Re: [Xen-ia64-devel] Time for hybrid virtualization?

[Joseph Szczypek <joseph.szczypek@xxxxxx>]

Hi everyone,

I've been reading the hybrid virtualization discussions.  Could someone 
explain the relationship of a VT-Dom0 to guests?  I ask because I see 
several 'requirements' being raised on the xen-ia64-devel list with 
respect to the hybrid virtualization idea, things like PV DomU should 
work, PV Dom0 should still be around, etc.   I'm hoping someone could 
help clarify things.
Here is my assumption:
VT-Dom0 would have native IO, native FW access, and some paravirtualized 
'stuff' (process context switching?, what else?)  No PV Dom0 like we 
have today would exist.
My questions:
What type guests would work:
  - HVM only?
     * Qemu still required?   
  - HVM guest with PV-on-HVM drivers?
     * does this mean a front-end/back-end would still exist, but now 
between a VT-Dom0 and HVM DomU?
  - PV guests would no longer exist?

Would VT-Dom0 be unique?
I'm assuming it would be unique to Dom0, not quite like PV Dom0 today, 
but also not a 'standard umodified guest'.  With that in mind, will 
there still be support issues in terms of different things to support 
(today it's PV Dom0 plus PV guest plus HVM guest support - tomorrow it 
would be hybrid Dom0 (VT with PV hooks) plus HVM guest support (assuming 
no PV guest would exist).
-Joe

Alex Williamson wrote:
> Hi all,
>
>    I got a pointer to re-aim-7 and thought the high-systime workload
> might give us a good worst case scenario.  This workload does no I/O and
> a lot of the tests produce very high system time.  Here's the results:
>
>
>
>                  Max JPM
>              % of native
> Native
>                242347.19
>                  100.00%
> Para-virt
>                218694.95
>                   90.24%
> Full-virt
>                 58289.32
>                   24.05%
>
> Not a pretty picture for HVM.  My test system is a 2-socket, dual core
> Montvale w/ threads disabled (4-way), 16GB RAM total.  This is the same
> system I used for the kernel build tests.  The guest domain was
> configured for 4-way, 8G, and I used mem=8G to get the native test to
> use the same.  PV-on-HVM drivers did not improve the full-virt numbers.
> I've attached a graph of the runs.  This is obviously a concern for a
> VT-mode dom0.  We probably need to profile the HVM run to see if these
> are things that could be easily paravirtualized for a hybrid mode guest.
>
>         Alex
>
>   
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