From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-comment-return-986-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id C652C985DCE for ; Wed, 11 Dec 2019 15:33:46 +0000 (UTC) Date: Wed, 11 Dec 2019 10:33:38 -0500 From: "Michael S. Tsirkin" Message-ID: <20191211101541-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Subject: [virtio-comment] thoughts on: virtio: skipping used buffers without IN_ORDER Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline To: virtio-comment@lists.oasis-open.org List-ID: Hello! At the moment, if a device uses multiple buffers, it has to write out a descriptor per buffer. The only exception is with IN_ORDER where device can skip buffers, with driver keeping track of IDs. IN_ORDER is however quite limited in what it can do. It's not a good fit for storage, and probably not for RX networking. It's not hard to extend IN_ORDER so it doesn't apply to specific rings. A harder question is still writing a single descriptor in this case. One somewhat easy fix it just to allow descriptors to include multiple IDs. E.g. address is ignored in used descriptors, we can fit 4 extra IDs in there. For descriptors where we don't care about the length, we can stick a couple more IDs on top of that. I can't say it's all very elegant. Also, is that enough of a win? We can still end up with multiple descriptors. More thoughts? Thanks, --=20 MST This publicly archived list offers a means to provide input to the=0D OASIS Virtual I/O Device (VIRTIO) TC.=0D =0D In order to verify user consent to the Feedback License terms and=0D to minimize spam in the list archive, subscription is required=0D before posting.=0D =0D Subscribe: virtio-comment-subscribe@lists.oasis-open.org=0D Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org=0D List help: virtio-comment-help@lists.oasis-open.org=0D List archive: https://lists.oasis-open.org/archives/virtio-comment/=0D Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf= =0D List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lis= ts=0D Committee: https://www.oasis-open.org/committees/virtio/=0D Join OASIS: https://www.oasis-open.org/join/