[PATCH] mm: micro-optimise rmap
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>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/rmap.c b/mm/rmap.c
index f5a6966..7e975ca 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -439,22 +439,23 @@
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 */