From 38a76013ad809beb0b52f60d365c960d035bd83c Mon Sep 17 00:00:00 2001 From: Michel Lespinasse Date: Mon, 8 Oct 2012 16:31:50 -0700 Subject: mm: avoid taking rmap locks in move_ptes() During mremap(), the destination VMA is generally placed after the original vma in rmap traversal order: in move_vma(), we always have new_pgoff >= vma->vm_pgoff, and as a result new_vma->vm_pgoff >= vma->vm_pgoff unless vma_merge() merged the new vma with an adjacent one. When the destination VMA is placed after the original in rmap traversal order, we can avoid taking the rmap locks in move_ptes(). Essentially, this reintroduces the optimization that had been disabled in "mm anon rmap: remove anon_vma_moveto_tail". The difference is that we don't try to impose the rmap traversal order; instead we just rely on things being in the desired order in the common case and fall back to taking locks in the uncommon case. Also we skip the i_mmap_mutex in addition to the anon_vma lock: in both cases, the vmas are traversed in increasing vm_pgoff order with ties resolved in tree insertion order. Signed-off-by: Michel Lespinasse Cc: Andrea Arcangeli Cc: Rik van Riel Cc: Peter Zijlstra Cc: Daniel Santos Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mm.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'include/linux/mm.h') diff --git a/include/linux/mm.h b/include/linux/mm.h index 0e6f9c9f2123..0d5f823ce3fc 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1060,7 +1060,8 @@ vm_is_stack(struct task_struct *task, struct vm_area_struct *vma, int in_group); extern unsigned long move_page_tables(struct vm_area_struct *vma, unsigned long old_addr, struct vm_area_struct *new_vma, - unsigned long new_addr, unsigned long len); + unsigned long new_addr, unsigned long len, + bool need_rmap_locks); extern unsigned long do_mremap(unsigned long addr, unsigned long old_len, unsigned long new_len, unsigned long flags, unsigned long new_addr); @@ -1410,7 +1411,8 @@ extern void __vma_link_rb(struct mm_struct *, struct vm_area_struct *, struct rb_node **, struct rb_node *); extern void unlink_file_vma(struct vm_area_struct *); extern struct vm_area_struct *copy_vma(struct vm_area_struct **, - unsigned long addr, unsigned long len, pgoff_t pgoff); + unsigned long addr, unsigned long len, pgoff_t pgoff, + bool *need_rmap_locks); extern void exit_mmap(struct mm_struct *); extern int mm_take_all_locks(struct mm_struct *mm); -- cgit v1.2.3