On Mon, May 08, 2023 at 12:20:42AM +0100, Matthew Wilcox wrote: > > I see there's a couple of spots on the schedule open, so here's something > fun we could talk about. > > Highmem was originally introduced to support PAE36 (up to 64GB) on x86 > in the late 90s. It's since been used to support a similar extension > on ARM (maybe other 32-bit architectures?) > > Things have changed a bit since then. There aren't a lot of systems > left which have more than 4GB of memory _and_ are incapable of running a > 64-bit kernel. Actual limit is lower. With 3G/1G userspace/kernel split you will have somewhere about 700Mb of virtual address space for direct mapping. But, I would like to get rid of highmem too. Not sure how realistic it is. -- Kiryl Shutsemau / Kirill A. Shutemov
