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On the vast majority of today's computers, the dominant form of
computation is GUI-based user interaction. In such an
environment, the user's perception is the final arbiter of
performance. Human-factors research shows that a user's
perception of performance is affected by unexpectedly long delays.
However, most performance-tuning techniques currently rely on
throughput-sensitive benchmarks. While these techniques improve
the average performance of the system, they do little to detect or
eliminate response-time variabilities--in particular, unexpectedly
long delays.
We introduce a measurement infrastructure that allows us to
improve user-perceived performance by helping us to identify and
eliminate the causes of the unexpected long response times that
users find unacceptable. We describe TIPME (The Interactive
Performance Monitoring Environment), a collection of
measurement tools that allowed us to quickly and easily diagnose
interactive performance "bugs" in a mature operating system. We
present two case studies that demonstrate the effectiveness of our
measurement infrastructure. Each of the performance problems we
identify drastically affects variability in response time in a mature
system, demonstrating that current tuning techniques do not
address this class of performance problems.
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