Command: sar -S
%swpused
Percentage of used swap space.
%swpcad
Percentage of cached swap memory in relation to the
amount of used swap space.
The cached swap memory is memory that once was swapped out,
is swapped back in but still also is in the swap area (if
memory is needed it doesn't need to be swapped out again because
it is already in the swap area. This saves I/O).