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水晶礦脈

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不可思議之水晶礦脈

不可思議之水晶礦脈

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    水晶礦脈 水晶礦脈 Presentation Transcript

    • Context Switching Group 1 – Presented by David Calhoun Question 3.7: What are the actions taken by the kernel to context-switch between processes?
    • Multitasking (real life) (Look carefully...)
    • Multitasking (OS) (process scheduler)
    • What is a context switch? -process of suspending and resuming processes -triggered by interrupt (for instance, an IO interrupt), preemptive multitasking, or as part of user/kernel mode switching -process context represented by the Process Control Block (PCB)
    • Process Control Block (PCB) The PCB is "the manifestation of a process in an operating system" Harvey M. Deitel (1984) [1982]. An introduction to operating systems
    • What's in the PCB?
    • PCB components
      • -PCB implementations differ, but generally contain:
      • Process ID (PID)
      • Process state (fig 3.2) (ready, running, waiting, etc)
      • Registers (including Program Counter)
      • Memory management info (address space of the process)
      More complete list: p. 104
    • Overhead
      • Switching contexts
      • involves a lot of
      • overhead (typically a
      • few milliseconds).
      • Think of the overhead
      • involved in multitasking
      • in real life.