buffercache

The thing to clear buffer cache on linux:
  free -m && sync && sudo bash -c 'echo 3 > /proc/sys/vm/drop_caches' && free -m
                  total        used        free      shared  buff/cache   available
    Mem:          32167       11254       11951         448        8960       20006
    Swap:         32695        4648       28047
    [sudo] password for donhatch:
                  total        used        free      shared  buff/cache   available
    Mem:          32167       11219       19703         448        1243       20108
    Swap:         32695        4648       28047

And by the way, to make it swap in that swapped-out stuff so the machine is usable again
after a swapping disaster:
sudo swapoff -va
(that actually permanently disables swap.  which I think I like anyway.
to turn it back on: sudo swapon -va)