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

Nick Piggin
2005-06-23T07:33:33Z

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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?

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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);
}