Ruby User-Space Markers

Some work has been done in Ruby to include support for SystemTap user-space markers in Red Hat Enterprise Linux 6.2 and allow SystemTap to probe the start and completion of each Ruby function. The Ruby user-space probes available are:

ruby.function.entry classname:string methodname:string file:string line:long $arg1:long $arg2:long $arg3:long $arg4:long
ruby.function.return classname:string methodname:string file:string line:long $arg1:long $arg2:long $arg3:long $arg4:long
ruby.gc.begin
ruby.gc.end
ruby.line file:string line:long $arg1:long $arg2:long
ruby.object.free classname:string $arg1:long
ruby.raise classname:string file:string line:long $arg1:long $arg2:long $arg3:long
ruby.rescue file:string line:long $arg1:long $arg2:long
ruby.ruby__probe probe_point:string probe_data:string $arg1:long $arg2:long

Using Ruby User-Space Markers

To use the Ruby user-space markers on a Fedora you will need:

RPMs:
- ruby
- systemtap, systemtap-runtime
Membership to the appropriate unix groups (or root) to use systemtap in general. See also http://sourceware.org/systemtap/man/stap-server.8.html

Examples Scripts for Ruby Probing

Short example scripts:

"top" for Ruby, rubyfuntop.stp
tracing Ruby function calls, ruby-example.stp
counting method calls: http://lukas.zapletalovi.com/2012/01/probing-ruby-apps-with-systemtap-in.html

The SystemTap Ruby user-space probes provide similar functionality to the probe points used in:

http://tenderlovemaking.com/2011/12/05/profiling-rails-startup-with-dtrace/