From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754958AbaGNMja (ORCPT ); Mon, 14 Jul 2014 08:39:30 -0400 Received: from mail.efficios.com ([78.47.125.74]:47941 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754575AbaGNMjZ (ORCPT ); Mon, 14 Jul 2014 08:39:25 -0400 Date: Mon, 14 Jul 2014 12:39:26 +0000 (UTC) From: Mathieu Desnoyers To: Peter Zijlstra Cc: Thomas Gleixner , LKML , John Stultz , Steven Rostedt Message-ID: <1154261133.13906.1405341566164.JavaMail.zimbra@efficios.com> In-Reply-To: <20140714094750.GO9918@twins.programming.kicks-ass.net> References: <20140711133623.530368377@linutronix.de> <20140711133709.835700036@linutronix.de> <20140714094750.GO9918@twins.programming.kicks-ass.net> Subject: Re: [patch 54/55] timekeeping: Provide fast and NMI safe access to CLOCK_MONOTONIC[_RAW] MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [206.248.138.119] X-Mailer: Zimbra 8.0.7_GA_6021 (ZimbraWebClient - FF30 (Linux)/8.0.7_GA_6021) Thread-Topic: timekeeping: Provide fast and NMI safe access to CLOCK_MONOTONIC[_RAW] Thread-Index: BfeNE5gAcsbYb1pJr1Ukc0rO90/9Qw== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- Original Message ----- > From: "Peter Zijlstra" > To: "Thomas Gleixner" > Cc: "LKML" , "John Stultz" , "Steven Rostedt" > , "Mathieu Desnoyers" > Sent: Monday, July 14, 2014 5:47:50 AM > Subject: Re: [patch 54/55] timekeeping: Provide fast and NMI safe access to CLOCK_MONOTONIC[_RAW] > > On Fri, Jul 11, 2014 at 01:45:19PM -0000, Thomas Gleixner wrote: > > +static struct tk_fast tk_fast_raw ____cacheline_aligned; > > +static struct tk_fast tk_fast_mono ____cacheline_aligned; > > Question to the 'trace maniacs'; why do you lot need access to mono_raw? > > I would much prefer to limit choice here. For LTTng, which I guess qualifies as bring part of the aforementioned trace maniacs group, we only need the "tk_fast_mono" clock. We don't need mono_raw. We can then correlate with user-space traces by using tk_fast_mono in kernel-space and using CLOCK_MONOTONIC in userspace. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com