From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [PATCH RESEND 5/5] vhost-blk: Add vhost-blk support Date: Fri, 20 Jul 2012 15:56:19 -0500 Message-ID: <87obnaup70.fsf@codemonkey.ws> References: <1342169711-12386-1-git-send-email-asias@redhat.com> <1342169711-12386-6-git-send-email-asias@redhat.com> <87mx2vrjdl.fsf@codemonkey.ws> <20120719130957.GD9303@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Asias He , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org To: "Michael S. Tsirkin" Return-path: In-Reply-To: <20120719130957.GD9303@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org "Michael S. Tsirkin" writes: > On Thu, Jul 19, 2012 at 08:05:42AM -0500, Anthony Liguori wrote: >> Of course, the million dollar question is why would using AIO in the >> kernel be faster than using AIO in userspace? > > Actually for me a more important question is how does it compare > with virtio-blk dataplane? I'm not even asking for a benchmark comparision. It's the same API being called from a kernel thread vs. a userspace thread. Why would there be a 60% performance difference between the two? That doesn't make any sense. There's got to be a better justification for putting this in the kernel than just that we can. I completely understand why Christoph's suggestion of submitting BIOs directly would be faster. There's no way to do that in userspace. Regards, Anthony Liguori > > -- > MST