On 5 Apr 2018, at 12:03, Michal Hocko wrote: > On Thu 05-04-18 18:55:51, Kirill A. Shutemov wrote: >> On Thu, Apr 05, 2018 at 05:05:47PM +0200, Michal Hocko wrote: >>> On Thu 05-04-18 16:40:45, Kirill A. Shutemov wrote: >>>> On Thu, Apr 05, 2018 at 02:48:30PM +0200, Michal Hocko wrote: >>> [...] >>>>> RIght, I confused the two. What is the proper layer to fix that then? >>>>> rmap_walk_file? >>>> >>>> Maybe something like this? Totally untested. >>> >>> This looks way too complex. Why cannot we simply split THP page cache >>> during migration? >> >> This way we unify the codepath for archictures that don't support THP >> migration and shmem THP. > > But why? There shouldn't be really nothing to prevent THP (anon or > shemem) to be migratable. If we cannot migrate it at once we can always > split it. So why should we add another thp specific handling all over > the place?
Then, it would be much easier if your "unclutter thp migration" patches is
merged,
plus the patch below:
diff --git a/mm/migrate.c b/mm/migrate.c
index 60531108021a..b4087aa890f5 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1138,7 +1138,9 @@ static ICE_noinline int unmap_and_move(new_page_t
get_new_page,
int rc = MIGRATEPAGE_SUCCESS;
struct page *newpage;
- if (!thp_migration_supported() && PageTransHuge(page))
+ if ((!thp_migration_supported() ||
+ (thp_migration_supported() && !PageAnon(page))) &&
+ PageTransHuge(page))
return -ENOMEM;
newpage = get_new_page(page, private)
--
Best Regards
Yan Zi
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