What is memory pressure?
How hard macOS is working to fit everything in memory: calm, getting tight or short.
Memory pressure is macOS’s own measure of how hard it’s working to fit everything into memory. It isn’t the same as “memory used”: a Mac can use almost all of its memory and still be calm, because macOS keeps things around in case they’re needed again.
- Calm: plenty of headroom.
- Getting tight: macOS is compressing memory to make room.
- Short of memory: macOS is moving memory to disk (swap). This is the slowness you feel.
Procession shows the level macOS reports, never its own guess. The line moves within the band macOS reports.
Swap that’s left over from earlier isn’t slowing anything now. macOS clears it over time, or when you restart.