On Tue, Feb 7, 2017 at 9:40 AM, Kirill A. Shutemov <kirill@xxxxxxxxxxxxx> wrote: > On Tue, Feb 07, 2017 at 08:56:56AM -0800, Dan Williams wrote: >> On Tue, Feb 7, 2017 at 12:44 AM, Kirill A. Shutemov >> <kirill@xxxxxxxxxxxxx> wrote: >> > On Mon, Feb 06, 2017 at 09:30:22AM -0800, Dan Williams wrote: >> >> On Mon, Feb 6, 2017 at 9:27 AM, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: >> >> > On Mon, Feb 06, 2017 at 08:24:48AM -0800, Dan Williams wrote: >> >> >> > Also can be use this opportunity >> >> >> > to fold ->huge_fault into ->fault? >> > >> > BTW, for tmpfs we already use ->fault for both small and huge pages. >> > If ->fault returned THP, core mm look if it's possible to map the page as >> > huge in this particular VMA (due to size/alignment). If yes mm maps the >> > page with PMD, if not fallback to PTE. >> > >> > I think it would be nice to do the same for DAX: filesystem provides core >> > mm with largest page this part of file can be mapped with (base aligned >> > address + lenght for DAX) and core mm sort out the rest. >> >> For DAX we would need plumb pfn_t into the core mm so that we have the >> PFN_DEV and PFN_MAP flags beyond the raw pfn. > > Sounds good to me. > >> >> >> Hmm, yes, just need a scheme to not attempt huge_faults on pte-only handlers. >> >> > >> >> > Do we need anything more than checking vma->vm_flags for VM_HUGETLB? >> >> >> >> s/VM_HUGETLB/VM_HUGEPAGE/ >> >> >> >> ...but yes as long as we specify that a VM_HUGEPAGE handler must >> >> minimally handle pud and pmd. >> > >> > VM_HUGEPAGE is result of MADV_HUGEPAGE. It's not required to have THP in >> > the VMA. >> >> Filesystem-DAX and Device-DAX specify VM_HUGEPAGE by default. > > But why? Looks like abuse of the flag. Good question, that's been there since DAX was initially added and I don't see a good reason for it currently. I'll take a look at what you have for huge-tmpfs support. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
