From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1BB57C433EF for ; Mon, 9 May 2022 19:02:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240371AbiEITG1 (ORCPT ); Mon, 9 May 2022 15:06:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47050 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235698AbiEITG0 (ORCPT ); Mon, 9 May 2022 15:06:26 -0400 X-Greylist: delayed 1645 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Mon, 09 May 2022 12:02:30 PDT Received: from a4-15.smtp-out.eu-west-1.amazonses.com (a4-15.smtp-out.eu-west-1.amazonses.com [54.240.4.15]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5A8971F929A; Mon, 9 May 2022 12:02:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/simple; s=ob2ngmaigrjtzxgmrxn2h6b3gszyqty3; d=urbackup.org; t=1652120094; h=Message-ID:Date:MIME-Version:From:Subject:To:Cc:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; bh=moCKIlR1VoGBDZv7bxLTB0rBLKiRz1QcPC33EzoNnt0=; b=C4lPPFd/BL1NLovwh7MWYmrvYs820UC3KP7QN8CoQZTJ0GLWjcnwO2NN8zxHEE58 h7eL/Ie+WMnJRxCiGE+kr6LE2RFcFOaZd+FrNuV/YgRDvQ/24XsOLFRhz7pM9KLNqr9 BJKdJ44XvY6fhWNkjCYti4tvQZp0UKjPHsozKq6Y= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/simple; s=ihchhvubuqgjsxyuhssfvqohv7z3u4hn; d=amazonses.com; t=1652120094; h=Message-ID:Date:MIME-Version:From:Subject:To:Cc:References:In-Reply-To:Content-Type:Content-Transfer-Encoding:Feedback-ID; bh=moCKIlR1VoGBDZv7bxLTB0rBLKiRz1QcPC33EzoNnt0=; b=lzPMZQwKC5VH4ANqtvKfzIX194vwwB+Oxsf4b+F2oMy/se9Bm89BPKWK17ZFrroA pVWEXnsGs0foBMQ6lfAlmY/LNDP8rHU6HUS/g6GPtPG0Kd+qBMeXlXWfk116ct69ces abUhf0RTuXETFcMXYvXMsHVyKPv/u6+sWTxdHSdU= Message-ID: <01020180aa080721-08a3231e-71b7-4fb2-a411-cac2cbf85ae3-000000@eu-west-1.amazonses.com> Date: Mon, 9 May 2022 18:14:54 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 From: Martin Raiber Subject: Re: [RFC PATCH] ubd: add io_uring based userspace block driver To: Ming Lei , Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, io-uring@vger.kernel.org, Gabriel Krisman Bertazi , ZiyangZhang , Xiaoguang Wang References: <20220509092312.254354-1-ming.lei@redhat.com> In-Reply-To: <20220509092312.254354-1-ming.lei@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Feedback-ID: 1.eu-west-1.zKMZH6MF2g3oUhhjaE2f3oQ8IBjABPbvixQzV8APwT0=:AmazonSES X-SES-Outgoing: 2022.05.09-54.240.4.15 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 09.05.2022 11:23 Ming Lei wrote: > This is the driver part of userspace block driver(ubd driver), the other > part is userspace daemon part(ubdsrv)[1]. > > The two parts communicate by io_uring's IORING_OP_URING_CMD with one > shared cmd buffer for storing io command, and the buffer is read only for > ubdsrv, each io command is indexed by io request tag directly, and > is written by ubd driver. > > For example, when one READ io request is submitted to ubd block driver, ubd > driver stores the io command into cmd buffer first, then completes one > IORING_OP_URING_CMD for notifying ubdsrv, and the URING_CMD is issued to > ubd driver beforehand by ubdsrv for getting notification of any new io request, > and each URING_CMD is associated with one io request by tag. > > After ubdsrv gets the io command, it translates and handles the ubd io > request, such as, for the ubd-loop target, ubdsrv translates the request > into same request on another file or disk, like the kernel loop block > driver. In ubdsrv's implementation, the io is still handled by io_uring, > and share same ring with IORING_OP_URING_CMD command. When the target io > request is done, the same IORING_OP_URING_CMD is issued to ubd driver for > both committing io request result and getting future notification of new > io request. > > Another thing done by ubd driver is to copy data between kernel io > request and ubdsrv's io buffer: > > 1) before ubsrv handles WRITE request, copy the request's data into > ubdsrv's userspace io buffer, so that ubdsrv can handle the write > request > > 2) after ubsrv handles READ request, copy ubdsrv's userspace io buffer > into this READ request, then ubd driver can complete the READ request > > Zero copy may be switched if mm is ready to support it. > > ubd driver doesn't handle any logic of the specific user space driver, > so it should be small/simple enough. > > [1] ubdsrv > https://github.com/ming1/ubdsrv/commits/devel Great! It would be interesting to do some tests on how much faster (IOPS) this is than doing this via fuse: https://github.com/uroni/fuseuring