What is virtual memory and how does it enhance system performance?
This OS question tests understanding of memory abstraction and swapping mechanisms.
Why Interviewers Ask This
Virtual memory allows running larger applications than physical RAM permits. Interviewers want to know if you understand paging, swapping, and the role of the MMU. This is key for optimizing application memory usage and debugging performance bottlenecks.
How to Answer This Question
Define virtual memory as a technique that provides an illusion of large contiguous memory. Explain the role of the page table and swap space. Discuss demand paging and how it loads pages only when needed. Mention thrashing as a potential downside.
Key Points to Cover
- RAM and disk integration
- Page tables
- Demand paging
- Thrashing risk
Sample Answer
Virtual memory extends physical RAM by using disk space as overflow, allowing programs to use more memory than physically available. The OS maps virtual addresses to physical ones using page tables. Demand paging loads pages into RAM only when accessed, saving memory. While it enables running large apps, excessive swapping can cause thrashing, slowing down the system significantly.
Common Mistakes to Avoid
- Confusing with cache
- Ignoring disk I/O cost
- Not explaining mapping
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