Mac after the upgrade may appear inexplicable lag, running slow and other issues, if you encounter this problem can try the following methods to recover under:
I. Booting in Safe Mode：
1. Restart your Mac and then immediately press and hold theShiftkey. The Apple logo will appear on the display.
2. Release the login window when you see itShiftlinchpin
3. If the Mac boots successfully, restart it without pressing any buttons
At this point you'll notice that the Mac does run a lot faster, and the lagging eases up so much.
Second, if this is still lagging you can reset SMC and NVRAM:
1、Shut down the machine, re-plug the power supply
2. While the power is off, pressShift+Control+Optionkey, then simultaneously press the power button for 10 seconds
3. Release all the keys in connecting the power supply
4. Power on
Third, reset the NVRAM:
Immediately after turning on the computer, press and holdCommand+Option+P+Rkeys for 20 seconds, during which time you will hear three rattling sounds before releasing all keys
Please don't worry, appealing all these operations will not affect any data and information on the computer, reset SMC and reset NVRAM are the ones that can help the MAC to reset the device's power-on circuit and free up the device's error memory.
Through the above operation, the running speed of the computer is indeed greatly improved, and personally tested to be effective! All of the above methods of operation from the Apple official customer service, hereby record.