Re: [PATCH V2 2/5] mm/hugetlb: Distinguish between migratability and movability

[Anshuman Khandual <anshuman.khandual@arm.com>]

On 10/19/2018 07:29 AM, Naoya Horiguchi wrote:
> On Fri, Oct 12, 2018 at 09:29:56AM +0530, Anshuman Khandual wrote:
>> During huge page allocation it's migratability is checked to determine if
>> it should be placed under movable zones with GFP_HIGHUSER_MOVABLE. But the
>> movability aspect of the huge page could depend on other factors than just
>> migratability. Movability in itself is a distinct property which should not
>> be tied with migratability alone.
>>
>> This differentiates these two and implements an enhanced movability check
>> which also considers huge page size to determine if it is feasible to be
>> placed under a movable zone. At present it just checks for gigantic pages
>> but going forward it can incorporate other enhanced checks.
> 
> (nitpicking...)
> The following code just checks hugepage_migration_supported(), so maybe
> s/Movability/Migratability/ is expected in the comment?
> 
>   static int unmap_and_move_huge_page(...)
>   {
>           ...
>           /*
>            * Movability of hugepages depends on architectures and hugepage size.
>            * This check is necessary because some callers of hugepage migration
>            * like soft offline and memory hotremove don't walk through page
>            * tables or check whether the hugepage is pmd-based or not before
>            * kicking migration.
>            */
>           if (!hugepage_migration_supported(page_hstate(hpage))) {
> 
Sure, will update this patch only unless other changes are suggested.