Introduction¶

Documentation outline¶

This documentation describes the following aspects of Zephelin and the associated projects:

• Introduction - provides general information on Zephelin, its use cases and capabilities

• Using and customizing Zephelin - describes how to build, test and use the profiling middleware

• Zephelin configuration - describes build-time and runtime configuration of Zephelin library

• Memory profiling - describes memory profiling, along with memory events

• Tracing code scopes - describes the use of tracing code scopes

• Trace capture debug interface - provides information on the debug interface for capturing traces

• Instrumentation - shows how to use instrumentation subsystem with Zephelin

• CTF to TEF conversion - describes how traces are converted and processed

• Adding support for new AI inference libraries - depicts how to track a new runtime

• Zephelin Trace Viewer - describes the tool for trace visualization and provides sample applications for various tracing features

• Live tracing of events from the board - describes how to trace the execution in real-time

• Zephelin usage examples - aggregates and describes various example applications present in the project

• Troubleshooting - collects the most common problems with building, capturing and converting traces, along with their solutions

• Zephelin’s developer guidelines - summarizes and links resources regarding development of Zephelin

• Zephelin benchmarking - provides details on the overhead introduced by the library based on different options

Zephelin¶

Zephyr Profiling Library (ZPL), or Zephelin for short, is a library which enables capturing and reporting runtime performance metrics, for the profiling and detailed analysis of Zephyr applications, with a special focus on applications running AI/ML inference workloads.

It collects traces from execution with either:

• Tracing subsystem and predefined or user-provided events - allowing to track functions, sections of code, loops, etc.

• Instrumentation subsystem - allowing to leverage the instrumentation feature of a compiler to automatically trace functions defined in the source, with a possibility to filter functions of interest

Zephelin is an official external module for Zephyr RTOS.

Use cases for Zephelin¶

Zephelin can be used to analyze:

• Regular Zephyr applications

• Internals of the Zephyr RTOS with the help of the instrumentation subsystem

• AI models

• AI runtimes

• Multithreaded applications

Zephelin trace collection¶

Zephelin collects:

• Traces

• User-defined code scopes

• CPU load

• Memory usage (from runtime and RAM/ROM reports)

• Die temperature

• Model-related data:

  • Global - inference time

  • Per-layer:

    • Memory consumption

    • Total runtime of each layer, and of each layer type

    • Dimensions of tensors

The above data is later processed by west zpl-<backend>-capture commands (described in Trace collection) and enhanced using west zpl-prepare-trace (described in CTF and TEF trace processing).