-操作系统精髓与设计原理(第五版)+课后题答案1

-操作系统精髓与设计原理(第五版)+课后题答案1

CHAPTER 2 OPERATING SYSTEM

OVERVIEW

Review Questions

2.1 Convenience: An operating system makes a computer more convenient

to use. Efficiency: An operating system allows the computer system resources to be used in an efficient manner. Ability to evolve: An

operating system should be constructed in such a way as to permit the effective development, testing, and introduction of new system functions without interfering with service.

2.5 The execution context, or process state, is the internal data by which the

operating system is able to supervise and control the process. This

internal information is separated from the process, because the operating system has information not permitted to the process. The context includes all of the information that the operating system needs to manage the

process and that the processor needs to execute the process properly. The context includes the contents of the various processor registers, such as the program counter and data registers. It also includes information of use to the operating system, such as the priority of the process and whether the process is waiting for the completion of a particular I/O event.

Problems

2.1 The answers are the same for (a) and (b). Assume that although processor

operations cannot overlap, I/O operations can. 1 Job: TAT = NT Processor utilization = 50% 2 Jobs: TAT = NT Processor utilization = 100% 4 Jobs: TAT = (2N – 1)NT Processor utilization = 100% 2.4 A system call is used by an application program to invoke a function

provided by the operating system. Typically, the system call results in transfer to a system program that runs in kernel mode.

-操作系统精髓与设计原理(第五版)+课后题答案1

CHAPTER 3

PROCESS DESCRIPTION AND

CONTROL

Review Questions

3.5 Swapping involves moving part or all of a process from main memory to

disk. When none of the processes in main memory is in the Ready state, the operating system swaps one of the blocked processes out onto disk into a suspend queue, so that another process may be brought into main memory to execute.

3.10 The user mode has restrictions on the instructions that can be executed

and the memory areas that can be accessed. This is to protect the operating system from damage or alteration. In kernel mode, the

operating system does not have these restrictions, so that it can perform its tasks. Problems

3.1 Creation and deletion of both user and system processes. The

processes in the system can execute concurrently for information sharing, computation speedup, modularity, and convenience.

Concurrent execution requires a mechanism for process creation and deletion. The required resources are given to the process when it is created, or allocated to it while it is running. When the process terminates, the OS needs to reclaim any reusable resources. Suspension and resumption of processes. In process scheduling, the

OS needs to change the process's state to waiting or ready state when it is waiting for some resources. When the required resources are

available, OS needs to change its state to running state to resume its execution. Provision of mechanism for process synchronization. Cooperating

processes may share data. Concurrent access to shared data may result in data inconsistency. OS has to provide mechanisms for processes synchronization to ensure the orderly execution of cooperating processes, so that data consistency is maintained. Provision of mechanism for process communication. The processes

executing under the OS may be either independent processes or

cooperating processes. Cooperating processes must have the means to communicate with each other. Provision of mechanisms for deadlock handling. In a

multiprogramming environment, several processes may compete for a finite number of resources. If a deadlock occurs, all waiting processes

-操作系统精髓与设计原理(第五版)+课后题答案1

will never change their waiting state to running state again, resources are wasted and jobs will never be completed.

3.3 Figure 9.3 shows the result for a single blocked queue. The figure readily generalizes to multiple blocked queues.

-操作系统精髓与设计原理(第五版)+课后题答案1

CHAPTER 4

PROCESS DESCRIPTION AND

CONTROL

Review Questions

4.2 Less state information is involved.

4.5 Address space, file resources, execution privileges are examples.

4.6 1. Thread switching does not require kernel mode privileges because all

of the thread management data structures are within the user address space of a single process. Therefore, the process does not switch to the kernel mode to do thread management. This saves the overhead of two mode switches (user to kernel; kernel back to user). 2. Scheduling can be application specific. One application may benefit most from a simple round-robin scheduling algorithm, while another might benefit from a priority-based scheduling algorithm. The scheduling algorithm can be tailored to the application without disturbing the underlying OS scheduler. 3. ULTs can run on any operating system. No changes are required to the underlying kernel to support ULTs. The threads library is a set of application-level utilities shared by all applications.

4.7 1. In a typical operating system, many system calls are blocking. Thus,

when a ULT executes a system call, not only is that thread blocked, but also all of the threads within the process are blocked. 2. In a pure ULT strategy, a multithreaded application cannot take advantage of

multiprocessing. A kernel assigns one process to only one processor at a time. Therefore, only a single thread within a process can execute at a time. Problems

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