Collecting Garbage on the Blockchain
summary
An incremental garbage collector for a WebAssembly blockchain (Internet Computer) that bounds GC work to fit transaction instruction limits and avoid unbounded stop the world pauses. It uses snapshot-at-beginning conservative marking, per-run empty call stack at phase boundaries, partitioned heaps with 32 MB partitions, incremental evacuation compaction using Brooks forwarding pointers, and a separate updating phase that patches all pointers so reclaimed memory is available immediately. Measurements show bounded pause behavior, slightly lower total instruction cost than alternatives, higher peak heap due to forwarding and copy space, and better scalability past previous GC instruction limits.
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chapters (11)
- 0:00Introduction to blockchain garbage collection
- 1:24Transactional execution model
- 3:32Moto language GC basics
- 4:57Incremental GC requirements
- 6:00Moto incremental GC design
- 9:34Evacuation phase pointers
- 11:26Updating phase patching
- 12:50Experimental results
- 15:39Scalability trade-offs
- 16:41Key takeaways
- 17:02Q&A
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