On Tue 26-03-13 16:35:35, Naoya Horiguchi wrote: [...] > The differences is that migrate_huge_page() has one hugepage as an argument, > and migrate_pages() has a pagelist with multiple hugepages. > I already told this before and I'm not sure it's enough to answer the question, > so I explain another point about why this patch do like it. OK, I am blind. It is + list_move(&hpage->lru, &pagelist); + ret = migrate_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL, + MIGRATE_SYNC, MR_MEMORY_FAILURE); which moves it from active_list and so you have to put it back. > I think that we must do putback_*pages() for source pages whether migration > succeeds or not. > But when we call migrate_pages() with a pagelist, > the caller can't access to the successfully migrated source pages > after migrate_pages() returns, because they are no longer on the pagelist. > So putback of the successfully migrated source pages should be done *in* > unmap_and_move() and/or unmap_and_move_huge_page(). If the migration succeeds then the page becomes unused and free after its last reference drops. So I do not see any reason to put it back to active list and free it right afterwards. On the other hand unmap_and_move does the same thing (although page reference counting is a bit more complicated in that case) so it would be good to keep in sync with regular pages case. > And when we used migrate_huge_page(), we passed a hugepage to be migrated > as an argument, so the caller can still access to the page even if the > migration succeeds. [...] -- Michal Hocko SUSE Labs -- 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>