GC.start

Initiates garbage collection, even if explicitly disabled by GC.disable.

Keyword arguments:

• full_mark: a boolean value specifying whether to perform a major garbage collection cycle:

  • true: initiates a major garbage collection cycle, meaning all objects (old and new) are marked. When another Ractor’s object space exists (a live Ractor, or a terminated one not yet absorbed), or one was absorbed since the last global collection, and global is true (the default), the cycle is a global collection instead; see global.

  • false: initiates a minor garbage collection cycle, meaning only young objects are marked.

• immediate_mark: a boolean value specifying whether marking is performed incrementally:

  • true: marking is completed before the method returns.

  • false: marking is performed in parts, interleaved with program execution both before the method returns and afterward; therefore marking may not be completed before the return. Note that if full_mark is false, marking is always immediate, regardless of the value of immediate_mark.

• immediate_sweep: a boolean value specifying whether sweeping is deferred (lazy sweep):

  • true: sweeping is completed before the method returns.

  • false: sweeping is performed in parts, interleaved with program execution both before the method returns and afterward; therefore sweeping may not be completed before the return.

• global: a boolean value specifying, when another Ractor’s object space exists, whether to collect every Ractor’s heap together in a single stop-the-world mark/sweep cycle:

  • true: with another Ractor’s object space present (see full_mark) it runs a stop-the-world cycle and reclaims shareable and cross-Ractor garbage. This option, although it defaults to true, is ignored unless full_mark, immediate_mark and immediate_sweep are all true. With a single object space it has no effect and the other options apply as usual. This option is also ignored unless you’re using the default GC.

  • false: collect only the calling Ractor’s own objects. Shareable objects and cross-ractor garbage are not swept.

  GC.stat counts a local major collection under :major_gc_count, a local minor collection under :minor_gc_count, and a global collection under :global_gc_count for the calling Ractor.

Note that these keyword arguments are implementation- and version-dependent, are not guaranteed to be future-compatible, and may be ignored in some implementations.