openSUSE 13.2 with the latest kernel 3.16.7-7 got to the state where there was
not enough free memory available. Swap was full and no process held the memory
at first glance. The system ran for several weeks. There was no page allocation
failure or out of memory message in the log.

/proc/meminfo, slabinfo and zoneinfo are attached with the list of processes. 

According to Michal Hocko it could be fixed by
5ddacbe92b806cd5b4f8f154e8e46ac267fff55c in upstream kernel. It is not present
in 3.16.7 version.

Unfortunately I had to turn off the computer due to power down in the building
and cannot reproduce it again.