The CPU as a Resource

The CPU as a Resource

You should not be overly concerned if your system has no idle time. In fact, you should be concerned if it does; unused CPU time is a wasted resource that cannot be recovered. A busy CPU implies you are not wasting processor cycles.

There are two conflicting definitions of good performance ? high throughput and better response time. They conflict because the highest throughput entails keeping the CPU busy 100 percent of the time, while the best response time allows the user to access the CPU quickly. Obviously, the CPU is easiest to access when it is not busy. You need to decide which of these definitions is your priority. The end result is usually a compromise in favor of response time because of user sensitivities.

The Compute Queue

Processes in the computable (COM) state are said to be ready to run and, thus, in the compute queue. As we saw when we discussed scheduling, the COM state is the best one for your process since it indicates that your process is utilizing the CPU. If your process is computable, but cannot be resident in memory because of memory resource shortages, your process is considered computable, but outswapped. This state (COMO) will cause a major performance hit because it takes time to bring your process fully into memory.

With the relatively inexpensive price of memory today, you should rarely (if ever) see a process in a COMO state. This state is the worst possible condition...

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