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User profile for user: tsmart46
tsmart46 Author
User level: Level 1
4 points

kernalmanagerd using upwards of 80% CPU after Big Sur Update

I have been having some major problems with my MacBook Pro (13-inch, 2017, Two Thunderbolt 3 ports) after updating from Catalina to Big Sur 11.0.1. Specifically I have been having a problem with my Mac overheating with the fans constantly on after startup, even remaining idle. Checking the Activity Monitor, I see that kernalmanagerd is using upwards of 80% of my CPU for seemingly no reason. This will also burn through a fully charged battery in under 2 hours.

I have tried restarting my Mac, deleting Malwarebytes, resetting the SMC and the PRAM (although I may have done these wrong as I have never done this before and am not very tech literate), but this issue still remains. What does kernalmanagerd do and does anyone have any suggestions for how this can be fixed?

Note: I also do not have Sophos Home or Dropbox, nor any other kind of antivirus which I have heard perviously can cause this problem.

MacBook Pro 13″, macOS 11.0

Posted on Nov 24, 2020 10:34 AM

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User profile for user: Old Toad
Old Toad
User level: Level 10
210,509 points

Posted on Nov 24, 2020 10:52 AM

Try killing the process in Activity Monitor, run for a bit and check to see if it comes back. If not then reboot normally and check again.


Next, if necessary, boot into Safe Mode by booting with the Shift key held down and check there to see if the problem persists.  Reboot normally and test again.


Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files



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Question marked as Top-ranking reply
User profile for user: Old Toad
Old Toad
User level: Level 10
210,509 points

Nov 24, 2020 10:52 AM in response to tsmart46

Try killing the process in Activity Monitor, run for a bit and check to see if it comes back. If not then reboot normally and check again.


Next, if necessary, boot into Safe Mode by booting with the Shift key held down and check there to see if the problem persists.  Reboot normally and test again.


Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files



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kernalmanagerd using upwards of 80% CPU after Big Sur Update

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