Re: [Qemu-devel] OOM don't like qemu-kvm

[Stefan Hajnoczi]

On Wed, Mar 20, 2013 at 01:16:54AM +0800, Peter Cheung wrote:
> Hi All    My compuer is i7 with 32 GB ram without swap, i try to launch 28 vm 
> with 1GB ram each, it runs smoothly.If I launch 64 VMs, after the VMs eat up 
> all the memory, the linux hang. If the linux is lack of memory, the OOM will 
> try to kill process, right? And the OOM should pick those qemu-kvm processes 
> to kill, but seems the OOM don't pick qemu-kvm or the OOM failed to kill 
> qemu-kvm processes.
>     If I turn on swap, although 64 VMs with 1GB ram each will make my 
> computer very slow, but at least it won't hang.
> Can anybody explain this?

Did you check dmesg for error messages from the kernel?

If the system is locked up you can use the SysRq key combinations to
print out the list of tasks, list of currently held locks, force the OOM
killer to run, and print backtraces for all CPUs.

http://en.wikipedia.org/wiki/Magic_SysRq_key

This should allow you to debug the issue further.  If you decide it's a
kernel issue, then address@hidden or the Linux kernel mailing list
would be more appropriate than qemu-devel.

Stefan