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First API's don't support it, can't pin memory (which is what a PBO does). Then oh well they are not taking advantage of it. Move the goal post much? TBDR came

First API's don't support it, can't pin memory (which is what a PBO does). Then oh well they are not taking advantage of it. Move the goal post much? TBDR came to prominence in UMA mobile architectures, it's a big part of what allows it to perform so well with limited memory bandwidth. The M1 is just an evolution of Apples mobile designs and PowerVR before that. Mali GPU's are UMA and alway have been AFAIK https://community.arm.com/developer/tools-software/graphics/b/blog/posts/memory-management-on-embedded-graphics-processors https://community.arm.com/developer/tools-software/graphics/...

kllrnohj 5y ago
> First API's don't support it, can't pin memory (which is what a PBO does). Then oh well they are not taking advantage of it. Move the goal post much? No, they don't, so no, I didn't move the goal posts at all. PBOs are a transfer object. You cannot sample from them on the GPU. The only thing you can do with PBOs is copy them to something you can use on the GPU. As such, PBOs do not let you take advantage of UMA. In fact, their primary benefit is for non-UMA in the first place. UMA systems have no issues blocking glTexImage2D until the copy to GPU memory is done, but non-UMA ones do. And non-UMA ones are what gave us PBOs. > TBDR came to prominence in UMA mobile architectures, it's a big part of what allows it to perform so well with limited memory bandwidth. Support that with a theory or evidence of literally any kind. There's nothing at all in TBDR's sequence of events that has any apparent benefit from UMA. Here: https://developer.arm.com/solutions/graphics-and-gaming/developer-guides/learn-the-basics/tile-based-rendering/tile-based-gpus https://developer.arm.com/solutions/graphics-and-gaming/deve... Look at that the sequence of steps. ARM doesn't even bother including a CPU in there, so which step would UMA be helping with? What UMA can do here is improve the power efficiency by reducing the cost of sending the command buffers to the GPU, but that's not going to get you a performance improvement as those command buffers are not very big. If sending data from the CPU to GPU was such a severe bottleneck then you'd see the impact of things like reducing the PCI-E bandwidth on discreet GPUs, but you don't.

kllrnohj 5y ago

> First API's don't support it, can't pin memory (which is what a PBO does). Then oh well they are not taking advantage of it. Move the goal post much? No, they don't, so no, I didn't move the goal posts at all. PBOs are a transfer object. You cannot sample from them on the GPU. The only thing you can do with PBOs is copy them to something you can use on the GPU. As such, PBOs do not let you take advantage of UMA. In fact, their primary benefit is for non-UMA in the first place. UMA systems have no issues blocking glTexImage2D until the copy to GPU memory is done, but non-UMA ones do. And non-UMA ones are what gave us PBOs. > TBDR came to prominence in UMA mobile architectures, it's a big part of what allows it to perform so well with limited memory bandwidth. Support that with a theory or evidence of literally any kind. There's nothing at all in TBDR's sequence of events that has any apparent benefit from UMA. Here: https://developer.arm.com/solutions/graphics-and-gaming/developer-guides/learn-the-basics/tile-based-rendering/tile-based-gpus https://developer.arm.com/solutions/graphics-and-gaming/deve... Look at that the sequence of steps. ARM doesn't even bother including a CPU in there, so which step would UMA be helping with? What UMA can do here is improve the power efficiency by reducing the cost of sending the command buffers to the GPU, but that's not going to get you a performance improvement as those command buffers are not very big. If sending data from the CPU to GPU was such a severe bottleneck then you'd see the impact of things like reducing the PCI-E bandwidth on discreet GPUs, but you don't.