20. Belady's Anomaly
The discussion centers around page replacement strategies in memory management, particularly exploring Belady’s anomaly, which occurs when an increased number of page frames leads to more page faults. Key algorithms such as LRU (Least Recently Used) and optimal algorithms are presented, highlighting their inability to exhibit Belady’s anomaly as they adaptively manage recently accessed pages. The chapter further delves into memory allocation strategies for processes and addresses concepts like page buffering and thrashing.
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What we have learnt
- Belady's anomaly occurs when increasing frame numbers causes more page faults due to non-subset page references.
- LRU and optimal algorithms effectively manage pages to avoid Belady's anomaly by keeping recently used pages accessible.
- Different memory allocation strategies can improve memory utilization and address specific needs of processes.
Key Concepts
- -- Belady’s Anomaly
- A situation in which increasing the number of page frames results in an increase in the number of page faults.
- -- Page Buffering
- A method of keeping a pool of free frames to minimize wait times for writing dirty pages during replacement.
- -- LRU Algorithm
- Least Recently Used algorithm that replaces the page that has not been used for the longest period.
- -- Fixed Allocation Scheme
- A memory allocation method where a fixed number of frames are allocated to each process.
- -- Thrashing
- A condition where excessive page faults lead to decreased system performance, often due to insufficient memory.
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