From mboxrd@z Thu Jan 1 00:00:00 1970 From: Asias He Subject: Re: [PATCH 0/5] Add vhost-blk support Date: Wed, 18 Jul 2012 16:47:27 +0800 Message-ID: <5006781F.1060900@redhat.com> References: <1342107302-28116-1-git-send-email-asias@redhat.com> <50052276.2080906@redhat.com> <500527BA.9000001@redhat.com> <50052E7E.6020100@redhat.com> <20120717112645.GA9363@redhat.com> <20120717115450.GA9796@redhat.com> <20120717124859.GA9883@redhat.com> <50056275.6000407@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: "Michael S. Tsirkin" , Stefan Hajnoczi , linux-kernel@vger.kernel.org, linux-aio@kvack.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, Benjamin LaHaise , Alexander Viro , linux-fsdevel@vger.kernel.org To: Paolo Bonzini Return-path: In-Reply-To: <50056275.6000407@redhat.com> Sender: owner-linux-aio@kvack.org List-Id: kvm.vger.kernel.org On 07/17/2012 09:02 PM, Paolo Bonzini wrote: > Il 17/07/2012 14:48, Michael S. Tsirkin ha scritto: >> On Tue, Jul 17, 2012 at 01:03:39PM +0100, Stefan Hajnoczi wrote: >>> On Tue, Jul 17, 2012 at 12:54 PM, Michael S. Tsirkin wrote: >>>>> Knowing the answer to that is important before anyone can say whether >>>>> this approach is good or not. >>>>> >>>>> Stefan >>>> >>>> Why is it? >>> >>> Because there might be a fix to kvmtool which closes the gap. It >>> would be embarassing if vhost-blk was pushed just because no one >>> looked into what is actually going on. >> >> Embarrasing to whom? Is someone working on an optimization that >> makes the work in question redundant, with posting just around >> the corner? Then maybe the thing to do is just wait a bit. > > Of course there is work going on to make QEMU perform better. Not sure > about lkvm. Of course for lkvm also. >>> And on the flipside, hard evidence of an overhead that cannot be >>> resolved could be good reason to do more vhost devices in the future. >> >> How can one have hard evidence of an overhead that cannot be resolved? > > Since we do have two completely independent userspaces (lkvm and > data-plane QEMU), you can build up some compelling evidence of an > overhead that cannot be resolved in user space. This does not build the hard evidence either. How can one prove that userspace lkvm and data-plane QEMU can not be improved further? The same for vhost-blk. >>> Either way, it's useful to do this before going further. >> >> I think each work should be discussed on its own merits. Maybe >> vhost-blk is just well written. So? What is your conclusion? > > If it's just that vhost-blk is written well, my conclusion is that lkvm > people should look into improving their virtio-blk userspace. We take > hints from each other all the time, for example virtio-scsi will have > unlocked kick in 3.6. > > Why can't vhost-* just get into staging, and we call it a day? OK. I'm fine with staging. -- Asias -- To unsubscribe, send a message with 'unsubscribe linux-aio' in the body to majordomo@kvack.org. For more info on Linux AIO, see: http://www.kvack.org/aio/ Don't email: aart@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753140Ab2GRIpm (ORCPT ); Wed, 18 Jul 2012 04:45:42 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33023 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752521Ab2GRIpg (ORCPT ); Wed, 18 Jul 2012 04:45:36 -0400 Message-ID: <5006781F.1060900@redhat.com> Date: Wed, 18 Jul 2012 16:47:27 +0800 From: Asias He User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120615 Thunderbird/13.0.1 MIME-Version: 1.0 To: Paolo Bonzini CC: "Michael S. Tsirkin" , Stefan Hajnoczi , linux-kernel@vger.kernel.org, linux-aio@kvack.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, Benjamin LaHaise , Alexander Viro , linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 0/5] Add vhost-blk support References: <1342107302-28116-1-git-send-email-asias@redhat.com> <50052276.2080906@redhat.com> <500527BA.9000001@redhat.com> <50052E7E.6020100@redhat.com> <20120717112645.GA9363@redhat.com> <20120717115450.GA9796@redhat.com> <20120717124859.GA9883@redhat.com> <50056275.6000407@redhat.com> In-Reply-To: <50056275.6000407@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/17/2012 09:02 PM, Paolo Bonzini wrote: > Il 17/07/2012 14:48, Michael S. Tsirkin ha scritto: >> On Tue, Jul 17, 2012 at 01:03:39PM +0100, Stefan Hajnoczi wrote: >>> On Tue, Jul 17, 2012 at 12:54 PM, Michael S. Tsirkin wrote: >>>>> Knowing the answer to that is important before anyone can say whether >>>>> this approach is good or not. >>>>> >>>>> Stefan >>>> >>>> Why is it? >>> >>> Because there might be a fix to kvmtool which closes the gap. It >>> would be embarassing if vhost-blk was pushed just because no one >>> looked into what is actually going on. >> >> Embarrasing to whom? Is someone working on an optimization that >> makes the work in question redundant, with posting just around >> the corner? Then maybe the thing to do is just wait a bit. > > Of course there is work going on to make QEMU perform better. Not sure > about lkvm. Of course for lkvm also. >>> And on the flipside, hard evidence of an overhead that cannot be >>> resolved could be good reason to do more vhost devices in the future. >> >> How can one have hard evidence of an overhead that cannot be resolved? > > Since we do have two completely independent userspaces (lkvm and > data-plane QEMU), you can build up some compelling evidence of an > overhead that cannot be resolved in user space. This does not build the hard evidence either. How can one prove that userspace lkvm and data-plane QEMU can not be improved further? The same for vhost-blk. >>> Either way, it's useful to do this before going further. >> >> I think each work should be discussed on its own merits. Maybe >> vhost-blk is just well written. So? What is your conclusion? > > If it's just that vhost-blk is written well, my conclusion is that lkvm > people should look into improving their virtio-blk userspace. We take > hints from each other all the time, for example virtio-scsi will have > unlocked kick in 3.6. > > Why can't vhost-* just get into staging, and we call it a day? OK. I'm fine with staging. -- Asias