Vernier

Next-generation Ruby sampling profiler. Tracks multiple threads, GVL activity, GC pauses, idle time, and more.

Examples

Livestreamed demo: Pairin' with Aaron (YouTube)

Sidekiq jobs from Mastodon (time, threded) : https://share.firefox.dev/44jZRf3

Puma web requests from Mastodon (time, threded) : https://share.firefox.dev/48FOTnF

Rails benchmark - lobste.rs (time) : https://share.firefox.dev/3Ld89id

require "irb" (retained memory) : https://share.firefox.dev/3DhLsFa

Installation

gem 'vernier'

Usage

Retained memory

Record a flamegraph of all retained allocations from loading irb.

ruby -r vernier -e 'Vernier.trace_retained(out: "irb_profile.json") { require "irb" }'

The output can then be viewed in the Firefox Profiler (demo) or the profile-viewer gem (a Ruby-customized version of the firefox profiler.

Time

Vernier.trace(out: "time_profile.json") { some_slow_method }

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/jhawthorn/vernier. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

Resources

• https://profiler.firefox.com/docs/#/
• https://github.com/firefox-devtools/profiler/tree/main/docs-developer
• https://github.com/tmm1/stackprof
• ruby/ruby#5500

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the Vernier project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.