From January 1 2018 -> April 1 2018 I’m working on a project to write a new Ruby CPU profiler! It’s a sampling profiler, and the goal of this project is to make it dead simple to figure out where any running Ruby process is spending its time.

The idea is that there are 2 ways to run it:

1. Find the PID of an already-running program and profile it (run-profiler -p $PID)
2. Start a new program and profile it (run-profiler ruby my-program.rb)

The hard part of this project is that this profiler is a separate process so it doesn’t have much inside information about what the Ruby profiler is doing. So “how do you figure out what $ARBITRARY_RUBY_PROCESS is actually doing?” is my main focus.

The code is at https://github.com/jvns/ruby-stacktrace/ right now. I’ve been blogging about my progress on the project: you can see all the posts under the ruby-profiler category.