How to know which processes are paging to/from disk (as opposed to other VMM management) in OS X, and how much exactly: sudo dtrace -n maj_fault'{@[execname] = count()}' reference (with examples and other options): http://wikis.sun.com/display/DTrace/vminfo+Provider I had been meaning to look for ways to do this, and tried some of the tools included in OS X (Activity Monitor, top, Instruments, vm_stat, vmmap, top, ...). But nothing really helped, and/or seemed to miss the exact level of information I was targeting (only resulting in real I/O; relationship between I/O and process; realtime... ). Finally I had the inspiration to google for "dtrace pagefaults". Bingo. (dtrace in this example isn't realtime, but is the best approximation so far, and I'm guessing some tuning should fix it. Heck, it's a one-liner!) Learning dtrace is still something I'd love to do, and once again it is tempting me to let it jump to the front of queue... (Mhm, wi...