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#OS SIERRA SLOW MAC OS#
Another way to fix slow Mac Wi-Fi is to delete or remove the previously existing Wi-Fi preferences in the Mac OS Sierra. I tend to use my laptop in short sprints and close the lid in between, so the system wasn't getting enough fully-awake-and-running time to get its background tasks done, and Power Nap wasn't cutting it. Remove Existing Wi-Fi Preferences in Mac OS Sierra. In my case the best solution was to just leave my MacBook Pro up and running (open, plugged into AC power and set to not go to sleep) overnight while all those background processes got all their "things to do after a major OS update" work out of the way. During this time my machine ran slowly, not because of high CPU usage, but because of disk contention. When I updated to Sierra, my Time Machine backups didn't complete on my laptop for a few days because there was too much disk contention as Photos was reindexing my large photo library to apply all the new content-recognition algorithms to everything.
Time Machine (backupd) has a lot of new stuff to back up.Spotlight (mds, mdworker) has to reindex a lot of things because the update changed a lot of files.In my experience this was especially true of the upgrade to Sierra. One major cause of slowness after a major macOS upgrade is a bunch of system processes contending for disk access as they update their databases.