This is my RAM usage when I run OpenSTLinux on my custom STM32MP151 board with 512 MB RAM.
Is that OK?

STM32MP151AAC3 custom board with STM32-OS as operating system: https://github.com/DanielMartensson/STM32-Computer
STM32MP257FAK3 custom board with STM64-OS as operating system: https://github.com/DanielMartensson/STM64-Computer