"Kirill A. Shutemov" <kir...@shutemov.name> writes: > On Sun, May 18, 2014 at 07:45:59PM -0400, Matthew Wilcox wrote: >> On Sat, May 17, 2014 at 03:33:05AM +0300, Kirill A. Shutemov wrote: >> > Below is my attempt to play with the problem. I've took one function -- >> > page_referenced_one() -- which looks ugly because of different APIs for >> > PTE/PMD and convert it to use vpte_t. vpte_t is union for pte_t, pmd_t >> > and pud_t. >> > >> > Basically, the idea is instead of having different helpers to handle >> > PTE/PMD/PUD, we have one, which take pair of vpte_t + pglevel. >> >> I can't find my original attempt at this now (I am lost in a maze of >> twisted git trees, all subtly different), but I called it a vpe (Virtual >> Page Entry). >> >> Rather than using a pair of vpte_t and pglevel, the vpe_t contained >> enough information to discern what level it was; that's only two bits >> and I think all the architectures have enough space to squeeze in two >> more bits to the PTE (the PMD and PUD obviously have plenty of space). > > I'm not sure if it's possible to find a single free bit on all > architectures. Two is near impossible.
On ppc64 we don't have any free bits. > > And what about 5-level page tables in future? Will we need 3 bits there? > No way. -aneesh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
