Why is a mac typically slow/laggy after upgrading the OS? [closed]
I recently updated macOS to a new major version (Big Sur). I've read many claims that a newly upgraded macOS installation may be slow/laggy for 1–7 days because it needs to perform "various maintenance routines" and a user should wait through this period, after which time their computer will become efficient and stable again.
I'm looking for clarification around the popular and folkloric notions of what macOS needs to do after an OS upgrade that make it inherently slow/laggy for a limited time.
I see two categories of info, but I'm mainly interested in the first:
- Inherent reasons the OS needs to be slow (e.g. Siri/Spotlight reindexing)
- Universally common reasons for slowness (e.g. iCloud synchronization issues or native Mac apps performing background updates)
Solution 1:
Right after an upgrade, system applications and services might need to do background work, which could mean that the user experiences the system as "slower than usual".
As you mention in your question, this can include Spotlight reindexing, but could also be for example Photos rescanning photos to create metadata.
There's no need to have to believe in any "folklore" though. You can easily determine whether or not your computer, after an upgrade, is engaged in such activities. Simply start Activity Monitor and look at the CPU time taken up by such services.
As you mention, these types of background operations completely within a fairly limited amount of time - and then you'll experience the performance level that you'll probably become accustomed to after a while. It might be the exact same performance level you saw right after upgrading, and it might be better. It's usually a quite individual experience.