Remote Steering and Visualization

Online trace analysis does not necessarily require user control if one looks at it as a uni-directional information stream that can be continuously delivered to an application developer. However, the high rate at which information is likely to be generated in a native tracing approach suggests the need for advanced user control. Ideally, the user should be able to retrieve new trace data whenever he thinks it is necessary. At the VNG display client, this could be accomplished by adding a ``retrieve'' option that allows the user to specify how many recent events are to be loaded and analyzed by the analysis server. Such a request could translate all the way to trace generation. Even more sophisticated online control of the runtime system by the application developer would include:

• Enabling and disabling of certain processes
• Filtering of unwanted events
• Switching between a profile only mode and a detailed trace mode

While our infrastructure was designed to provide the necessary communication methods for those control requests, our present implementation allows for the trace analyzer to only work with whatever trace data is presently available from the TAU trace reader interface. This is not a limitation for our current purposes of validating the system implementation.