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Unformatted text preview: ss is reactivated, the cycle counter is set to the value it had when the process was last deactivated, effectively freezing the counter while the process is inactive. Of course, the counter will still be affected by the overhead of kernel operation and by cache effects, but at least the effects of other processes will not be as severe. Already some systems support this feature. In terms of our protocol, this will allow us to use cycle-based timing to get accurate measurements of durations greater than around 0.01 second, even on heavily loaded systems. Variable Rate Clocks. In an effort to reduce power consumption, future systems will vary the clock rate, since power consumption is directly proportional to the clock rate. In that case, we will not have a simple conversion between clock cycles and nanoseconds. It even becomes difﬁcult to know which unit should be used to express program performance. For a code optimizer, we gain more insight by counting cycles, but for someone implementing an application with re...
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- Spring '10
- The American