[Xen-users] XP HVM performance

Matthieu Patou
Thu, 25 Jun 2009 07:28:57 -0000

I recently reinstalled an XP over my xen 3.2.1 (my conf is at the end of
the mail).

And it''s working but I find it a bit (well a big bit ...) too slow and
use a lot of CPU.

For instance just having a taskmanager running use between 10/15% of CPU
as reported by taskmanager and xm top.

When I run iozone the CPU usage is almost 95% whereas on a real XP
workstation it''s only a few percents.

The server hosting this XP is a 4 core Xeon E5320  @ 1.86GHz and I have
only dom0 with 2 VCPU and 1 VCPU in XP.

I know that running XP in XEN will bring a penalty but I wasn''t
expecting such penalty.

Do I miss something ?

I also use the latest GPL PV drivers and found with iozone that the
throughput is 1/3 of the raw capacity of the disk (as measured in dom0).
Does this number seems normal to you or once more am I missing something ?

Finally I also did some tests with more than one VCPU but if the whole
system load reduced somehow (which is logical) the IO perf where even
worse. Is it a good idea to use more than one VCPU in HVM ?




my conf:
import os, re, time
arch = os.uname()[4]
if re.search(''64'', arch):
     arch_libdir = ''lib64''
else:
     arch_libdir = ''lib''
kernel = "/usr/lib/xen-3.2-1/boot/hvmloader"
builder=''hvm''
memory = 512
shadow_memory = 8
name = "ecvssvz01"
vif = [ ''bridge=br2'' ]
disk = [
''phy:/dev/vg00/xphvm,hda,w'',''phy:/dev/hdb,hdd:cdrom,r'']
device_model = ''/usr/'' + arch_libdir +
''/xen-3.2-1/bin/qemu-dm''
boot="d"
acpi = 1
apic = 1
sdl=0
vnc=1
usb=1
usbdevice=''tablet''
rtc_timeoffset=-(time.altzone)
localtime=0
vncconsole=0
monitor=1
serial=''pty''
vncviewer = 0
stdvga=0
vcpus = 1

Matthieu