[pebal]

Compaction doesn't necessarily guarantee cache friendliness. While it does ensure contiguity, object layout can still be arbitrary. True cache performance often depends on the locality of similar objects — for example, memory pools are known for their cache efficiency. It's worth noting that Go deliberately avoids compaction, which suggests there's a trade-off at play.

[pizlonator]

I'm not saying that compaction guarantees cache friendliness.

I'm saying you have no evidence to suggest that not compacting is better for cache friendliness. You haven't presented such evidence.

[pebal]

As I mentioned earlier, take a look at the Golang. It's newer than Java, yet it uses a non-moving GC. Are you assuming its creators are intentionally making slower this language?