Garbage? Garbage? GARRRRRBAAAAAAGG GGEEEEEEE mrb / lightning talks @ pp / May 3, 2013

I Like Garbage

I Like Thinking About Garbage

I Like Thinking About Looking For Garbage

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What is Garbage Collection?

Automatic memory management for your computer programs.

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“Living” vs. “Dead”

What memory are you using, and what memory can be reclaimed?

Your objects form a graph.

Traversing graphs is hard.

The Big Algorithms • Mark and Sweep • Reference Counting • Generational

Ruby makes a lot of garbage.

Ruby’s Garbage Story https://bugs.ruby-lang.org/issues/8339 https://bugs.ruby-lang.org/attachments/3686/gc-strategy- en.pdf

Ruby’s Current GC • Mark And Sweep • Conservative • Bitmap Marking • Non-Recursive Marking • No Moving • Favors C Extensions

Rubyists wrote C extensions to make certain Ruby code run faster.

The primitive Garbage Collector supports these C extensions.

Now, this same Garbage Collector is what is preventing Ruby code from being as fast as it could be.

“Despite the best efforts of Koichi and other contributors, Ruby Core's concern with backwards compatibility (particularly regarding the C Extension API) keeps MRI lagging more than a decade behind Ruby implementations like Rubinius and JRuby which already have precise, generational and incremental garbage collectors.” - Vincent Marti (@vmg) https://github.com/blog/1489-hey-judy-don-t-make-it-bad

RGenGC Is... • An awesome, fearless hack • Likely to make some Ruby code run faster • Certain to not break compatibility with C extensions • Progress

RGenGC Isn’t... • The answer to Ruby’s problems • Likely to make all Ruby code faster in the long run • Going to draw people to Ruby • Limitless Progress

In Conclusion • We need to figure this out • We can find a way forward

Thanks!