Short Answer

[问答题]

Short Answer

1. List at least two advantages of User-Level Thread over Kernel-Level Thread.

2. What are the four necessary conditions of deadlock? Please briefly describe the meaning of each condition.

3. List and briefly describe three common schemes for defining the logical structure of a directory.

4. What is the difference between simple paging and virtual memory paging?

5. What are the three major methods of allocating disk space? Describe their advantages and disadvantages respectively.

6. List three basic process states and describe the meaning of each state.

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Short Answer

1. （ 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.

2. 略 .

3. 略 .

4. Simple paging: all the pages of a process must be in main memory for process to run,

unless overlays are used. Virtual memory paging: not all pages of a process need be in main memory frames for the process to run.; pages may be read in as needed.

5. 略 .

6. 略

发表于 2017-05-16 21:25:38 回复(0)