PPT Slide
Approximating the Working Set
- The working set approximation algorithm:
- When a page fault occurs, scan through all the pages that process has in memory.
- If the ref bit is set, set the “time of last use” of that page to the current virtual time (accum. CPU time) of the process.
- If the ref bit is NOT set, check the “time of last use” for the page. If the page has not been used within T (working set window) time units then remove the page.
- Bring in the new page and add it to the resident set of the program.
- Another variation, which we won’t cover, is the WSClock paging algorithm. It is more efficient than the above approximation algorithm.
- Skip section 12.5.