I solved this problem by reinstalling Xcode 8.1:
- Open the Application folder in Finder.
- Find the Xcode file and go to the trash, then empty the trash
- Go to the App Store Find "Xcode" in the search
- Install xcode
After installation, you do not need to enter Apple IDs in Settings> Account (but you should check if everything is ok)
After reinstalling Xcode 8.1, SourseKitservise loads the processor by 15-20% (see screenshot) 
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