Companion

A Generation that has not yet been added to the generations. When this becomes fuller than approximately maximumNewestGenerationSize, queue it and create a new one.

Record a newly created chunk in the latest generation, triggering eviction of some of the least recently used chunks if necessary.

An L2Chunk has been invalidated. Remove it from its generation.

Deal with the fact that the given chunk has just been invoked, resumed, restarted, or otherwise continued. Optimize for the most common case that the chunk is already in the newest generation, but also make it reasonably quick to move it there from an older generation.