Hi, On 25/08/2023 12:34, Vlad Zahorodnii wrote:
I'm really curious here, and these aren't rhetorical questions: why would anyone expect to be a difference in performance, as far as QPainter is concerned? Isn't it ultimately just using a CPU-based renderer onto a block of memory? Why should it make a difference where that memory comes from / how it's managed / etc.? Are we're talking about "far memory" (NUMA-like) scenarios?
It makes a difference to the compositor. The compositor will have to upload pixel data from RAM to VRAM so it can composite the windows using OpenGL or Vulkan. If the client provides dmabuf client buffers, the compositor can skip the uploading step thus reduce the amount of time it takes to compose a frame.
Thanks, this part was OK with me. I was confused by the previous emails possibly implying that QPainter-based painting *alone* was making a difference between DMA and SHM, and couldn't understand why.
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