라즈베리 파이 GPU_MEM 설정

라즈베리 파이는 메모리를 공유하는데

GPU에 할당되는 메모리에 따라 사용가능한 기능이 제한이 된다.

gpu_mem GPU memory in megabyte. Sets the memory split between the ARM and GPU. ARM gets the remaining memory. Min 16. Default 64

[링크 : http://elinux.org/RPiconfig]

[링크 : https://www.raspberrypi.org/documentation/configuration/config-txt.md]

요약하면.. GPU에 최저 할당 가능한 

16MB는 2D로만 쓸 수 있고(FullHD 해상도 가능)

32MB 부터 3d 가속과 비디오 가속이 가능

128MB 는 raspBMC 라는 녀석의 권장 설정값

기능적으로는 32MB 부터 전부사용은 가능하다.

256MB version

For older RaspberryPi, with 256 MB of RAM, 4 splits are available:

240/16 - The most RAM size ARM can get (240MB) with mimial GPU memory. It's the best for general computing when you don't need 3D graphics or hardware video acceleration. It has enough memory to handle 1920x1200x16bpp framebuffer resolution. While 32bpp is also working, it's not recommended since it leaves very small amount of free memory for GPU.

-

224/32 - This one is deprecated in favor of 240/16 split. It has 3D and hardware video decoding build in but since there is not enough memory to actually use it, there's little point in using it. Unless you have some problems with 240/16 split or want to use 32bpp framebuffer at highest resolution. It is possible it will be deleted in the future.

192/64 - You need at least 64MB of GPU split to use hardware video acceleration or 3D graphics. It may not be enough GPU memory for hardware accelerated video playback at highest resolution or if you need a lot of GPU memory for things like textures.

128/128 - The most RAM GPU can get. Use it when you need a lot of memory for 3D graphic card and hardware accelerated video playback in high resolution. This split is needed for RaspBMC to work properly or to play fullHD video content with omxplayer without problems.

512MB version

New versions of RaspberryPi has 512 MB of RAM. You have 4 additional splits designed for this version:

496/16 and 448/64 - like 240/16 and 192/64 split for 256MB respectively but with 256MB more RAM available for ARM. Since GPU has only 16 MB/64MB or RAM, all the limitations from 240/16/192/64 still apply.

384/128 - Similar to 128/128 split for 256MB - you should get all the graphic chip features but with reasonable amount of ARM memory. This will probably be the most universal split right now.

256/256 - Some bonus graphic card memory if you really need it, like for big textures and similar things. While 256MB of ARM memory is bigger than you could possibly have in older RaspberryPis, I don't think this one will be used on many occasions.

[링크 : http://raspberrypi.stackexchange.com/.../what-is-the-optimum-split-of-main-versus-gpu-memory]