https://stackoverflow.com/questions/41224738/how-to-calculate-system-memory-usage-from-proc-meminfo-like-htop

htop author here. These are the calculations I make to get the numbers for the green, blue and yellow bars in the memory meter:

    Total used memory = MemTotal - MemFree
    Non cache/buffer memory (green) = Total used memory - (Buffers + Cached memory)
    Buffers (blue) = Buffers
    Cached memory (yellow) = Cached + SReclaimable - Shmem
    Swap = SwapTotal - SwapFree

