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<h1>README</h1>
<table class="header-table">
<tr class="top-aligned-row">
<td><strong>Path:</strong></td>
<td>README
</td>
</tr>
<tr class="top-aligned-row">
<td><strong>Last Update:</strong></td>
<td>Thu Jun 22 16:06:01 Mountain Standard Time 2006</td>
</tr>
</table>
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<div id="description">
<h1>ruby-prof</h1>
<h2>Overview</h2>
<p>
ruby-prof is a fast code profiler for Ruby. Its features include:
</p>
<ul>
<li>Speed - it is a C extension and therefore many times faster than the
standard Ruby profiler.
</li>
<li>Flat Profiles - similar to the reports generated by the standard Ruby
profiler
</li>
<li>Graph profiles - similar to GProf, these show how long a method runs, which
methods call it and which methods it calls.
</li>
<li>Threads - supports profiling multiple threads simultaneously
</li>
<li>Recursive calls - supports profiling recursive method calls
</li>
<li>Reports - can generate both text and cross-referenced html reports
</li>
<li>Output - can output to standard out or to a file
</li>
</ul>
<h2>Requirements</h2>
<p>
ruby-prof requires Ruby 1.8.2 or higher.
</p>
<p>
If you are running Linux or Unix you’ll need a C compiler so the
extension can be compiled when it is installed.
</p>
<p>
If you are running Windows, then install the Windows specific RubyGem which
includes an already built extension.
</p>
<h2>Install</h2>
<p>
ruby-prof is provided as a RubyGem. To install:
</p>
<p>
<tt>gem install ruby-prof</tt>
</p>
<p>
If you are running Windows, make sure to install the Win32 RubyGem which
includes a pre-built binary.
</p>
<h2>Usage</h2>
<p>
There are three ways of running ruby-prof.
</p>
<h3>ruby-prof executable</h3>
<p>
The first is to use ruby-prof to run the Ruby program you want to profile.
For more information refer to the ruby-prof <a
href="bin/ruby-prof.html">documentation</a>.
</p>
<h3>ruby-prof API</h3>
<p>
The second way is to use the ruby-prof API to profile particular segments
of code.
</p>
<pre>
require 'ruby-prof'
# Profile the code
RubyProf.start
...
[code to profile]
...
result = RubyProf.stop
# Print a flat profile to text
printer = RubyProf::TextPrinter.new(result)
printer.print(STDOUT, 0)
</pre>
<p>
Alternatively, you can use a block to tell ruby-prof what to profile:
</p>
<pre>
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)
</pre>
<h3>require unprof</h3>
<p>
The third way of using ruby-prof is by requiring unprof.rb:
</p>
<pre>
require 'unprof'
</pre>
<p>
This will start profiling immediately and will output the results using a
flat profile report.
</p>
<p>
This method is provided for backwards compatibility. Using <a
href="bin/ruby-prof.html">ruby-prof</a> provides more flexibility.
</p>
<h2>Reports</h2>
<p>
ruby-prof can generate flat profile and graph profile reports.
</p>
<p>
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 <a
href="examples/flat_txt.html">examples/flat.txt</a>.
</p>
<p>
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. Graph profiles
can be generated in text and html. Since the html is cross-referenced it is
easier to work with. An example text graph profile is located at <a
href="examples/graph_txt.html">examples/graph.txt</a> while an example html
graph file is located at <a
href="examples/graph_html.html">examples/graph.html</a>.
</p>
<p>
Reports are created by printers. The current printers include:
</p>
<ul>
<li><a href="../classes/RubyProf/FlatPrinter.html">RubyProf::FlatPrinter</a> -
Creates a flat report in text format
</li>
<li><a href="../classes/RubyProf/GraphPrinter.html">RubyProf::GraphPrinter</a>
- Creates a call graph report in text format
</li>
<li><a
href="../classes/RubyProf/GraphHtmlPrinter.html">RubyProf::GraphHtmlPrinter</a>
- Creates a call graph report in HTML (separate files per thread)
</li>
</ul>
<p>
To use a printer:
</p>
<pre>
result = RubyProf.end
printer = RubyProf::GraphPrinter.new(result)
printer.print(STDOUT, 0)
</pre>
<p>
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. For more information please
see the documentation for the different printers.
</p>
<h2>Timing Data</h2>
<p>
Depending on the mode and platform, ruby-prof can measure time in three
ways - process time, wall time and cpu time.
</p>
<p>
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.
</p>
<p>
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.
</p>
<p>
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.
</p>
<p>
To set the clock_mode:
</p>
<pre>
RubyProf.clock_mode = RubyProf::PROCESS_TIME
RubyProf.clock_mode = RubyProf::WALL_TIME
RubyProf.clock_mode = RubyProf::CPU_TIME
</pre>
<p>
This default value is PROCESS_TIME.
</p>
<p>
You may also specify the clock_mode by using the RUBY_PROF_CLOCK_MODE
environment variable:
</p>
<pre>
export RUBY_PROF_CLOCK_MODE=process
export RUBY_PROF_CLOCK_MODE=wall
export RUBY_PROF_CLOCK_MODE=cpu
</pre>
<p>
Note that these values have changed since ruby-prof-0.3.0.
</p>
<p>
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.
</p>
<p>
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.
</p>
<p>
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:
</p>
<pre>
export RUBY_PROF_CPU_FREQUENCY=<value>
</pre>
<p>
You can also directly set the cpu frequency by calling:
</p>
<pre>
RubyProf.cpu_frequency = <value>
</pre>
<h2>Recursive Calls</h2>
<p>
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 can detect
recursive calls any cycle calls, but does not currently report these in its
output.
</p>
<p>
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.
</p>
<h2>Performance</h2>
<p>
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. On the low
end overhead is around 10% while on the high end its can around 80%.
</p>
<h2>Windows Binary</h2>
<p>
The Windows binary is built with the latest version of MinGW.
</p>
<h2>License</h2>
<p>
See LICENSE for license information.
</p>
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