From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752607Ab1A0Ruq (ORCPT ); Thu, 27 Jan 2011 12:50:46 -0500 Received: from mail3.caviumnetworks.com ([12.108.191.235]:18833 "EHLO mail3.caviumnetworks.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751376Ab1A0Rup (ORCPT ); Thu, 27 Jan 2011 12:50:45 -0500 Message-ID: <4D41B06F.8070804@caviumnetworks.com> Date: Thu, 27 Jan 2011 09:50:39 -0800 From: David Daney User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.15) Gecko/20101027 Fedora/3.0.10-1.fc12 Thunderbird/3.0.10 MIME-Version: 1.0 To: Coly Li CC: linux-kernel@vger.kernel.org, Wang Cong , Yong Zhang , linux-mips , Ralf Baechle Subject: Re: [PATCH 1/7] MIPS: add unlikely() to BUG_ON() References: <1296130356-29896-1-git-send-email-bosong.ly@taobao.com> <1296130356-29896-2-git-send-email-bosong.ly@taobao.com> In-Reply-To: <1296130356-29896-2-git-send-email-bosong.ly@taobao.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 27 Jan 2011 17:50:45.0114 (UTC) FILETIME=[B904ADA0:01CBBE4A] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Please Cc: linux-mips@linux-mips.org for MIPS patches. On 01/27/2011 04:12 AM, Coly Li wrote: > Current BUG_ON() in arch/mips/include/asm/bug.h does not use unlikely(), > in order to get better branch predict result, source code should call > BUG_ON() with unlikely() explicitly. This is not a suggested method to > use BUG_ON(). > > This patch adds unlikely() inside BUG_ON implementation on MIPS code, > callers can use BUG_ON without explicit unlikely() now. > > I have no usable MIPS hardware to build and test the fix, any test result > of this patch is welcome. > > Signed-off-by: Coly Li > Cc: David Daney > Cc: Wang Cong > Cc: Yong Zhang > --- > arch/mips/include/asm/bug.h | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/arch/mips/include/asm/bug.h b/arch/mips/include/asm/bug.h > index 540c98a..6771c07 100644 > --- a/arch/mips/include/asm/bug.h > +++ b/arch/mips/include/asm/bug.h > @@ -30,7 +30,7 @@ static inline void __BUG_ON(unsigned long condition) > : : "r" (condition), "i" (BRK_BUG)); > } > > -#define BUG_ON(C) __BUG_ON((unsigned long)(C)) > +#define BUG_ON(C) __BUG_ON((unsigned long)unlikely(C)) > NAK. __BUG_ON() expands to a single instruction. Frobbing about with unlikely() will have no effect on the generated code and is thus gratuitous code churn. David Daney