Next time I hit this, I will try running latencytop, but I suspect I'm entering into a memory pressure situation and latencytop might show the results of the pressured system, but not the reason for the pressure :-/
Next time I hit this, I will try running latencytop, but I suspect I'm entering into a memory pressure situation and latencytop might show the results of the pressured system, but not the reason for the pressure :-/