[Mesa-dev] bad performance issue in GPU & CPU data sharing

[Zong, Wei]

Hello,



I'm using GLES shader to run algorithms on image frames, I got very bad performance issue in GPU & CPU data sharing, especially retrieve data from GPU to CPU.



Basically, I use glGenBuffers/glBindBuffer/glBufferData(target, size, data, usage) to create GPU buffer object and initialize GPU data store with CPU data pointer. After GLES shader finished the processing, I use glMapBufferRange to retrieve processed image data back to CPU, and for some reason I have to do an extra data copy from the gl map pointer to another CPU buffer, this is super slow.



Here's the code snippet https://github.com/intel/libxcam/blob/master/modules/gles/gl_buffer.cpp#L94

https://github.com/intel/libxcam/blob/master/modules/gles/gl_buffer.cpp#L127



I wonder If there has other efficient way to sharing data between CPU & GPU GLES shader?



Thanks,

Zong Wei

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