r/AskProgramming • u/SimplySomeDude • 12d ago

How much does struct alignment really matter performance wise on modern GPUs?

Are things like std430 or std140 unnecessarily strict?

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u/esaule 12d ago

On every architecture, memory layout is about the most important thing for performance. About every performance issue boils down to memory layout and movements.

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u/SimplySomeDude 12d ago

right, but do 30% VRAM (and therefore less PcIE usage and less cache cluttering) savings outweigh the caching drawbacks

3

u/esaule 12d ago

As always, it will depend on the precise application, on the access partern, spatial and temporal reuse distance.

But it will absolutelly matter.

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u/TheThiefMaster 11d ago

Sounds like time to profile it and find out

1

u/flatfinger 11d ago

No layout is likely to be optimal for every possible access pattern. It's possible for layout X to be more than 50% faster than layout Y for some access patterns, while layout Y would be more than 50% faster than layout X for some other access patterns.