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Thu, 07 Aug 2025 09:02:54 -0700 (PDT) MIME-Version: 1.0 References: <20250807152720.62032-1-ryncsn@gmail.com> <20250807152720.62032-4-ryncsn@gmail.com> In-Reply-To: <20250807152720.62032-4-ryncsn@gmail.com> From: Jann Horn Date: Thu, 7 Aug 2025 18:02:17 +0200 X-Gm-Features: Ac12FXw-L14MzSZIbdhDuuuaGoNtnHc6MgG8djKeHfkzC15_DWV0euBIlOkenb4 Message-ID: Subject: Re: [RFC PATCH 3/3] mm/mincore: avoid touching the PTL To: Kairui Song Cc: linux-mm@kvack.org, Andrew Morton , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Pedro Falcato , Matthew Wilcox , Hugh Dickins , David Hildenbrand , Chris Li , Barry Song , Baoquan He , Nhat Pham , Kemeng Shi , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: wobj8egz3m7mgckwzok6eubkmpyxswap X-Rspamd-Queue-Id: 57E5E40012 X-Rspamd-Server: rspam10 X-Rspam-User: X-HE-Tag: 1754582576-650766 X-HE-Meta: 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 FV0Bv66X FsV10Rj/2yz+y1w3xCkAY8zS3KZaIy6D5LvwFk7+BPP0vJaYjfyrYtWmSI0yhytNWhppAgd0ebxvp4qJx9W56OeQaA59eol7+Qfs3Fq5tnCTZOBal91a8rNERljYftWZsASqlFx36JlNvj2VqNuFHKv3jBOdI9auK10SmcAcKg3pOrKFR6vkhRPi8VmJNAk0urL4NK+Y9NbK2urLi+gXvUmtvMVi9bX1Hfowv 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 Thu, Aug 7, 2025 at 5:27=E2=80=AFPM Kairui Song wrote= : > mincore only interested in the existence of a page, which is a > changing state by nature, locking and making it stable is not needed. > And now neither mincore_page or mincore_swap requires PTL, this PTL > locking can be dropped. This means you can race such that you end up looking at an unrelated page of another process, right? And your patch intentionally allows that to happen in order to make mincore() faster?