Thrashing in Virtual Memory Which factors most significantly influence whether a system experiences thrashing (excessive paging) under demand-paged virtual memory?

Introduction / Context:
Thrashing occurs when a system spends most of its time servicing page faults rather than executing useful work. Understanding the causes helps administrators and developers prevent severe performance collapse on multitasking systems.

Given Data / Assumptions:

• Demand-paged virtual memory is in use.
• Multiple processes may compete for limited physical frames.
• Locality of reference varies by program structure and phase.

Concept / Approach:
Thrashing is governed by the working-set sizes of active processes versus the total available frames. Code/data structure (program structure), total footprint (program size), and physical memory capacity collectively determine whether working sets fit in RAM with acceptable fault rates.

Step-by-Step Solution:
Assess program structure: tight loops and cache-friendly access improve locality.Evaluate program size: larger footprints need more frames to avoid constant eviction.Examine RAM: insufficient frames force frequent page replacement, amplifying faults.Adjust multiprogramming level or allocate more frames to stabilize working sets.

Verification / Alternative check:
Monitoring page fault rates and residency per process typically reveals that increasing frames or reducing active processes drops fault rates sharply, confirming the interplay among structure, size, and RAM.

Why Other Options Are Wrong:
Selecting only one factor ignores the combined effect; all listed aspects materially contribute to thrashing risk.

Common Pitfalls:

• Attributing thrashing solely to “insufficient RAM” while ignoring poor locality.
• Failing to consider phase changes in a program’s working set.
• Overcommitting memory by raising the degree of multiprogramming too high.

Final Answer:
All of the above.