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[209.85.208.52]) by smtp.gmail.com with ESMTPSA id n4-20020a509344000000b00565a9c11987sm1251795eda.76.2024.02.27.15.00.51 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 27 Feb 2024 15:00:51 -0800 (PST) Received: by mail-ed1-f52.google.com with SMTP id 4fb4d7f45d1cf-55a035669d5so8572350a12.2 for ; Tue, 27 Feb 2024 15:00:51 -0800 (PST) X-Forwarded-Encrypted: i=1; AJvYcCW9agrzktmjaHi+gNbc+hMxLzC3EqohUZSyeUwzRIWAoGOjHN+bU761ro4Pa34X1Jhwy3XMtKuAvHcfC8QucDhiKEI= X-Received: by 2002:a17:906:a44d:b0:a3d:9a28:52e6 with SMTP id cb13-20020a170906a44d00b00a3d9a2852e6mr7525309ejb.50.1709074851487; Tue, 27 Feb 2024 15:00:51 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Linus Torvalds Date: Tue, 27 Feb 2024 15:00:34 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [LSF/MM/BPF TOPIC] Measuring limits and enhancing buffered IO To: Kent Overstreet Cc: Dave Chinner , Luis Chamberlain , lsf-pc@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-mm , Daniel Gomez , Pankaj Raghav , Jens Axboe , Christoph Hellwig , Chris Mason , Johannes Weiner , Matthew Wilcox Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: ED85C1C0027 X-Stat-Signature: zdhjd1oxhuebbrs865rneyzi7d4tsu5r X-HE-Tag: 1709074854-119258 X-HE-Meta: U2FsdGVkX1/ITlHAyWKIizKNthexrz4LT+icDUAsmIcP42T1wZMdyJjOSA5MNHP1Jt+882j9CxDkVUUbGWYwiQkLUpyjTCwTql9YaH15nWEQ4DRnqoGGn1t7zXaF+otHahsaHAkZCv3NCnoNWg16wZwUWR3yhuRMlD0iODz3Rbw0mrxHeG7j3PaKwD+uxr05lP/MLSAxjrY16hHeIWfC68QqBF8RRP0lAbe+OpUf39ZnM70ckM7RtWv//iKrTpPP7Ios7KN9+r/fJHXc9SkuJBODdXmri4BKt4hYVuKa1fT/e8a1aTmP78Ef0kL6VrwGP9VURYVp7n/yUQj941GPVvNQgXe+xNcmeVy4EuUu8tnXxClBGutDgSNKSebZSN1/fqCWCqIz8J/Zt+a6aEKIkK+PqQW9HdiVvdbnrPuntWabRCOPVH/+u7wZ6uT94khRJM+lLEgWpDyFS2btMVFKV7yklHSAckXW4wucnRLhdO+e7XrRGLrWSPpREWIHqtiLVsJaqbGKN1jxzBXE2RpBu1KDkgUYVhtjO3D0Jnp/yx/F8svZvnETvZE/erAKg/+YwZbjhC6kkKVOsGhcRVMJ4RGGGBygGTwMYEKt25PsPvUgilqu+AB8gNiK5Sb+eAKHKTZ+wgcKTLpBMyDnJ4njrJLhg/NKZK11REB9AHKLoonrJehEOAe47G7jUjSNq9LFxXqvTkKgRWVHvDp+VaXwGwmO1EJrllErnrh/MZdUlKmNipDy/3bV2rubFzuZXiKLdjNA+MOfLEk9OkCBJkhfHYjQ0Ic273/hypdRfb+ffwPUdDkYxMihR9I6bpBy5tLNkkql8OykQb+lq4aWoqm/mwQdk5hhczjm7WzQSXJ/M4UbwkN3OGc7Sh3B+gauTzgrbhwSL790YvX1LEU7W/WvDdmdV/GKxhohEp6SSBKb7CHrh1DdqWobuyAsfIc7lwooPp82zs7g/JKl/OxSNBA 3xFwUs23 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000008, 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 Tue, 27 Feb 2024 at 14:46, Linus Torvalds wrote: > > For example, a purely "local lock" model would be to just lock all > pages in order as you write them, and not unlock the previous page > until you've locked the next one. Thinking more about this, maybe that doesn't really guarantee much. The final state would be that even with concurrent overlapping writes, one writer did its overlapping write fully and you'd never have mixed ABAB kind of results, but you could still have concurrent readers see the two writes progressing concurrently. Of course, since readers aren't serialized as-is, I'm not sure if "readers can see intermediate state" is anything new or relevant anyway. Maybe the worry isn't worth it. Linus