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Sat, 11 Feb 2023 03:02:26 +0900 (KST) Received: from epsmtrp2.samsung.com (unknown [182.195.40.14]) by epcas5p1.samsung.com (KnoxPortal) with ESMTPA id 20230210180226epcas5p1bd2e1150de067f8af61de2bbf571594d~CiIwABZH_1487214872epcas5p12; Fri, 10 Feb 2023 18:02:26 +0000 (GMT) Received: from epsmgms1p1new.samsung.com (unknown [182.195.42.41]) by epsmtrp2.samsung.com (KnoxPortal) with ESMTP id 20230210180226epsmtrp2275bcf6dc658d13c0b572e6d296630b5~CiIv-UX6u0770607706epsmtrp25; Fri, 10 Feb 2023 18:02:26 +0000 (GMT) X-AuditID: b6c32a4a-909fc7000000d97e-41-63e686b21beb Received: from epsmtip1.samsung.com ( [182.195.34.30]) by epsmgms1p1new.samsung.com (Symantec Messaging Gateway) with SMTP id F6.58.05839.2B686E36; Sat, 11 Feb 2023 03:02:26 +0900 (KST) Received: from localhost.localdomain (unknown [107.110.206.5]) by epsmtip1.samsung.com (KnoxPortal) with ESMTPA id 20230210180224epsmtip1ad2e07de90dfb2af216925f3260f223c~CiIuqVOBK2565325653epsmtip1N; Fri, 10 Feb 2023 18:02:24 +0000 (GMT) From: Kanchan Joshi To: lsf-pc@lists.linux-foundation.org Cc: linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, io-uring@vger.kernel.org, axboe@kernel.dk, hch@lst.de, kbusch@kernel.org, ming.lei@redhat.com, Kanchan Joshi Subject: [LSF/MM/BPF ATTEND][LSF/MM/BPF Topic] Non-block IO Date: Fri, 10 Feb 2023 23:30:33 +0530 Message-Id: <20230210180033.321377-1-joshi.k@samsung.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFuplk+LIzCtJLcpLzFFi42LZdlhTXXdT27Nkg3Xn5SxW3+1ns1i5+iiT xbvWcywWR/+/ZbOYdOgao8XeW9oW85c9ZbfY93ovs8Whyc1MDpwel8+Wemxa1cnmsXlJvcfk G8sZPXbfbGDzeL/vKptH35ZVjB6fN8kFcERl22SkJqakFimk5iXnp2TmpdsqeQfHO8ebmhkY 6hpaWpgrKeQl5qbaKrn4BOi6ZeYAHaekUJaYUwoUCkgsLlbSt7Mpyi8tSVXIyC8usVVKLUjJ KTAp0CtOzC0uzUvXy0stsTI0MDAyBSpMyM74tmklc8Fd/op197ezNzA+4eli5OSQEDCROH72 KmsXIxeHkMBuRon//XOYIJxPjBKHp+1mhHC+MUpMP3ySFaZlzvW5LBCJvYwSm7YeZIZwPjNK zP3yEcjh4GAT0JS4MLkUpEFEQFXi7/ojYA3MAscZJRbOvMQMkhAWsJZ4c/wcO4jNAlR0/9RE JhCbV8BS4lvPBCaIbfISMy99Z4eIC0qcnPmEBcRmBoo3b50NtlhC4Cu7xNlpK9kgGlwkfrye C2ULS7w6voUdwpaS+PxuL1Q8WeLSzHNQC0okHu85CGXbS7Se6gd7gBnogfW79CF28Un0/n7C BBKWEOCV6GgTgqhWlLg36Sk0UMQlHs5YAmV7SLzc+wBsk5BArMSX9h3MExjlZiH5YBaSD2Yh LFvAyLyKUTK1oDg3PbXYtMAoL7UcHpnJ+bmbGMHpUstrB+PDBx/0DjEycTAeYpTgYFYS4a20 eZYsxJuSWFmVWpQfX1Sak1p8iNEUGKwTmaVEk/OBCTuvJN7QxNLAxMzMzMTS2MxQSZxX3fZk spBAemJJanZqakFqEUwfEwenVANT9qXjJjfetZp6/3FNqFaSmueVvO95YPxtcy/bXq3GipfG cfvYVt1u+H2Yj//uum26k+X9t7m+9laR2fft2Da78BvFE+QWdJiavDmsdspwR4ZhzEptI4np 1zs/presmWJgL/I7k18n9UrNg96Te0UjwjQ5hZL3iJ5h9IperhGYnRg2zTTa8dyH3kf+RooJ V9Z+D7uke2xXTf+LLWnbvsueYO4+uiJi5cYrHx5qTotPbnfbramw1djr7Nu6pnUB3NMMNd// EF3KOCHzcuvE2Amt0ksL2rnL5+7Y/cFGJEbo1PZu0Q2fnxr1XhLxWxq7jMttqZsL++q7k9Jm +5cGm/72XXFZTeO70fcmBddFhrpKLMUZiYZazEXFiQAXBT3cIAQAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFjrKLMWRmVeSWpSXmKPExsWy7bCSnO6mtmfJBh/XsVqsvtvPZrFy9VEm i3et51gsjv5/y2Yx6dA1Rou9t7Qt5i97ym6x7/VeZotDk5uZHDg9Lp8t9di0qpPNY/OSeo/J N5Yzeuy+2cDm8X7fVTaPvi2rGD0+b5IL4IjisklJzcksSy3St0vgyvi2aSVzwV3+inX3t7M3 