An Aside: Working Sets (cont)
From observations of running programs ...
- in any given window of time,
a process is likely to access only a small subset of its pages
Known as the working set model (cf locality of reference)
Only need to hold, at a given time, the process's working set of pages
Implications:
- if each process has a relatively small working set,
can hold pages for many active processes in memory at same time
- if only need to hold some of process's pages in memory,
process address space can be larger than physical memory
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