Re: [patch][rfc] 2/5: micro optimisation for mm/rmap.c

[Nick Piggin]

William Lee Irwin III wrote:
> On Thu, Jun 23, 2005 at 05:06:35PM +1000, Nick Piggin wrote:
>
> > +		index = (address - vma->vm_start) >> PAGE_SHIFT;
> > +		index += vma->vm_pgoff;
> > +		index >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
> > +		page->index = index;
>
>
> linear_page_index()

Ah indeed it is, thanks. I'll queue this up as patch 2.5, then?

Use linear_page_index in mm/rmap.c, as noted by Bill Irwin.

Index: linux-2.6/mm/rmap.c
===================================================================
--- linux-2.6.orig/mm/rmap.c
+++ linux-2.6/mm/rmap.c
@@ -448,16 +448,11 @@ void page_add_anon_rmap(struct page *pag
 
 	if (atomic_inc_and_test(&page->_mapcount)) {
 		struct anon_vma *anon_vma = vma->anon_vma;
-		pgoff_t index;
-
 		BUG_ON(!anon_vma);
 		anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
 		page->mapping = (struct address_space *) anon_vma;
 
-		index = (address - vma->vm_start) >> PAGE_SHIFT;
-		index += vma->vm_pgoff;
-		index >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
-		page->index = index;
+		page->index = linear_page_index(vma, address);
 
 		inc_page_state(nr_mapped);
 	}