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Old 11-09-2008, 05:10 PM   #1
relpats_eht
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Virtual Machines eating 100% CPU


Well, for starters, I'm running Gentoo amd64 on an Inspiron 1720 with a 2GHz Core2Duo and 2 GB of ram using kernel version 2.6.26 patched with TuxOnIce.

Now, I've run into a mysterious problem I've been unable to pin down where any virtual machine (be that VirtualBox, VMWare, KVM, etc) uses 100% of one cpu. I've been unable to find a solution, only correlating problems.

After searching the net, I've found a few other people with a similar problem, and from what I've seen, all of us are using laptops with Core2Duo's. I'm not sure about the kernel versions, but I think they are all greater than 2.6.24. However, I've determined 2.6.24 still posses the problem (if it is even kernel based).

One person who had a similar problem noticed it appear only after switching from Ubuntu 8.4 to 8.10. This leads me to believe the kernel Ubuntu 8.10 brought in a kernel configuration possesing this particular problem not found in 8.4, but I'm quite uncertain about that, it is merely my best guess.

Any thoughts on what is causing this little problem?
 
Old 11-09-2008, 05:46 PM   #2
syg00
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What happens if you come up on only one CPU ?.
 
Old 11-09-2008, 05:49 PM   #3
relpats_eht
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I'm not entirely sure what you mean, but if you are talking about setting processor affinity to only one CPU or the other, the result is the same, 100% usage of whichever CPU the process is set on.
 
Old 11-09-2008, 06:21 PM   #4
syg00
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No I actually meant coming up with one CPU - pass maxcpus=1 to the bootloader so it runs "non-SMP". Just to eliminate SMP issues as a possibility. I've been thinking of trying out KVM on my core2duo laptop - maybe I should get organised and test it myself when I get home.
 
Old 11-09-2008, 10:00 PM   #5
jlliagre
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High virtual machine CPU usage might be due to the guest kernel configuration.

You can try adding parameters to disable acpi (acpi=false) or lower the kernel h/w clock check from 1kHZ to 100Hz (divider=10).
 
Old 11-10-2008, 06:25 PM   #6
syg00
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Interesting. I threw virt-manager at Fedora9, and set up a qemu KVM guest to install Archlinux on. Install went o.k., but it panics starting init. One CPU loops at 100% - regardless of whether I define the guest as 1 or 2 engines; don't know if that is expected for a panic at that stage. Got sidetracked and lost interest at that point - will investigate further.
 
  


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