Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932539Ab3D3RwF (ORCPT ); Tue, 30 Apr 2013 13:52:05 -0400 Received: from oproxy6-pub.bluehost.com ([67.222.54.6]:58605 "HELO oproxy6-pub.bluehost.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1760855Ab3D3RwD (ORCPT ); Tue, 30 Apr 2013 13:52:03 -0400 Message-ID: <1367344318.8833.59.camel@Wailaba2> Subject: Re: [PATCH 2/3] posix_timers: Defer per process timer stop after timers processing From: Olivier Langlois To: Frederic Weisbecker Cc: Ingo Molnar , LKML , Chris Metcalf , Christoph Lameter , Geoff Levand , Gilad Ben Yossef , Hakan Akkan , Kevin Hilman , Li Zhong , Oleg Nesterov , "Paul E. McKenney" , Paul Gortmaker , Peter Zijlstra , Steven Rostedt , Thomas Gleixner Date: Tue, 30 Apr 2013 13:51:58 -0400 In-Reply-To: <20130430125423.GB8272@somewhere> References: <1366305822-5499-1-git-send-email-fweisbec@gmail.com> <1366305822-5499-3-git-send-email-fweisbec@gmail.com> <1366345802.2855.38.camel@Wailaba2> <1366950479.7911.22.camel@Wailaba2> <20130430125423.GB8272@somewhere> Organization: Trillion01 Inc Content-Type: text/plain; charset="ISO-8859-1" X-Mailer: Evolution 3.8.1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Identified-User: {5686:box610.bluehost.com:olivierl:trillion01.com} {sentby:smtp auth 173.178.230.31 authed with olivier@trillion01.com} Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 915 Lines: 27 > > > Maybe the condition around the posix_cpu_timer_schedule() block inside > > cpu_timer_fire() could even be a good candidate for 'unlikely' > > qualifier. > > Well, cpu_timer_fire() is probably not a fast path. So helping branch > prediction there probably won't have much measurable effect in practice. > Frederic, I'm totally sure that you are right on the measurable effect. When I did propose the 'unlikely' qualifier, please note, that I also had a documentary purpose in mind. Would you have searched the 'likely' path that does posix_cpu_timer_schedule() when you did modify the code if the 'unlikely' tag would have been present? Greetings, Olivier -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/