Unformatted text preview: that are either very short (less than around 10 millisecond) or very long (greater than 449 450 CHAPTER 9. MEASURING PROGRAM EXECUTION TIME
Time Scale (1 Ghz Machine) Microscopic
Integer Add FP Multiply FP Divide 1 ns
Disk Access Screen Refresh Keystroke 1s
1.E+00 Keystroke Interrupt Handler 1 µs 1 ms
1.E-03 Time (seconds) 1.E-06 Figure 9.1: Time Scale of Computer System Events. The processor hardware works at a microscopic a time scale in which events having durations on the order of a few nanoseconds (ns). The OS must deal on a macroscopic time scale with events having durations on the order of a few milliseconds (ms). around 1 second), even on heavily loaded machines. Times between around 10 milliseconds and 1 second require special care to measure accurately. Much of the understanding of performance measurement is part of the folklore of computer systems. Different groups and individuals have developed their own techniques for measuring program performance, but there is no widely available body of literature on the subject. Companies and research groups concerned with getting highly accura...
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