I've noticed that LDom version 2.0 (called now Oracle VM Server for SPARC 2.0) has a new feature called "CPU whole core allocation". The documentation says we can create "Whole-Core Constraints" with these commands (notice the "-c" argument in command):
ldm add-vcpu -c number
ldm set-vcpu -c number
ldm remove-vcpu -c number
We are using here a T5240 server, Solaris 10 on it, currently using LDom 1.1 version, with 3 Guest LDOMs running. This server has T2+ processor, 2 of it. One CPU has 8 cores and one core has 8 threads. So in total 2 CPU x 8 Cores x 8 Threads = 128 threads. That corresponds to 128 VCPU in LDOM point of view.
If I count the cores, that is 16 cores in total.
For example, in one of the Guest LDOM, 40 VCPU is allocated:
-bash-3.00$ psrinfo -pv
The physical processor has 24 virtual processors (0-23)
UltraSPARC-T2+ (chipid 0, clock 1165 MHz)
The physical processor has 16 virtual processors (24-39)
UltraSPARC-T2+ (chipid 1, clock 1165 MHz)
When I allocate a complete core to a Guest Domain (using the Whole-core constraint feature), from Guest Domain point of view, it will still appear as 8 VCPU, or it will appear as 1 CPU in the Guest domain? So I wonder whether the whole-core allocation is still splitting the core into threads in the guest domain?
I read the documentation but this is not very clear to me. I don't have LDom 2.0 installed so cannot test it.
The whole-core constraints option simply informs the management software to allocate all strands of a core to the designated virtual domain. If the core has 8 strands, then those 8 strands will appear as 8 VCPUs to the virtual domain.