On Tue 29-11-16 07:50:06, Naoya Horiguchi wrote: > On Mon, Nov 28, 2016 at 03:21:54PM +0100, Michal Hocko wrote: > > On Tue 08-11-16 08:31:49, Naoya Horiguchi wrote: > > > Introduces CONFIG_ARCH_ENABLE_THP_MIGRATION to limit thp migration > > > functionality to x86_64, which should be safer at the first step. > > > > Please make sure to describe why this has to be arch specific and what > > are arches supposed to provide in order to enable this option. > > OK, the below will be added in the future version: > > Thp migration is an arch-specific feature because it depends on the > arch-dependent behavior of non-present format of page table entry. > What you need to enable this option in other archs are: > - to define arch-specific transformation functions like __pmd_to_swp_entry() > and __swp_entry_to_pmd(), > - to make sure that arch-specific page table walking code can properly > handle > !pmd_present case (gup_pmd_range() is a good example), > - (if your archs enables CONFIG_HAVE_ARCH_SOFT_DIRTY,) to define soft dirty > routines like pmd_swp_mksoft_dirty.
Thanks this is _much_ better! -- Michal Hocko SUSE Labs
