jit.p (LuaJIT Profiler) Reference

Module defined in lua/common/jit/p.lua. LuaJIT's built-in low-overhead profiler CLI interface. Collects stack samples and outputs top-N lists, annotated source, or raw data for flame graphs.

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Exports

This module has no M table exports. It is used via luajit -jp or require("jit.p").start(mode, outfile).

Entry Points

start(mode, outfile)

Start the profiler with the given mode string and optional output file.

• Parameters:
  • mode - string - Profiler mode flags (see below)
  • outfile - string|nil - Output file path (- for stdout, nil for stderr)

Mode Flags

• f - Stack dump: function name (default)
• F - Stack dump: always prepend module
• l - Stack dump: module:line
• <number> - Stack dump depth (callee < caller)
• s - Split stack after first level (implies depth >= 2)
• p - Show full path for module names
• v - Show VM states
• z - Show zones
• r - Show raw sample counts (default: percentages)
• a / A - Annotate excerpts/complete source files
• G - Raw output for graphical tools (flame graphs)
• m<number> - Minimum sample percentage (default: 3)
• i<number> - Sampling interval in ms (default: 10)

Internal Notes

• Uses jit.profile low-level API for sampling
• Callbacks accumulate samples in a counting table
• prof_top sorts and displays top-N callers
• prof_annotate overlays sample counts on source lines
• prof_finish stops profiling and dumps results
• Requires jit.vmdef for VM state names