From: Nick Piggin Date: Sat, 3 Sep 2005 22:54:47 +0000 (-0700) Subject: [PATCH] mm: micro-optimise rmap X-Git-Tag: v2.6.14-rc1~972 X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=2822c1aa574d277b9ba0130b1e71c1a5874bc04a;p=linux-2.6-omap-h63xx.git [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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/rmap.c b/mm/rmap.c index f5a6966b7eb..7e975ca24c7 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -439,22 +439,23 @@ int page_referenced(struct page *page, int is_locked, int ignore_token) 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 */