2002 FREENIX Track Technical Program - Abstract
Inferring Scheduling Behavior with
Hourglass
John
Regehr, School of Computing, University of Utah
Abstract
Although computer programs explicitly represent
data values, time values are usually implicit. This makes it
difficult to analyze and debug real-time programs whose correctness depends
partially on the time at which results are computed. This paper
shows how to use Hourglass, an instrumented, synthetic real-time
application, to make inferences about what is happening on a
computer at millisecond and microsecond granularities. These
inferences are possible because Hourglass records a very
fine-grained map of when each of its threads runs, and because
Hourglass supports a variety of thread
execution models that model the
properties and requirements of non-synthetic real-time
applications. We conclude that between measurements and inferences,
surprisingly detailed knowledge about scheduling behavior can be
obtained without modifying, or even explicitly interacting with,
the operating system kernel.
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