On Thursday 19 June 2008, JD wrote: > Stating the obvious that virtualization cannot be as fast > as running on raw HW is not the issue at all.
I would suggest you to read some papers about full virtualization
and first.
> I am noticing 100% cpu utilization by VBox when I run
> apps on guest, which when run on host, do not use more
> than 15 - 20 % of cpu. So no matter what "optimizations"
> are implemented in VBox, I and others are seeing cpu
> utilization that is up to 5 times the utilization as when
> app is run on host. On V-Tech cpu's this is likely not as
> extreme.
> So, I am finding that virtualization in general
> is not very practical for these older non-VTech cpu's.
The 100% CPU load you experience is a probably a bug which can be
fixed. Most people are satisfied with VirtualBox and its performance.
I guess there is some bad interaction between your hardware, your
host operating system and your guest. We have dozens of guests here
running very fast and showing a low CPU load on the host -- with
VT-x and AMD-V disabled. Note that some guests behave very unfriendly
to virtualization. Take Windows 3.x/95/98: These don't execute `hlt`
during the idle state (as modern operating systems do) but do
something like
void reschedule()
{
for (;;)
{
thread_t *t = ready_list;
if (t)
switch_to(t);
else
/* ready list is empty -- nothing to do */
;
}
}
Catching this case is obviously difficult as the VMM cannot know
if the guest is _really_ idle or if the guest does some calculation.
Try this endless loop on your host, you will experience a 100% CPU
load as well. Note, this was only an example. The reason for the
high load on your host might be different.
I agree with Michael. You make statements here about virtualization
and its performance just from your observation but obviously without
any expertise. Please don't bitch people willing to help you.
Kind regards,
Frank
--
Dr.-Ing. Frank Mehnert Sun Microsystems http://www.sun.com/
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