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10 Cards in this Set
- Front
- Back
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What is a program? What are the four componenets of a program?
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A program is complied code. The four components of a program are:
1. Executable format information. 2. Text Segment. 3. Data Segment. 4. BSS Segment. |
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What is a process? What are the components of a process?
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A process is a running instance of a program. There are four components of a process:
1. Program (Text, data, BSS). 2. Address space. 3. Stack. 4. Heap. |
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What is a PCB? What is contained in a PCB?
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A PCB (process control block) is a per-process os state needed across system calls. A PCB conatins:
-File descriptor table; working directory -UID, GID -priority; state -signal state and handlers -pipes -... |
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What is contained in the context of a process?
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The context of a process contains all the information necessary to resume a suspended process. That is: Registers (incl. PC, SP, Status Register), Configuration (memory space, caches).
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What is meant by context switching?
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Saving the entire context of a process into the PCB. Loading a different context into the CPU. Makes things appear as if they were running simultaneously.
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What are the pitfalls and drawbacks of context switching?
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-Pitfalls: Kernel is running on the same CPU using the registers it is trying to restore. the order in which the registers are restored is very important. Drawbacks: context switching is slow, 100% overhead, context switchings too frequent then comp appears slow. 4. Too infrequent, comp appears unresponsive.
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What are the benefits of context switching?
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- provides mechanism for sharing cpu
- prevents wasted cpu time -some activities are slow and now processes don't have to run while waiting and the cpu cna process switch. |
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What are three types of multitasking?
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Batch(context switches only when a process is doen executing), cooperative (context switches when running process calls yield funtion), preemptive (CPU has a timer interrupt, wuantums etc.)
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What are the states that a process can be in?
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-Runnning: the process is actively running on the CPU.
-Ready: the process is eligible to run but is currently not running -Blocked: the process is not eligible to run (eg waiting for i/o) |
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What state transitions are available between running, ready, and blocked?
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Caused by scheduler:
- Ready -> Running - Running -> Ready Caused by blocking request (ie i/o request: - Running -> Blocked Blocked -> Ready |
