= ruby-prof

== Overview

ruby-prof is a fast code profiler for Ruby.  Its features include:

* Speed - it is a C extension and therefore many times faster than the standard Ruby profiler.
* Modes - Ruby prof can measure a number of different parameters, including
          call times, memory usage and object allocations. 
* Reports - can generate text and cross-referenced html reports
  - Flat Profiles - similar to the reports generated by the standard Ruby profiler
  - Graph profiles - similar to GProf, these show how long a method runs, which methods call it and which methods it calls.
  - Call tree profiles - outputs results in the calltree format suitable for the KCacheGrind profiling tool.
* Threads - supports profiling multiple threads simultaneously
* Recursive calls - supports profiling recursive method calls


== Requirements

ruby-prof requires Ruby 1.8.4 or higher.

If you are running Linux or Unix you'll need a C compiler so the extension
can be compiled when it is installed.

If you are running Windows, then install the Windows specific RubyGem which
includes an already built extension.


== Install

The easiest way to install ruby-prof is by using Ruby Gems.  To install:

<tt>gem install ruby-prof</tt>

If you are running Windows, make sure to install the Win32 RubyGem which 
includes a pre-built binary.

ruby-prof is also available as a tarred gzip archive and zip archive. 

== Usage

There are three ways of running ruby-prof.

=== ruby-prof executable

The first is to use ruby-prof to run the Ruby program
you want to profile.  For more information refer to
the ruby-prof documentation[link:files/bin/ruby-prof.html].

=== ruby-prof API

The second way is to use the ruby-prof API to profile
particular segments of code.  

  require 'ruby-prof'
  
  # Profile the code
  RubyProf.start
  ...
  [code to profile]
  ...
  result = RubyProf.stop
  
  # Print a flat profile to text
  printer = RubyProf::FlatPrinter.new(result)
  printer.print(STDOUT, 0)
  
Alternatively, you can use a block to tell ruby-prof what
to profile:

  require 'ruby-prof'
  
  # Profile the code
  result = RubyProf.profile do
    ...
    [code to profile]
    ...
  end
  
  # Print a graph profile to text
  printer = RubyProf::GraphPrinter.new(result)
  printer.print(STDOUT, 0)

  
=== require unprof

The third way of using ruby-prof is by requiring unprof.rb:

  require 'unprof'

This will start profiling immediately and will output the results
using a flat profile report.

This method is provided for backwards compatibility.  Using
{ruby-prof}[link:files/bin/ruby-prof.html] provides more flexibility.
  

== Reports

ruby-prof can generate a number of different reports:

* Flat Reports
* Graph Reports
* HTML Graph Reports
* Call graphs

Flat profiles show the overall time spent in each method.  They
are a good of quickly identifying which methods take the most time.
An example of a flat profile and an explanation can be found in
{examples/flat.txt}[link:files/examples/flat_txt.html].

Graph profiles also show the overall time spent in each method.
In addition, they also show which methods call the current
method and which methods its calls.  Thus they are good for
understanding how methods gets called and provide insight into
the flow of your program.  An example text graph profile
is located at {examples/graph.txt}[link:files/examples/graph_txt.html].

HTML Graph profiles are the same as graph profiles, except
output is generated in hyper-linked HTML. Since graph profiles
can be quite large, the embedded links make it much easier to
navigate the results.  An example html graph profile
is located at {examples/graph.html}[link:files/examples/graph_html.html].

HTML Graph profiles are the same as graph profiles, except
output is generated in hyper-linked HTML. Since graph profiles
can be quite large, the embedded links make it much easier to
navigate the results.  An example html graph profile
is located at {examples/graph.html}[link:files/examples/graph_html.html].

Call graphs output results in the calltree profile format which is used
by KCachegrind.  Call graph support was generously donated by Carl Shimer.
More information about the format can be found at
the {KCachegrind}[link:http://kcachegrind.sourceforge.net/cgi-bin/show.cgi/KcacheGrindCalltreeFormat] site.

== Printers

Reports are created by printers.  Supported printers include:

* RubyProf::FlatPrinter - Creates a flat report in text format
* RubyProf::GraphPrinter - Creates a call graph report in text format
* RubyProf::GraphHtmlPrinter - Creates a call graph report in HTML (separate files per thread)
* RubyProf::CallTreePrinter - Creates a call tree report compatible with KCachegrind.

To use a printer:

  result = RubyProf.end
  printer = RubyProf::GraphPrinter.new(result)
  printer.print(STDOUT, 0)

The first parameter is any writable IO object such as STDOUT or a file.
The second parameter, which has a default value of 0, specifies 
the minimum percentage a method must take to be printed.  Percentages
should be specified as integers in the range 0 to 100.  For more
information please see the documentation for the different printers.


== Measurements

Depending on the mode and platform, ruby-prof can measure various
aspects of a Ruby program.  Supported measurements include:

* process time
* wall time
* cpu time
* object allocations
* memory usage

Process time measures the time used by a process between any two moments.
It is unaffected by other processes concurrently running 
on the system. Note that Windows does not support measuring process
times - therefore, all measurements on Windows use wall time.

