From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932196AbcEFRdf (ORCPT ); Fri, 6 May 2016 13:33:35 -0400 Received: from mail-lf0-f42.google.com ([209.85.215.42]:36585 "EHLO mail-lf0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756308AbcEFRde (ORCPT ); Fri, 6 May 2016 13:33:34 -0400 Date: Fri, 6 May 2016 20:33:30 +0300 From: "Kirill A. Shutemov" To: Andrea Arcangeli Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Alex Williamson Subject: Re: [PATCH 2/3] mm: thp: microoptimize compound_mapcount() Message-ID: <20160506173330.GA9879@node.shutemov.name> References: <1462547040-1737-1-git-send-email-aarcange@redhat.com> <1462547040-1737-3-git-send-email-aarcange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1462547040-1737-3-git-send-email-aarcange@redhat.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 06, 2016 at 05:03:59PM +0200, Andrea Arcangeli wrote: > compound_mapcount() is only called after PageCompound() has already > been checked by the caller, so there's no point to check it again. Gcc > may optimize it away too because it's inline but this will remove the > runtime check for sure and add it'll add an assert instead. > > Signed-off-by: Andrea Arcangeli Acked-by: Kirill A. Shutemov > --- > include/linux/mm.h | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 263f229..726ba80 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -471,8 +471,7 @@ static inline atomic_t *compound_mapcount_ptr(struct page *page) > > static inline int compound_mapcount(struct page *page) > { > - if (!PageCompound(page)) > - return 0; > + VM_BUG_ON_PAGE(!PageCompound(page), page); > page = compound_head(page); > return atomic_read(compound_mapcount_ptr(page)) + 1; > } -- Kirill A. Shutemov