Did anyone investigate where those improvements actually came from or what’s happening in their old fork when those scheduling misses occur? That version of NuttX is ancient (4-5 years old). Most of the flash savings have to do with portions of PX4 they absorb, but barely use. You can already fit PX4 multicopter on less than half a meg of flash like the crazyflie. Personally I would have liked to see an apples-to-apples comparison of chibios and nuttx, but I doubt there’s interest at this point.
There are still parts of ChibiOS that look nice, but the licensing is a pain and convoluted (http://www.chibios.org/dokuwiki/doku.php?id=chibios:licensing:start), and ultimately I don’t see how it would move a project like PX4 further along in a meaningful way. Does it provide better hardware support? Does it bring us closer to something certified for safety critical use?
PX4 is structured much differently and doesn’t really have a main loop frequency. We can already run the rate controller much faster than other parts of the system and will likely do so by default after implementing some driver architecture changes that have been in planning for a long time. Most of the system has no need to run that fast. You also have to pay attention to end to end latency, and not just frequency.