MD7h6WLk5JAQMJGYc30uSxcjF4eQwG5GiR+TNrBBJMQlmq/9YIewhSVW/nvODlH0kVHi8f/b rF2MHBxsApoSFyaXgtSICKhK/F1/BGwQs8BFRolNq06DNQsLWEu8OX4OzGYBKrp/aiITiM0r YCnxrWcCE8QCeYmZl76zQ8QFJU7OfMICYjMDxZu3zmaewMg3C0lqFpLUAkamVYySqQXFuem5 xYYFhnmp5XrFibnFpXnpesn5uZsYwSGtpbmDcfuqD3qHGJk4GA8xSnAwK4nwVto8SxbiTUms rEotyo8vKs1JLT7EKM3BoiTOe6HrZLyQQHpiSWp2ampBahFMlomDU6qBKWvLtzMbH/A6XlzV 39B3fcvVW+q3D+06s/Zg1auUGfx8m++3FWSJzZ6UWuky+8tSD/vdl7YyOG3fEBIiwbavm6PP M4P3hqnPbQuF5VcErAO3WFw22OAxuevi8TJj75Ko08JuBkfesXgXVzEd+aN4q2adr/S8t2wf Skz/1j0uvPBoybIidellp9p1+PxeznHytjqrHvqxzLdz+af3bBqzE+LuyR27PfXxxZe79k3a 92vnoWubuu5st1HnCj3eoX+7YelTN627yWd2qtaHSs677vPJrDlar2S6VsakvPUy1rayfBu3 xFwIDLgj1NbF28d8lOdSbOS0CpaZ115d+H3VR3ClwMtDK3TaFee1yb69/UCJpTgj0VCLuag4 EQDC8v5d2AIAAA== X-CMS-MailID: 20230210180226epcas5p1bd2e1150de067f8af61de2bbf571594d X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" CMS-TYPE: 105P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20230210180226epcas5p1bd2e1150de067f8af61de2bbf571594d References: Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org is getting more common than it used to be. NVMe is no longer tied to block storage. Command sets in NVMe 2.0 spec opened an excellent way to present non-block interfaces to the Host. ZNS and KV came along with it, and some new command sets are emerging. OTOH, Kernel IO advances historically centered around the block IO path. Passthrough IO path existed, but it stayed far from all the advances, be it new features or performance. Current state & discussion points: --------------------------------- Status-quo changed in the recent past with the new passthrough path (ng char interface + io_uring command). Feature parity does not exist, but performance parity does. Adoption draws asks. I propose a session covering a few voices and finding a path-forward for some ideas too. 1. Command cancellation: while NVMe mandatorily supports the abort command, we do not have a way to trigger that from user-space. There are ways to go about it (with or without the uring-cancel interface) but not without certain tradeoffs. It will be good to discuss the choices in person. 2. Cgroups: works for only block dev at the moment. Are there outright objections to extending this to char-interface IO? 3. DMA cost: is high in presence of IOMMU. Keith posted the work[1], with block IO path, last year. I imagine plumbing to get a bit simpler with passthrough-only support. But what are the other things that must be sorted out to have progress on moving DMA cost out of the fast path? 4. Direct NVMe queues - will there be interest in having io_uring managed NVMe queues? Sort of a new ring, for which I/O is destaged from io_uring SQE to NVMe SQE without having to go through intermediate constructs (i.e., bio/request). Hopefully,that can further amp up the efficiency of IO. 5. I hope to send some code/PoC to discuss the stuff better. [1]https://lore.kernel.org/linux-nvme/20220805162444.3985535-1-kbusch@fb.com/