On Sat, 5 Nov 2011, Andrea Arcangeli wrote: > migrate was doing a rmap_walk with speculative lock-less access on > pagetables. That could lead it to not serialize properly against > mremap PT locks. But a second problem remains in the order of vmas in > the same_anon_vma list used by the rmap_walk. > > If vma_merge would succeed in copy_vma, the src vma could be placed > after the dst vma in the same_anon_vma list. That could still lead > migrate to miss some pte. > > This patch adds a anon_vma_moveto_tail() function to force the dst vma > at the end of the list before mremap starts to solve the problem. > > If the mremap is very large and there are a lots of parents or childs > sharing the anon_vma root lock, this should still scale better than > taking the anon_vma root lock around every pte copy practically for > the whole duration of mremap. > > Update: Hugh noticed special care is needed in the error path where > move_page_tables goes in the reverse direction, a second > anon_vma_moveto_tail() call is needed in the error path. > Is this still needed? It's missing in linux-next. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>