And you might also encounter issues with Type 2 virtualization software such as VirtualBox or VMWare Workstation.
(I will still stick to WSL 1 because of that).
That doesn't sound right. Hyper-V is a Type-1 hypervisor, so by definition the Windows installation would not be running in its own VM (for some definition of VM).
And its pretty much exactly the same for Qemu/KVM on Linux, where Intel VT-x or AMD SVM hardware extensions are used to implement Type-1 virtualisation.
I've been using Hyper-V for about 5 years and never noticed any performance impact worth mentioning. Type 1 hypervisor VMs are still technically running on the metal.
1.) The Hyper-V component isn't installed on my Windows 20H1 install. WSL 2 may use Hyper-V technology, but the full thing does not appear to be installed.
2.) So far, VirtualBox is working just fine. I haven't noticed any issues yet while using several virtual machines. Nothing seems amiss at all.
The complete Hyper-V suit you use to manually create and run VM does not need to be installed by default, but that's irrelevant. Windows provides more and more features that relies on the hypervisor, e.g. Windows Sandbox, Edge Protected Mode, Credential Guard, etc.
Those features (and WSL2) are not available when you are not running under the hypervisor.
MS also provides an API so that third party VM tools can run, and Virtual Box can use it, but still recently it had tons of issues. Maybe the situation is somehow better now, I don't know. I don't think this is an option with VMWare though.
VMWare has a tech preview of the next version of Workstation which should work with the new Windows 2004 [2]
[1] https://forums.virtualbox.org/viewtopic.php?p=470529#p470529
[2] https://blogs.vmware.com/workstation/2020/01/vmware-workstat...
I'd be a little surprised if it really is measurable - just win10 with/without hyper-v? I seem to recall xen (which should be comparable) having a pretty low impact?
For ML, 3D, games and what not is probably better to keep Linux in another kind of VM.
I don't consider it odd. It is the way a Type 1 hypervisor works. Windows puts in some effort to hide most of that from the user.
In my understanding on how a Hypervisor works, the only thing that I'm almost confident to say is that there is an impact but it's probably not noticeable or highly related to your workload (maybe on I/O?).
People will probably not care about that impact in fact (considering that Hyper-V is enabled by default and there are multiple security features of Windows now relying on Hyper-V).