[libvirt-users] starting a domain only when you have enough resources

[Andrei Perietanu]

Hi all,

I am running KVM on a 3.18 kernel. The system runs and Atom processor with
2Gb RAM.

Using KVM you obviously can over allocate your resources: say you have 4
guests each configured with 1GB ram. Running all four at the same time,
depending on the workload, can crash the system - I get a kernel trace when
this happens.

But let's consider a simpler case: one guest with 1.5 Gb RAM, ubuntu 14.03.
During the installation the system will again crash.
The memory statistics (top or proc/meminfo) will show that the FreeMemory
goes down to 12Mb when this happens - which kind of makes sense considering
the host will require some RAM to run.

But the question is: does libvirt offer any way to prevent this from
happening?

Some way of not allowing the user to start a guest unless you have enough
free memory. I know how much ram each guest has configured but that is not
enough. I need to know how much the system has available, and just reading
the free memory statistic does not help much since that is only a snapshot
- when running a guest you can have 1gb free now, and 10 mb free 2 min
later.

Any ideas?

Thanks,
Andrei

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