Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752206AbZGXJkq (ORCPT ); Fri, 24 Jul 2009 05:40:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751962AbZGXJkp (ORCPT ); Fri, 24 Jul 2009 05:40:45 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:55707 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1750893AbZGXJko (ORCPT ); Fri, 24 Jul 2009 05:40:44 -0400 Message-ID: <4A698195.3020504@cn.fujitsu.com> Date: Fri, 24 Jul 2009 17:40:37 +0800 From: Xiao Guangrong User-Agent: Thunderbird 2.0.0.6 (Windows/20070728) MIME-Version: 1.0 To: Peter Zijlstra CC: Ingo Molnar , Thomas Gleixner , Steven Rostedt , Frederic Weisbecker , Zhaolei , kosaki.motohiro@jp.fujitsu.com, Mathieu Desnoyers , Anton Blanchard , LKML Subject: Re: [PATCH v3 3/4] ftrace: add tracepoint for hrtimer References: <4A604E46.5050903@cn.fujitsu.com> <4A605009.8060806@cn.fujitsu.com> <1247827801.15751.4.camel@twins> <4A641BFC.2050508@cn.fujitsu.com> <1248091771.15751.8578.camel@twins> <4A66DDB6.4000700@cn.fujitsu.com> <1248257598.27058.1227.camel@twins> <4A6834EA.3070303@cn.fujitsu.com> <1248343661.27058.1722.camel@twins> In-Reply-To: <1248343661.27058.1722.camel@twins> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1178 Lines: 41 Peter Zijlstra wrote: > On Thu, 2009-07-23 at 18:01 +0800, Xiao Guangrong wrote: >> Peter Zijlstra wrote: >> >>> OK, so what you want to measure is the time of the actual callback >>> happening (hrtimer_entry) vs that where you would have expected it to >>> happen (hrtimer_start + delay), right? >>> >> Yes >> >>> So what's wrong with printing the expected expiration time in the >>> hrtimer_start tracepoint in the cheap clock units? >>> >> Is "cheap clock units" means jiffies time? > > Nah, something like cpu_clock() which is monotonic per-cpu and should > have high resolution where available. > Hi Peter, Thanks for your valuable suggestion. I have do some test for it, and it very suitable for CLOCK_MONOTONIC clock, but if the hrtimer's clock is CLOCK_REALTIME, however xtime is needed to get the real time. In addition, it make TP_fast_assign() become a slow path, we should avoid it if possible. Thanks, Xiao > -- 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/