Is there a GC in Java that does not introduce latency (stop-the-world) by perhaps running 100% concurrently?

Just curious. I heard something about the new G1GC addressing that latency problem. I can't / don't want to use RTSJ.

Thanks in advance

I don't think there are any zero-pause garbage collectors. But generally speaking a low-pause collector like CMS will do the job.

The problems with pauses and pause reduction are as follows:

A zero-pause (or almost zero-pause) collection regime significantly increases overheads for normal program execution. This is particularly true with multithreaded languages like Java.
Schemes that use a dedicated thread or threads to do garbage collection can get swamped if the application generates too much garbage.
Any GC scheme will give you poor performance if the application's memory usage patterns are too "lumpy" and/or you don't have enough physical and virtual memory.

You might be interested in something like the Zing JVM.

Azul systems have put a lot of effort into low-latency JVM tuning. I believe there are also some interesting technical papers that explain how this is done.

Matt Ball

It sounds like you're looking for the CMS GC — concurrent mark sweep.