Abstract
We present a temporal debugger, capable of examining time flow of soft real-time applications. The debugger is attached to a simulator modelling an entire workstation in sufficient detail to run commodity operating systems and workloads. Whereas traditional debuggers need to interfere with program execution, thereby changing the temporal behaviour, a debugger operating on a simulated system does not disturb the timing of the target program. The temporal debugger therefore allows non-intrusive and reproducible debugging of real-time applications in general-purpose operating systems.

We have implemented the temporal debugger by modifying the GNU debugger to operate on applications running in a simulated machine. Debugger implementation is difficult because the debugger expects application-related data, whereas the simulator provides low-level data. We introduce a technique, virtual machine translation, for mapping simulator data to the debugger by parsing operating system data structures in the simulated system.

The debugger environment allows execution time measurement and collection of statistics from multiple levels of the system: hardware, operating system, and application. We show how this profiling data can help a programmer explain missed deadlines; the statistics are correlated to deadline violations, thereby exposing differences between executions when deadlines are met and when they are missed.

The temporal debugger is demonstrated with a debugging session of an MPEG video decoder running in a Linux system. We show how the debugger can be used to detect that the decoder fails to render some frames in time, and how the causes for deadline violations are found by correlating rendering time with runtime statistics.

Link to the paper
Simulation-Based Debugging and Profiling of Soft Real-Time Applications
to be presented at
ARTES graduate student conference in Lund March 8-9, 2001.

ASTEC seminar
March 13, 2001

Place: Information technology, Uppsala University
Room: 1113
Time: 15.15-16.00 (+ discussions)

Room 1113 is in building 1, floor 1, room 13 (in the southern part of the building).

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There will be an extended period for discussions after the seminar.

Speakers are encouraged to give an short (5 min) introduction to the subject at the begining of the talk.
Listeners are excused if they have to leave after 16.00.