Safari (web browser on the Mac) does annoy me now and again by pretending it needs lots and lots of memory which then slows my whole Mac down.
I’ve just had to force quit Safari which was demanding 5.16GB of virtual memory. This was playing havoc with other stuff I was doing on the Mac.
Once I quit Safari, all was fine and everything speeded up.
I am not sure why Safari gets this demanding with memory, but it does happen quite a lot, so every so often I have to quit Safari and restart.