[libvirt] Need Info on virNodeGetCellsFreeMemory

[Daniel P. Berrange]

On Thu, Aug 28, 2008 at 02:02:19AM +0530, ajishrao wrote:
> Hi, 
>     how to find the memory utilization of the whole which is running
> with some guest? By libvirt I can only see virNodeGetCellsFreeMemory
> relevant API, But didn't understand how to use it. 

The answer varies depending on just what sort of memory usage you're trying
to measure.

 - virNodeInfo - provides the total RAM installed in the host machine
 - virDomainInfo - provides info for a single VM

While in theory you could sum the memory for each active domain, and
subtract it from the node info data, this doesn't take into account
memory usage from processes running in the host OS. Hence we have

  - virNodeGetFreeMemory - returns total free memory on the host

  - virNodeGetCellsFreeMemory - returns free memory on one or more NUMA
                                memory cells

Intel x86_64 machines  don't current do NUMA, so the latter isn't very
interesting unless you're on AMD x86 or  Intel ia64 machines.

If you don't know/care about NUMA, then just call virNodeGetFreeMemory


Daniel
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