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 <rjo...@redhat.com> 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<N>=... 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
