Infrastructure Software

Hi OVM people,

We're trying to determine the best configuration for hard-partitioning and licensing and I have a disagreement with my linux sys admin!

I've just read the Oracle white paper Hard Partitioning With Oracle VM Server for x86 - June 2012 which talks about sockets, cores and threads and how to assign these to your VCPUs and VMs - so I understand the concepts.

Also I believe Oracle license by core (not thread but core).

My question is: If I have assigned 4 VCPUs to a VM (CPU0-3), which are actually 4 threads (our cores are using hyperthreading) and I make sure these threads belong to 2 cores then surely I should only pay license for 2 cores.

My Linux sys admin tells me to ignore the threads and that we have to license for 4 cpus ie. the VCPUs

For example in our site we have the following.

2 sockets with 4 cores in each and each core is hyperthreaded 2 threads per core - thus we have 16 threads / VCPUs - we want our VMs to have 4 VCPUs each

xenpm get-cpu-topology

CPU core socket

CPU0 0 0
CPU1 1 0
CPU2 9 0
CPU3 10 0

CPU4 0 1
CPU5 1 1
CPU6 9 1
CPU7 10 1

CPU8 0 0
CPU9 1 0
CPU10 9 0
CPU11 10 0

CPU12 0 1
CPU13 1 1
CPU14 9 1
CPU15 10 1

I've added a split between the sockets to help clarify this, I find Oracle's numbering confusing but anyway this is my understanding:
2 sockets 0 and 1
4 cores per socket 0,1,9,10
2 threads per core, CPU0 and CPU8 are the two threads in core 0 socket 0

so to assign 4 threads to VMx that run in 2 physical cores I assume I would assign CPU0,CPU8, CPU1,CPU9 - and have to license for 2 cores right?

Would this have any performance implications?
would it be better to use two cores in two seperate sockets?

We've currently configured VMx with CPU0-CPU3 - performance is good, but this is 4 threads across 4 cores so I assume a 4 cpu license.

BTW we did configure VMx with CPU0-1 (ie 2 threads in 2 cores) but performance was bad, cpu load was high with high %steal

thanks in anticipation of interesting answers :-)

Jeremy