Garbage collection (GC) is a big challenge in multi-Ractor systems. In the current implementation, all Ractors share a global heap, and GC requires stopping all Ractors to perform GC. This approach negatively impacts object allocation and GC performance.

Ideally, GC should be executed in parallel for each Ractor's local heap. However, shareable objects make it difficult to track references and implement fully parallel GC.

To address this, we propose Ractor-local GC, which focuses on collecting non-shareable, Ractor-local objects in parallel, while continuing to perform global GC for shareable objects by pausing all Ractors, as in the current system. This hybrid approach allows most GC operations to run in parallel, improving overall performance. Furthermore, since shareable objects are expected to be relatively few compared to non-shareable objects, the frequency of global GC should remain low.

This talk will present the design of Ractor-local GC and the progress of its implementation.