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Thu, 09 Jan 2025 10:50:54 -0800 (PST) Received: from joshuahahn-mbp.thefacebook.com ([2620:10d:c091:500::6:51c5]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2f55942188csm1931297a91.23.2025.01.09.10.50.52 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Thu, 09 Jan 2025 10:50:53 -0800 (PST) From: Joshua Hahn To: lsf-pc@lists.linux-foundation.org Cc: Joshua Hahn , linux-mm@kvack.org, linux-kernel@vger.kernel.org, gourry@gourry.net, ying.huang@linux.alibaba.com, hyeonggon.yoo@sk.com, honggyu.kim@sk.com, kernel-team@meta.com Subject: [LSF/MM/BPF TOPIC] Weighted interleave auto-tuning Date: Thu, 9 Jan 2025 13:50:48 -0500 Message-Id: <20250109185048.28587-1-joshua.hahnjy@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 81A124000C X-Stat-Signature: ktipahd5bqo84b1wx64a9b9eo6fe15xz X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1736448655-571584 X-HE-Meta: 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 F9i2gK7m XxTSXWeIQkhG51VlTilW8IMIdZllO4BNMNGOkrNCv4tdXHqDPm+c5c+j8UorELptNyAUBEn9+SU1VaM+q3cOauAVFe5y99OPw8Isf+SP988AVfuZ5VptIMV3OZlqMgfxBysQ9AAe0mTh/7KsROmQlubzUdWpECjkrtJ1zlkT8w4reZC7FelSsV4ufVwC4yNgBqnfPmF7Y9Jb3IjSGr35zXLjl8Ge3SKpgnP0OIoyOBYvjvxmM7d+GR85/jQJh0jUd3852n/oDO5dCdAqUi50l5IuaLTAXYXetqXg5TJSvC8qw5UGm7UkThMMVYn6dDghNUA80Je2cKVjJ68AgWh8Uv9iV3NxnZJq44OW7U6EKYij/B050y2A9YPLZP9CKjoHHVvRI/UiM9PHH9zmu/fiY3DxNrHWRV2mooF7dj/XWhD1At8aa7cDZq96Vnt9WF0fdG8x/imjkAfdgFakrdMRiGgUPOh8xHS86c0AyJhY22fmolNTLDKImRRit9LJrpgJlf9tXNyUGsibFkcdGzCJmJ4gha4gsEqLGv0+pVoaeGP9kSqg2nxLBJqhziOSO1l22b5Jl X-Bogosity: Ham, tests=bogofilter, spamicity=0.216921, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hello everyone, I hope everyone has had a great start to 2025! Recently, I have been working on a patch series [1] with Gregory Price that provides new default interleave weights, along with dynamic re-weighting on hotplug events and a series of UAPIs that allow users to configure how they want the defaults to behave. In introducing these new defaults, discussions have opened up in the community regarding how best to create a UAPI that can provide coherent and transparent interactions for the user. In particular, consider this scenario: when a hotplug event happens and a node comes online with new bandwidth information (and therefore changing the bandwidth distributions across the system), should user-set weights be overwritten to reflect the new distributions? If so, how can we justify overwriting user-set values in a sysfs interface? If not, how will users manually adjust the node weights to the optimal weight? I would like to revisit some of the design choices made for this patch, including how the defaults were derived, and open the conversation to hear what the community believes is a reasonable way to allow users to tune weighted interleave weights. More broadly, I hope to get gather community insight on how they use weighted interleave, and do my best to reflect those workflows in the patch. Of course, I would also love to hear your thoughts about this topic in this thread, or in the RFC thread (attached) as well. Have a great day! Joshua [1] https://lore.kernel.org/all/20241219191845.3506370-1-joshua.hahnjy@gmail.com/