On Tue, Oct 22, 2019 at 01:30:26PM -0400, Jerome Glisse wrote: > > Smart drivers can test somehow for pfn == zero_page and optimize? > > There is nothing to optimize here, i do not know any hardware that > have a special page table entry that make all memory access return > zero. Presumably any GPU could globally dedicate one page of internal memory as a zero page and remap CPU zero page to that internal memory page? This is basically how the CPU zero page works. I suspect mlx5 could do the same with its internal memory, but the internal memory is too limited to make this worth while. mlx5 also has a specially 'zero MR' that always reads as zero (and discards writes), but it doesn't quite fit well into the ODP flow. Jason
