Tweaking Ruby GC parameters for fun, speed, and profit

Whether you are building a Robot, controlling a Radar, or creating a Web App, the Ruby Garbage Collector (GC) can help you. The stats exposed by the Garbage Collector since Ruby v2.1 caught my attention and pushed me to dig deeper. Both Ruby 2.1 and 2.2 brought great performance improvements. From a practical point of view, we will discuss how to use the GC to enhance the performance of your software, from configuration parameters to different approaches on how you can change them yourself.

Transcript

1. RailsConf 2016
   Tweaking Ruby GC
   parameters for fun,
   speed, and profit
   I mean: for fun!
   Helio Cola
   http://hac-rods.me
   @hacrods
   

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2. RailsConf 2016
   So, why I am here talking about GC?
   

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3. RailsConf 2016
   hac-rods.me
   Hi, I am Helio Cola!
   • ~15 years developing SW
   • ~10 years doing C/C++ on Solaris
   • 5/6 years since I found happiness
   • ~4 years full time happiness
   • I go by @hacrods on the internet…
   

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4. RailsConf 2016
   So, let’s get it started and talk about
   Ruby Garbage Collector
   

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5. RailsConf 2016
   Terms
   • GC: Garbage Collector
   • RGenGC: Restricted Generational GC
   • RIncGC: Restricted Incremental GC
   • CoW: Copy-on-write technique
   • ab: Apache Benchmark Tool
   

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6. RailsConf 2016
   Agenda
   • Why I am here talking about Ruby GC
   • A couple bits about its history
   • Configuration parameters
   • My approach to measure & tuning
   • Some of my findings
   • QA
   

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7. RailsConf 2016
   Why I am here… Ruby Garbage Collector
   

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8. RailsConf 2016
   Why I am here… GC
   • Once upon a time there was a Rails App
   • Why? How? How can I?
   

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9. RailsConf 2016
   Why I am here… GC
   • I did do a lot research on it…
   • I had a really great time learning & doing all this
   • I wanted to share it
   • And my talk got accepted!!!! :-)
   

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10. RailsConf 2016
    A bit about the history of Ruby GC
    

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11. RailsConf 2016
    A brief history about Ruby GC
    • Ruby 1.8: Simple Mark & Sweep
    • Ruby 1.9.3: Lazy Sweep
    • Ruby 2.0: Bitmap Masking (CoW friendly)
    • Ruby 2.1: RGenGC
    • Ruby 2.2: RIncGC and Symbol GC
    Reference: http://tmm1.net/ruby21-rgengc/
    

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12. RailsConf 2016
    A brief history about Ruby GC
    by
    Aman Gupta
    Reference: http://tmm1.net/ruby21-rgengc/
    

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13. RailsConf 2016
    Ruby 1.8: Simple Mark & Sweep
    Reference: http://tmm1.net/ruby21-rgengc/
    

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14. RailsConf 2016
    Ruby 1.9.3: Lazy Sweep
    Reference: http://tmm1.net/ruby21-rgengc/
    

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15. RailsConf 2016
    Ruby 2.0: Bitmap Masking (CoW)
    Reference: http://tmm1.net/ruby21-rgengc/
    

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16. RailsConf 2016
    Ruby 2.0.x: 2.0.0-p647
    

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17. RailsConf 2016
    Ruby 2.1: RGenGC
    Reference: http://tmm1.net/ruby21-rgengc/
    

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18. RailsConf 2016
    Ruby 2.2: RIncGC / Symbol GC
    • Symbols now gets collected by GC!
    • RIncGC
    https://engineering.heroku.com/blogs/2015-02-04-incremental-gc/
    

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19. RailsConf 2016
    Ruby 2.2: RIncGC / Symbol GC
    • RIncGC
    • Not a silver bullet
    • Don’t affect throughput or response time
    Reference: https://engineering.heroku.com/blogs/2015-02-04-incremental-gc/
    

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20. RailsConf 2016
    Ruby 2.1.x & 2.2.x
    

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21. RailsConf 2016
    Configuration parameters
    

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22. RailsConf 2016
    GC Parameters: ruby 2.0.x
    • RUBY_GC_MALLOC_LIMIT
    • RUBY_HEAP_MIN_SLOTS
    • RUBY_FREE_MIN
    https://github.com/ruby/ruby/blob/v2_0_0_647/gc.c#L3296
    

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23. RailsConf 2016
    GC Parameters: Ruby >= 2.1.x
    • RUBY_GC_HEAP_INIT_SLOTS
    • RUBY_GC_HEAP_FREE_SLOTS
    • RUBY_GC_HEAP_GROWTH_FACTOR
    • RUBY_GC_HEAP_GROWTH_MAX_SLOTS
    • RUBY_GC_HEAP_OLDOBJECT_LIMIT_FACTOR
    Reference: https://github.com/ruby/ruby/blob/v2_1_7/gc.c#L5705
    

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24. RailsConf 2016
    GC Parameters: Ruby >= 2.1.x
    • RUBY_GC_MALLOC_LIMIT
    • RUBY_GC_MALLOC_LIMIT_MAX
    • RUBY_GC_MALLOC_LIMIT_GROWTH_FACTOR
    Reference: https://github.com/ruby/ruby/blob/v2_1_7/gc.c#L5705
    

