Suddenly this morning my macbook pro became extremely slow and laggy. Just performing trivial tasks such as right-clicking, marking an icon, opening activity monitor, scrolling a web page, changing the active window, orchanging safari tabs will leave the mac in a frozen state for 20-40 seconds. I'm typing this post half-blind, as what I type only shows some 10 seconds later.
macOS Sierra 10.12.1
MacBook Pro, 13", Mid 2012
2.9 GHz Intel Core i7
8GB RAM 1600 MHz DDR3
In Activity Monitor, strangely, most active processes are listed with a 0.0% CPU usage. Why would that be?
I have also reset the SCM and PRAM, with no apparent improvements. The hardware diagnostics said nothing was wrong. Disk Utility repair said everything seems to be okay with the volume. Attached are some screen shots of activity monitor. I could post some console output as well, but I don't know what is relevant.
I really have no idea of what is going on. The computer has never lagged like this. Recently, about a month ago, a certified Apple repair shop replaced the logic board, but that should not affect this, right? I am currently backup up my data, preparing for a clean install of the OS, but copying files is taking a very long time. I will report back when that is done. Does anyone have any idea of why this might happen?