the reasonable assumption is that the CPU still mmap()es the file into the GPU’s address space, and then the CPU pages in data from the SSD as the GPU generates page misses.
You seem to know quite a bit about this - just wondering - how does this work? The GPU can generate PCIe bus traffic to do RAM reads or writes, but how does it cause a page fault in the CPU? Is this some kind of IOMMU? Is there any place I can read more about this?
I don't think the GPU can generate page faults in the traditional sense (which core would #PF be delivered to?). The CPU has to pre-fetch data before the GPU tries to use it. On the PS5, the GPU may be able to issue read requests directly to the IO coprocessor and have it load data off the SSD, run it through the decompressor, place the data into the requested DRAM addresses, and invalidate the necessary cache lines in any GPU or CPU cores. But I'm not sure that the PS5 can actually do that with zero CPU involvement.
You seem to know quite a bit about this - just wondering - how does this work? The GPU can generate PCIe bus traffic to do RAM reads or writes, but how does it cause a page fault in the CPU? Is this some kind of IOMMU? Is there any place I can read more about this?