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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 05A45C433EF for ; Wed, 6 Apr 2022 17:33:32 +0000 (UTC) Received: from localhost ([::1]:53914 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nc9X9-000293-IO for qemu-devel@archiver.kernel.org; Wed, 06 Apr 2022 13:33:31 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:56686) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nc9Vw-0001JD-FD for qemu-devel@nongnu.org; Wed, 06 Apr 2022 13:32:16 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:59438) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nc9Vt-0002A6-So for qemu-devel@nongnu.org; Wed, 06 Apr 2022 13:32:15 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1649266331; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=gBsF+SU0EEI1vsb8WZTuk/GR3nXlygaVNg5hscMxn34=; b=Lpi9eB8VzIpmrtUDAPwquD4cnICHjFqYz/E79A5kKG7fxogRss813Sqika2LoDcrk5GWzl HfJSKp70VmvUDrrzmheprQaW9DbKDgmKVwzBdiUXBulLotu0++xBYtwS0bDnvDJYO6kzrM sEIpjUfVxI8bu6WcXE3+MfZ3OV8rArQ= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-589-99_HU7AKPpWBxPu2Si9Htg-1; Wed, 06 Apr 2022 13:32:08 -0400 X-MC-Unique: 99_HU7AKPpWBxPu2Si9Htg-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 2B5BA185A7B2; Wed, 6 Apr 2022 17:32:08 +0000 (UTC) Received: from redhat.com (unknown [10.39.193.182]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 621A84029A4; Wed, 6 Apr 2022 17:32:05 +0000 (UTC) Date: Wed, 6 Apr 2022 19:32:04 +0200 From: Kevin Wolf To: Stefan Hajnoczi Subject: Re: [RFC v2 1/8] blkio: add io_uring block driver using libblkio Message-ID: References: <20220405153323.2082242-1-stefanha@redhat.com> <20220405153323.2082242-2-stefanha@redhat.com> MIME-Version: 1.0 In-Reply-To: <20220405153323.2082242-2-stefanha@redhat.com> X-Scanned-By: MIMEDefang 2.85 on 10.11.54.9 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.129.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Fam Zheng , Eduardo Habkost , Thomas Huth , Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org, "Michael S. Tsirkin" , Laurent Vivier , Eric Blake , qemu-devel@nongnu.org, Alberto Faria , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , Yanan Wang , Hanna Reitz , Paolo Bonzini , John Snow , Markus Armbruster , sgarzare@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 05.04.2022 um 17:33 hat Stefan Hajnoczi geschrieben: > libblkio (https://gitlab.com/libblkio/libblkio/) is a library for > high-performance disk I/O. It currently supports io_uring with > additional drivers planned. > > One of the reasons for developing libblkio is that other applications > besides QEMU can use it. This will be particularly useful for > vhost-user-blk which applications may wish to use for connecting to > qemu-storage-daemon. > > libblkio also gives us an opportunity to develop in Rust behind a C API > that is easy to consume from QEMU. > > This commit adds an io_uring BlockDriver to QEMU using libblkio. For now > I/O buffers are copied through bounce buffers if the libblkio driver > requires it. Later commits add an optimization for pre-registering guest > RAM to avoid bounce buffers. It will be easy to add other libblkio > drivers since they will share the majority of code. > > Signed-off-by: Stefan Hajnoczi > +static BlockDriver bdrv_io_uring = { > + .format_name = "io_uring", > + .protocol_name = "io_uring", > + .instance_size = sizeof(BDRVBlkioState), > + .bdrv_needs_filename = true, > + .bdrv_parse_filename = blkio_parse_filename_io_uring, > + .bdrv_file_open = blkio_file_open, > + .bdrv_close = blkio_close, > + .bdrv_getlength = blkio_getlength, > + .has_variable_length = true, This one is a bad idea. It means that every request will call blkio_getlength() first, which looks up the "capacity" property in libblkio and then calls lseek() for the io_uring backend. For other backends like the vhost_user one (where I just copied your definition and then noticed this behaviour), it involve a message over the vhost socket, which is even worse. .has_variable_length was only meant for the host_floppy/cdrom drivers that have to deal with media change. Everything else just requires an explicit block_resize monitor command to be resized. Kevin