Newer Java GCs are very low latency (microsecond). You trade performance and memory for that low latency though. AFAIK, they are still compacting.
Still though, probably makes sense to do it in a lower level language. It's just far easier in C++ to decide that "Hey, you know what, I just want a big memory block that I control".
I've even heard of game devs doing things like having per frame allocators. They get super fast allocation because they just pointer bump and at the end they simply reset the pointer back to location 0. I'm sure trading systems could do something similar.
The point is that a one millisecond pause is unacceptable. Low latency Java GCs have average latencies of one millisecond, 99th percentile latencies of 10 milliseconds, and 99.9th percentile latencies are neither measured nor optimized for.
I don't consider it realistic to think that garbage collected languages might ever be usable in the context of game engines or HFT.
Game engines are already written in GCed languages. Java in particular.
You may be right that a 10ms pause is unacceptable for HFT. However, for a FPS, 10ms is more than acceptable. It translates to 1 or 2 missed frames in the worst case.
A bigger issue with using Java in particular for games is it's lack of value types. Writing high performance code for java is just that much harder because the language gets in the way.
The only serious engine I know of that's written in Java is Minecraft and its performance problems are notorious.
Microsoft XNA and Unity's .net support were also pretty popular but the popular games written in those languages (like Bastion) didn't have many heavyweight assets or allocator pressure.
Still though, probably makes sense to do it in a lower level language. It's just far easier in C++ to decide that "Hey, you know what, I just want a big memory block that I control".
I've even heard of game devs doing things like having per frame allocators. They get super fast allocation because they just pointer bump and at the end they simply reset the pointer back to location 0. I'm sure trading systems could do something similar.