On 10/19/2010 01:16 PM, Jerry Franz wrote:
On 10/19/2010 03:47 AM, Dennis Jacobfeuerborn wrote:
On 10/19/2010 09:41 AM, Pasi Kärkkäinen wrote:
It's because of the x86_64 architecture, afaik.
There was some good technical explananation about it, but I can't remember the url now.
In that case I'll have to call this advice extremely bogus and you probably should refrain from passing it on. The only way I can see this being true is some weird corner case.
There appear to be some interactions with the Intel VT-d processor features.
http://www.xen.org/files/xensummit_intel09/xensummit2009_IOVirtPerf.pdf
If I understand that paper correctly, HVM+VT-d outperforms PV by quite a lot (if you have VT-d support on your system).
Thanks for that link. Just to make my criticism of the initial claim more clear: I don't claim that HVM can never be faster than PV but that you need to understand when exactly this is the case. For example I'm not sure that x86_64 vs. x86 really enters into this but I can definitely see VT-d making an impact there.
Regards, Dennis