To see current swap usage
sysctl -a | grep swap
Use only when when your system is in a very bad shape
$ sudo pkill -HUP -u _windowserver
To monitor, what's creating/updating these swap files, run:
$ sudo fs_usage | grep swapfile
Or for page ins/outs, run:
$ sudo fs_usage | grep PAGE_
To see what WindowServer process is doing exactly, run:
$ sudo spindump -reveal $(pgrep WindowServer)
or for kernel_task, run:
$ sudo spindump -reveal 0