CST 334 Week 5

This week in CST 334, Virtual memory rules and the operating system's handling of page replacement under memory strain were the main topics of discussion. When physical memory is full and the OS has to choose which pages to remove to create room for others, I discovered how important these policies are. We focused on four main algorithms: Random, Optimal, FIFO (First-In-First-Out), and LRU (Least Recently Used).

These policies are essential for maintaining system responsiveness and preventing excessive disk usage when multitasking with large processes. Because it depends on future information of memory access, the optimal replacement strategy, while ideal, cannot be applied in practical systems. Nonetheless, it provides a useful standard by which to compare actual policies. Because of Belady's Anomaly, which states that expanding memory might actually result in more page errors, I discovered that the FIFO technique was shockingly incorrect. By utilizing the idea of temporal locality, LRU, on the other hand, closely resembles the performance of the optimum policy by using recent access history to make more intelligent eviction judgments.Average Memory Access Time, or AMAT, was a crucial idea that brought everything together. Because accessing data from disk is more expensive than accessing data from memory, it demonstrated how slight variations in hit/miss rates may have a significant effect on performance. This demonstrated why OS design places such a high value on memory efficiency.

Overall, this week helped me understand more thoroughly how the OS strikes a compromise between performance and memory efficiency and deepened my respect for the clever algorithms that operate in the background of each memory request.