Swapper Subsystem Files Structure

swap.c: it moves pages around in the lru lists
swapfile.c: it handles actual swapping of the pages to backing store
                  it also provides function calls to control swapping from usermode
swap_state.c: it handles swap cache
vmscan.c: glues the swapper subsystem to the memory manager.
                 provides more high-level functions that the memory manager.
                 kswapd is here.