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b=OzV1Iic2K0TUMTrBbT5fK8X7C6A4aWz4pzAe1tPMBnx2TNo1FW33ZkD7Z9ZhYEHYX udfnJ64qUWrQJoRZAdTf2ftf16YShoGKjSjv3CaTjsdCeN4mz8ziGZW/yIdOsv7kjB UFIm/no8sqYVSrF+wVlV0cgar5KDdyFdUARp+cKOlyLRt3zPJnKHBxp7k3nt5GTYsc AK2wUk4OhuJJk99B+3K2oFhMNQBlyXQCOsH8LDFQvZXpYXW9Z1yY8LjKUMcNzAb+Z3 iX6u6RGXIVCQz9xKP4RSZBVgjiOHYu9710GYkZiqa5QPIaxp69RIZdIfBX3ZG/UgnD Cwj1Yo3RS+uTA== Message-ID: <9c807ff8-b4ad-43d5-8034-ec7fcd0fe5d6@kernel.org> Date: Tue, 6 Jan 2026 19:46:25 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7] page_alloc: allow migration of smaller hugepages during contig_alloc To: Gregory Price , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, vbabka@suse.cz, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, richard.weiyang@gmail.com References: <20251221124656.2362540-1-gourry@gourry.net> 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: CEE661C000B X-Stat-Signature: hmpeearm7ajp7tk74yoc11nst5okmn8i X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1767725192-955311 X-HE-Meta: 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 sSZ07Lta 5yn76RanMUb+T/jZ2swdbhBYl786rEnAGNahBU8M10ZWnPaOo8qB/rsLjByxmy/yUrhDB+cfOBVyPpB98E2wS9tN1hccpgCcBf9inaIZwX7h/sh00m3I4ndBsruuoFctRnuWBG36/xdZJULS1DuIKfRiO2eyf6wJw2GBPoodAa9apXLaVdh+KuLf4YrOnA6InhpClgKIEuLoTk2vvIRZndnFJiUWroBbKHE/ZPTWogAJB/sUWK6oKcfmH5Icmz1n0/fo4tVVYEzeZJjVz9gNMbDySzkELk2/TRCcnRsP2/fahQ8BSTwPc7nmp7SXMhZvmxq+I/sLFKaG9RFV6qMx89sDj8KoPRVbR8NpRUwXOuY90QmTta27sjUVn2Q== 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: > - return false; > + /* > + * Only consider ranges containing hugepages if those pages are > + * smaller than the requested contiguous region. e.g.: > + * Move 2MB pages to free up a 1GB range. > + * Don't move 1GB pages to free up a 2MB range. > + * > + * This makes contiguous allocation more reliable if multiple > + * hugepage sizes are used without causing needless movement. > + */ > + if (PageHuge(page)) { > + unsigned int order; > + > + if (!IS_ENABLED(CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION)) > + return false; > + > + if (skip_hugetlb) { > + *skipped_hugetlb = true; > + return false; > + } > + > + page = compound_head(page); > + order = compound_order(page); > + if ((order >= MAX_FOLIO_ORDER) || > + (nr_pages <= (1 << order))) > + return false; > + > + /* > + * Reaching this point means we've encounted a huge page > + * smaller than nr_pages, skip all pfn's for that page. > + * > + * We can't get here from a tail-PageHuge, as it implies > + * we started a scan in the middle of a hugepage larger > + * than nr_pages - which the prior check filters for. > + */ > + i += (1 << order) - 1; Assuming page != compound_head(page), you'd be skipping too much. You'd only have to skip as many pages as pages are left in this compound page. I think we have similar code elsewhere: see has_unmovable_pages(). Apart from that LGTM. -- Cheers David