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RE: [Xen-users] Using the -xen kernel rather than -xen0/U

  • To: "Nicolai Lang" <nicolai@xxxxxxxxxx>, xen-users@xxxxxxxxxxxxxxxxxxx
  • From: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
  • Date: Thu, 5 Apr 2007 13:15:20 +0200
  • Delivery-date: Thu, 05 Apr 2007 04:15:31 -0700
  • List-id: Xen user discussion <xen-users.lists.xensource.com>
  • Thread-index: AcdwEc45fChF6g82QRuZlDHXjsFGlQGc+YXwAAhDNTAAL8UzQAADPxIA
  • Thread-topic: [Xen-users] Using the -xen kernel rather than -xen0/U


> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Nicolai Lang
> Sent: 05 April 2007 10:54
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: RE: [Xen-users] Using the -xen kernel rather than -xen0/U
> Hey Mats,
> > relatively slow speed, I'd expect you're not planning to run 
> > tens or hundreds of guests... ;-) So is the saving of maybe 
> > 2-4 megabyte per guest worth the bother of figuring out 
> > exactly which options in the kernel you actually need and how 
> > to strip off the bits you don't need?
> Thanks, if it is only in that amount then I will run with the combined
> kernel (if it aint broke, don't fix it ;) ).
> I will be running a max of 10 guests (more like 5-7).
> But I have two extra questions that arise as I was playing 
> with my first
> guests:
> 1)
> The dom0 is of course installed as AMD64 architechture. I was 
> considering
> installing the guests as i386, sincen I then will be able to 
> run them under
> my spare (3 year old Dell PE 1600) Xeon server. 
> Is that a sensible choice? 

At present (3.0.4), para-virtual guests will need to run at the same
"bitness" as the Dom0, so you either use 64-bit all over, or 32-bit. 

HVM (fully virtualized) guests can be whatever bitness is less or equal
to Dom0. 

There is little difference between running 32 and 64-bit (most of it is
marginally to the advantage of 64-bit, but unless you really need huge
amounts of memory, I'd say you wouldn't be able to tell any difference
other than by specific benchmarks). 
> 2)
> I choose the processor because it was on stock, reasonably priced, and
> because it should support HVM
> (http://wiki.xensource.com/xenwiki/HVM_Compatible_Processors),
>  but I do not
> see any HVM messages during boot, nor do CPUinfo flags 
> contain the vmx flag.
> The processor is an AMD Athlon 64 X2 - 3800+ 2.0GHz BOX - AM2 EE, the
> motheboard an Asus M2N-E.

/proc/cpuinfo should contain "svm" (but not "vmx", as that's the Intel
name for their corresponding technology). ["svm" is in your

All AM2 processors are HVM compatible except if they are called

> Have I made a blunder? Does the HVM demand a certain motherboard? I'm
> attaching cpuinfo and dmesg
> Thank's in advance.
> Best regards
> Nicolai

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