From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH V4 3/3] virtio-blk: Add bio-based IO path for virtio-blk Date: Mon, 30 Jul 2012 15:42:47 +0200 Message-ID: <20120730134247.GA6041@lst.de> References: <1343442065-15646-1-git-send-email-asias@redhat.com> <1343442065-15646-4-git-send-email-asias@redhat.com> <20120729111115.GD8977@redhat.com> <87a9yim2qg.fsf@rustcorp.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <87a9yim2qg.fsf@rustcorp.com.au> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Rusty Russell Cc: kvm@vger.kernel.org, "Michael S. Tsirkin" , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Christoph Hellwig List-Id: virtualization@lists.linuxfoundation.org On Mon, Jul 30, 2012 at 11:25:51AM +0930, Rusty Russell wrote: > I consider this approach a half-way step. Quick attempts on my laptop > and I couldn't find a case where the bio path was a loss, but in theory > if the host wasn't doing any reordering and it was a slow device, you'd > want the guest to do so. > > I'm not sure if current qemu can be configured to do such a thing? The host kernel will do the I/O scheduling for you unless you explicitly disable it. And we should be able to assume an administrator will only disable it when they have a reason for it - if not they'll get worse performance for non-virtualized workloads as well.