Re: [Xen-users] XP HVM performance

Matthieu Patou
Thu, 25 Jun 2009 11:02:56 -0000

On 06/25/2009 11:37 AM, James Harper wrote:
>> 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 ?
>>
>>
>
> Please try putting /PATCHTPR in your boot.ini (make a copy of the
> existing line in case it causes a problem). That will get GPLPV to patch
> the windows kernel to stop using one of the hardware APIC registers so
> often (intel) or at all (amd). Let me know if that affects the speed in
> any way.
>
>
I was already using it because otherwise the system is so slow.
I tried john the ripper on dom0, domU with /patchtpr and without. The
two first are very close and the third one is little behind the second
but not so far ...
So it seems that some applications are OK with XP in Xen some others not ...
Am I the only one to feel this problem so badly ?

Matthieu.