Question

A given processor requires 1000 cycles to perform a context switch and start an interrupt handler (and the same number of cycles to switch back to the program that was running when the interrupt occurred), or 500 cycles to poll an I/O device. An I/O device attached to that processor makes 150 requests per second, each of which takes 10,000 cycles to resolve once the handler has been started. By default, the processor polls every 0.5 ms if it is not using interrupts. a. How many cycles per second does the processor spend handling l/O from the device if interrupts are used? b. How many cycles per second are spent on I/O if polling is used (include all polling attempts)? Assume the processor only polls during time slices when user programs are not running, so do not include any context-switch time in your calculation. C. How often would the processor have to poll for polling to take as many cycles per second as interrupts?

Answer 1

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