Changing the memory distribution of Raspberry Pi (Memory Split) On Raspberry Pi is an SDRAM semiconductor memory, which is used as a “shared memory”. This means that the memory of the CPU and the graphics memory of the GPU must share the memory capacity of the SDRAM chip.
On the software side, you can set how much memory should be allocated to the graphics memory of the GPU. By default, the GPU memory is 64 MB in size. The remainder of 256, 512 or 1,024 MBytes is then available for the main memory.

How big should the graphics memory be?
It depends on what you do with Raspberry Pi. Basically, one could say that if you can do without a graphical output, then you could set the graphics memory to 0 MB. But it is not that easy. To boot  Raspberry Pi, the GPU needs at least 16 MB of graphics memory. Less is not possible.
If you do not need the window manager because you run Raspberry Pi as a server or gateway, for example, then you can lower the memory for the GPU. At least 16 MB.