From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [PATCH v3 3/6] vbus: add a "vbus-proxy" bus model for vbus_driver objects Date: Mon, 17 Aug 2009 08:54:26 -0500 Message-ID: <4A896112.9030407@codemonkey.ws> References: <20090814154125.26116.70709.stgit@dev.haskins.net> <20090814154308.26116.46980.stgit@dev.haskins.net> <20090815103243.GA26749@elte.hu> <4A870964.9090408@codemonkey.ws> <20090816071607.GB29537@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Gregory Haskins , kvm@vger.kernel.org, Avi Kivity , alacrityvm-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, "Michael S. Tsirkin" To: Ingo Molnar Return-path: Received: from mail-yw0-f173.google.com ([209.85.211.173]:41023 "EHLO mail-yw0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752473AbZHQNy1 (ORCPT ); Mon, 17 Aug 2009 09:54:27 -0400 In-Reply-To: <20090816071607.GB29537@elte.hu> Sender: netdev-owner@vger.kernel.org List-ID: Ingo Molnar wrote: >> I think the reason vbus gets better performance for networking >> today is that vbus' backends are in the kernel while virtio's >> backends are currently in userspace. Since Michael has a >> functioning in-kernel backend for virtio-net now, I suspect we're >> weeks (maybe days) away from performance results. My expectation >> is that vhost + virtio-net will be as good as venet + vbus. If >> that's the case, then I don't see any reason to adopt vbus unless >> Greg things there are other compelling features over virtio. >> > > Keeping virtio's backend in user-space was rather stupid IMHO. > I don't think it's quite so clear. There's nothing about vhost_net that would prevent a userspace application from using it as a higher performance replacement for tun/tap. The fact that we can avoid userspace for most of the fast paths is nice but that's really an issue of vhost_net vs. tun/tap. From the kernel's perspective, a KVM guest is just a userspace process. Having new userspace interfaces that are only useful to KVM guests would be a bad thing. Regards, Anthony Liguori