q:process stateu 有哪些 ? 何種情形下會做 transition?
DESCRIPTION
Q:Process Stateu 有哪些 ? 何種情形下會做 transition?. As a process executes, it changes state new : The process is being created running : Instructions are being executed waiting : The process is waiting for some event to occur ready : The process is waiting to be assigned to a processor - PowerPoint PPT PresentationTRANSCRIPT
3.1 Silberschatz, Galvin and Gagne ©2009Operating System Concepts – 8th Edition
Q:Process Stateu有哪些 ?何種情形下會做transition?
As a process executes, it changes state
new: The process is being created
running: Instructions are being executed
waiting: The process is waiting for some event to occur
ready: The process is waiting to be assigned to a processor
terminated: The process has finished execution
3.2 Silberschatz, Galvin and Gagne ©2009Operating System Concepts – 8th Edition
Q:所謂 context主要是包含哪些資料 ? 或問所謂 PCB主要是包含哪些資料 ?
Information associated with each process
Process state
Program counter
CPU registers
CPU scheduling information
Memory-management information
Accounting information
I/O status information
3.3 Silberschatz, Galvin and Gagne ©2009Operating System Concepts – 8th Edition
Q:何謂 Context Switch?
When CPU switches to another process, the system must save the state of the old process and load the saved state for the new process via a context switch
Context of a process represented in the PCB
Context-switch time is overhead; the system does no useful work while switching
Time dependent on hardware support
3.4 Silberschatz, Galvin and Gagne ©2009Operating System Concepts – 8th Edition
Q:(a)簡單說明 OS如何由 process A 到 B 做 context switching?
3.5 Silberschatz, Galvin and Gagne ©2009Operating System Concepts – 8th Edition
Q:Describe the difference among short-term, medium-term, and long-term scheduling?
Long-term scheduler (or job scheduler) – selects which processes should be brought into the ready queue
Short-term scheduler (or CPU scheduler) – selects which process should be executed next and allocates CPU
3.6 Silberschatz, Galvin and Gagne ©2009Operating System Concepts – 8th Edition
Addition of Medium Term Scheduling
3.7 Silberschatz, Galvin and Gagne ©2009Operating System Concepts – 8th Edition
Schedulers (Cont)
Short-term scheduler is invoked very frequently (milliseconds) (must be fast)
Long-term scheduler is invoked very infrequently (seconds, minutes) (may be slow)
The long-term scheduler controls the degree of multiprogramming
3.8 Silberschatz, Galvin and Gagne ©2009Operating System Concepts – 8th Edition
Q:說明 I/O-bound process & CPU-bound process?
Processes can be described as either:
I/O-bound process – spends more time doing I/O than computations, many short CPU bursts
CPU-bound process – spends more time doing computations; few very long CPU bursts
3.9 Silberschatz, Galvin and Gagne ©2009Operating System Concepts – 8th Edition
Q:何謂 Interprocess Communication?可能方法 ?
Processes within a system may be independent or cooperating
Cooperating process can affect or be affected by other processes, including sharing data
Reasons for cooperating processes:
Information sharing
Computation speedup
Modularity
Convenience
Cooperating processes need interprocess communication (IPC)
Two models of IPC
Shared memory
Message passing
3.10 Silberschatz, Galvin and Gagne ©2009Operating System Concepts – 8th Edition
Communications Models
3.11 Silberschatz, Galvin and Gagne ©2009Operating System Concepts – 8th Edition
Q:Blocking (TRX) vs nonblocking?
Message passing may be either blocking or non-blocking
Blocking is considered synchronous
Blocking send has the sender block until the message is received
Blocking receive has the receiver block until a message is available
Non-blocking is considered asynchronous
Non-blocking send has the sender send the message and continue
Non-blocking receive has the receiver receive a valid message or null