WindowsXP horrible slow with multicore enabled?!

[SawyerX]

Im using WindowsXP guest on win7 host and its horrible slow when I enable more cores of my Q9300.
With one core it works just like 2.x.x did. When I enable 2 cores it slows down and when I enable 4 cores it gets to crawling speeds up to the point where it is useless and host CPU utilization is horrible high. It uses all 4 cores just to open up IE.

It locks up pretty regularly and it was impossible to install windows XP when I had 2 cores enabled. I was able to install just one instanc out of 10 trys but even this locked up later when using.

[finthamoussu]

Same problem here, i tried on 2 machines (Macbook and Desktop both with OSX host and intel core 2 duo).

[poup99]

I am having the same problem but with a windows 7 64 bits guest in an Ubuntu 64 bits host with VB 3.0 with phenom x4 940 processor. If i use 1 processor i am having a decent performance but when i select more then 1 processor the performance is slowed to near unusable.

[Marian Kechlibar]

Im using WindowsXP guest on win7 host and its horrible slow when I enable more cores of my Q9300.
With one core it works just like 2.x.x did. When I enable 2 cores it slows down and when I enable 4 cores it gets to crawling speeds up to the point where it is useless and host CPU utilization is horrible high. It uses all 4 cores just to open up IE.

It locks up pretty regularly and it was impossible to install windows XP when I had 2 cores enabled. I was able to install just one instanc out of 10 trys but even this locked up later when using.

Yes, I have the same problem. I wrote about them to the following thread: http://forums.virtualbox.org/viewtopic.php?f=7&t=19527 (It is in "Linux hosts" rather than "Windows guests" forum).

Your description matches my experience to a T.

I have some suspicion that hard drive access may be the real culprit (if more than one core tries to access the drive at the same time).

[Jensen]

I experience a very slow Windows Guest with 2 CPUs here too.

I run a WindowsXPPro SP3 guest inside an Ubuntu Jaunty Host. Both 32Bit. VirtualBox ist 3.0.2. I enabled SMP and booted the Windows Guest. Everything works fine, but only one CPU is used. I searched the forum an found one thread: http://forums.virtualbox.org/viewtopic.php?f=2&p=84602 and another one http://forums.virtualbox.org/viewtopic.php?f=2&t=19878. As i was unable to install the "ACPI Multiprocessor PC" via the device-manager i tried:
a) manually replacing the DLLs as descibed here: http://www.handaware.com/multiprocessor_XP.html
b) enable SMP support via the HAL-Tools from here: http://www.hardware.info/en-US/news/ym2 ... t_anymore/

Both times a got a Windows Guest horribly slow, using all CPU resources.
As a work-around setting the number of CPUs available to 1 fixes the problem, but this leaves me with a single-core Guest running an SMP-aware virtualbox. Not quiet optimal...

All hints are very welcome.
Regards, Jens

[Perryg]

@jensen,
You might want to read Chapter 13. Known limitations in the Users Guide.

[Jensen]

@jensen,
You might want to read Chapter 13. Known limitations in the Users Guide.

Ok this is how it feels when

The following Guest SMP (multiprocessor) limitations exist: Bad performance with 32-bit guests on AMD CPUs.

kicks in
Missed that part in the first place. Thanks Perryg!. So i guess i will come back in VirtualBox 3.2 or something like this.

[Perryg]

Ok but with hyper-threading if you use a 32 bit host you will not see any improvement using SMP I don't believe. My system is 32 bit and I run (4) vm's at the same time. They work as fast as the host. IMHO. With the exception of moving huge files which are slower.

[pogga]

Might be worth upgrading to v3.2 now cos of this (taken from the Changelog):

VMM: guest SMP performance improvements

At least kick the wheels of the newer version and see does it do anything for performance.