On Wed, Sep 27, 2017 at 8:39 AM, Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> wrote: > On Wed, Sep 27, 2017 at 01:35:27PM +0200, Jan Kara wrote: [..] >> Hum, this is an interesting option. So do you suggest that filesystems >> supporting DAX would always setup mappings with VM_MIXEDMAP and without >> VM_HUGEPAGE and thus we'd get rid of dependency on S_DAX flag in ->mmap? >> That could actually work. The only possible issue I can see is that >> VM_MIXEDMAP is still slightly different from normal page mappings and it >> could have some performance implications - e.g. copy_page_range() does more >> work on VM_MIXEDMAP mappings but not on normal page mappings. > > It looks like having VM_MIXEDMAP always set for filesystems that support DAX > might affect their memory's NUMA migration in the non-DAX case? > > 8e76d4e sched, numa: do not hint for NUMA balancing on VM_MIXEDMAP mappings Addressed separately here: c1ef8e2c0235 mm: disable numa migration faults for dax vmas
