From: Nick Piggin <nickpiggin@yahoo.com.au>
Microoptimise page_add_anon_rmap. Although these expressions are used only in
the taken branch of the if() statement, the compiler can't reorder them inside
because atomic_inc_and_test is a barrier.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
mm/rmap.c | 21 +++++++++++----------
1 files changed, 11 insertions(+), 10 deletions(-)
diff -puN mm/rmap.c~mm-micro-optimise-rmap mm/rmap.c
--- 25/mm/rmap.c~mm-micro-optimise-rmap Tue Jul 26 13:29:10 2005
+++ 25-akpm/mm/rmap.c Tue Jul 26 13:29:10 2005
@@ -443,22 +443,23 @@ int page_referenced(struct page *page, i
void page_add_anon_rmap(struct page *page,
struct vm_area_struct *vma, unsigned long address)
{
- struct anon_vma *anon_vma = vma->anon_vma;
- pgoff_t index;
-
BUG_ON(PageReserved(page));
- BUG_ON(!anon_vma);
inc_mm_counter(vma->vm_mm, anon_rss);
- anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
- index = (address - vma->vm_start) >> PAGE_SHIFT;
- index += vma->vm_pgoff;
- index >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
-
if (atomic_inc_and_test(&page->_mapcount)) {
- page->index = index;
+ 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;
+
inc_page_state(nr_mapped);
}
/* else checking page index and mapping is racy */
_