From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Yang, Sheng" Subject: Re: [PATCH 2/5] kvmtrace: make cycle calculation architecture aware Date: Fri, 11 Jul 2008 09:06:56 +0800 Message-ID: <200807110906.57123.sheng.yang@intel.com> References: <1215439013-11480-1-git-send-email-ehrhardt@linux.vnet.ibm.com> <200807101822.16163.sheng.yang@intel.com> <48760F6D.5000709@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, Hollis Blanchard , Christian Ehrhardt , cotte@de.ibm.com, xiantao.zhang@intel.com, kvm-ppc@vger.kernel.org To: Avi Kivity Return-path: Received: from mga11.intel.com ([192.55.52.93]:28828 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753442AbYGKBFj (ORCPT ); Thu, 10 Jul 2008 21:05:39 -0400 In-Reply-To: <48760F6D.5000709@qumranet.com> Content-Disposition: inline Sender: kvm-owner@vger.kernel.org List-ID: On Thursday 10 July 2008 21:32:29 Avi Kivity wrote: > Yang, Sheng wrote: > > On Wednesday 09 July 2008 23:03:19 Hollis Blanchard wrote: > >> On Wed, 2008-07-09 at 11:17 +0200, Christian Ehrhardt wrote: > >>> So the question that is left before changing that is, if the > >>> original author had something special in mind chosing cycles > >>> here. I added Eric on CC for that. > >>> > >>> I wait with my resubmission of the patch series until all > >>> architectures agree *hope* on using getnstimeofday() - after an > >>> ack from all sides I would revise my patch series and submit > >>> that changes alltogether. > >> > >> I got an email bounce from Eric the last time I tried to email > >> him, so I'm not sure he's still with Intel. > >> > >> However, I don't think he had any special intention; I think he > >> was just porting xentrace to KVM. > > > > Eric had completed his internship in Intel, so... > > > > I like the term "timestamp" too. I think he used "cycles" only > > because there is a function called get_cycles(). > > > > But instead of getnstimeofday(), I suggest using ktime_get() > > here. It's little more precise than getnstimeofday(), and ktime_t > > is more easily to be handled. And I think the overhead it brought > > can be ignored too. > > What is the overhead of ktime_get()? Well, I just means it wrapped getnstimeofday(), and compared to rdtscll(), it got little overhead... :) -- Thanks Yang, Sheng