From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [GIT PULL] AlacrityVM guest drivers for 2.6.33 Date: Tue, 22 Dec 2009 10:27:33 -0600 Message-ID: <4B30F375.6050103@codemonkey.ws> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit 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" To: Andi Kleen Return-path: In-Reply-To: <20091222162110.GG10314@basil.fritz.box> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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 >