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25. RailsConf 2016
    GC Parameters: Ruby >= 2.1.x
    • RUBY_GC_OLDMALLOC_LIMIT
    • RUBY_GC_OLDMALLOC_LIMIT_MAX
    • RUBY_GC_OLDMALLOC_LIMIT_GROWTH_FACTOR
    Reference: https://github.com/ruby/ruby/blob/v2_1_7/gc.c#L5705
    

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26. RailsConf 2016
    Reference: https://github.com/ruby/ruby/blob/v2_1_7/gc.c#L5705 / https://github.com/ruby/ruby/blob/v2_2_3/gc.c#L6972
    https://github.com/ruby/ruby/blob/v2_3_0/gc.c#L7256
    Ruby v2.1.7
    And also:
    v2.2.x & v2.3.x
    

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27. RailsConf 2016
    Running it
    $ export RUBY_GC_HEAP_INIT_SLOTS=800000
    $ export RUBY_GC_HEAP_FREE_SLOTS=32768
    $ export RUBY_GC_MALLOC_LIMIT=33554432
    $ export RUBY_GC_MALLOC_LIMIT_MAX=50331648
    $ rails s
    

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28. RailsConf 2016
    My approach to measure & tuning
    

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29. RailsConf 2016
    Me: measuring & tuning
    • Find out if your current/default experience is good,
    normal, bad, or really bad.
    

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30. RailsConf 2016
    Me: measuring & tuning
    • Research mode, reading mode, studying mode,
    read ruby source code, compile it…
    ✴ I have to upgrade the one with 2.0.x
    ✴ I don’t know yet if my app with 2.1.x is in good or bad shape
    • And after a lot of research…
    

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31. RailsConf 2016
    So, what now?!
    • Let me start by running it all on my laptop
    … and ab it!
    … and… still doesn’t look like my production app!
    

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32. RailsConf 2016
    So, and now what?!
    • A couple of days go by…
    … testing, measuring, analyzing data, thinking about what I am seeing…
    • Some well known reasons:
    • My laptop isn’t like my AWS servers
    • I don’t have the same amount of data
    • My ab calls aren’t reflecting very well the traffic from my real users
    … so… the app on my laptop won’t be like it is in prod servers!
    

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33. RailsConf 2016
    So…
    • Sleep on it
    • Go spend a day doing something else
    • Grab a teammate and talk to him
    • Explain what you are doing to someone else
    (or at least try to explain! :-)
    • Plan your next steps
    

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34. RailsConf 2016
    And: either this or that
    • You may open your eyes to something else
    • Or you establish a laptop baseline
    DEV
    PROD
    

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35. RailsConf 2016
    Finally: I got this
    

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36. RailsConf 2016
    Change, Measure & Analyze
    • Do that over & over & over again…
    • Analyze your data, document your numbers in a
    piece of paper or notepad
    • Make one single change (at a time) and re-run your
    tests
    

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37. RailsConf 2016
    Again: either this or that
    • If you will find something that improves your app
    ̣ Document it nicely and share with your team
    ̣ Make a small talk out of it
    ̣ And you won’t sweat to make it into the
    Production environment!
    • Or that will happen…
    

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38. RailsConf 2016
    Some of my findings
    

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39. RailsConf 2016
    Some of my findings
    Parameters I changed:
    • RUBY_GC_HEAP_INIT_SLOTS
    • RUBY_GC_HEAP_FREE_SLOTS
    • RUBY_GC_MALLOC_LIMIT
    • RUBY_GC_MALLOC_LIMIT_MAX
    

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40. RailsConf 2016
    Some of my findings
    A few comparisons:
    • Ruby 2.0.0 vs Ruby 2.1.7 (before)
    • Ruby 2.1.7: before and after
    • Ruby 2.2.3: before and after
    • Ruby 2.1.7 vs Ruby 2.2.3 (after)
    

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41. RailsConf 2016
    Ruby 2.0.0 vs Ruby 2.1.7
    

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42. RailsConf 2016
    v2.0.0
    v2.1.7
    

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43. RailsConf 2016
    v2.0.0
    v2.1.7
    

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44. RailsConf 2016
    Ruby 2.1.7 before vs after
    

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45. RailsConf 2016
    v2.1.7
    before
    v2.1.7
    after
    

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46. RailsConf 2016
    v2.1.7
    before
    v2.1.7
    after
    

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47. RailsConf 2016
    Ruby 2.2.3 before vs after
    

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48. RailsConf 2016
    v2.2.3
    before
    v2.2.3
    after
    

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49. RailsConf 2016
    v2.2.3
    before
    v2.2.3
    after
    

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50. RailsConf 2016
    Ruby 2.1.7 vs 2.2.3 (after)
    

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51. RailsConf 2016
    v2.1.7
    after
    v2.2.3
    after
    

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52. RailsConf 2016
    v2.1.7
    after
    v2.2.3
    after
    

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53. RailsConf 2016
    Thank you!
    Q&A?!
    Helio Cola
    http://hac-rods.me
    @hacrods
    

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54. RailsConf 2016
    Thanks
    Thanks to these folks that helped me along the way
    NoTwitterErik
    costasd@something.gr
    

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