[pebal]

It doesn't matter if objects die young — the other objects on the heap are still moved around periodically, which reduces performance. When you're using a moving GC, you also have additional read barriers that non-moving GCs don't require.

[gf000]

Is that period really that big of a concern when your threads in any language might be context switched away by the OS? It's not a common occurrence on a CPU-timeline at all.

Also, it's no accident that every high-performance GC runtime went the moving, generational way.

[pebal]

That time may seem negligible, since the OS can context switch threads anyway, but it’s still additional time during which your code isn’t doing its actual work.

Generations are used almost exclusively in moving GCs — precisely to reduce the negative performance impact of data relocation. Non-moving GCs are less invasive, which is why they don’t need generations and can be fully concurrent.