HORRIBLE SMP performance on XP Guest

[z5d69]

As a preface, I KNOW that I'm not providing a lot of information but wanted to know if this was a common issue without resolution before posting more.

I have a fairly new (within 2 months) quad core AMD system with 8 GB of ram running openSUSE 11.4 64-bit.

When I allocate 1.5 GB of ram and a single processor to this Windows XP (SP 3) 32-bit system, it runs fine, no pauses, latency, etc. In the hopes of increasing performance, I changed it to 2 virtual processors (this is a pretty inactive host system... 90% idle). . It installed a new driver allowing it to recognize the additional CPU. After this, performance was HORRIBLE, at least 10x longer for the same activities and processor (guest and host) consumption is minimal. Performance went back to good after changing to a single processor again. Even dropping down to a different userid on the login screen took several minutes to complete. This is nothing I would have considered CPU intensive. Now, I have virtualization activated in virtualbox however the ONLY change I made was 1 processor to 2. Historically, this was a pain point for VMWare and older versions of Virtualbox (based on searching goolgle, not my own experiences) but I was hoping for a confirmation/workaround?

Again, happy to provide additional details but I'm suspicious that this is a known issue.

[Perryg]

Even Microsoft does not encourage changing the HAL after an install. You can try to find/use HALu but this only works some of the time. IMHO
I have installed the guest with SMP and tried converting one to SMP and the difference was huge.

[z5d69]

I don't disagree with what you're saying but my understanding, with XP, was that adding cores under a single processor was supported just fine (single core to double core, etc. ) versus multi-processor (multiple slots each with X cores in the slot). Maybe my terminology is wrong. It's SMP in the context of multiple cores/processing units, but not in the context of multiple physical CPU slots (which is how I thought Windows defined "multiple processors"). Is converting to multiple cores a problem physically as well or is this a matter of virtualbox handles 2 cores as 2 processors in virtualization?

[Perryg]

What are you actually changing to get the two cores? If it is the processor count in the guest settings then yes it is adding another processor (or core in 32-bit) to the mix.
Either way you can try it yourself. Install another version with the processor count to 2 at the beginning and test the results yourself. I am fairly certain that you will see a huge difference.

[z5d69]

Will do, I was just trying to avoid reinstalling software, the OS, additional resources, etc. if possible.

[Perryg]

Like i said try it on a new install first and don't activate it. just for testing.
Or search for HALu here. Somewhere it is saved.
HALu site:forums.virtualbox.org in google should do it.

[z5d69]

just wondering, if the second processor/core/whatever is recognized in the guest (both device manager and task manager), wouldn't that indicate that everything updated to dual core/processor okay? I'm just trying to figure out what I should see looking different. I read through the HALu discussions and it looks like it's to resolve issues where the second processor isn't seen versus IS seen but performance is bad?

[z5d69]

as an example, I show an "ACPI Multiprocessor PC" under computer and multiple (number of processors allocated to the VM) "Processors" titled "AMD Phenom II X4 980 Processor" in the device manager.

[Perryg]

OK you know what you want.

[z5d69]

Okay, it works fine now in SMP mode, at least on an install with no software. I'm assuming same for once the software is on it.

So,
1. if you add a virtual processor does this issue come up again?
2. the device manager setting looks IDENTICAL to how it looked when I added the CPU in the already-installed OS. Is there any way, on XP, to see where it's configured for SMP (maybe a flag in the registry, etc.)? I read the HALu documentation and it's unclear what it's changing since just increasing the cpus and rebooting appears to provide the same indicators (see question above on ACPI, etc.).

[Perryg]

IIRC there are at least 3 files that need to be replaced. If you simply change the HAL to multi-processor that is when you see the very slow performance. You would need to ask Microsoft for the definitive answer, but the only thing that I could get from them and I used to work with the idiots is they do not suggest nor support updating to multi-processor.

[z5d69]

Okay, that's good to know. It's not a virtualbox problem and I'm glad for the help... More than I got from VMWare .

Thanks again.

[vbox4me2]

What you can do is make 2 installs and compare them on file level to see whats different when installing with 2 cpu's.