On Wed, Jan 12, 2022 at 06:37:03PM +0000, Matthew Wilcox wrote: > But let's go further than that (which only brings us to 32 bytes per > range). For the systems you care about which use an identity mapping, > and have sizeof(dma_addr_t) == sizeof(phys_addr_t), we can simply > point the dma_range pointer to the same memory as the phyr. We just > have to not free it too early. That gets us down to 16 bytes per range, > a saving of 33%. Even without an IOMMU the dma_addr_t can have offsets vs the actual physical address. Not on x86 except for a weirdo SOC, but just about everywhere else.
