Ultra

Ultra is an advanced profiler for .NET Applications available on Windows and macOS (Apple Silicon).

📽️ Check this video for a quick tour of ultra! 📽️

✨ Features

• Sampling profiler - ETW based on Windows (up to 8190 samples/second), in-process sampler over EventPipe on macOS ARM64 (up to 1000 samples/second)
• UI based on https://profiler.firefox.com/
  • Traces shareable online: Check this example: ✨ https://share.firefox.dev/3Cya7YW ✨
  • Timeline visualization
  • Flamegraph / Stack Chart visualization
  • Call Tree visualization
  • Marker Chart and Marker Table visualization
• Precise kernel, native and managed function call stacks
• Categorization of functions:
  • .NET, .NET JIT, .NET GC, .NET CLR, Native, Kernel
• .NET GC Memory track
• JIT Compile Time Event Markers
  • See which function is getting compiled
• GC Events Markers
  • GC Allocation Ticks: Details about allocations.
  • GCHeapStats: Statistics about the GC
  • GCSuspendEE, GCRestartEE, GC Start, GC Stop events
• Lightweight trace files - e.g. Generates only a few MB for 10s
• Requires net8.0+ via dotnet global tool

Screenshot of a trace generated by ultra visualized with https://profiler.firefox.com. Check this trace online here!

🧑‍💻 Usage

You need to have installed a .NET 10.0+ SDK

$ dotnet tool install -g Ultra # The command ultra.exe will be available from your PATH

Windows

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🚨 The profiler requires to run from an elevated prompt with administrative rights 🚨

This is required to allow to collect full stack traces, including kernel and native functions.

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Example: open a terminal with administrative rights, to profile an executable called my_commands.exe:

$ ultra.exe profile -- my_command.exe arg0 arg1 arg2...

⚠️ Notice the -- separator to separate the arguments to ultra.exe from the arguments to the profiled application.

Profiling a running application just requires the PID of the process to profile:

$ ultra.exe profile 15243 # PID of the process to profile
# Wait for a bit and press only one CTRL+C to stop the profiling

macOS (Apple Silicon)

On macOS, no elevated privileges are required. The profiler injects a small sampler library into the launched process to collect native and managed call stacks.

$ ultra profile -- my_command arg0 arg1 arg2...

Current limitations on macOS:

• Only ARM64 (Apple Silicon) is supported.
• Only launching a program is supported - attaching to a running process with a PID is not (the sampler library can only be injected at process startup).
• The maximum sampling frequency is 1000 samples/second (--sampling-interval minimum is 1ms).
• Kernel call stacks are not collected (user-space native and managed call stacks are).
• Symbols of system libraries living in the dyld shared cache (e.g. libsystem_pthread.dylib) are not resolved.

⚗️ 3rd-Party

• MCP server for Ultra with UltraMCP to let your AI Coding Agent query profiling results by @KirillOsenkov

📖 User Guide

For more details on how to use Ultra, please visit the user guide.

🪪 License

This software is released under the BSD-2-Clause license.

🤗 Author

Alexandre Mutel aka xoofx.