From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758393Ab3LFSYe (ORCPT ); Fri, 6 Dec 2013 13:24:34 -0500 Received: from mga01.intel.com ([192.55.52.88]:16023 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753446Ab3LFSYd (ORCPT ); Fri, 6 Dec 2013 13:24:33 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.93,842,1378882800"; d="scan'208";a="445883641" From: Andi Kleen To: Jaegeuk Kim Cc: unlisted-recipients:;;linux-fsdevel@vger.kernel.org (no To-header on input), linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, Chao Yu Illegal-Object: Syntax error in Cc: address found on vger.kernel.org: Cc: unlisted-recipients:; (no To-header on input)linux-fsdevel@vger.kernel.org ^-missing end of address Subject: Re: [PATCH] f2fs: add unlikely() macro for compiler more aggressively References: <1386310509-5864-1-git-send-email-jaegeuk.kim@samsung.com> Date: Fri, 06 Dec 2013 10:24:31 -0800 In-Reply-To: <1386310509-5864-1-git-send-email-jaegeuk.kim@samsung.com> (Jaegeuk Kim's message of "Fri, 06 Dec 2013 15:15:09 +0900") Message-ID: <87siu5vnvk.fsf@tassilo.jf.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jaegeuk Kim writes: > struct page *page; > repeat: > page = grab_cache_page(mapping, index); > - if (!page) { > + if (unlikely(!page)) { This is completely pointless, gcc already considers any test for NULL unlikely. In general i would advise against splattering unlikely all over your code, the benefits are very minimal and programers often get it wrong. -Andi -- ak@linux.intel.com -- Speaking for myself only