Poor performance with FreeBSD 10.1 under Xen 4.2

[Rainer Duffner]

> Am 02.04.2015 um 19:58 schrieb Andrew Daugherity <adaugherity at tamu.edu>:
> 
> On Mar 30, 2015, at 6:52 PM, Andrew Daugherity <adaugherity at tamu.edu> wrote:
>> On Mar 28, 2015, at 8:16 AM, Roger Pau Monné <roger.pau at citrix.com> wrote:
>>> I'm Ccing feld because IIRC he found something similar on one of his
>>> boxes, that also had VTx but no EPT (just like yours). Would it be
>>> possible for you to try the same set of tests on a different hardware?
>> 
>> I think you're on to something.  I copied this FreeBSD 10.1 VM to a system running the same version of Xen (and same SLES in the Dom0), but with an Opteron 2360SE CPU (which has both SVM and NPT), and it is *much* faster (and feels more responsive too):
>> [snip]
>>> Also, if even FreeBSD 10.1 compiled without XENHVM shows this issue it
>>> means there's something in the generic code that doesn't work well when
>>> running virtualized on this specific hardware, but I'm afraid figuring
>>> it out is not trivial. One place to start would be asking on
>>> freebsd-hackers and freebsd-virt.
>> 
>> I suppose this performance delta with presence of EPT/NPT vs. lack thereof means it's time to take it to those lists?  My next step will be to test 10.1 under KVM on the Xeon to confirm whether it's a Xen issue or strictly EPT.
> 
> It seems I spoke too soon.  I booted into the "default" (non-Xen) Linux kernel on the Xeon E5420 box and launched the same FreeBSD 10.1 VM under KVM, and performance is much, much better:
> 



Hi,

I have access to Xen at work (and will continue to do so - we intend to use and offer FreeBSD in our „Cloud“-platform (Apache CloudStack).

AFAIK, we have no KVM. Just Xen.


Unfortunately, I’ve got little time currently, but I will try to get a VM where I can run this during the next week.

I will also collect the hardware-details of the host (AFAIK, we’ve got HP DL380G8 servers with lots of RAM and two CPUs).



Rainer