Uploaded byDavid Paluy
Debugging and Profiling Rails Application
The document discusses debugging and profiling a Ruby on Rails application that is using excessive memory. It explains how the Ruby garbage collector works and that allocating too many objects can lead to longer garbage collection times and eventually running out of memory. Various tools are presented for debugging memory issues, including pry-debugger, ObjectSpace.count_objects, enabling heap dumps, and gdb.rb. Profiling tools discussed include Benchmark, ruby-prof, and perftools.rb for measuring time, allocations, memory usage, and garbage collection metrics. The key message is that allocating too many objects leads to slowdowns from longer garbage collection, so examining the heap and using debugging and profiling tools is important.
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Debugging and Profiling Rails Application
- 1. Debugging and Profiling Rails App David Paluy January 2013
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- 4. Agenda ● “Winter is coming!” ● Garbage Collector ● Debug Tools ● Profiling Tools
- 5. The Task: Send~30,000 e-mails
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- 7. How Ruby Works? Physical RAM Process Heap Ruby Heap Ruby Heap Ruby Ruby Ruby Ruby Ruby Ruby Object Object Object Object Object Object
- 8. New Object allocation FreeList A L L F O R C E A E T E D
- 9. New Object allocation FreeList A L L O C A T E D
- 10. New Object allocation FreeList is empty A L L O C A T E D
- 11. New Object allocation FreeList is empty – Call GC A L L O C A T E D
- 12. GC Process ● GC finds non-reachable objects and adds them to Free List ● If Free List is still empty, another Heap allocated
- 13. MRI GC ● “Conservative”: any bit pattern could be a pointer (may produce false positive) ● “Stop the world”: no other Ruby code can execute during GC ● “Mark & Sweep”: mark all objects in use, than sweep away unmarked objects
- 14. More Objects =>Longer GC => Slow
- 15. In our case– Out of Memory!
- 16. How to Debug? ● gem "pry-debugger" https://github.com/nixme/pry-debugger ● gem "debugger-pry" https://github.com/pry/debugger-pry
- 17. Tools ● ObjectSpace.count_objects ● GC debug - Enable heap dump support ● gdb.rb (only Linux) Note: memprof works only with Ruby 1.8
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- 19. Enable heap dumpsupport to Ruby Install custom patched version of ruby Usage:
- 20. https://github.com/tmm1/gdb.rb Attached to existing process and examine the HEAP
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- 22. Profiling Tools ● Ruby Benchmark ● ruby-prof ● perftools.rb (Google perftools for Ruby)
- 23. Benchmark ● gem 'benchmark_suite' https://github.com/evanphx/benchmark_suite
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- 25. ruby-prof Measurements ● 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)
- 26. perftools.rb https://github.com/tmm1/perftools.rb gem 'rack-perftools_profiler', :require=> 'rack/perftools_profiler'
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- 29. Summary ● More Objects => Longer GC => Slow ● Examine your HEAP ● Use Tools
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