운영체제 연습문제 3장

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운영체제 연습문제 3장 조선대학교 이준 교수님꺼!!

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3.1 Describe the differences among short-term, medium-term, and longterm
scheduling.
Answer:
• Short-term (CPU scheduler)—-selects from jobs in memory those
jobs that are ready to execute and allocates the CPU to them.
• Medium-term—-used especially with time-sharing systems as an
intermediate scheduling level. A swapping scheme is implemented
to remove partially run programs from memory and reinstate them
later to continue where they left off.
• Long-term (job scheduler)—-determines which jobs are brought into
memory for processing.
The primary difference is in the frequency of their execution. The shortterm
must select a new process quite often. Long-term is usedmuch less
often since it handles placing jobs in the system and may wait a while
for a job to finish before it admits another one.
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16 Chapter 3 Processes
3.2 Describe the actions taken by a kernel to context-switch between processes.
Answer: In general, the operating system must save the state of the
currently running process and restore the state of the process scheduled
to be run next. Saving the state of a process typically includes the
values of all the CPU registers in addition to memory allocation. Context
switches must also perform many architecture-specific operations,
including flushing data and instruction caches.
3.3 Consider the RPC mechanism. Describe the undesirable circumstances
that could arise from not enforcing either the "at most once" or "exactly
once" semantics.Describe possible uses for amechanism that had neither

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