perftools.rb

perftools.rb

gperftools for ruby code
(c) 2012 Aman Gupta (tmm1)
http://www.ruby-lang.org/en/LICENSE.txt

gperftools (formerly known as google-perftools): http://gperftools.googlecode.com

Usage (in a webapp)

Use rack-perftools_profiler:

require 'rack/perftools_profiler'
config.middleware.use ::Rack::PerftoolsProfiler, :default_printer => 'gif'

Simply add profile=true to profile a request:

curl -o 10_requests_to_homepage.gif "http://localhost:3000/homepage?profile=true&times=10"

Usage (from Ruby)

Run the profiler with a block:

require 'perftools'
PerfTools::CpuProfiler.start("/tmp/add_numbers_profile") do
  5_000_000.times{ 1+2+3+4+5 }
end

Start and stop the profiler manually:

require 'perftools'
PerfTools::CpuProfiler.start("/tmp/add_numbers_profile")
5_000_000.times{ 1+2+3+4+5 }
PerfTools::CpuProfiler.stop

Usage (externally)

Profile an existing ruby application without modifying it:

$ CPUPROFILE=/tmp/my_app_profile \
  RUBYOPT="-r`gem which perftools | tail -1`" \
  ruby my_app.rb

Profiler Modes

The profiler can be run in one of many modes, set via an environment variable before the library is loaded:

• CPUPROFILE_REALTIME=1

  Use walltime instead of cputime profiling. This will capture all time spent in a method, even if it does not involve the CPU.

  For example, sleep() is not expensive in terms of cputime, but very expensive in walltime. walltime will also show functions spending a lot of time in network i/o.

• CPUPROFILE_OBJECTS=1

  Profile object allocations instead of cpu/wall time. Each sample represents one object created inside that function.

• CPUPROFILE_METHODS=1

  Profile method calls. Each sample represents one method call made inside that function.

The sampling interval of the profiler can be adjusted to collect more (for better profile detail) or fewer samples (for lower overhead):

• CPUPROFILE_FREQUENCY=500

  Default sampling interval is 100 times a second. Valid range is 1-4000

Reporting

pprof.rb --text /tmp/add_numbers_profile

pprof.rb --pdf /tmp/add_numbers_profile > /tmp/add_numbers_profile.pdf

pprof.rb --gif /tmp/add_numbers_profile > /tmp/add_numbers_profile.gif

pprof.rb --callgrind /tmp/add_numbers_profile > /tmp/add_numbers_profile.grind
kcachegrind /tmp/add_numbers_profile.grind

pprof.rb --gif --focus=Integer /tmp/add_numbers_profile > /tmp/add_numbers_custom.gif

pprof.rb --text --ignore=Gem /tmp/my_app_profile

For more options, see pprof documentation

Examples

pprof.rb --text

Total: 1735 samples
    1487  85.7%  85.7%     1735 100.0% Integer#times
     248  14.3% 100.0%      248  14.3% Fixnum#+

pprof.rb --gif

• Simple require 'rubygems' profile

• Comparing redis-rb with and without SystemTimer based socket timeouts

• Sinatra vs. Merb vs. Rails

• C-level profile of EventMachine + epoll + Ruby threads before and after a 6 line EM bugfix

• C-level profile of a ruby/rails vm

  • 12% time spent in re_match_exec because of excessive calls to rb_str_sub_bang by Date.parse

Installation

Just install the gem, which will download, patch and compile gperftools for you:

sudo gem install perftools.rb

Or build your own gem:

git clone git://github.com/tmm1/perftools.rb
cd perftools.rb
gem build perftools.rb.gemspec
gem install perftools.rb

Use via a Gemfile:

gem 'perftools.rb', :git => 'git://github.com/tmm1/perftools.rb.git'

You'll also need graphviz to generate call graphs using dot:

sudo brew    install graphviz ghostscript # osx
sudo apt-get install graphviz ps2pdf      # debian/ubuntu

If graphviz fails to build on OSX Lion, you may need to recompile libgd, see here

Advantages over ruby-prof

• Sampling profiler

  • perftools samples your process using setitimer() so it can be used in production with minimal overhead.

Profiling the Ruby VM and C extensions

To profile C code, download and build an unpatched perftools (libunwind or ./configure --enable-frame-pointers required on x86_64).

Download:

wget http://gperftools.googlecode.com/files/gperftools-2.0.tar.gz
tar zxvf gperftools-2.0.tar.gz
cd gperftools-2.0

Compile:

./configure --prefix=/opt
make
sudo make install

Profile:

export LD_PRELOAD=/opt/lib/libprofiler.so                 # for linux
export DYLD_INSERT_LIBRARIES=/opt/lib/libprofiler.dylib   # for osx
CPUPROFILE=/tmp/ruby_interpreter.profile ruby -e' 5_000_000.times{ "hello world" } '

Report:

pprof `which ruby` --text /tmp/ruby_interpreter.profile

TODO

• Add support for heap profiling to find memory leaks (PerfTools::HeapProfiler)
• Allow both C and Ruby profiling
• Add setter for the sampling interval

Resources

• GoRuCo 2009 Lightning Talk on perftools.rb @ 21:52

• Ilya Grigorik's introduction to perftools.rb

• Google Perftools

• Analyzing profiles and interpreting different output formats