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[2003:cb:c707:5c00:e650:bcd7:e2a0:54fe]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4282baccccfsm50752385e9.29.2024.08.01.02.36.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 01 Aug 2024 02:36:16 -0700 (PDT) Message-ID: <37ae59f2-777a-4a58-ae58-4a20066364dd@redhat.com> Date: Thu, 1 Aug 2024 11:36:14 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 05/11] mm: Add fast_only bool to test_young and clear_young MMU notifiers To: James Houghton , Andrew Morton , Paolo Bonzini Cc: Ankit Agrawal , Axel Rasmussen , Catalin Marinas , David Matlack , David Rientjes , James Morse , Jason Gunthorpe , Jonathan Corbet , Marc Zyngier , Oliver Upton , Raghavendra Rao Ananta , Ryan Roberts , Sean Christopherson , Shaoqin Huang , Suzuki K Poulose , Wei Xu , Will Deacon , Yu Zhao , 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 References: <20240724011037.3671523-1-jthoughton@google.com> <20240724011037.3671523-6-jthoughton@google.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: DBF1A100003 X-Stat-Signature: ubphfkf69uo5rfbsa5m4mpouesfcpep9 X-HE-Tag: 1722504982-942647 X-HE-Meta: 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 Vr8BzvHg HH3wDcD+Zt7qIKqHikCrrcdBD8hlVwaFjexVSbkAz1IRuO7pj2vFpGwd6TiKWQ73ZOWli9G2plb6Tr9aN2LHoMyQFgKFkXZZIUiomQs2Wee9xzvHSJ+13QA/MP09Q2uITiErM5SVNyc1MsRDyaSqerV9Ufv9ncOu8FHnweYS2L3OU0J558mxxt4wCfA7gvxkY97rwYkeSQs+P13goxKiG4qyHI5z9CKAPZhhGoOzjoLek/8vPrC4qVo3gZWbbArdPibVbTiiTr6NcfuMFw/X5MiPLOa8Jv3oL+9rpqzCl/BI+xoGeh16DP3csyBo08Y5yj86Kpq67QeJg9QXojRQeotEIQ2oA12adhMrgoqYB/H+c8uo2ZLDviEQ482HdKXoNf6NF4fQZyOjxCr0vqxbwy5FqEmiQA/LgeQLuFHBqb7RZvU4= 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 24.07.24 03:10, James Houghton wrote: > For implementers, the fast_only bool indicates that the age information > needs to be harvested such that we do not slow down other MMU operations, > and ideally that we are not ourselves slowed down by other MMU > operations. Usually this means that the implementation should be > lockless. But what are the semantics if "fast_only" cannot be achieved by the implementer? Can we add some documentation to the new functions that explain what this mysterious "fast_only" is and what the expected semantics are? Please? :) -- Cheers, David / dhildenb