Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756782Ab3HZOWb (ORCPT ); Mon, 26 Aug 2013 10:22:31 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:33718 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751429Ab3HZOWa (ORCPT ); Mon, 26 Aug 2013 10:22:30 -0400 X-Authority-Analysis: v=2.0 cv=KJ7Y/S5o c=1 sm=0 a=Sro2XwOs0tJUSHxCKfOySw==:17 a=Drc5e87SC40A:10 a=dRXjL8aGtIIA:10 a=5SG0PmZfjMsA:10 a=kj9zAlcOel0A:10 a=meVymXHHAAAA:8 a=KGjhK52YXX0A:10 a=vCXdsJORpdIA:10 a=3nbZYyFuAAAA:8 a=fVj-U3WoxfrRRX2cS3kA:9 a=CjuIK1q_8ugA:10 a=EvKJbDF4Ut8A:10 a=Sro2XwOs0tJUSHxCKfOySw==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 67.255.60.225 Date: Mon, 26 Aug 2013 10:22:29 -0400 From: Steven Rostedt To: Yoshihiro YUNOMAE Cc: Hidehiro Kawai , Masami Hiramatsu , linux-kernel@vger.kernel.org, yrl.pp-manager.tt@hitachi.com Subject: Re: [RFC PATCH 00/11] trace-cmd: Support the feature recording trace data of guests on the host Message-ID: <20130826102229.6e0129fe@gandalf.local.home> In-Reply-To: <521AB37E.4050800@hitachi.com> References: <20130819094620.26597.79499.stgit@yunodevel> <20130820120006.1a4118c5@gandalf.local.home> <521AB37E.4050800@hitachi.com> X-Mailer: Claws Mail 3.9.2 (GTK+ 2.24.20; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2201 Lines: 49 On Mon, 26 Aug 2013 10:46:38 +0900 Yoshihiro YUNOMAE wrote: > > The --date option is used because the two machines are not in sync with > > the trace time stamp. What the date option does, is to sync the > > timestamp up with the gettimeofday and the output reports that. This > > allows the two boxes to report information that is relatively close to > > how the two interacted. > > Oh, I didn't know the --date option. > As you mentioned, we can merge trace data in chronological order by > using --date option if the times of those machines are synchronized by > NTP. > > > If the guest and the host have the same clock, then the --date option > > is not needed and the two should be able to be merged normally. > > No, we can not assure that the guest and the host have the same clock > even if it is running on the same physical machine, because both kernel > doesn't share it, there is some difference between them. So, we still > need time synchronizing guest-host by NTP and --date option. > > However, there are cases that times of those machines cannot be > synchronized. For example, although multiple users can run guests on > virtualization environments (e.g. multi-tenant cloud hosting), there > are no guarantee that they use the same NTP server. Moreover, even if > the times are synchronized, trace data cannot exactly be merged because > the NTP-synchronized time granularity may not be enough fine for > sorting guest-host switching events. Right, unless there's some other means no synchronize between boxes, this is currently the best we have. > > > Also, I haven't released it yet (will soon), but trace-cmd handles > > multiple buffers too. That is, with the multiple buffers that ftrace > > has, it will create and read from them as well as report them. > > Is it commit ID d56f30679f9811a91ed471c8e081cc7ffbed1e62? > We can download the feature from your git repository. Yep. -- Steve -- 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/