[asterisk-users] Virtual machine timing (KVM)

[David Backeberg]

On Mon, Feb 22, 2010 at 10:51 AM, Jonathan Addleman <jono at redowl.ca> wrote:
> David Backeberg wrote:
>> Timers are built on the premise that they have access to either a real
>> timing device, or unobstructed access to a processor which clicks
>> through a proc cycle at a pre-determined rate. Once you break those
>> rules, don't be surprised when the timers stop working, and 'bad
>> things' happen.
>
> Forgive the possibly stupid question, but do these problems you describe
> apply equally to the dom0 as to any domU's in a xen system? I used to
> think not, but now I'm starting to realize that I'm probably mistaken...

http://wiki.xensource.com/xenwiki/Scheduling

It sounds like there are multiple ways to do scheduling in a Xen situation.

The best way to avoid overloading the system is to deliberately
underutilize the system, but then what's the point of virtualization?
The supposed benefits of virtualization are power savings, and better
utilization of existing resources. If you're using it for other
reasons like a development environment, you'll probably be fine.

To be clear, you may get away with virtualization and never run into
any problems. But you have to know who to blame when you DO run into
problems. Having problems of the sort uniquely caused by starving
virtual kernels for resources is not going to be the fault of
asterisk, but rather a failure to anticipate the downside of trying to
use virtualization with asterisk.