Working set

Assume that initially, only 2 pages of a process are in memory.

• The one containing the first instruction.

• The one containing the start of the stack.

After execution starts and for a while, page faults will be frequent.

Then the process will enter a phase in which page faults will be almost inexistent.

• Corresponds to a period where, accordingly to the principle of locality of reference, the fraction of the address space that the process is currently referencing is all present in the main memory.

This set of pages is called the working set of the process.

Over time the working set of the process will vary, not only with respect to the number but also with the specific pages that define it.