18. Page Replacement Algorithms
The chapter extensively explores the design and management of cache memory, focusing on virtually indexed and physically tagged cache mechanisms, along with various page replacement strategies. It highlights the trade-offs involved in cache indexing methods, such as issues with cold misses during context switches and the synonym problem in set-associative caches. The chapter also delves into efficient page replacement algorithms, using examples like FIFO and LRU while addressing practical challenges in their implementation.
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Sections
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What we have learnt
- The advantages and disadvantages of virtually indexed and physically indexed caching methods.
- The impact of page replacement strategies on system performance and page fault rates.
- The synonym problem in caches and solutions like page coloring to mitigate these issues.
Key Concepts
- -- Virtual Memory
- A memory management capability that provides an 'idealized abstraction' of the storage resources that are actually available on a computer.
- -- Page Replacement Algorithms
- Strategies used by an operating system to determine which memory pages to swap out when new pages are required in physical memory.
- -- TLB (Translation Lookaside Buffer)
- A cache that memory management hardware uses to reduce the time taken to access the memory locations.
- -- FIFO (First In First Out)
- A page replacement algorithm that removes the oldest page in memory first.
- -- LRU (Least Recently Used)
- A page replacement algorithm that removes the page that has not been used for the longest period of time.
- -- Cold Misses
- Cache misses that occur when a cache is initially empty and data needs to be loaded from main memory.
- -- Synonym Problem
- A scenario where different virtual addresses map to the same physical address, leading to cache conflicts.
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