Ntoskrnl.exe causes 100% gpu usage, and after that drop to 0% and back to 100% again. How to fix it?
My 2 cents
1) ntoskrnl.exe is an important part of Windows Operating System. It is not related specifically to virtual machine and the issue of high CPU used reported regardless of VM. Therefore, I think that your question is best to be ask in windows's forum (according to your version of windows).
2) Some malware disguises itself as ntoskrnl.exe, particularly when not located in the C:\Windows\System32 folder. Therefore, you should check the ntoskrnl.exe process on your PC to see if it is a threat.
3) I found multiple posts online about the issue. I recommend to search Google and get more information.
As mentioned this issue related to the OS and not to the virtual machine, and I am not expert in windows. Therefore, all that I write below is base on Google founding and anything that you do is on your responsibility. I recommend again to ask the question in windows forums.
Start in the following link as this is the official Microsoft forum: https://answers.microsoft.com/en-us/windows/forum/windows_10-performance/ntoskrnlexe-causing-high-cpu-usage/a1d2c97c-b208-4450-835f-cfb63462f07b
If you need more information then check this post. In first glance it looks like a full explanation with guide on fixing the issue: https://appuals.com/high-cpu-or-disk-usage-by-ntoskrnl-exe-on-windows-10/
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