Does someone know what this actually does? Googling gives you a couple of hits and that's about committing the changes. No actual discussion what it is or why would you want it.
The RT PREEMPT RPi howto guy says "Most people also disable the Low Latency Mode (llm) for the SD card". Cool, but why? It should be common knowledge if most people want to do that.. If I had to guess I'd hazard that the low-latency SDHC bits conflict with the RT patch bit and produce unpredictable latency for your "realtime" code?