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From: Muchun Song In-Reply-To: Date: Wed, 28 Jan 2026 10:43:13 +0800 Cc: Oscar Salvador , Mike Rapoport , Vlastimil Babka , Lorenzo Stoakes , Zi Yan , Baoquan He , Michal Hocko , Johannes Weiner , Jonathan Corbet , kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Andrew Morton , David Hildenbrand , Matthew Wilcox , Usama Arif , Frank van der Linden Content-Transfer-Encoding: quoted-printable Message-Id: <25C01EB2-FC77-43A5-A737-7BD3D2D98EDE@linux.dev> References: <20260121162253.2216580-1-kas@kernel.org> <20260121162253.2216580-10-kas@kernel.org> To: Kiryl Shutsemau X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 79A1D40002 X-Stat-Signature: 45qss6yyymxtf8p46ckxnhmmchaj94wk X-HE-Tag: 1769568237-863459 X-HE-Meta: U2FsdGVkX19kUXnql7X8vtr3oGebCfMtZ+2Y9sd1oR7WkIFWYe0Sx8oB3+3OttQiAuXfKoryU4Y9Zk7Yo/eir123ok0EtGmMfupRQyd6JX7wc3Lgb891nxScHy8lMZkl9C5iyl8dOzzgVh0dgYIbw33egdEgOUJSoNnjFfJF9Wb7JoUC18hv5SGCypMaaQ8TJognUgCtIM5L7IhWPYl57U2cqtc8mdptTAu9dx8466C1lUB2oGSiTzg22kZrHvp8ytHTCM2qDoRdBRi7+iyFX18GIYGprbavchxliGciVZrqTf48zkY9BFYLhR5RyZQ+12Y/2vwv4ei4zv++Zpl2P+ogVEy4AuC1dti9YjFFsImxeqKAATQXehzb6XL0QBMpBl1k5TCdzJjoMhMsUihAdG82WsA1m5aDtlbCLo4cT/aIlHM7ipN6CkYmSBtI7mC0SQ8pCKrJARHGmAOqpbcv/wjvHGsF6l4/iBbiqyc6/epsGnI3rKn3rOFvVKYjgZwqN2KKPLJKRCTG/AqnsL9JVVEs6tPGDWm8LQn/PCbhBvUSWnVXfmJPwRy0QZO6xNUH9E0GSOmoLAvTC5c2AIbQfP7bnn00N85YTx/N0RCBW71ZDmFbn++y9rRIufx5KtDmTRzjs8LVB/habsRke4VGPR0VPJYEJy1vKkg68MFUHkEr9ATFxeukFAkgqnumuYATw0wIo/pw1NJe3+nlC9Ycr4n6YoTN0fGvRQNRQoYhVX5yfXDfNsB7FJ6p4LLgGPZzFflXBF0S5MIB/oDCVx7sXP7q/NIMOmw26ps6aJgggqeceg3v999O51d+vHtYFouQV6LKjs/xGipuT9tg1yBLQGQ4P5QQ5YXxxUShIoyQN1Lku2R7YmU1zUDmmGb7BFXzxzTI8co4L1ZFySyMbRHuo6XDzSkpeMEL+CpwBwZY8SQQxWuSD6C4+lC8yadL8RBrNeOm1hUTULqc/t92Hcy xKQ9MkNS wAMSFslmjE8l3T9+dbJvoPU231WqoD3JN7KV5ZqEY46X0B7p7CiIpLi84DwBloiJmOTU7g0bLRZj3kGOTYh128laiZ1MFdzmfYZ+Ci3s1FWiTY0M252dpw2MQAC3cQ8GCHky13A7BQ36gdO4q/TswL+LgIOW4Ozy6YSkLhT7EO5PMgvpZinvF31hr6IY4do7fenC8xPR/x5vck5CqaRKfILseSYFMgMaIVmwUp08xIb/8A1wtALzOzhMZkszaMEUTR6lu 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: > On Jan 27, 2026, at 22:51, Kiryl Shutsemau wrote: >=20 > On Thu, Jan 22, 2026 at 03:00:03PM +0800, Muchun Song wrote: >>> + if (pfn) >>> + return pfn_to_page(pfn); >>> + >>> + tail =3D alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0); >>> + if (!tail) >>> + return NULL; >>> + >>> + p =3D page_to_virt(tail); >>> + for (int i =3D 0; i < PAGE_SIZE / sizeof(struct page); i++) >>> + prep_compound_tail(p + i, NULL, order); >>> + >>> + spin_lock(&hugetlb_lock); >>=20 >> hugetlb_lock is considered a contended lock, better not to abuse it. >> cmpxchg() is enought in this case. >=20 > We hit the lock once per node (excluding races). Its contribution to = the > lock contention is negligible. spin_lock() is easier to follow. I will > keep it. I don't think cmpxchg() is hard to follow. It=E2=80=99s precisely = because of your abuse that interrupts still have to be disabled here=E2=80=94hugetlb_= lock must be an irq-off lock. Are you really going to use spin_lock_irq just because =E2=80=9Cit feels simpler=E2=80=9D to you? >=20 > Ack for the rest of your comments. >=20 >=20 > --=20 > Kiryl Shutsemau / Kirill A. Shutemov