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Highly Surmountable Challenges in Ruby+OMR JIT Compilation
- 1. Matthew Gaudet, February 4th, 2017 Highly Surmountable Challenges in Ruby+OMR JIT Compilation
- 3. An Open Source Toolkit for Language Runtime Technologies.
- 5. Goal: Compatibility! Integrate vs. Replace
- 6. +
- 8. 8
- 9. Status Update: 13 Months later
- 10. 10
- 11. 11 No JIT….
- 13. 13
- 14. 14
- 15. Today: Branch ruby_2_4_omr is current default. – Based of ruby_2_4 tag JIT Compiler Hooked up and running Travis tests for OS/X and Linux – Known issues in make test-all – Passing make test with count=0 Populated and tagged Issue Tracker Performance: Less specialization to micro benchmarks, means lower seeming performance. – Better software engineering https://github.com/rubyomr-preview/ruby/issues/
- 16. JIT integration Functional Correctness has been primary objective – Aiming for pass of test suite at all optimization levels. –No restrictions on native code used by extension modules Have added some optimizations, but haven’t done much in the way of tuning. Simple compilation control
- 18. Our Goal: YES Be Part of Delivering 3x3
- 19. Why? We think Ruby could really benefit from having a JIT compiler. Lots of pre-built JIT compiler technology in OMR, with potential for exploitation in Ruby. What’s in it for us? Validation of the OMR approach –Community improvement: Having multiple consumers helps us make it better for everyone!
- 21. Competition and Collaboration Having multiple JITs for CRuby could be a really good thing! Share the load of creating interface and infrastructure that all JITs for CRuby can rely on. Competition helps push things forward Collaboration helps solve hard problems! 21
- 27. Make Tradeoffs that are Right for the Ruby Community JIT Compilation: Trade startup speed for peak speed. Trade footprint for speed.
- 28. What do we prioritize? Time to First Request? Time to Peak Performance? Peak Performance? 100 64 69 36 25 30 25 26 25 26 25 1 2 3 4 5 6 7 8 9 10 11 Time per Iteration (s) Prioritization will be driven by benchmarks from the community.
- 29. 1. Some CPU intensive applications: OptCarrot 2. Some memory intensive application: 3. A startup benchmark: time ruby -e “def f; ‘100’; end; puts f”? 4. Some web application framework benchmark(s)? http://rubykaigi.org/2016/presentations/MattStudies.html Benchmarks to aim for? http://engineering.appfolio.com/appfolio-engineering/2016/12/8/benchmarking-rails
- 31. MRI Garbage Collector Ruby IL Generator Optimizer Code Generator Runtime Code Cache YARV Interpreter
- 32. JIT VM Symbiosis VMJIT Performance Information JIT ↔ VM Interface
- 33. Infrequent Event Notification Operations such as Basic Operation Redefinition Constant Modification Class Hierarchy changes. Unlocks: –More aggressive specialization, class hierarchy optimization. Don’t create code for things that haven’t happened yet!
- 34. Stack Peeking Notification A hook that fires when some piece of code wants to look at a stack frame – Give the JIT compiler a chance to materialize what it should have looked like. Unlocks –On Stack Replacement: Don’t Execute Code for Things that might happen!
- 35. Basic Block Frequencies How many times has this basic block been executed? Unlocks: Better Optimization: Don’t spend time compiling on things that won’t get executed! ?
- 36. Type Profiling What types have we seen for this value? Unlocks: Speculation and Specialization: Generate code for the cases we think will happen!
- 39. Much of MRI’s core functionality is written in C! A problem for the optimization horizon!
- 40. Optimization Horizon Solutions? Rewrite all of core in Ruby. ‘Lift the Core’ 40
- 41. Optimization Horizon Solutions? Incremental Ruby-fication: More promising… and easy to get started on in Ruby! Convert prelude.rb to a ‘prelude’ directory, where Ruby implementations live. – Startup concerns (parse overheads) – can be mitigated with YARV bytecode serialization. – Longer term: JIT AOT Compilation maybe! 41
- 43. An admission:
- 45. JIT Testing is Hard! Normal Tests Finish quickly Coverage with minimal repetition. Local reasoning / isolation No special command lines Compiler Stress Tests Need to run code multiple times! – Allow the JIT to kick in, profile data to be collected, and consumed Potentially require global reasoning. Run in multiple VM instances under different options. Writing test cases that can effectively stress the JIT compiler is an art
- 46. JIT Testing is Hard! Other problems: Isolating test cases from each other Time accuracy trade off Coverage All these problems of JIT testing will also be equally true when running a gem’s test suite with a JIT...
- 47. My Personal Ruby Hero Patched ruby/spec to allow it to work with repetition Great win for JIT testing!
- 49. Keeping up with the firehose? How do we keep up to date with the Ruby core? Some is good software engineering… callback generation was done precisely to address this concern. But more still needed!
- 50. The JIT Needs some cleanup Callback Generator Ruby code isn’t very good! –https://github.com/rubyomr-preview/ruby/issues/74 Great task for someone good at writing Ruby! The makefiles need love – https://github.com/rubyomr-preview/ruby/issues/8
- 51. OMR Challenges
- 52. OMR is evolving! We’ve only been open source for 4.5 months! Still working on improving our interfaces, our integration story. Need to build out a community! This is where you can help!
- 53. Mentorship I’m committed to helping anyone who wants to contribute to Ruby+OMR get up and running. I’ll write documentation for things that are unclear I’ll answer email! I’ll help guide implementationI’ll be on slack! I’ll schedule a video chat with you!
- 54. Ruby+OMR needs community interest to survive!
- 55. My To-Do List! 1. Make My Mentorship Commitment Clear! 2. I need to start collecting feedback from ruby-core on what we would need to do to get community members interested. 3. I need to start demonstrating the kinds of VM changes a JIT will need.
- 56. The Audience To-Do List! 1. Give Ruby+OMR a try 2. Open Issues! 3. Ask about helping! Little things are equally appreciated!
- 57. My thoughts on hitting 3x3: 57 The Work Ahead! JIT Work VM Work The VM Work I hope can be shared among competition!
- 58. Thank you so much!