Wall time measures the real-world time elapsed between any two moments.
If there are other processes concurrently running on the system
that use significant CPU or disk time during a profiling run
then the reported results will be too large.

CPU time uses the CPU clock counter to measure time.  The returned
values are dependent on the correctly setting the CPU's frequency.
This mode is only supported on Pentium or PowerPC platforms.

Object allocation reports show how many objects each method in
a program allocates.  This support was added by Sylvain Joyeux
and requires a patched Ruby interpreter.  For more information, see:
http://rubyforge.org/tracker/index.php?func=detail&aid=11497&group_id=426&atid=1700

Memory usage reports show how much memory each method in a program
uses.  This support was added by Alexander Dymo and requires a
patched Ruby interpreter.  For more information, see:
http://rubyforge.org/tracker/index.php?func=detail&aid=17676&group_id=1814&atid=7062.


To set the measurement:

* RubyProf.measure_mode = RubyProf::PROCESS_TIME
* RubyProf.measure_mode = RubyProf::WALL_TIME
* RubyProf.measure_mode = RubyProf::CPU_TIME
* RubyProf.measure_mode = RubyProf::ALLOCATIONS
* RubyProf.measure_mode = RubyProf::MEMORY

The default value is RubyProf::PROCESS_TIME.

You may also specify the measure_mode by using the RUBY_PROF_MEASURE_MODE
environment variable:

* export RUBY_PROF_MEASURE_MODE=process
* export RUBY_PROF_MEASURE_MODE=wall
* export RUBY_PROF_MEASURE_MODE=cpu
* export RUBY_PROF_MEASURE_MODE=allocations
  
Note that these values have changed since ruby-prof-0.3.0.  

On Linux, process time is measured using the clock method provided 
by the C runtime library. Note that the clock method does not
report time spent in the kernel or child processes and therefore
does not measure time spent in methods such as Kernel.sleep method.
If you need to measure these values, then use wall time.  Wall time
is measured using the gettimeofday kernel method.

On Windows, timings are always wall times.  If you set the clock 
mode to PROCESS_TIME, then timing are read using the clock method
provided by the C runtime library.  Note though, these values are
wall times on Windows and not process times like on Linux.
Wall time is measured using the GetLocalTime API.

If you use wall time, the results will be affected by other
processes running on your computer, network delays, disk access,
etc.  As result, for the best results, try to make sure your
computer is only performing your profiling run and is 
otherwise quiescent.

On both platforms, cpu time is measured using the RDTSC assembly
function provided by the Pentium and PowerPC platforms. CPU time
is dependent on the cpu's frequency.  On Linux, ruby-prof attempts 
to read this value from "/proc/cpuinfo."  On Windows, you must
specify the clock frequency.  This can be done using the
RUBY_PROF_CPU_FREQUENCY environment variable:

  export RUBY_PROF_CPU_FREQUENCY=<value>
  
You can also directly set the cpu frequency by calling:

  RubyProf.cpu_frequency = <value> 


== Recursive Calls

Recursive calls occur when method A calls method A and cycles
occur when method A calls method B calls method C calls method A.
ruby-prof detects both direct recursive calls and cycles.  Both
are indicated in reports by a dash and number following a method
name.  For example, here is a flat profile from the test method
RecursiveTest#test_recursive:


%self     total     self     wait    child    calls  name
100.00      2.00     2.00     0.00     0.00        2  Kernel#sleep
  0.00      2.00     0.00     0.00     2.00        0  RecursiveTest#test_cycle
  0.00      0.00     0.00     0.00     0.00        2  Fixnum#==
  0.00      0.00     0.00     0.00     0.00        2  Fixnum#-
  0.00      1.00     0.00     0.00     1.00        1  Object#sub_cycle-1
  0.00      2.00     0.00     0.00     2.00        1  Object#sub_cycle
  0.00      2.00     0.00     0.00     2.00        1  Object#cycle
  0.00      1.00     0.00     0.00     1.00        1  Object#cycle-1

Notice the presence of Object#cycle and Object#cycle-1.  The -1 means
the method was either recursively called (directly or indirectly).

However, the self time values for recursive calls should always 
be accurate.  It is also believed that the total times are
accurate, but these should be carefully analyzed to verify their veracity.

== Multi-threaded Applications

Unfortunately, Ruby does not provide an internal api
for detecting thread context switches.  As a result, the
timings ruby-prof reports for each thread may be slightly
inaccurate.  In particular, this will happen for newly 
spanned threads that immediately go to sleep.  For instance,
if you use Ruby's timeout library to wait for 2 seconds,
the 2 seconds will be assigned to the foreground thread
and not the newly created background thread.  These errors
can largely be avoided if the background thread performs an
operation before going to sleeep. 


== Performance

Significant effort has been put into reducing ruby-prof's overhead
as much as possible.  Our tests show that the overhead associated
with profiling code varies considerably with the code being
profiled.  Most programs will run approximately twice as slow
while highly recursive programs (like the fibonacci series test)
will run three times slower.

== Windows Binary

The Windows binary is built with the latest version of MinGW.  The source
repository also includes a Microsoft VC++ 2005 solution.  If you wish to run
a debug version of ruby-prof on Windows, then it is highly recommended
you use VC++.


== License

See LICENSE for license information.