OS & Hardware

With FIFO page replacement, adding physical pages can sometimes increase page faults. What is this phenomenon called?

  1. AThrashing
  2. BBélády's anomaly
  3. CCopy-on-write
Show answer and explanation

Answer: B. Bélády's anomaly

Intuitively, more physical pages should mean fewer page faults, but with FIFO certain access sequences are known to fault more when the page count grows from three to four. This is Bélády's anomaly. It cannot occur with stack algorithms such as LRU, where the set of pages held with more frames always contains the set held with fewer. Thrashing is constant replacement from memory shortage, and copy-on-write copies pages on write.

  • A. Thrashing is constant replacement from memory shortage.
  • B. Correct. With FIFO, more pages can mean more faults.
  • C. Copy-on-write copies a page when it is written.
Practice this topic Back to topic

More OS & Hardware questions

  1. What is the state called in which physical memory is so short that pages are constantly evicted and reloaded and little work gets done?
  2. Memory access time is 100 ns and handling a page fault takes 8 ms. If a page fault occurs once per million accesses, what is the average access time approximately?
  3. During a context switch, what must be saved for the process being switched out?
  4. Why can a process context switch degrade performance more than the time spent saving and restoring registers would suggest?
  5. What is the advantage of tagging each TLB entry with an ASID (address space identifier)?