@guruevi what im seeing (if im reading the output of cat /proc/meminof right!) is that CMA is holding on to its memory allocation and not giving it up - im trying to allocate as many hugepages as i can for my application and cant get much above the 1250 size even with a reboot.
So having done a load more reading and following the tips here - is all i need to do change the dts file and recompile that to remove hardware / drivers from the kernel at boot time rather than recompile the kernel each time? That would save me a lot of time! Sorry if thats a noob question but im a noob when it comes to messing with kernels!
You should be able to reclaim that memory by only modifying device tree but I cannot promise you that it won’t crash - if it does, you would need to deselect the drivers in kernel options and recompile the kernel.