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Instantaneous percentage of CPU utilization on Windows?!? |
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The author states that "On Microsoft Windows PC systems, the system load is given as an instantaneous percentage of CPU utilization." That's not possible, there is no CPU "speedometer" on any processor chip set that I know of. An operating system can only recognize two basic states: idle (0% utilization) or not idle (100% utilization). To report a utilization between 0% and 100% requires that it average the two basic states over some time period. Most operating systems do this by sampling the current state during each clock interrupt and incrementing one of the two state counters (most operating systems also have sub-counters under Not Idle such as Wait I/O in UNIX or processing nested interrupts). The utilization that is then reported is the difference between the counters over some sampling interval divided by the total samples during the interval and that is what is reported as utilization. As for what time interval Windows utilities such as perfmon and the Logs & Alerts Service use I have no clue.
== Processes or jobs? ==
The article talks about "each process that is using CPU". I think it's more common to talk about "each job", which isn't necessarily synonymous. For example, a process with two threads can count as two jobs.
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