How to distinguish between I/O bound and CPU bound jobs ?

How does a long term scheduler decide which job is I/O bound and which one is CPU bound?

I heard that by using cpu burst we can distinguish between I/O bound and CPU bound jobs, but how is the CPU burst ca开发者_StackOverflow中文版lculated without processing the program?

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Generally, the CPU scheduler assigns time slices to processes/threads and switches between them whenever a) the time slice has run out or b) the process/thread blocks for I/O.

An I/O-bound job will be blocking for I/O very often, while a process/thread that always makes use of his full time slice can be assumed to be CPU-bound. So by distinguishing whether a process/thread blocks at the end of the time slice or by calling some wait_for_io_completion() function, you can effectively characterize those types of processes.

Note, that in real life, things get more complicated, because most of the time applications are not either I/O-bound or CPU-bound but switch roles all the time. This is why scheduling is about heuristics and not about correct solutions, because you cannot (always) predict the future.

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CPU bound uses more of its time doing computations than I/O bound.

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answered by tumaini kami david Answers. Generally, the CPU scheduler assigns time slices to processes/threads and switches between them whenever a) the time slice has run out or b) the process/thread blocks for I/O. ... CPU bound uses more of its time doing computations than I/O bound.strong text

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IO BOUND PROCESS : Io bound process spends more time doing io than computations,many short cpu burst. COU BOUND PROCESS : process spends more time doing computations;few very long cpu bursts.