Optimal number of virtual CPUs, cores, and threads

Patrick_3000

Contributor
Joined
Apr 28, 2021
Messages
167
I have SCALE installed on the following physical hardware: AMD Ryzen 7 Pro 5750G with 128 GB ECC memory. Therefore, I have one physical CPU, with 8 physical cores and 16 physical threads. I have an all-SSD pool (NVME) for VMs, with my datasets on a separate HDD pool.

I have two VMs: one Linux Mint and the other Windows 10.

What I'm wondering is the optimal number of virtual CPUs, cores, and threads. Currently, for each VM, I have specified 2 CPUs, 2 cores, and 2 threads, with host passthrough. Everything seems to work, but I'm wondering if this is the optimal setup. I actually don't understand what the correlation is, if any, between virtual and physical CPUs, cores, and threads. If anyone has any insights or suggestions, I'd appreciate hearing them.
 

sfatula

Guru
Joined
Jul 5, 2022
Messages
608
Virtual CPU x cores x threads = how many physical threads you are allocating. Optimal? Depends on what you need to accomplish with the VM and how fast you want it. It could be a low number of a high number.
 

Patrick_3000

Contributor
Joined
Apr 28, 2021
Messages
167
Virtual CPU x cores x threads = how many physical threads you are allocating. Optimal? Depends on what you need to accomplish with the VM and how fast you want it. It could be a low number of a high number.
Thanks. Now I understand what they mean, so I'll figure it out based on what I'm using the VMs for.
 

Whattteva

Wizard
Joined
Mar 5, 2013
Messages
1,824
90% of people only needs 1 or 2 cores/threads (I usually just do 2 cores x1 thread). I'd recommend to start from there and add more as you need. Allocating too many cores/threads can actually result in very slow performance.
 
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