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 23:07:31 -0600 Message-ID: <4E041B93.9030302@gmail.com> References: <4E026123.4060208@fb.com> <4E034C2C.30509@gmail.com> <4E03968A.5010008@fb.com> <20110624001100.GD8058@somewhere.redhat.com> <4E03DDB0.3050502@fb.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-iy0-f174.google.com ([209.85.210.174]:61256 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750968Ab1FXFHg (ORCPT ); Fri, 24 Jun 2011 01:07:36 -0400 In-Reply-To: <4E03DDB0.3050502@fb.com> Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: Arun Sharma Cc: Frederic Weisbecker , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org On 06/23/2011 06:43 PM, Arun Sharma wrote: > On 6/23/11 5:11 PM, Frederic Weisbecker wrote: > >> >> I'm confused, you first said it happens with new tools on older kernel. >> >> Can you tell us which combination of kernel/user raises the error? and >> which error. >> I tried to repeat your examples below using perf-core tip (3.0-rc3, af07ce3e77). > > perf-3.0 + 2.6.38 > > perf record -agR gives: > > Can't find id 9's machine > Found 1 unknown events! This does not reproduce on 2.6.38.8-32.fc15.x86_64 running bare metal or 2.6.38 in a VM. If you are running bare metal try -e cpu-clock and see if it is cycles related. I doubt it, but that should be the only difference in the tests. That said, I did see that message while working on the gettimeofday patches a few weeks ago. I believe the root cause was the early mixture of cycles and tracepoints -- something I fixed before sending out the patches (sample_type hack as well as how the time-of-day trace events were added to the event list). > > perf-3.0 + 2.6.32 > > perf record -ag > perf script > > samples have bogus timestamps I'm surprised by this one. I tried with an older Fedora 12 VM (2.6.32.21 kernel). I don't get timestamps with perf-script and perf-report -D shows -1 which is what I expect given that SAMPLE_TIME attribute is not set by default. One difference here is that VM's default to cpu-clock for the event. > > perf-3.0 + 2.6.32 > > perf record -agR > perf script > > error: Samples do not contain timestamps And this one did not work out so well with the F-12 VM. It caused a kernel panic - top line on console is perf_swevent_hrtimer (lines scrolled off the top). > > perf-3.0 + any kernel > > perf record -agT > perf script > > is happy everywhere. Thanks! Which is what I would expect. Glad to see my version of reality apply elsewhere. ;-) David > > -Arun >