Under what conditions does thrashing occur, and what are common mitigation strategies?

• A. Thrashing occurs when the working set fits in memory; mitigate by increasing page size.
• B. Thrashing occurs when the working set does not fit in available memory, causing excessive paging; mitigations include increasing physical memory or reducing load.
• C. Thrashing is caused by network congestion; mitigation is to increase bandwidth.
• D. Thrashing occurs when CPU caches are too large; mitigation is to reduce cache size.

Answer: (B)

Thrashing happens when the set of pages actively needed by all running processes—the working set—does not fit in the available physical memory. When memory becomes overcommitted, the system spends most of its time swapping pages in and out, causing many page faults and putting CPU work into paging rather than useful computation. The result is a dramatic drop in system performance and responsiveness.

Mitigation focuses on reducing memory pressure or increasing available memory. Increasing physical memory provides more frames for pages so the working sets can be kept resident. Reducing load or the number of active processes lowers the total memory demand, allowing the working sets to fit. Other effective approaches include tuning page replacement choices and managing working sets more carefully, but the core idea is to prevent memory overcommitment that triggers paging thrash.

Why the other options don’t fit: thrashing is a memory paging problem, not caused by network conditions. It isn’t about cache size in the CPU either; caches are a different layer, and having larger caches doesn’t address excessive paging in main memory.