My MacBook pro late 2011 15" has 800% usage with kernel_task

So my MacBook Pro is getting super slow and laggy after a while of usage. I updated to Sierra today and my kernel_task is sky-rocketing - hitting up to 1100% and I have no idea why? I've tried all kinds of things like an SMC and PRAM reset and it didn't work. Has anyone had the same issue? Does anyone have a fix?

Edit: I have 8GB of RAM and a 250GB SSD with 35GB of free space.

So after long time of surfing the web i found this which fixed the issue:

1. Reboot into recovery mode (Command + R on boot prior to startup chime), select Utilities/Terminal, csrutil disable (repeat process, use csrutil enable after removing the file), reboot.

2. Go to About this mac under the apple in the upper left and click on More info

3. Click on system report

4. make a note of what it says after Model Identifier (MacBookPro8,2 is mine).

5. From the Root drive (not home folder): – System Library – Extensions – IOPlatformPluginFamily.kext (alt-click/View Contents) – Plugins – ACPI_SMC_PlatformPlugin.kext – View Contents – Resources -– find the name from step 3 and move it to a folder that you can find again if needed.

6. Restart and you’re done (other than enabling SIP).

I can use my Mac again!