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 X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 17A28C433B4 for ; Thu, 15 Apr 2021 14:18:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E0A2B6124B for ; Thu, 15 Apr 2021 14:18:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233270AbhDOOSW (ORCPT ); Thu, 15 Apr 2021 10:18:22 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:28890 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230056AbhDOOSW (ORCPT ); Thu, 15 Apr 2021 10:18:22 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618496278; 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=IOewNMfPKKreZaktQJpTbBLLtYdk3yANsE5YR8AZsrE=; b=KXSgGbCegOEB8+S8PQg6Q9BiIdiDhoxkQATj9FDdYGC3QeFRsarGybnicop9QwVNifkk1O qjBtGh1+1W+3XrAvyITku+Kh+fbKvEqSGsGn95917QJaDF7meAB/7IW8iuwUTX3T0bfUu2 QCicWAMMr7VT3rA/6kd43yWqpoVdo6Q= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-130-zPBktbWMNaCxZdXJ3ywBsA-1; Thu, 15 Apr 2021 10:17:55 -0400 X-MC-Unique: zPBktbWMNaCxZdXJ3ywBsA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5981D801814; Thu, 15 Apr 2021 14:17:52 +0000 (UTC) Received: from localhost (ovpn-114-209.ams2.redhat.com [10.36.114.209]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4D7495D723; Thu, 15 Apr 2021 14:17:47 +0000 (UTC) Date: Thu, 15 Apr 2021 15:17:47 +0100 From: Stefan Hajnoczi To: Yongji Xie Cc: "Michael S. Tsirkin" , Jason Wang , Stefano Garzarella , Parav Pandit , Christoph Hellwig , Christian Brauner , Randy Dunlap , Matthew Wilcox , viro@zeniv.linux.org.uk, Jens Axboe , bcrl@kvack.org, Jonathan Corbet , Mika =?iso-8859-1?Q?Penttil=E4?= , Dan Carpenter , virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, kvm@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: Re: Re: [PATCH v6 10/10] Documentation: Add documentation for VDUSE Message-ID: References: <20210331080519.172-1-xieyongji@bytedance.com> <20210331080519.172-11-xieyongji@bytedance.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="MPbHG8vrrTTLxD+q" Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org --MPbHG8vrrTTLxD+q Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Apr 15, 2021 at 04:33:27PM +0800, Yongji Xie wrote: > On Thu, Apr 15, 2021 at 3:19 PM Stefan Hajnoczi wro= te: > > On Thu, Apr 15, 2021 at 01:38:37PM +0800, Yongji Xie wrote: > > > On Wed, Apr 14, 2021 at 10:15 PM Stefan Hajnoczi wrote: > > > > On Wed, Mar 31, 2021 at 04:05:19PM +0800, Xie Yongji wrote: > > It's not obvious to me that there is a fundamental difference between > > the two approaches in terms of performance. > > > > > On the other > > > hand, we can handle the virtqueue in a unified way for both vhost-vdpa > > > case and virtio-vdpa case. Otherwise, userspace daemon needs to know > > > which iova ranges need to be accessed with pread(2)/pwrite(2). And in > > > the future, we might be able to avoid bouncing in some cases. > > > > Ah, I see. So bounce buffers are not used for vhost-vdpa? > > >=20 > Yes. Okay, in that case I understand why mmap is used and it's nice to keep virtio-vpda and vhost-vdpa unified. Thanks! Stefan --MPbHG8vrrTTLxD+q Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmB4SwsACgkQnKSrs4Gr c8iNcgf/SlAcQNeAhYZD3E8EAxA7kj75HWb2bs314xQK1UuM8yPecd9e468z8oN6 e0lS0+RDTiPjrV+Nlpgs6+xVqLAjatBXGWiauZeed+q6kMlAlt9OiZApRG3/AACc spwkoFaL9mPKBS5lAaGAEiJqd3ZjA1EpKbXq8klSFDVYLXkfD8qyxxsAUlREsH6t s0yoJqiZlLqcDPcfPw4aCEOZteP3MNSinotRCHDDQ6X0cDpcqCyInpClclxd507Z fxz/hu7w1vEbPIGcp6O5VsaUolPr74X0HS4lkDRN32vh8OkDnGsoDiNQg0sduQ5u FV/ND4nsUIUTsXxlBnLOcX2Cj1V4/w== =wUKZ -----END PGP SIGNATURE----- --MPbHG8vrrTTLxD+q--