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Mon, 10 Jun 2024 22:34:11 -0700 (PDT) MIME-Version: 1.0 References: <20240611002145.2078921-1-jthoughton@google.com> <20240611002145.2078921-5-jthoughton@google.com> In-Reply-To: <20240611002145.2078921-5-jthoughton@google.com> From: Yu Zhao Date: Mon, 10 Jun 2024 23:33:34 -0600 Message-ID: Subject: Re: [PATCH v5 4/9] mm: Add test_clear_young_fast_only MMU notifier To: James Houghton Cc: Andrew Morton , Paolo Bonzini , Ankit Agrawal , Axel Rasmussen , Catalin Marinas , David Matlack , David Rientjes , James Morse , Jonathan Corbet , Marc Zyngier , Oliver Upton , Raghavendra Rao Ananta , Ryan Roberts , Sean Christopherson , Shaoqin Huang , Suzuki K Poulose , Wei Xu , Will Deacon , Zenghui Yu , kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: 796E98000C X-Rspamd-Server: rspam01 X-Stat-Signature: o1135znf4ymoqiw5zemjmprjcwadrg33 X-HE-Tag: 1718084053-585206 X-HE-Meta: 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 SqXF61Ex Cad/p56d5qBknhqHZSLsQNnSlPtG5Nve/EooZGnZ1YPLwZ9/yerr1vXQelxkOgJCHrCVGcNu6s5IV/n3Ivvjd0wP0to3dSBQSqGbVgnRIIxMpfP70VwH9FG38jciAwgw0UvfuPgpZLsIdigshRB/5+QHjr9Shn8F5NVWu5yi3YUAQk5cTdmXfq3r/Vl7vfV78VB1x+wfINz+Nh/IjAjI+Fpp/TwErfMO2f6D+u6GbQHGW8sDTrKOtihweS+WQWs/9q2Okh+bnlrKOQOqUT5t28GcwnoASoanHmVJ6 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000052, 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 Mon, Jun 10, 2024 at 6:22=E2=80=AFPM James Houghton wrote: > > This new notifier is for multi-gen LRU specifically Let me call it out before others do: we can't be this self-serving. > as it wants to be > able to get and clear age information from secondary MMUs only if it can > be done "fast". > > By having this notifier specifically created for MGLRU, what "fast" > means comes down to what is "fast" enough to improve MGLRU's ability to > reclaim most of the time. > > Signed-off-by: James Houghton If we'd like this to pass other MM reviewers, especially the MMU notifier maintainers, we'd need to design a generic API that can benefit all the *existing* users: idle page tracking [1], DAMON [2] and MGLRU. Also I personally prefer to extend the existing callbacks by adding new parameters, and on top of that, I'd try to consolidate the existing callbacks -- it'd be less of a hard sell if my changes result in less code, not more. (v2 did all these, btw.) [1] https://docs.kernel.org/admin-guide/mm/idle_page_tracking.html [2] https://www.kernel.org/doc/html/latest/mm/damon/index.html