Messages in this thread | ![/](/images/icornerl.gif) | | Date | Tue, 6 Aug 2019 10:58:22 +0000 | From | Balbir Singh <> | Subject | Re: [PATCH] mm/mmap.c: refine data locality of find_vma_prev |
| |
On Tue, Aug 06, 2019 at 04:11:23PM +0800, Wei Yang wrote: > When addr is out of the range of the whole rb_tree, pprev will points to > the biggest node. find_vma_prev gets is by going through the right most > node of the tree. > > Since only the last node is the one it is looking for, it is not > necessary to assign pprev to those middle stage nodes. By assigning > pprev to the last node directly, it tries to improve the function > locality a little. > > Signed-off-by: Wei Yang <richardw.yang@linux.intel.com> > --- > mm/mmap.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index 7e8c3e8ae75f..284bc7e51f9c 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -2271,11 +2271,10 @@ find_vma_prev(struct mm_struct *mm, unsigned long addr, > *pprev = vma->vm_prev; > } else { > struct rb_node *rb_node = mm->mm_rb.rb_node; > - *pprev = NULL; > - while (rb_node) { > - *pprev = rb_entry(rb_node, struct vm_area_struct, vm_rb); > + while (rb_node && rb_node->rb_right) > rb_node = rb_node->rb_right; > - } > + *pprev = rb_node ? NULL > + : rb_entry(rb_node, struct vm_area_struct, vm_rb);
Can rb_node ever be NULL? assuming mm->mm_rb.rb_node is not NULL when we enter here
Balbir Singh
| ![\](/images/icornerr.gif) |