Messages in this thread | | | Date | Mon, 21 Sep 2009 09:32:32 +0200 | From | Ingo Molnar <> | Subject | Re: [tip:perfcounters/core] x86, perf_counter, bts: Optimize BTS overflow handling |
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* Metzger, Markus T <markus.t.metzger@intel.com> wrote:
> >-----Original Message----- > >From: tip tree robot [mailto:bounces.tip@hpa.at.zytor.com] On Behalf Of tip-bot for Markus Metzger > >Sent: Friday, September 18, 2009 9:19 PM > >To: linux-tip-commits@vger.kernel.org > >Cc: linux-kernel@vger.kernel.org; hpa@zytor.com; mingo@redhat.com; a.p.zijlstra@chello.nl; Metzger, > >Markus T; tglx@linutronix.de; mingo@elte.hu > >Subject: [tip:perfcounters/core] x86, perf_counter, bts: Optimize BTS overflow handling > > > >Commit-ID: 5622f295b53fb60dbf9bed3e2c89d182490a8b7f > >Gitweb: http://git.kernel.org/tip/5622f295b53fb60dbf9bed3e2c89d182490a8b7f > >Author: Markus Metzger <markus.t.metzger@intel.com> > >AuthorDate: Tue, 15 Sep 2009 13:00:23 +0200 > >Committer: Ingo Molnar <mingo@elte.hu> > >CommitDate: Fri, 18 Sep 2009 20:43:20 +0200 > > > >x86, perf_counter, bts: Optimize BTS overflow handling > > > >Draining the BTS buffer on a buffer overflow interrupt takes too > >long resulting in a kernel lockup when tracing the kernel. > > > >Restructure perf_counter sampling into sample creation and sample > >output. > > > >Prepare a single reference sample for BTS sampling and update the > >from and to address fields when draining the BTS buffer. Drain the > >entire BTS buffer between a single perf_output_begin() / > >perf_output_end() pair. > > > >Signed-off-by: Markus Metzger <markus.t.metzger@intel.com> > >Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> > >LKML-Reference: <20090915130023.A16204@sedona.ch.intel.com> > >Signed-off-by: Ingo Molnar <mingo@elte.hu> > > > Ingo, > > This change should speed up BTS overflow handling enough to support > branch tracing the kernel. > Would you please drop 1653192f510bd8114b7b133d7289e6e5c3e95046 > that disabled kernel tracing to work around the issue.
Please send a proper patch that re-enables the (previously unreliable) aspect of BTS tracing, with a changelog that explains that the feature now works and with an indication that you've tested it.
Ingo
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