IPA FE Subject A 2026 Question 5
A question IPA Japan published in 令和８年度 基本情報技術者試験 科目A 公開問題 問5, translated into English. ITPEC is based on the same exams.
In a computer system that uses virtual storage, when the degree of multiprogramming was increased, page-ins and page-outs occurred frequently, and the response speed of the system slowed down sharply. What is such a phenomenon called?
Explanation
Thrashing — when too many processes share too little real memory, the system spends its time paging instead of doing useful work.
In virtual storage, each process needs a certain set of pages in real memory (its working set) to run efficiently. Raising the degree of multiprogramming divides the page frames among more processes. Once their working sets no longer fit, every process keeps causing page faults: pages are paged out only to be paged in again soon after, and the processor waits on paging I/O. Throughput falls and response time rises sharply. The remedy is to lower the degree of multiprogramming or add real memory.
Answer (b)
Why not others:
- •(a) Overlay — runs a program larger than memory by splitting it into segments that take turns in the same memory area; it is a technique, not a slowdown
- •(c) Memory compaction — moves allocated areas together so that scattered free areas merge into one block
- •(d) Roll-out — saves the memory area of a running job to auxiliary storage to free memory for a job of higher priority (roll-in brings it back)
Key rule: Frequent page-ins and page-outs with a sudden drop in performance after the degree of multiprogramming is raised is the signature of thrashing.
Software · AI-written, may contain errors
This question comes from the past questions IPA Japan publishes, translated into English by ITPEC Practice. ITPEC Practice is an independent study tool and is not affiliated with IPA or ITPEC. See the original paper (PDF) or Report an issue.