Taming the OOM killer

The problem is that the system is more dynamic than that. Swap space is
moved to and from physical memory on demand; there is almost never much
free physical memory, because free memory is wasted memory, so the first
sign you get that you're about to run out of memory is when you're out of
*swap* and still allocating more (reducing the various caches and paging
text pages out as you go).