[cogman10]

Gotta be honest, I have a hard time arguing for G1 over ZGC. It seems to me like any situation you'd want G1 you probably want ZGC instead. That default 200ms target latency is already pretty long. If you've made that tradeoff for G1 because you wanted lower latency, you probably are going to be happier with ZGC.

I also find that the parallel collector is often better than G1, particularly for small heaps. With modern CPUs, parallel is really fast. Those 200ms pauses are pretty easy to achieve if you have something like a 4gb heap and 4 cores.

The other benefit of the parallel collector is the off heap memory allocation is quiet low. It was a nasty surprise to us with G1 how much off heap memory was required (with java 11, I know that's gotten a lot better).

[spockz]

We have many apps that run on <1 core just fine for the business logic and run on K8S. If we then use a parallel or concurrent garbage collector it will eat through the cpu limit of the app in a blink causing the process not to be scheduled for several ticks. This introduces more latency than the GC cycles themselves would when using a serial GC than runs frequently enough.