From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <42BA5F7B.30904@yahoo.com.au> Date: Thu, 23 Jun 2005 17:06:35 +1000 From: Nick Piggin MIME-Version: 1.0 Subject: [patch][rfc] 2/5: micro optimisation for mm/rmap.c References: <42BA5F37.6070405@yahoo.com.au> <42BA5F5C.3080101@yahoo.com.au> In-Reply-To: <42BA5F5C.3080101@yahoo.com.au> Content-Type: multipart/mixed; boundary="------------060707040302090207070309" Sender: owner-linux-mm@kvack.org Return-Path: To: linux-kernel , Linux Memory Management Cc: Hugh Dickins , Badari Pulavarty List-ID: This is a multi-part message in MIME format. --------------060707040302090207070309 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit 2/5 --------------060707040302090207070309 Content-Type: text/plain; name="mm-microopt-rmap.patch" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="mm-microopt-rmap.patch" 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 Index: linux-2.6/mm/rmap.c =================================================================== --- linux-2.6.orig/mm/rmap.c +++ linux-2.6/mm/rmap.c @@ -442,22 +442,23 @@ 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 */ --------------060707040302090207070309-- Send instant messages to your online friends http://au.messenger.yahoo.com -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org