On Thu, 2018-03-01 at 14:57 -0700, Logan Gunthorpe wrote: > > On 01/03/18 02:45 PM, Logan Gunthorpe wrote: > > It handles it fine for many situations. But when you try to map > > something that is at the end of the physical address space then the > > spares-vmemmap needs virtual address space that's the size of the > > physical address space divided by PAGE_SIZE which may be a little bit > > too large... > > Though, considering this more, maybe this shouldn't be a problem... > > Lets say you have 56bits of address space.
We use only 52 in practice but yes. > That's 64PB. If you use need > a sparse vmemmap for the entire space it will take 16TB which leaves you > with 63.98PB of address space left. (Similar calculations for other > numbers of address bits.) We only have 52 bits of virtual space for the kernel with the radix MMU. > So I'm not sure what the problem with this is. > > We still have to ensure all the arches map the memory with the right > cache bits but that should be relatively easy to solve. > > Logan
