Will there be performance issues running WSL2 on an Intel big.LITTLE CPU ?

[dsyx]

The current kernel version of WSL2 is: Linux 5.15.74.2-microsoft-standard-WSL2, but Intel's Thread Director Coming to Linux 5.18 to Fix Alder Lake Performance Issues. This means that WSL2 may have thread scheduling issues when running on Intel big.LITTLE CPUs.

Should/can I upgrade the kernel version? Or is there a way to run WSL2 only on P cores or E cores?

Thanks.

[0xbadfca11]

It doesn't matter which virtual CPU the Linux kernel inside WSL schedules on.
It's the hypervisor's scheduler that actually decides which physical CPU to run on.
(You can see this by running taskset 1 yes > /dev/null and looking at top 1 and taskmgr.exe.)

And those features are hidden by virtualization.

[dsyx]

@0xbadfca11
But I'm a bit concerned about the hypervisor's scheduler scheduling my CPU-bound process in WSL2 onto the E core.

[tusharsnx]

similar issue is being tracked here #9121

[linzj]

I am running on Windows Server 2022, and in most case the heavy task simply schedule to the E cores.

[borjamunozf]

any new info about this?

[linzj]

I change the scheduler type of the hypervisor to 4, aka the root scheduler. Then the problem is solved.

[borjamunozf]

this applies to Windows 11? Or only Windows Server? The bcdedit does not show anything and it seems that root scheduler is the default (theorically)

We have huge performance issues in Windows 11 and WSL #11966

[linzj]

I have check my Windows 11 which is a client version OS. It defaulted to hypervisor 4. But my server version is not that case.

[dsyx]

I would recommend that the WSL config file provide a CPU affinity option, which would allow users to lock WSL to certain cores/threads instead of letting the scheduler run freely.