From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [GIT PULL] AlacrityVM guest drivers for 2.6.33 Date: Mon, 21 Dec 2009 17:43:09 +0200 Message-ID: <4B2F978D.7010602@redhat.com> References: <4B1D4F29.8020309@gmail.com> <20091218215107.GA14946@elte.hu> <4B2F9582.5000002@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: 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: Gregory Haskins Return-path: In-Reply-To: <4B2F9582.5000002@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 12/21/2009 05:34 PM, Gregory Haskins wrote: > >> I think it would be fair to point out that these patches have been objected to >> by the KVM folks quite extensively, >> > Actually, these patches have nothing to do with the KVM folks. You are > perhaps confusing this with the hypervisor-side discussion, of which > there is indeed much disagreement. > This is true, though these drivers are fairly pointless for virtualization without the host side support. I did have a few issues with the guest drivers: - the duplication of effort wrt virtio. These drivers don't cover exactly the same problem space, but nearly so. - no effort at scalability - all interrupts are taken on one cpu - the patches introduce a new virtual interrupt controller for dubious (IMO) benefits > From my research, the reason why virt in general, and KVM in particular > suffers on the IO performance front is as follows: IOs > (traps+interrupts) are more expensive than bare-metal, and real hardware > is naturally concurrent (your hbas and nics are effectively parallel > execution engines, etc). > > Assuming my observations are correct, in order to squeeze maximum > performance from a given guest, you need to do three things: A) > eliminate as many IOs as you possibly can, B) reduce the cost of the > ones you can't avoid, and C) run your algorithms in parallel to emulate > concurrent silicon. > All these are addressed by vhost-net without introducing new drivers. -- error compiling committee.c: too many arguments to function