Overloading Physical Memory

Two Basic Strategies
Swapping
Paging

Swapping
When there is not enough memory, suspend processes
Simple, but inefficient
Process only needs working set to make progress
Can never use more virtual memory than there is physical memory

Paging
More fine grained
Each process only needs its working set in core
Extra memory can be used as a data cache
Very complicated algorithms
Must manage thousands or millions of frames
Page eviction
Speculative paging
Must be very smart: disk accesses are thousands of times slower than memory accesses