= 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

== 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 you may need to install the
Windows specific RubyGem which includes an already built extension (see Install section).

== Install

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

  gem install ruby-prof

If you on windows mswin [not mingw] (check via ruby -v) and
don't have an MSVC compiler, please install v0.8.1 which
has a prebuilt binary
C:> gem install ruby-prof -v0.8.1

If you're on mingw, please install the devkit first, then install the latest gem version (via gem install ruby-prof).

== 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 documentation of the
ruby-prof command.


=== 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)

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, {})

Starting with the 0.6.1 release, ruby-prof also supports pausing and resuming
profiling runs.

  require 'ruby-prof'

  # Profile the code
  RubyProf.start
  [code to profile]
  RubyProf.pause
  [other code]
  RubyProf.resume
  [code to profile]
  result = RubyProf.stop

Note that resume will automatically call start if a profiling run
has not yet started.  In addition, resume can also take a block:

  require 'ruby-prof'

  # Profile the code
  RubyProf.resume do
    [code to profile]
  end

  data = RubyProf.stop

With this usage, resume will automatically call pause at the
end of the block.

=== require unprof

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

  require 'unprof'

This will start profiling immediately at that point and will output the results
using a flat profile report when the process ends.

== Method Elimination

Starting with release 0.9.0, ruby-prof supports eliminating methods from profiling
results. This is useful for reducing connectivity in the call graph, making it easier to
identify the source of performance problems when using a graph printer.

For example, consider Integer#times: it's hardly ever useful to know how much time is
spent in the method itself. We're much more interested in how much the passed in block
contributes to the time spent in the method which contains the Integer#times call.

Methods are eliminated from the collected data by calling `eliminate_methods!` on the
profiling result, before submitting it to a printer.

  result = RubyProf.stop
  result.eliminate_methods!([/Integer#times/])

The argument given to `eliminate_methods!` is either an array of regular expressions, or
the name of a file containing a list of regular expressions (line separated text).

After eliminating methods the resulting profile will appear exactly as if those methods
had been inlined at their call sites.

== Benchmarking full load time including rubygems startup cost ==

If you want to get a more accurate measurement of what takes all of a gem's bin/xxx
command to load, you may want to also measure rubygems' startup penalty.
You can do this by calling into bin/ruby-prof directly, ex:

$ gem which ruby-prof
  g:/192/lib/ruby/gems/1.9.1/gems/ruby-prof-0.10.2/lib/ruby-prof.rb

now run it thus (substitute lib/ruby-prof.rb with bin/ruby-prof):

$ ruby g:/192/lib/ruby/gems/1.9.1/gems/ruby-prof-0.10.2/bin/ruby-prof g:\192\bin\some_installed_gem_command

or

$ ruby g:/192/lib/ruby/gems/1.9.1/gems/ruby-prof-0.10.2/bin/ruby-prof ./some_file_that_does_a_require_rubygems_at_the_beginning.rb

== Profiling Tests

Starting with the 0.6.1 release, ruby-prof supports profiling tests cases
written using Ruby's built-in unit test framework (ie, test derived from
Test::Unit::TestCase).  To enable profiling simply add the following line
of code to within your test class:

        include RubyProf::Test

Each test method is profiled separately.  ruby-prof will run each test method
once as a warmup and then ten additional times to gather profile data.
Note that the profile data will *not* include the class's setup or
teardown methods.

Separate reports are generated for each method and saved, by default,
in the test process's working directory.  To change this, or other profiling
options, modify your test class's PROFILE_OPTIONS hash table. To globally
change test profiling options, modify RubyProf::Test::PROFILE_OPTIONS.


== Profiling Rails

To profile a Rails application it is vital to run it using production like
settings (cache classes, cache view lookups, etc.).  Otherwise, Rail's
dependency loading code will overwhelm any time spent in the application
itself (our tests show that Rails dependency loading causes a roughly 6x
slowdown).  The best way to do this is create a new Rails environment,
profile.rb.

