[Xen-users] XP HVM performance

[Matthieu Patou <mat+Informatique.xen@xxxxxxxxx>]

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

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