New PDF release: An Operating Systems Vade Mecum

By Raphael A. Finkel

ISBN-10: 0136377602

ISBN-13: 9780136377603

ISBN-10: 0136379508

ISBN-13: 9780136379508

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Accepted processes are serviced by RR. The priority of a new process increases at rate a . The priority of an accepted process increases at rate b . Both a and b are Policies 45 parameters; that is, they can be adjusted to tune the method. When the priority of a new process reaches the priority of an accepted process, that new process becomes accepted. If all accepted processes finish, the highest priority new process is accepted. Assume that there are no ready processes, when the first one, A, arrives.

Intrinsic properties: characteristics that distinguish one process from another. Intrinsic characteristics include service-time requirements, storage needs, resources held, and the amount of transput required. This sort of information may be placed in the context block. For example, the MVS operating system for the IBM 370 gives a longer quantum to processes holding certain resources. Tops-10 gives a higher priority to processes using small amounts of main store, particularly if the main store is tied down, that is, prevented from being displaced by other processes.

Say a process p requires t time in execution before it can leave the ready list because it will either finish or will need to wait for something. Then we define the following service measures for that process. response time T : time that p is present; finish time − arrival time missed time M : T − t penalty ratio P : T / t response ratio R : t / T The response time T counts not only how long p needs, but also how long it sits in the ready list while other processes are run. It might wait its turn for a while.

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An Operating Systems Vade Mecum by Raphael A. Finkel


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