From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Ahern Subject: Re: Using a new perf tool against an older kernel Date: Thu, 23 Jun 2011 23:14:19 -0600 Message-ID: <4E041D2B.5020808@gmail.com> References: <4E026123.4060208@fb.com> <4E034C2C.30509@gmail.com> <4E03968A.5010008@fb.com> <4E039BC7.4050802@gmail.com> <20110624001145.GE8058@somewhere.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pv0-f174.google.com ([74.125.83.174]:50845 "EHLO mail-pv0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751974Ab1FXFOW (ORCPT ); Fri, 24 Jun 2011 01:14:22 -0400 In-Reply-To: <20110624001145.GE8058@somewhere.redhat.com> Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: Frederic Weisbecker Cc: Arun Sharma , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org On 06/23/2011 06:11 PM, Frederic Weisbecker wrote: > On Thu, Jun 23, 2011 at 02:02:15PM -0600, David Ahern wrote: >> >> >> On 06/23/2011 01:39 PM, Arun Sharma wrote: >>> On 6/23/11 7:22 AM, David Ahern wrote: >>> >>>> I have not seen issues like this using newer perf userspace against >>>> older kernels. For example, my laptop was running Fedora 14 (2.6.35) and >>>> now Fedora 15 (2.6.38.8) and I typically use latest perf builds (e.g., >>>> testing patches). >>> >>> I narrowed it down to PERF_SAMPLE_RAW: >>> >>> perf record -ag -- sleep 1 >>> >>> is fine, but: >>> >>> perf record -agR -- sleep 1 >>> >>> fails for me most of the time. The reason I needed to use the -R in the >>> first place is that "perf script" fails on older kernels with: >>> >>> Samples do not contain timestamps. >>> >>> With the newer perf, I don't get errors, but the timestamp field is >>> invalid. So I need to use the -R flag to get valid timestamps + >>> stacktraces out of "perf script". >> >> That should have been fixed. >> >> And -T on record gets the timestamps. >> >> David > > Right, it would be nice to suggest that from perf script when timestamps > are not recorded. Timestamps are enabled by default, but that output option is removed if the samples do not have timestamps. That message is generated if the user requests timestamps (-f time) in the perf-script output and the samples do not have timestamps, but Arun did not request that. Arun's mileage with perf-3.0 definitely varies from what I've seen. David