I recently applied the rt patch to my kernel in an attempt to lower the worst-case latency of sending messages over USB. Unfortunately I have seen no improvement in the worst-case over the unpatched kernel. Is there a patch I need for libusb, or even another way to communicate over USB to take advantage of the RT kernel to lower the worst-case latency?
For the most part the
RT kernel will make subtle changes to insure your
frame time is not over run.
Even then it is generally considered that the difference is very small, its more of a "if you aren't quite there, this might tip you over" adjustment.
If your USB performance is not good enough for what you are doing, you could try to reduce the number of devices connected to your system to free up additional hardware resources.
Or perhaps a faster version of USB.
As far as I know there isn't a means you could directly impact how fast your usb latency is unfortunately.