The flight recorder
Michael M. Gorlick · 1991
Instrumenting and monitoring real-time systems is an old and perennial problem.Many different solutions have been proposed and implemented, each usually involving some combination of software probes and bus snooping.We propose an alternative approach, the use of a monitoring device attached as a coprocessor to the target system.The coprocessor has a small and simple instruction set, imposes a very modest burden on the target system, is highly programmable, and can concurrently monitor a broad spectrum of events ranging from the kernel to the application level.We discuss the logical architecture of the monitoring coprocessor and illustrate how it can be applied to answer a wide variety of monitoring questions.