The time taken to service a page fault is on average 10 ms and the memory access time is 20 μs.

step 1 We want average memory access time. And that is equal to H times T -sive -M, which is the memory

The time taken to service a page fault is on average 10 ms...

The time taken to service a page fault is on average 10 $\mathrm{ms}$ and the memory access time is $20 \mu \mathrm{s}$. If the hit ratio is $70 \%$, calculate the average access time. (A) $3018 \mu \mathrm{s}$ (B) $4014 \mu \mathrm{s}$ (C) $3014 \mu \mathrm{s}$ (D) $4024 \mu \mathrm{s}$

The time taken to service a page fault is on average 10 $\mathrm{ms}$ and the memory access time is $20 \mu \mathrm{s}$. If the hit ratio is $70 \%$, calculate the average access time.
(A) $3018 \mu \mathrm{s}$
(B) $4014 \mu \mathrm{s}$
(C) $3014 \mu \mathrm{s}$
(D) $4024 \mu \mathrm{s}$

Key Concepts

Effective Access Time Calculation

Effective access time is computed as a weighted average based on the probability of a page hit and a page fault. It combines the fast memory access time with the slower page fault service time, reflecting the actual average time required per memory access in a system employing virtual memory.

Virtual Memory

Virtual memory is a memory management technique that allows the execution of processes that may not be completely in main memory by using disk space to extend the available memory. It introduces the concept of pages and page faults, which are central to understanding how memory access times can vary.

Page Fault

A page fault occurs when a program attempts to access a page that is not currently in main memory, triggering a disk I/O to retrieve the page. Because disk access is significantly slower than memory access, page faults have a substantial impact on overall system performance.

Hit Ratio

The hit ratio is the percentage of memory accesses that are successfully resolved without incurring a page fault. It is critical for determining the average access time since higher hit ratios reduce the frequency of expensive page fault handling.

Memory Access Time

Memory access time refers to the time required to access data in physical memory when it is already loaded (a cache hit). It is generally very fast compared to the time taken to service a page fault, making it an essential component in calculating the overall effective memory performance.

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