Processor Trace Trigger Tracing for Efficient Debug Sampling
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Solution Overview
Problem
Current processor trace systems lack the ability to efficiently utilize performance monitoring events and debug register matches as trigger events for tracing operations, leading to performance degradation and limited sampling frequency, which hinders effective debugging and performance tuning.
Innovation Solution
The introduction of Trace Trigger Tracing (TTT) technology, which allows new conditions and events such as performance monitoring events and debug register matches to be used as triggers for tracing operations, enabling the configuration of actions like pausing or resuming traces and generating specific data packets with IP attribution details.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If processor trace systems continuously capture all execution data, then complete tracing information is obtained, but performance degradation occurs and sampling frequency is limited
Solution Approach 1:
The patent implements periodic sampling of trace data at configurable intervals rather than continuous capture. The trace sampling unit selectively captures trace information based on time-based sampling periods, allowing the system to obtain representative tracing data while reducing the performance overhead associated with continuous monitoring of all processor events.
Solution Approach 2:
The patent extracts only the most relevant trace information based on trigger conditions and sampling criteria. The trace filtering mechanism identifies and extracts specific trace events that match predetermined conditions, discarding unnecessary data. This extraction approach maintains information quality for debugging while minimizing the performance impact of trace collection.
2Measurement precision
If trace sampling frequency is increased to capture more events, then tracing precision is improved, but performance overhead increases
Solution Approach 1:
The patent dynamically adjusts trace sampling parameters including sampling frequency, trigger thresholds, and filtering criteria based on system conditions and debugging needs. The trace sampling unit can modify sampling intervals and selection criteria to optimize the balance between tracing precision and performance overhead, allowing high precision when needed and reduced overhead during normal operation.
Solution Approach 2:
The patent implements partial sampling where only specific trace events matching predetermined conditions are captured at high frequency, while other events are sampled at lower frequencies or not captured at all. This partial action approach focuses tracing resources on the most critical events, achieving sufficient precision for debugging without the full performance cost of comprehensive high-frequency sampling.
3Loss of information
If all trace data is captured and stored, then complete debugging information is available, but data processing complexity increases
Solution Approach 1:
The patent applies filtering and sampling criteria in advance before trace data is generated and stored. The trace sampling unit pre-configures selection criteria and trigger conditions to identify which events warrant capture. This preliminary filtering action reduces the volume of data requiring storage and subsequent processing, making the debugging information more manageable while retaining the most relevant details.
Solution Approach 2:
The patent segments trace data into different categories based on event types, priority levels, and relevance to specific debugging objectives. The trace sampling unit organizes captured information into structured formats with different sampling rates and retention policies for different event classes. This segmentation reduces overall data processing complexity by allowing targeted analysis of specific event types rather than processing a monolithic data stream.
Data Source
AI summary
Apparatus and method for a processor trace trigger tracing. A processor, comprising: a plurality of processing cores configurable as a plurality of logical processors; processor trace circuitry to perform trace operations to capture and process information related to program code executed by one or more of the logical processors; a debug unit to perform debug operations and collect debug data related to execution of the program code; a performance monitoring unit (PMU) comprising a plurality of counter registers, the PMU to collect performance data related to execution of the program code; and a plurality of trigger units, each trigger unit associated with a logical processor of the plurality of logical processors and configured to communicate trigger event data to the processor trace circuitry in response to trigger events received from at least one of the debug unit and the PMU in accordance with values of configuration bits in a corresponding trigger unit configuration register.