I have a new Skylake laptop (Thinkpad T460p) running an up-to-date Tumbleweed
with kernel 4.7.2-2-default
I noticed that the system started swapping despite 16GB RAM and little mem
usage.

A look at /proc/meminfo revealed that the memory is used by the kernel slab:

Slab:           12410408 kB
SReclaimable:      83752 kB
SUnreclaim:     12326656 kB

and slabtop shows one process permanently acquiring new pages:
  OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE NAME                   
3065838 3065838 100%    4.00K 3065838        1  12263352K kmalloc-4096

I'm not really sure where else to look or what other information to post, but
will attach everything you request....