Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753208AbZG1BnP (ORCPT ); Mon, 27 Jul 2009 21:43:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753125AbZG1BnP (ORCPT ); Mon, 27 Jul 2009 21:43:15 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:46312 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751597AbZG1BnO (ORCPT ); Mon, 27 Jul 2009 21:43:14 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 From: KOSAKI Motohiro To: Steven Rostedt Subject: Re: [PATCH 0/3] Add walltime support for ring-buffer Cc: kosaki.motohiro@jp.fujitsu.com, Zhaolei , Frederic Weisbecker , Ingo Molnar , LKML In-Reply-To: References: <4A698F90.90501@cn.fujitsu.com> Message-Id: <20090728103227.D7FB.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.50.07 [ja] Date: Tue, 28 Jul 2009 10:43:11 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1403 Lines: 38 Hi Zhaolei, > Hi Zhaolei, > > Could you not just save the wall time in some 64bit format within the > current timestamp? Right now there's three clocks that can be used by > ftrace. Two that you can really get two (I need to add access to the > third). The default clock is sched_clock. But there's an option to get to > global_clock: > > debug/tracing/options/global-clock > > # echo 1 > /debug/tracing/options/global-clock > > Will enable the global clock. Perhaps we can add a "wall clock" version > that will map the timestamps to the wall clock? > > I really hate adding any more fields to the ring buffer headers. That > takes away from the amount that you can record per page. I think wall-time recording on every event is too slow. slower tracer isn't useful. Instead, Can we make pseudo wall-time recording event periodically? In nowadays, many workload run on cluster machine environment. Then We often need compare different machines tracing log. it mean TSC isn't sufficient. but nobody want performance reduce. Fortunatelly, ntp time adjustment is not happend so frequently. we don't need wall-time on _every_ event. Thanks. -- 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/