Xen project Mailing List

On 15 May 2014 17:36, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:

On Thu, 2014-05-15 at 17:04 +0200, Stefan Vroom wrote:
> If I understand correctly PV drivers must be available on the
> operating system of the unprivileged domain (our operating system).

True.

> ÂIf this is true we only have access to emulated devices which I
> currently use.

This will most likely be the performance bottleneck then I'm afraid.

> ÂThe operating system itself has drivers for realtek8139, 8169, pcnet,
> e100 and e100 I believe. However I could not get all of the emulated
> drivers to work. Pcnet worked but as said the results aren't quite
> satisfying.

e1000 supposedly virtualises better than other NICs, so you might have
some luck with that.

I'd highly recommend you investigate writing some PV drivers for your
OS. Depending on licensing you can find examples in both Linux and
{Net,Free}BSD, as well as GPL drivers for Windows and (BSD) drivers in
the "minios" example PV OS shipped with Xen.

Ian.

We upgraded the system to Xen 4.4.
However Xen platform pci is enabled and we are using the pcnet device model.

From the wiki:

"In dom0 in the "/etc/xen/<vm>" configuration file use the following syntax:

vif = [ 'mac=00:16:5e:02:07:45, bridge=xenbr0, model=e1000' ]
disk = [ 'phy:/dev/vg01/vm01-disk0,hda,w', ',hdc:cdrom,r' ]
xen_platform_pci=1

With this example configuration when "xen_platform_pci" is enabled ("1"), the guest VM can use optimized PVHVM drivers: xen-blkfront for disk, and xen-netfront for network. When "xen_platform_pci" is disabled ("0"), the guest VM will use Xen Qemu-dm emulated devices: emulated IDE disk and emulated intel e1000 nic. "

So this should result in just using PV and no emulation. The pcnet driver on our end seems to be okay with that as our VM is able to establish an internet connection. Does this mean we are using PV after all? If so how come our driver is working here as PV driver? What is a PV driver all about really?

In case of using a PV driver I think we can best follow the steps on: http://wiki.xen.org/wiki/Network_Throughput_and_Performance_Guide#Symptoms.2C_probable_causes.2C_and_advice to improve further performance.

Thanks again.

Here's my configuration file:

builder='hvm'

vcpus='1'

memory='256'

disk=['/usr/img/gp.raw,,hda,w']

name='VrooM'

vif=['mac=00:16:3e:01:01:01, bridge=xenbr0, model=pcnet']

boot='dc'

acpi='1'

apic='1'

viridian='1'

xen_platform_pci='1'

sdl='0'

vnc='1'

vnclisten='0.0.0.0'

vga="cirrus"

usb='1'

usbdevice='tablet'

serial='pty'

device_model_version="qemu-xen"

device_model_override="/usr/bin/qemu"

Re: [Xen-users] Improving the performance of a Xen VM