linux-kernel - [PATCH V8 21/25] perf tools: Add Intel PT support for using MTC packets

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Date:	Fri, 17 Jul 2015 19:33:56 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	Jiri Olsa <jolsa@...hat.com>
Subject: [PATCH V8 21/25] perf tools: Add Intel PT support for using MTC packets

MTC packets are a new Intel PT feature.

MTC packets provide finer grain timestamp information
than TSC packets.

Support for this feature is indicated by
/sys/bus/event_source/devices/intel_pt/caps/mtc
which contains "1" if the feature is supported and
"0" otherwise.

MTC packets can be requested using a PMU config term
e.g. perf record -e intel_pt/mtc/u sleep 1

The frequency of MTC packets can also be specified.
e.g. perf record -e intel_pt/mtc,mtc_period=2/u sleep 1

The default value is 3 or the nearest lower value
that is supported.  0 is always supported.

Valid values are given by:
/sys/bus/event_source/devices/intel_pt/caps/mtc_periods
which contains a hexadecimal value, the bits of which
represent valid values e.g. bit 2 set means value 2
is valid.

The value is converted to the MTC frequency as:

	CTC-frequency / (2 ^ value)

e.g. value 3 means one eighth of CTC-frequency

Where CTC is the hardware crystal clock, the frequency of
which can be related to TSC via values provided in cpuid
leaf 0x15.

If an invalid value is entered, the error message
will give a list of valid values e.g.

	$ perf record -e intel_pt/mtc_period=15/u uname
	Invalid mtc_period for intel_pt. Valid values are: 0,3,6,9

tools/perf/Documentation/intel-pt.txt is updated in
a later patch as there are a number of new features
being added.

For more information refer to the June 2015 or later Intel 64 and
IA-32 Architectures SDM Chapter 36 Intel Processor Trace.

Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
---
 tools/perf/arch/x86/util/intel-pt.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/tools/perf/arch/x86/util/intel-pt.c b/tools/perf/arch/x86/util/intel-pt.c
index faae9289bcf6..a5de01dad868 100644
--- a/tools/perf/arch/x86/util/intel-pt.c
+++ b/tools/perf/arch/x86/util/intel-pt.c
@@ -190,17 +190,33 @@ static int intel_pt_pick_bit(int bits, int target)
 static u64 intel_pt_default_config(struct perf_pmu *intel_pt_pmu)
 {
 	char buf[256];
+	int mtc, mtc_periods = 0, mtc_period;
 	int psb_cyc, psb_periods, psb_period;
 	int pos = 0;
 	u64 config;

 	pos += scnprintf(buf + pos, sizeof(buf) - pos, "tsc");

+	if (perf_pmu__scan_file(intel_pt_pmu, "caps/mtc", "%d",
+				&mtc) != 1)
+		mtc = 1;
+
+	if (mtc) {
+		if (perf_pmu__scan_file(intel_pt_pmu, "caps/mtc_periods", "%x",
+					&mtc_periods) != 1)
+			mtc_periods = 0;
+		if (mtc_periods) {
+			mtc_period = intel_pt_pick_bit(mtc_periods, 3);
+			pos += scnprintf(buf + pos, sizeof(buf) - pos,
+					 ",mtc,mtc_period=%d", mtc_period);
+		}
+	}
+
 	if (perf_pmu__scan_file(intel_pt_pmu, "caps/psb_cyc", "%d",
 				&psb_cyc) != 1)
 		psb_cyc = 1;

-	if (psb_cyc) {
+	if (psb_cyc && mtc_periods) {
 		if (perf_pmu__scan_file(intel_pt_pmu, "caps/psb_periods", "%x",
 					&psb_periods) != 1)
 			psb_periods = 0;
@@ -454,9 +470,17 @@ out_err:
 static int intel_pt_validate_config(struct perf_pmu *intel_pt_pmu,
 				    struct perf_evsel *evsel)
 {
+	int err;
+
 	if (!evsel)
 		return 0;

+	err = intel_pt_val_config_term(intel_pt_pmu, "caps/mtc_periods",
+				       "mtc_period", "caps/mtc",
+				       evsel->attr.config);
+	if (err)
+		return err;
+
 	return intel_pt_val_config_term(intel_pt_pmu, "caps/psb_periods",
 					"psb_period", "caps/psb_cyc",
 					evsel->attr.config);
-- 
1.9.1

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