There is a long-standing effort to reduce latencies still further that goes by the name of the kernel configuration option for these features, PREEMPT_RT. The project was started by Ingo Molnar, Thomas Gleixner, and Steven Rostedt and has had contributions from many more developers over the years. The kernel patches are at https://www.kernel.org/pub/linux/kernel/projects/rt, and there is a wiki, including an FAQ (slightly out of date), at https://rt.wiki.kernel.org.
Many parts of the project have been incorporated into mainline Linux over the years, including high-resolution timers, kernel mutexes, and threaded interrupt handlers. However, the core patches remain outside of the mainline because they are rather intrusive and (some claim) only benefit a small percentage of the total Linux user base. Maybe, one day, the whole patch set will...
