CPUPROFILE

CPUPROFILE is a term used for CPU profiling output files produced by various profiling tools. It refers to data collections that capture the program's execution over time, showing which functions were active and when. CPUPROFILE data is used to identify hot code paths, optimize performance, and understand program behavior under load.

Format and data model typically found in CPUPROFILE files vary by tool, but common elements appear across implementations. Many CPUPROFILE files use a JSON-based structure that includes a start and end time, a sampling interval, and a collection of nodes representing call frames. Each node usually contains a unique identifier and a callFrame with details such as functionName, script URL or file path, and the line and column numbers where the function is defined. A samples array references the node identifiers to indicate which function was active at each sampling point, while timeDeltas or similar fields record the timing between samples. Some variants also include metadata like process or thread identifiers or tool version. In some cases the file begins with a header line and is followed by JSON, while other variants are pure JSON with a .cpuprofile extension.

Generation and usage: CPUPROFILE data is produced by browser developer tools (for example, Chrome DevTools) and by profiling integrations in mobile and desktop environments (such as React Native and native profiling workflows). The resulting file can be imported into compatible viewers to render flame graphs, flame charts, or call trees, enabling developers to inspect function durations, stacking, and recursion patterns.

Limitations and compatibility: Because there is no single universal CPUPROFILE specification, the exact structure and field names can differ between tools. When sharing profiles, reliance on the exporting tool’s standard format improves interoperability, and some tools provide exporters to standard viewer formats.