce the set_zone_contiguous() in this patch here. But then, I think instead of + /* + * If the allocated memmap pages are not in a full section, keep the + * contiguous state as ZONE_CONTIG_NO. + */ + if (IS_ALIGNED(end_pfn, PAGES_PER_SECTION)) + new_contiguous_state = zone_contig_state_after_growing(zone, + pfn, nr_pages); + We'd actually unconditionally have to do that, no? -- Cheers David