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A profile printer that outputs DOT files. DOT is a graph description format which can be rendered with GraphViz to make pretty graphs such as this:

It's heavily inspired by perftools.rb, the best profiler I've ever used.


JRuby 1.6+. 1.7.0 is not supported, the 1.6 and 1.7 profiler printer APIs are not compatible, but making a 1.7 compatible version isn't hard and I'll do that as soon as I can.

You also need GraphViz, or another compatible tool such as CanViz, to render the graphs. GraphViz can be installed with Homebrew, apt, yum or be downloaded from

The long version

The JRuby profiler can be used to profile a block of code like this:

profile = JRuby::Profiler.profile do
  # your code goes here

The profile variable holds all the profiling data, it must be converted to DOT format and written to a file:'path/to/output.gv', 'w') do |io|
  printer =

Using the same code you can write JRuby's own (tabular) graph format (use GraphProfilePrinter) or HTML (use HtmlProfilePrinter). The built in profile printers can be used to get a report on the whole run too (e.g. --profile.graph or --profile.html), but because of some quirks with how JRuby sets up profiling it's not possible at this point to get a third party profiling printer to work that way -- at least not as far as I know.

In order to get profiling data you must run JRuby with the profiling API enabled, otherwise the profile output will be empty. This is done with the --profile.api flag:

ruby --profile.api ...

You can also set it in the JRUBY_OPTS environment variable if you don't run your application with the ruby command:


When you have a DOT file (i.e. the .gv file written by the code above), it can be rendered as a graph like this:

dot path/to/dot.gv -Tpdf -o path/to/output.pdf

The dot command is part of GraphViz, make sure you have it installed. To find out which output formats are supported by your installation of GraphViz run dot -Txxx.


Have a look in the examples directory and run to see some examples. For each .rb file in the directory it will generate a DOT file (.gv), a PNG and a PDF.

The DOT output is pretty straight forward, but the node labels are a mess (1999 called and wanted their tables back, but I this hacker ain't listening). If someone knows how to get different font sizes, horizontal rules and full text justification in DOT, please let me know.


© 2012 Theo Hultberg