[one-users] A question about the utilization of VMs

[Fabian Wenk]

Hello Adnan

On 24.11.2011 21:16, Adnan Pasic wrote:
> Is there a way to circumvent that? For my diploma thesis I need to utilize
> deployed VMs for a period of up to 12 hours. However, if KSM is active, the
> physical host doesn't hold this utilization, but adjusts the used memory
> pages.

I do not know, but I guess your 'lookbusy' tool is just 
allocating the memory, but not really using it (eg. filling it up 
with random data). I guess "using" the allocated memory should 
help you even with KSM turned on. I am not sure about freeing the 
used memory after the process has stopped. Usually this memory is 
just marked as free from the kernel, but will only be "purged" 
over time or when an other process is requesting memory. Probably 
your 'lookbusy' process needs to clear (fill with zeros?) the 
memory before ending. Then I guess KSM on the cluster node will 
do its work and reduces the memory usage of the VM.

> Since I want to measure the power consumption of the physical host under
> full VM utilization, I need the real memory to stay utilized as well, yet I

Does your 'lookbusy' process also use CPU cycles (eg. creating 
full load on the VM) or only memory? The most power consumption 
difference you will see on different CPU load and not memory 
allocation. Also the amount disk I/O does affect the power 
consumption.


bye
Fabian