A lot of lisps use BDW or other Boehm variants, which I do not believe are capable. Clasp uses MPS which is supposed to have extremely low pause times -- soft realtime capable?
Java has ZGC which is supposed to have guaranteed sub-ms pause times IIRC, so that should be realtime capable.
PTC and Aicas are the surviving companies on this domain.
Aonix, which was acquired by PTC, famously sold Java real time systems for military systems like missile tracking radars and battleship weapon targeting control systems, a domain where you need split second decisions taking place.
There are probably at least a dozen GC algorithms that provide sub-1ms pause times though, so very few applications wouldn't fit the latency requirements, as long as the other requirements are acceptable (typically higher memory use for forwarding pointers, copying, or delayed collection).
I'd be interested to know more about which ones provide this guarantee. This has been surprisingly difficult to Google for.
But as mentioned, boundedness is the important property, hard real time systems are not really fast in any way or shape (e.g. for a modern chip to calculate a missile trajectory you really barely need any time, but it not replying in the necessary time window which may be like half a sec, because GC/JIT compiler/OS interrupt is a no-go).
https://researcher.watson.ibm.com/researcher/view_group_subp...
The Recycler GC is measured around 2ms on old hardware, so it's surely less now because IIRC that pause time is only to copy the stack to a buffer to scan in a separate thread:
Java without the Coffee Breaks: A Nonintrusive Multiprocessor Garbage Collector, https://sites.cs.ucsb.edu/~ckrintz/racelab/gc/papers/bacon-c...
A study of 3 realtime concurrent copying collectors, CHICKEN, CLOVER and STOPLESS, all of which seem to "response times" less than 10 usecs:
A Study of Concurrent Real-Time Garbage Collectors, https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.353...
Parallel realtime collector, hard to quantify exact pause time because it's configurable and they make a good point that MMU is a better measure:
http://www.aladdin.cs.cmu.edu/papers/pdfs/y2001/rtg.pdf
Then you have various compile-time GC analyses you can apply to your language, like Perceus:
https://www.microsoft.com/en-us/research/uploads/prod/2020/1...
The problem with maximum pause times is that it's not necessarily a feature of all realtime collectors, which try to do work incrementally and so don't necessarily introduce pauses in the same way as traditional tracing GCs. As you can see above, some of them quantify realtime behaviour in various ways so you can trade off memory use, CPU utilization and max latency.