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

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

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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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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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RailsConf 2016 Why I am here… Ruby Garbage Collector

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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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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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RailsConf 2016 A bit about the history of Ruby GC

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

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

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

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

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RailsConf 2016 Ruby 2.0.x: 2.0.0-p647

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

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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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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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RailsConf 2016 Ruby 2.1.x & 2.2.x

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RailsConf 2016 Configuration parameters

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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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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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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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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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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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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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RailsConf 2016 My approach to measure & tuning

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

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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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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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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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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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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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RailsConf 2016 Finally: I got this

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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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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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RailsConf 2016 Some of my findings

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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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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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RailsConf 2016 Ruby 2.0.0 vs Ruby 2.1.7

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RailsConf 2016 v2.0.0 v2.1.7

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RailsConf 2016 v2.0.0 v2.1.7

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RailsConf 2016 Ruby 2.1.7 before vs after

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RailsConf 2016 v2.1.7 before v2.1.7 after

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RailsConf 2016 v2.1.7 before v2.1.7 after

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RailsConf 2016 Ruby 2.2.3 before vs after

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RailsConf 2016 v2.2.3 before v2.2.3 after

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RailsConf 2016 v2.2.3 before v2.2.3 after

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RailsConf 2016 Ruby 2.1.7 vs 2.2.3 (after)

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RailsConf 2016 v2.1.7 after v2.2.3 after

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RailsConf 2016 v2.1.7 after v2.2.3 after

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

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RailsConf 2016 Thanks Thanks to these folks that helped me along the way NoTwitterErik [email protected]