Disclaimer: This article is more as a quick check for me to go through if such situation happened again. Hopefully, this will be helpful to others as well.

From the last five days, I was noticing my macbook pro was sluggish. It was very hard to work with. When I checked the activity monitor, I saw kernel_task cpu process was around 1000%. This is too much and clearly the obvious reason for sluggishness of the system.

When I googled, I found that kernel_task overloads when the CPU overheats or by some software app where if kernel assumes that CPU might get overheat and take necessary precautions.

Though I fixed this issue the hard way(by downgrading the OS), the following could have been the possible culprits which I realised later:

  • VS Code - Running VS code in Workspace (showing two or more projects in same space)
  • Again VS Code - Many extensions. Though having more extensions was not my intention, looks like this automatically happened when I decided to sync my settings by signing in (It synced with my Home PC VS code settings, including extensions - somehow I had many extensions which I never bothered cleaning as it is not an issue on Windows)
  • Really the CPU is overheating - This I checked and it wasn’t that hot to declare as overheating in any sense. But maybe only by touch we can’t know this.
  • Maybe because of recent Big sur update?
  • I observed, it was only happening while the system is charging (tested on all ports).

I connected with online apple tech support. We did the following:

When all this didn’t work, we decided to re-install OS and if that too doesn’t work, we were in plan of hard resetting the whole system (wiping the whole data)

To re-install OS, press Command + Option + R while rebooting the system, till a globe is seen.

But unfortunately, the re-install of OS didn’t work. It was failing continuously with network connectivity issue. So, next day I visited nearest authorised service centre.

When I tested at the centre, strangely, the kernel_task was overloading only on 2nd port of left side of the laptop. This wasn’t the case before. And also, the system got way faster than before (when charging on other ports). Maybe this got a bit fixed by above reset steps which I will never know. But anyway, the tech support person recommended better to downgrade the OS version and reset the data. We did the same which actually fixed the issue. I wish there was better solution than downgrading the OS but the tech support person stated that they are seeing many similar issues when users upgraded the OS to Big sur.

I feel this might not be the only possible solution as I could have followed this stackoverflow link when I realised that the issue is only when charging and on the left side’s 2nd port of the laptop. Or just clean the dust by opening the laptop as suggested in this article. But anyway I was in no state of experimenting at that point. Now as a precaution, I bought a coolingpad to keep the CPU cool.