So to profile Rails:

1.  Create a new profile.rb environment - or simply copy the example file
    in ruby-prof/rails/environment/profile.rb

2.  Copy the file:

      ruby-prof/rails/profile_test_helper.rb

    To:

      your_rails_app/test/profile_test_helper.rb

3.  Create a new test directory for profiling:

      your_rails_app/test/profile


4.  Write unit, functional or integration tests specifically designed
    to profile some part of your Rails application.  At the top
    of each test, replace this line:

      require File.dirname(__FILE__) + '/../test_helper'

    With:

      require File.dirname(__FILE__) + '/../profile_test_helper'

    For example:

    require File.dirname(__FILE__) + '/../profile_test_helper'

    class ExampleTest < Test::Unit::TestCase
      include RubyProf::Test
      fixtures ....

      def test_stuff
        puts "Test method"
      end
    end

5.  Now run your tests.  Results will be written to:

      your_rails_app/tmp/profile


== Reports

ruby-prof can generate a number of different reports:

* Flat Reports
* Graph Reports
* HTML Graph Reports
* Call graphs
* Call stack reports
* More!

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}[http://github.com/rdp/ruby-prof/tree/master/examples/flat.txt].

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}[http://github.com/rdp/ruby-prof/tree/master/examples/graph.txt].

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}[http://github.com/rdp/ruby-prof/tree/master/examples/graph.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}[http://kcachegrind.sourceforge.net/cgi-bin/show.cgi/KcacheGrindCalltreeFormat]
site.

Call stack reports produce a HTML visualization of the time spent in
each execution path of the profiled code. An example can be found at
{examples/stack.html}[http://github.com/rdp/ruby-prof/tree/master/examples/call_stack.html].

Finally, there's a so called MultiPrinter which can generate several
reports in one profiling run. See
{examples/multi.stack.html}[http://github.com/rdp/ruby-prof/tree/master/examples/multi.stack.html].


== Printers

Reports are created by printers.  Supported printers include:

* RubyProf::FlatPrinter - Creates a flat report in text format
* RubyProf::FlatPrinterWithLineNumbers - same as above but more verbose
* RubyProf::GraphPrinter - Creates a call graph report in text format
* RubyProf::GraphHtmlPrinter - Creates a call graph report in HTML (separate files per thread)
* RubyProf::DotPrinter - Creates a call graph report in GraphViz's DOT format which can be converted to an image
* RubyProf::CallTreePrinter - Creates a call tree report compatible with KCachegrind.
* RubyProf::CallStackPrinter - Creates a HTML visualization of the Ruby stack
* RubyProf::MultiPrinter - Uses the other printers to create several reports in one profiling run
* More!

To use a printer:

  ...
  result = RubyProf.end
  printer = RubyProf::GraphPrinter.new(result)
  printer.print(STDOUT, :min_percent => 2)

The first parameter is any writable IO object such as STDOUT or a file.
The second parameter, 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.

The other option is :print_file => true (default false), which adds the filename to the
output (GraphPrinter only).

The MultiPrinter differs from the other printers in that it requires a directory path
and a basename for the files it produces.

   printer = RubyProf::MultiPrinter.new(result)
   printer.print(:path => ".", :profile => "profile")


== Measurements

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

* process time (RubyProf::PROCESS_TIME)
* wall time (RubyProf::WALL_TIME)
* cpu time (RubyProf::CPU_TIME)
* object allocations (RubyProf::ALLOCATIONS)
* memory usage (RubyProf::MEMORY)
* garbage collections runs (RubyProf::GC_RUNS)
* garbage collection time (RubyProf::GC_TIME)

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, measurements on Windows defaults to 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 (linux only).

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 and
the patch, please 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

Garbage collection runs report how many times Ruby's garbage collector
is invoked during a profiling session.  This support was added by Jeremy
Kemper 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

Garbage collection time reports how much time is spent in Ruby's garbage collector
during a profiling session.  This support was added by Jeremy Kemper
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
* RubyProf.measure_mode = RubyProf::GC_RUNS
* RubyProf.measure_mode = RubyProf::GC_TIME

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
* export RUBY_PROF_MEASURE_MODE=memory
* export RUBY_PROF_MEASURE_MODE=gc_runs
* export RUBY_PROF_MEASURE_MODE=gc_time

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 default to 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
manually 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>


== Multi-threaded Applications

Unfortunately, Ruby does not provide an internal api
for detecting thread context switches in 1.8.  As a result, the
timings ruby-prof reports for each thread may be slightly
inaccurate.  In particular, this will happen for newly
spawned threads that go to sleep immediately (their first call).
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 any
operation before going to sleep.

== 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.

Because of some threading difficulties in 1.9, it currently runs a 
bit slower there, as well.
http://www.ruby-forum.com/topic/201329

== License

See LICENSE for license information.

== Development

Code is located at http://github.com/rdp/ruby-prof

Google group/mailing list: http://groups.google.com/group/ruby-prof
