From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753135Ab1JLQv5 (ORCPT ); Wed, 12 Oct 2011 12:51:57 -0400 Received: from oz.csail.mit.edu ([128.30.30.239]:57148 "EHLO ozymandias.localdomain" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751404Ab1JLQv4 (ORCPT ); Wed, 12 Oct 2011 12:51:56 -0400 Date: Wed, 12 Oct 2011 12:51:54 -0400 From: Eric B Munson To: Peter Zijlstra Cc: eranian@google.com, mingo@elte.hu, anton@samba.org, linux-kernel@vger.kernel.org, paulus@samba.org, hbabu@us.ibm.com Subject: Re: Oprofile Regression Caused by commit e5d1367f17ba6a6fed5fd8b74e4d5720923e0c25 on PPC Message-ID: <20111012165154.GB6158@mgebm.net> References: <20111007204247.GA5444@mgebm.net> <20111010233842.GC24583@mgebm.net> <1318319095.14400.54.camel@laptop> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="4SFOXa2GPu3tIq4H" Content-Disposition: inline In-Reply-To: <1318319095.14400.54.camel@laptop> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --4SFOXa2GPu3tIq4H Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, 11 Oct 2011, Peter Zijlstra wrote: > On Mon, 2011-10-10 at 19:38 -0400, Eric B Munson wrote: > > On Fri, 07 Oct 2011, Eric B Munson wrote: > >=20 > > > This commit seems to have caused a regression with oprofile. It is f= airly easy > > > to trigger, simply run oprofile monitoring an event that will fire (s= omething > > > frequent like CPU cycles) causes oprofile to fail saying that the PMU= is in use. > > > If I disable CONFIG_CGROUP_PERF, everything goes back to working. I = suspect the > > > problem is that the PMU is being initialized without being reserved f= or perf. I > > > am not yet sure of the right fix yet so if you have any suggestions I= would > > > appreciate them. > > >=20 > > > Eric > >=20 > > This isn't the best description of the behavior we see, what happens is= at some > > point in the profiling session the MMCR register is clobbered by > > perf_cgroup_switch() which calls perf_pmu_enable() without reserving th= e PMC > > hardware. When this happens oprofile stops counting. It doesn't happe= n each > > time so some runs show event counts that are reasonable, but it can als= o lead to > > event counts that are smaller than expected, or completely missing. >=20 > What kernel are you testing? >=20 The problem seems to be fixed in 3.1-rc9 so I just need to identify the patch(es) that fixed it. Eric --4SFOXa2GPu3tIq4H Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iQIcBAEBAgAGBQJOlcWqAAoJEKhG9nGc1bpJ1ykP/0fuox+IucRsAPpEs5RH9N5M M2p7zRZYKs/FyASVm4qxZOG4WsiCusDTO9fsucu4auWaFGkVEv9c5qIcLcZuqLVR 7R97wJRlR5Hc/nV97pCflxBs6Pl+Ot7MkA7OsF6J8nmxvFJnASp2zcE4EPvIO+3q Fq/l1exWblpyX0KGg4Uq8bRS2spA4la6qqSekK3lYjw5vlVxV6SeNG1uSyyjIKmU c3kRmoNcUcRf7rlPtEym/QIN/Zt9msCzZBA+9c0CG3Axs3BoLBMT1x0eJPWB3RLk bZSMlk8b/oZvwSqNuEaMLNwgB5THqSARbX0MzEbSr1RI/zbvrrdhQZKV0GM1J+2h dMsiqsNw0yqflfaWerhMeUxp5iIYLy8nairuVNi3vmIGgpx9sW2bT/j+n2cyrEIR V044krOnJv7bTnAGCS7RrzZNwshD8Q5ruOniwLhTZniGZ6xOGgfH1CqFnnAjhv54 A69PmJrWE7kzyu7MgmbpnxQV4ygQzm3yrIOzn5CV0IazO7vX8Cuz0+MhZ1i3X05c C38iP+VLIkfbwJoYpm4H5YBt9HFdMhg1dnlUqWfcuECPE9NMMlz0IQw+EK/9yFIO Y89m4FDOQJFZZOACBIeRvjcZifZrrmJFnGZQmxKmhxUeMEzdtBHQgZwmxIwBLaPK OAqQtGSNCo2bO+fqxiyi =EYTK -----END PGP SIGNATURE----- --4SFOXa2GPu3tIq4H--