Operating Systems, unit: Virtual Memory. Core concepts, terminology, and worked-example cues a college student meets for this unit, building on prior units without repeating them. Front: a term, concept, or short problem cue. Back: the definition, explanation, or answer.
21 cards · basic cards · AI-written, checked twice. Edit anything.
- What is virtual memory?
- A memory management technique that gives processes the illusion of a large, contiguous address space, backed partly by disk
- What is the main benefit of virtual memory?
- Programs can run without being limited by the amount of physical RAM installed
- What is demand paging?
- Loading a page into physical memory only when it is actually accessed, not in advance
- What is swapping?
- Moving a process's memory between RAM and disk to free up physical memory
- What is a swap space (or swap file)?
- A reserved area of disk used to hold pages swapped out of physical memory
- What is thrashing?
- A condition where a system spends most of its time swapping pages in and out, with little actual progress
- What causes thrashing?
- Too many processes competing for too little physical memory, causing excessive page faults
- What is a page replacement algorithm used for?
- Deciding which page to remove from memory when a new page needs to be loaded and memory is full
- What is the FIFO page replacement algorithm?
- Replacing the oldest page that was loaded into memory
- What is the Least Recently Used (LRU) page replacement algorithm?
- Replacing the page that has not been used for the longest time
- What is the Optimal page replacement algorithm?
- Replacing the page that will not be used for the longest time in the future (a theoretical best case)
- What is Belady's Anomaly?
- A counterintuitive phenomenon where increasing the number of page frames can increase the number of page faults, seen in FIFO
- What is the working set of a process?
- The set of pages a process is actively using during a given time window
- What is the effective access time affected by page faults?
- It increases significantly, since disk access is far slower than RAM access
- What is copy-on-write, as a memory optimization?
- Sharing memory pages between processes until one attempts to modify it, at which point a private copy is made
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