In which scenario is the working set model most effective for preventing thrashing in a multiprogramming environment?

easy🔍 Pattern Recognition Q11 of Q15

Operating Systems - Thrashing - Working Set Model & Prevention

AWhen processes have highly variable and unpredictable memory access patterns

BWhen the system can allocate pages based on the current active set of pages each process uses

CWhen the system uses a fixed number of frames per process regardless of workload

DWhen the system relies solely on page-fault frequency without considering locality

Step-by-Step Solution

Step 1: Understand the working set model purpose
The working set model tracks the set of pages a process actively uses to allocate enough frames to avoid thrashing.
Step 2: Analyze each option
A is incorrect because unpredictable access patterns reduce the effectiveness of working set tracking.
B is correct because allocating frames based on the active working set directly prevents thrashing.
C is incorrect because fixed allocation ignores dynamic working set size, risking thrashing.
D is incorrect because page-fault frequency alone does not capture locality as precisely as working set.
Final Answer:
Option B -> Option B
Quick Check:
Working set model adapts allocation to active pages, preventing thrashing effectively.

Quick Trick: Working set = active pages -> allocate accordingly

Common Mistakes:

MISTAKES

Trap Explanation:

PITFALL

Options A and D seem plausible because they mention memory access and page faults, but they miss the key aspect of adapting allocation to the working set size.

Interviewer Note:

CONTEXT

Tests if candidate can identify when working set model is applicable to prevent thrashing.

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