[imtringued]

Letting the CPU burn cycles by accessing memory mapped device memory instead of using DMA like in the good old days? What even is this question?

[wtallis]

> accessing memory mapped device memory instead of using DMA like in the good old days

That's not actually an option for NVMe devices, is it? The actual NAND storage isn't available for direct memory mapping, and the only way to access it is to set up DMA transfers.