I've updated to MacOS Sierra a few days ago, and it has been really unstable (a lot of freezes and hangs, specially in XCode).
I noticed that in Console, the following two lines appear repeatedly, for different apps and services:
switching to keychain-db: /Users/user/Library/Keychains/login.keychain-db from /Users/user/Library/Keychains/login.keychain (0 1 1 1) not switching as we're not in ~/Library/Keychains/: /Library/Keychains/System.keychain (0)
Is there any issue with keychain? Could that be causing the freezes?