diff options
| author | Michel Lespinasse | 2012-10-08 16:31:50 -0700 |
|---|---|---|
| committer | Linus Torvalds | 2012-10-09 16:22:42 +0900 |
| commit | 38a76013ad809beb0b52f60d365c960d035bd83c (patch) | |
| tree | c63ba707ab17dd1ff1e90650faf74570daa3cf9f /include/linux/mm.h | |
| parent | 523d4e2008fd4a68b1a164e63e8c75b7b20f07e0 (diff) | |
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 <walken@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Daniel Santos <daniel.santos@pobox.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/mm.h')
| -rw-r--r-- | include/linux/mm.h | 6 |
1 files changed, 4 insertions, 2 deletions
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); |