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 14:02:15 -0600 Message-ID: <4E039BC7.4050802@gmail.com> References: <4E026123.4060208@fb.com> <4E034C2C.30509@gmail.com> <4E03968A.5010008@fb.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]:56272 "EHLO mail-pv0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932670Ab1FWUCT (ORCPT ); Thu, 23 Jun 2011 16:02:19 -0400 In-Reply-To: <4E03968A.5010008@fb.com> Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: Arun Sharma Cc: linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org 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 > > -Arun