[tleb_]

I see two use cases for a "big" swiotlb buffer: (1) many devices concurrently, as you said, or (2) ring buffers for devices that write continuously. Combine both and you require even more space; knowing the usecase and doing testing becomes required at this point.

[_flux]

While looking into it I found this guy wanting 64 MB swiotlb who was probably doing something like that: https://stackoverflow.com/questions/52833714/change-the-size...

Looks like an exception to the rule, though.

[tleb_]

I've worked on a project that required a bigger swiotlb as well, I don't remember the exact details though. I guess it's not that uncommon, but indeed the default value looks good.