CPU Cores With Hyperthreading

[M4T]

How does the hyperthreading work on virtual machines.

if you have a CPU with 22 Cores & 44 Threads.

Does that mean you can have say

22 Core - 11 dual core VM's

44 Threads - 22 dual core VM's

Both - 33 dual core VM's

is it down as 22 cores u can use or 44 or 66 if you add threads and cores together. ?

Matt

[a_p_]

A physical host wit 22 cores, and Hyperthreading enabled makes 44 logical CPUs on the Hypervisor. These 44 logical CPUs are the maximum that can be assigned to a single virtual machine (no matter how you configure it in means of cores per CPU). However, resources are scheduled by the Hypervisor, i.e. they are not dedicated to a single VM by default, so you can easily overcommit resources on a host. Depending on the VM's actual usage, the sum of assigned vCPUs to all VMs on the host can exceed the number of logical CPUs.

André

[M4T]

so I can use all 44, I can create 22 dual core VM's on each CPU.

does the host assign the cores automatically so if you had two quad core VM's it couldn't use the same 4 cores on each VM it would use say Core 0,1,2,3 & then Core 4,5,6,7

Matt

[a_p_]

Please take a look at https://www.vmware.com/files/pdf/techpaper/VMware-vSphere-CPU-Sched-Perf.pdf  which explains the concepts.

The point is, that VM's (like physical systems) usually only consume a fracture of the available resources, so that unused resources can be used for other workloads (and the ESXi Hypervisor itself).

André