Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753827AbZLVQ1j (ORCPT ); Tue, 22 Dec 2009 11:27:39 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752155AbZLVQ1h (ORCPT ); Tue, 22 Dec 2009 11:27:37 -0500 Received: from mail-yx0-f187.google.com ([209.85.210.187]:52707 "EHLO mail-yx0-f187.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750948AbZLVQ1g (ORCPT ); Tue, 22 Dec 2009 11:27:36 -0500 Message-ID: <4B30F375.6050103@codemonkey.ws> Date: Tue, 22 Dec 2009 10:27:33 -0600 From: Anthony Liguori User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.5) Gecko/20091209 Fedora/3.0-4.fc12 Thunderbird/3.0 MIME-Version: 1.0 To: Andi Kleen CC: Gregory Haskins , Avi Kivity , Ingo Molnar , kvm@vger.kernel.org, Andrew Morton , torvalds@linux-foundation.org, "linux-kernel@vger.kernel.org" , netdev@vger.kernel.org, "alacrityvm-devel@lists.sourceforge.net" Subject: Re: [GIT PULL] AlacrityVM guest drivers for 2.6.33 References: <4B2F9582.5000002@gmail.com> <4B2F978D.7010602@redhat.com> <4B2F9C85.7070202@gmail.com> <4B2FA42F.3070408@codemonkey.ws> <4B2FA655.6030205@gmail.com> <4B2FAE7B.9030005@codemonkey.ws> <4B2FB3F1.5080808@gmail.com> <4B300EF8.8010602@codemonkey.ws> <87637zdy9g.fsf@basil.nowhere.org> <4B30E654.40702@codemonkey.ws> <20091222162110.GG10314@basil.fritz.box> In-Reply-To: <20091222162110.GG10314@basil.fritz.box> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1628 Lines: 45 On 12/22/2009 10:21 AM, Andi Kleen wrote: >> So far, the only actual technical advantage I've seen is that vbus avoids >> EOI exits. >> > The technical advantage is that it's significantly faster today. > There are two separate pieces of code in question. There are front-end drivers and there are back-end drivers. Right now, there are only front-end drivers in the kernel today. The combination of vbus front-end drivers and *kernel* back-end drivers are faster than the *combination* of virtio front-end drivers and *userspace* back-end drivers. vhost-net is our kernel back-end driver. No one has yet established that the combination of virtio front-end driver and kernel back-end driver is really significantly slower than vbus. > Maybe your proposed alternative is as fast, or maybe it's not. Who knows? > > >> We think we understand why vbus does better than the current userspace >> virtio backend. That's why we're building vhost-net. It's not done yet, >> but our expectation is that it will do just as well if not better. >> > That's the vapourware vs working code disconnect I mentioned. One side has hard > numbers&working code and the other has expectations. I usually find it sad when the > vapourware holds up the working code. > We're not talking about vaporware. vhost-net exists. Regards, Anthony Liguori > -Andi > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/