Trace Data Timestamping Selective Timing Indications
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Solution Overview
Problem
The finite bus bandwidth and trace buffer size in data processing systems limit the volume of trace elements that can be generated and analyzed, particularly in complex systems with multiple processors, where cycle-accurate tracing increases data volume significantly, leading to bandwidth and storage constraints.
Innovation Solution
A data processing apparatus with monitored circuitry that produces a stream of trace elements, where detection circuitry identifies a subset of activities and adds timing indications only to those elements, reducing bandwidth usage while maintaining timing accuracy for critical activities, allowing for focused tracing and correlation across multiple processors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cycle-accurate mode is enabled to include clock cycle indication for each trace element, then timing precision is improved, but trace data volume increases significantly
Solution Approach 1:
The patent applies local quality by providing timing indications selectively for specific types of trace events rather than uniformly for all events. Different event types (e.g., instruction fetch, decode, execute, memory access) receive timing indications based on their analytical value, creating non-uniform timing information distribution that optimizes the balance between timing precision and data volume.
Solution Approach 2:
The patent implements partial action by providing timing indications for only a subset of trace events that are most valuable for analysis. Rather than adding timing information to every single trace element, the system selectively adds timing indications to critical events, achieving sufficient timing precision for debugging and performance analysis while keeping trace data volume manageable.
2Loss of information
If comprehensive tracing of all activities is performed, then analysis completeness is improved, but bus bandwidth consumption increases
Solution Approach 1:
The patent applies local quality by enhancing specific trace events with timing information rather than uniformly processing all events. This selective enhancement focuses bus bandwidth on critical events that require precise timing analysis, while using more compact representations for less critical events, thereby maintaining analysis completeness while reducing overall bandwidth consumption.
Solution Approach 2:
The patent segments trace events into categories based on their analytical importance and applies different encoding strategies to each segment. Critical events receive full timing indications, while less critical events use compressed or differential timing representations, allowing comprehensive tracing capability while managing bus bandwidth through segmented processing.
3Quantity of substance
If trace buffer size is increased to store more trace elements, then trace capacity is improved, but device complexity increases
Solution Approach 1:
The patent changes the parameter of timing information representation by using differential encoding and selective timing indications. Instead of storing absolute timing values for all events, the system uses parameter changes (differences from previous timing values) and only includes timing information where needed, effectively increasing trace capacity without proportionally increasing buffer size or device complexity.
Data Source
AI summary
A data processing apparatus is provided, comprising monitored circuitry for performing activities, trace circuitry for producing a stream of trace elements representative of at least some of these activities, and detection circuitry for detecting the occurrence of a predetermined subset of the activities for which the trace circuitry is producing trace elements. When an activity in that predetermined subset of activities is detected a timing indication is added to the stream of trace elements. Hence, the valuable trace bandwidth- may be preserved, by limiting the trace elements for which a timing indication is added into the trace stream to a predetermined subset of the activities for which trace elements are generated, and the valuable global or relative timing accuracy of those activities represented in the trace stream is retained, without flooding the trace stream with timing indications.