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  • Operating System: Three Easy Pieces --- Mechanism: Limited Direct Execution (Note)

    In order to virtualize the CPU, the operating system needs to somehow share the physical

    CPU among many jobs  running seemingly at the same time. The basic idea is simple: run

    one process for a little while, then run another, and so forth. By time sharing the CPU in this

    manner, virtualization is achieved. There are a few challenges, however, in building such

    virtualization machinery. The first is performance: how can we implement virtualization without

    adding excessive overhead to the system? The second is control: how can we processes efficiently

    while retaining control over the CPU? Control is particularly important to the OS, as it is in

    charge of resources; without control, a process could simpley run forever and take over the

    machine, or access information that it should not be allowed to access. Attaining performance

    while maintaining control is thus one of the central challenges in building an Operating System.

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  • 原文地址:https://www.cnblogs.com/miaoyong/p/4855584.html
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