From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sog-mx-1.v43.ch3.sourceforge.com ([172.29.43.191] helo=mx.sourceforge.net) by sfs-ml-3.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1VA1q1-0008DD-6s for user-mode-linux-devel@lists.sourceforge.net; Thu, 15 Aug 2013 17:59:57 +0000 Received: from mx1.redhat.com ([209.132.183.28]) by sog-mx-1.v43.ch3.sourceforge.com with esmtp (Exim 4.76) id 1VA1q0-0006mf-07 for user-mode-linux-devel@lists.sourceforge.net; Thu, 15 Aug 2013 17:59:57 +0000 Date: Thu, 15 Aug 2013 18:59:45 +0100 From: "Richard W.M. Jones" Message-ID: <20130815175945.GO5918@redhat.com> References: <20130809204355.GA10864@redhat.com> <20130814175911.GG10864@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: List-Id: The user-mode Linux development list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: user-mode-linux-devel-bounces@lists.sourceforge.net Subject: Re: [uml-devel] Performance tests (was: Using UML in libguestfs) To: richard -rw- weinberger Cc: "user-mode-linux-devel@lists.sourceforge.net" On Thu, Aug 15, 2013 at 07:37:06PM +0200, richard -rw- weinberger wrote: > On Wed, Aug 14, 2013 at 7:59 PM, Richard W.M. Jones wrote: > > > > I performed some benchmarks against KVM: > > > > http://rwmj.wordpress.com/2013/08/14/performance-of-user-mode-linux-as-a-libguestfs-backend/#content > > > > Notes for those that don't want to read all that, there are at least > > two bugs I found: > > > > (1) fsync /dev/ubda (in the guest) is not honoured by the user-mode > > linux process. It should do an fsync on the corresponding backing file. > > What exactly does libguestfs do? http://libguestfs.org/ ... > > (2) The ssl=... serial port is really slow, at least 10 times > > slower than virtio-serial which is the equivalent KVM feature. > > libguestfs is chatty over the serial port, and so this has a > > significant knock-on impact all over the place. > > So, libguestfs transfers all data over a serial line?! Well, it requires an 8-bit clean, reliable, bi-directional connection into the guest. We used to use TCP/IP but it's pretty slow compared to virtio-serial and has a bunch of other problems. For the UML backend I used the serial port. There's no problem with it -- it works and it's reliable, it's just slow. > We could hack a faster transport into UML. > As UML is only a process we can very easily access > the host. > Have looked at hostfs? Not sure how hostfs would help? Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/ ------------------------------------------------------------------------------ Get 100% visibility into Java/.NET code with AppDynamics Lite! It's a free troubleshooting tool designed for production. Get down to code-level detail for bottlenecks, with <2% overhead. Download for free and get started troubleshooting in minutes. http://pubads.g.doubleclick.net/gampad/clk?id=48897031&iu=/4140/ostg.clktrk _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel