From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751768AbaIMN3F (ORCPT ); Sat, 13 Sep 2014 09:29:05 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:59073 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751136AbaIMN3E (ORCPT ); Sat, 13 Sep 2014 09:29:04 -0400 Message-ID: <54144672.9060807@roeck-us.net> Date: Sat, 13 Sep 2014 06:28:18 -0700 From: Guenter Roeck User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0 MIME-Version: 1.0 To: Richard Weinberger , Li RongQing CC: linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, fabf@skynet.be, jkosina@suse.cz, Paul McKenney , oleg@redhat.com, akpm@linux-foundation.org Subject: Re: [RFC][PATCH] signal: replace !likely with unlikely! References: <1410396496-13845-1-git-send-email-roy.qing.li@gmail.com> <20140911191830.GA31511@roeck-us.net> <541416AB.7000808@nod.at> In-Reply-To: <541416AB.7000808@nod.at> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Authenticated_sender: linux@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-CTCH-PVer: 0000001 X-CTCH-Spam: Unknown X-CTCH-VOD: Unknown X-CTCH-Flags: 0 X-CTCH-RefID: str=0001.0A020209.5414469E.0103,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0 X-CTCH-Score: 0.000 X-CTCH-ScoreCust: 0.000 X-CTCH-Rules: X-CTCH-SenderID: linux@roeck-us.net X-CTCH-SenderID-Flags: 0 X-CTCH-SenderID-TotalMessages: 7 X-CTCH-SenderID-TotalSpam: 0 X-CTCH-SenderID-TotalSuspected: 0 X-CTCH-SenderID-TotalConfirmed: 0 X-CTCH-SenderID-TotalBulk: 0 X-CTCH-SenderID-TotalVirus: 0 X-CTCH-SenderID-TotalRecipients: 0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: mailgid no entry from get_relayhosts_entry X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/13/2014 03:04 AM, Richard Weinberger wrote: > Am 13.09.2014 04:48, schrieb Li RongQing: >> I did not test, how to test it? > > Compare the object files of both variants to find out whether both create > semantically equivalent code and whether the un/likely have an effect. > i.e. objdump -S -d kernel/signal.o > I guess you can just remove the likely as gcc is smart enough to detect the "goto ret;" > as an unlikely taken branch. > Or just write similar test code and observe the result. When you are doing that, you might learn that if "(!likely(expression))" is _not_ the same as "if (unlikely(!expression))". Guenter