Windows 11 VM extremely slow after 2023-09 update

[Piipperi]

My Windows 11 VM in VMware Fusion has become extremely slow after the 2023-09 update. I tried updating to 2023-10 too which made no difference (updating to it took 4-5 hours).

I'm using a Macmini8,1 with 4 cores allocated to the VM out of 12 (CPU is i7-8700). The guest is so slow that I cannot even open anything else than Task Manager, which takes nearly a minute to open (with it then using 70-80% of the CPU). Changing the allocated cores has very minimal effect on the performance. 

Not 100% sure is it a Windows issue or a VMware issue, but the issue did start when I updated to 2023-09. I also have a Windows 10 VM with fewer cores allocated, but otherwise has the same settings, and it performs like normal. Updating to VMware Fusion 13.5 hasn't had any effect.

What should I try to help make my Windows 11 VM usable again?

[Technogeezer]

When you say that the VM is using 70-80% of the CPU, is that figure reported from the Mac or from Windows?

Have you used Task Manager from within the VM to determine if anything is consuming CPU resource?

What is the VM's guest operating system type set to in the VM's Settings? 

Have you tried turning off 3D acceleration if you have not done so already?

[ColoradoMarmot]

Ok, that's actually not a 12 core machine.  It's a 6 core machine with hyperthreading (which don't count).  Drop the number of cores to 3 and see if that helps.  Modern OS's have gotten really greedy with cores.

How much RAM is in the machine?  Make sure you leave at least 4GB for the host (more if you have other software running).

[Piipperi]

I am not sure where else it would be reported from than from Windows, since VMware Fusion is for macOS and macOS does not have Task Manager. 

VM's OS type is set to Windows 11 x64, and turning off 3D acceleration has no effect.

[Piipperi]

It's a 12 threaded CPU and VMware Fusion calls them cores. You gotta complain to the devs if you have a problem with that. 

And I already did say in the post I tried with different core amounts, and with less cores the VM is a lot slower. 

The computer has 64 GB of 2x DDR4 RAM, with 16 GB allocated to the virtual machine. Do you think 2023-09 has changed the RAM requirements or why do you think RAM could be related?

[Technogeezer]

Yes, macOS does not have a Task Manager (well it does, but it's called Activity Monitor).  What I meant to ask was to run Task Manager from within the VM and see what it's reporting.

[Technogeezer]

You might also want to see https://answers.microsoft.com/en-us/windows/forum/all/why-my-windows-is-slow-after-2023-10-cumulativ... - there evidently are reports of some of those updates causing performance issues even on Windows physical machines.

[Piipperi]

Which is what I have done already as said in the post. It's reporting that all cores are at 100% all the time with Task Manager just by itself using 70 - 80% of it.

[Technogeezer]

---

@Piipperi wrote:

Which is what I have done already as said in the post. It's reporting that all cores are at 100% all the time with Task Manager just by itself using 70 - 80% of it.

---

Thanks for the clarification - it wasn't clear from what you posted where the CPU utilization figures were coming from.

If Task Manager is reporting that high utilization, try turning down the refresh rate and see if that drops the Task Manager utilization. 

You may want to try backing out the Windows updates to before the  2023-09 update, then letting it reapply updates (I'd take a snapshot of the VM or shut it down and make a copy of it first). There are others reporting performance issues on the Microsoft boards and finding that backing out the updates and letting Windows reinstall them have gotten them over the issue.

[Piipperi]

Unfortunately, there is no option to uninstall the update. It only lists Visual Studio and .NET updates in the Uninstall Update menu.

[Technogeezer]

What build of Windows were you running before the 2023-09 update? 

I'm suspecting that there's something up with that Windows update. There are reports such as https://www.windowslatest.com/2023/10/14/windows-11-kb5031354-is-causing-major-issues/  and https://www.windowslatest.com/2023/09/17/windows-11-kb5030219-trashes-pcs-gaming-performance-issues-... 

If you can't fix the issue with information that's out there on the web, you may be faced with re-installing Windows and preserving your files.