Multiprocessing is already prevalent in servers where multiple clients present an obvious source of thread-level parallelism. However, the case for multiprocessing is less clear for desktop applications. Nevertheless, architects are designing processors that count on the availability of thread-level parallelism. Unlike server workloads, the primary requirement of interactive applications is to respond to user events under human perception bounds rather than to maximize end-to-end throughput. In this paper we report on the thread-level parallelism and interactive response time of a variety of desktop applications. By tracking the communication between tasks, we can focus our measurements on he portions of the benchmark's execution that have the greatest impact on the user. We find that running our benchmarks on a dual-processor machine improves response time of mouse-click events by as much as 36%, and 22% on average-out of a maximum possible 50%. The benefits of multiprocessing are even more apparent when background tasks are considered. In our experiments, running a simple MP3 playback program in the background increases response time by 14% on a uniprocessor while it only increases the response time on a dual processor by 4%. When response times are fast enough for further improvements to be imperceptible, the increased idle time after interactive episodes could be exploited to build systems that are more power efficient.
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