Unformatted text preview: Process Timers
As the example illustrated in Figure 9.7 shows, this timing mechanism is only approximate. Figure 9.7(b) shows the actual times used by the two processes. Process A executed for a total of 153.3 ms, with 120.0 in user mode and 33.3 in kernel mode. Process B executed for a total of 96.7 ms, with 73.3 in user mode and 23.3 in kernel mode. The interval accounting scheme makes no attempt to resolve time more ﬁnely than the timer interval. Practice Problem 9.3:
What would the operating system report as the user and system times for the execution sequence illustrated below. Assume a 10 ms timer interval. A B A B A Practice Problem 9.4:
On a system with a timer interval of 10 ms, some segment of process A is recorded as requiring 70 ms, combining both system and user time. What are the minimum and maximum actual times used by this segment? Practice Problem 9.5:
What would the counters record as the system and user times for the trace shown in Figure 9.3? How does this compare to the actual time during which the process was...
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