From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754988AbbJUN1s (ORCPT ); Wed, 21 Oct 2015 09:27:48 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:34044 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750859AbbJUN1r (ORCPT ); Wed, 21 Oct 2015 09:27:47 -0400 Date: Wed, 21 Oct 2015 15:27:42 +0200 From: Peter Zijlstra To: Andi Kleen Cc: acme@kernel.org, jolsa@kernel.org, linux-kernel@vger.kernel.org, Andi Kleen Subject: Re: [PATCH 3/5] perf, tools: Disable branch flags/cycles for --callgraph lbr Message-ID: <20151021132742.GF3604@twins.programming.kicks-ass.net> References: <1445366797-30894-1-git-send-email-andi@firstfloor.org> <1445366797-30894-3-git-send-email-andi@firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1445366797-30894-3-git-send-email-andi@firstfloor.org> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 20, 2015 at 11:46:35AM -0700, Andi Kleen wrote: > From: Andi Kleen > > Automatically disable collecting branch flags and cycles with > --call-graph lbr. This allows avoiding a bunch of extra MSR > reads in the PMI on Skylake. > > When the kernel doesn't support the new flags they are automatically > cleared in the fallback code. > > Signed-off-by: Andi Kleen > --- Arnaldo, ACK? > tools/perf/util/evsel.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c > index 8be867c..e8724b4 100644 > --- a/tools/perf/util/evsel.c > +++ b/tools/perf/util/evsel.c > @@ -36,6 +36,7 @@ static struct { > bool cloexec; > bool clockid; > bool clockid_wrong; > + bool lbr_flags; > } perf_missing_features; > > static clockid_t clockid; > @@ -573,7 +574,9 @@ perf_evsel__config_callgraph(struct perf_evsel *evsel, > } else { > perf_evsel__set_sample_bit(evsel, BRANCH_STACK); > attr->branch_sample_type = PERF_SAMPLE_BRANCH_USER | > - PERF_SAMPLE_BRANCH_CALL_STACK; > + PERF_SAMPLE_BRANCH_CALL_STACK | > + PERF_SAMPLE_BRANCH_NO_CYCLES | > + PERF_SAMPLE_BRANCH_NO_FLAGS; > } > } else > pr_warning("Cannot use LBR callstack with branch stack. " > @@ -1312,6 +1315,9 @@ fallback_missing_features: > evsel->attr.mmap2 = 0; > if (perf_missing_features.exclude_guest) > evsel->attr.exclude_guest = evsel->attr.exclude_host = 0; > + if (perf_missing_features.lbr_flags) > + evsel->attr.branch_sample_type &= ~(PERF_SAMPLE_BRANCH_NO_FLAGS | > + PERF_SAMPLE_BRANCH_NO_CYCLES); > retry_sample_id: > if (perf_missing_features.sample_id_all) > evsel->attr.sample_id_all = 0; > @@ -1414,6 +1420,12 @@ try_fallback: > } else if (!perf_missing_features.sample_id_all) { > perf_missing_features.sample_id_all = true; > goto retry_sample_id; > + } else if (!perf_missing_features.lbr_flags && > + (evsel->attr.branch_sample_type & > + (PERF_SAMPLE_BRANCH_NO_CYCLES | > + PERF_SAMPLE_BRANCH_NO_FLAGS))) { > + perf_missing_features.lbr_flags = true; > + goto fallback_missing_features; > } > > out_close: > -- > 2.4.3 >