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Very slow guest performance on VB 4.1.8-75467

PostPosted: 24. Feb 2012, 23:10
by -Manuel-
I've installed VB 4.1.8-75467 on a Dell Studio (Intel i5, 8GB RAM) today. If I start a RHEL 6 VM it starts very very slowly. The VM is absolutely unusable. Before I had VB 3 installed and the performance on all VMs was excellent. Have you got any idea what could be wrong with VB 4 and my Dell Notebook?

Thank you very much for your help.

Manuel

Re: Very slow guest performance on VB 4.1.8-75467

PostPosted: 24. Feb 2012, 23:14
by Perryg
You would need to provide some hard information for us to tell. Post the guests log file (as an attachment).

Re: Very slow guest performance on VB 4.1.8-75467

PostPosted: 25. Feb 2012, 11:39
by -Manuel-
Hello Perryg
Sorry about that. I attached the log file of a rhel 6 vm which is very slow (about 7 Minutes!!) to start. Before with VB 3 it took only about 30 seconds.

Thank you very much for your help.

Manuel

Re: Very slow guest performance on VB 4.1.8-75467

PostPosted: 25. Feb 2012, 13:07
by mpack
There are a lot of lines in the log beginning "PIT". I assume this is "Programmable Interval Timer". On my VMs (which run very sweetly) this gets set 3 or 4 times, usually with an interrupt frequency of 18.2Hz, the fastest being 100Hz. Your log shows a large number of consecutive events, with some crazy frequencies: one line has 85000Hz!

I don't know what is causing this, presumably some crappy bit of software installed in the guest is banging the hell out of the hardware timers. Unless that's the GAs (which might be embarrassing), then it looks like it isn't a VBox problem. Even running native this would be an excessive CPU overhead.

Re: Very slow guest performance on VB 4.1.8-75467

PostPosted: 25. Feb 2012, 15:05
by -Manuel-
Hello mpack
I've got the solution! I created a complete new VM for rhel6 and made a base installation. The new vm was running very well so I compared the settings from my very slow vm created along time ago with VB 3 and noticed that on the newly created vm under VB 4 "Enable IO APIC" (System --> Motherboard --> Extended Features) was selected. I selected it too and surprise surprise, the vm runs as expected!

Thank you very much for your help! I'm very happy now!

Manuel

Re: Very slow guest performance on VB 4.1.8-75467

PostPosted: 25. Feb 2012, 15:28
by Perryg
Normally I see this with RT kernels in a virtual machine.
You can set the timer frequency to 100Hz (optimal for virtual Linux machines) just by adding divider=10 as the kernel option and fix this. I am not sure how IO APIC would affect this and allow it to work, but if you still have an issue try the divider.

Re: Very slow guest performance on VB 4.1.8-75467

PostPosted: 28. Jul 2012, 19:28
by gearge
I can confirm, that selecting the "Enable IO APIC" (System --> Motherboard --> Extended Features: "Enable IO APIC") fixed the major performance issue associated with using a Red Hat Enterprise Linux 6.x x86_64 guest in VirtualBox 4.x.