virtualbox.org

Hi all,
I have a weird situation and want hear your thoughts on the issue.

I have created a virtual machine for TinyCore Linux (32 Bit, Kernel 3.0) distribution and I use this virtual machine (guest) on different host machines. I have also a custom application that runs on this virtual machine and this application is a bit CPU intensive.

First host machine is a windows xp 32 bit desktop PC with i5 3.0Ghz CPU (QUAD CORE), 4GB RAM. All virtualization support is enabled on BIOS.
Second host machine is a windows 7 64 bit laptop PC with i7 2.7Ghz CPU (QUAD CORE), 4GB RAM. All virtualization support is enabled on BIOS.

When I move my VM (32 bit linux guest) to xp 32 bit PC, my custom application consumes %4 CPU.
When I move my VM to windows 7 64 bit PC, the same application consumes %15 CPU. I could not find the reason behind this weird situation. I had thought that it should consume less CPU on i7 but it apperantly it consumes 3 times more CPU.

Is this performance degradation caused by executing a 32 bit Guest on 64 bit host? Or can there be any another reason that I can not see?

Thanks in advance.

Note that: My Guest is configured with 1 CPU core, Vt-x, EPT and NX/PAE support enabled.

It's different hosts, so I'm not certain that measures of CPU consumption are even comparable. And if they are, I don't know that the costs of performing particular operations on the host is similar. Win7 64bit has more bloat than XP, I would frankly expect it to use more CPU.

Also note that the actual consumption of CPU cycles is a good thing. I would expect that any program that I was using that is CPU intensive use as much of the ticks as it can and the closer to 100% the better. So in my world the higher number is actually better performance.

Thank you for the information.

Only think I try to learn is whether to have a 64 bit host executing a 32 bit guest causes the degradation in the performance?

Do we expect degradation in the performance when we mix the 64 bit and 32 bit host/guests?
Should we always run 64 bit guest on 64 bit host or 32 bit guest on 32 bit host?

32-bit guests on a 64-bit host works as well as 64-bit guests on 64-bit hosts and probably a little better due to the smaller overhead.
64-bit guests on a 32-bit host is another thing. I would expect major performance hits.

That said you original post does not actually show a performance issue and is why I explained that the more the better.