Understanding ruby-prof output - ruby

Question

I ran ruby-profiler on one of my programs. I'm trying to figure out what each fields mean. I'm guessing everything is CPU time (and not wall clock time), which is fantastic. I want to understand what the "---" stands for. Is there some sort of stack information in there. What does calls a/b mean?
Thread ID: 81980260
Total Time: 0.28
%total %self total self wait child calls Name
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0.28 0.00 0.00 0.28 5/6 FrameParser#receive_data
100.00% 0.00% 0.28 0.00 0.00 0.28 6 FrameParser#read_frames
0.28 0.00 0.00 0.28 4/4 ChatServerClient#receive_frame
0.00 0.00 0.00 0.00 5/47 Fixnum#+
0.00 0.00 0.00 0.00 1/2 DebugServer#receive_frame
0.00 0.00 0.00 0.00 10/29 String#[]
0.00 0.00 0.00 0.00 10/21 <Class::Range>#allocate
0.00 0.00 0.00 0.00 10/71 String#index
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100.00% 0.00% 0.28 0.00 0.00 0.28 5 FrameParser#receive_data
0.28 0.00 0.00 0.28 5/6 FrameParser#read_frames
0.00 0.00 0.00 0.00 5/16 ActiveSupport::CoreExtensions::String::OutputSafety#add_with_safety
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0.28 0.00 0.00 0.28 4/4 FrameParser#read_frames
100.00% 0.00% 0.28 0.00 0.00 0.28 4 ChatServerClient#receive_frame
0.28 0.00 0.00 0.28 4/6 <Class::Lal>#safe_call
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0.00 0.00 0.00 0.00 1/6 <Class::Lal>#safe_call
0.00 0.00 0.00 0.00 1/6 DebugServer#receive_frame
0.28 0.00 0.00 0.28 4/6 ChatServerClient#receive_frame
100.00% 0.00% 0.28 0.00 0.00 0.28 6 <Class::Lal>#safe_call
0.21 0.00 0.00 0.21 2/4 ChatUserFunction#register
0.06 0.00 0.00 0.06 2/2 ChatUserFunction#packet
0.01 0.00 0.00 0.01 4/130 Class#new
0.00 0.00 0.00 0.00 1/1 DebugServer#profile_stop
0.00 0.00 0.00 0.00 1/33 String#==
0.00 0.00 0.00 0.00 1/6 <Class::Lal>#safe_call
0.00 0.00 0.00 0.00 5/5 JSON#parse
0.00 0.00 0.00 0.00 5/8 <Class::Log>#log
0.00 0.00 0.00 0.00 5/5 String#strip!
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Answer 1

Each section of the ruby-prof output is broken up into the examination of a particular function. for instance, look at the first section of your output. The read_frames method on FrameParser is the focus and it is basically saying the following:
100% of the execution time that was profiled was spent inside of FrameParser#read_frames
FrameParser#read_frames was called 6 times.
5 out of the 6 calls to read_frames came from FrameParser#receive_data and this accounted 100% of the execution time (this is the line above the read_frames line).
The lines below the read_frames (but within that first section) method are all of the methods that FrameParser#read_frames calls (you should be aware of that since this seems like it's your code), how many of that methods total calls read_frames is responsible for (the a/b calls column), and how much time those calls took. They are ordered by which of them took up the most execution time. In your case, that is receive_frame method on the ChatServer class.
You can then look down at the section focusing on receive_frames (2 down and centered with the '100%' line on receive_frame) and see how it's performance is broken down. each section is set up the same way and usually the subsequent function call which took the most time is the focus of the next section down. ruby-prof will continue doing this through the full call stack. You can go as deep as you want until you find the bottleneck you'd like to resolve.