[PATCH RFC V3 3/5] perf,tool: partial time support

[kan . liang]

From: Kan Liang <kan.liang@xxxxxxxxx>

When multiple events are sampled it may not be needed to collect fine
grained time stamps on all events. The sample sites are usually nearby.
It's enough to have time stamps on the regular reference events.
This patchkit adds the ability to turn off time stamps per event. This
in term can reduce sampling overhead and the size of the perf.data.

Signed-off-by: Kan Liang <kan.liang@xxxxxxxxx>
---
 tools/perf/Documentation/perf-record.txt |  4 +++-
 tools/perf/util/evsel.c                  | 32 ++++++++++++++++++++++++++++++--
 tools/perf/util/parse-events.c           |  7 +++++++
 tools/perf/util/parse-events.h           |  1 +
 tools/perf/util/parse-events.l           |  1 +
 5 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 5b47b2c..df47907 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -49,7 +49,9 @@ OPTIONS
 	  These params can be used to set event defaults.
 	  Here is a list of the params.
 	  - 'period': Set event sampling period
-
+	  - 'time': Disable/enable time stamping. Acceptable values are 1 for
+		    enabling time stamping. 0 for disabling time stamping.
+		    The default is 1.
 	  Note: If user explicitly sets options which conflict with the params,
 	  the value set by the params will be overridden.
 
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 83c0803..1d58330 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -619,10 +619,37 @@ void perf_evsel__config(struct perf_evsel *evsel, struct record_opts *opts)
 	struct perf_event_attr *attr = &evsel->attr;
 	int track = evsel->tracking;
 	bool per_cpu = opts->target.default_per_cpu && !opts->target.per_thread;
+	bool sample_time = opts->sample_time;
 
 	attr->sample_id_all = perf_missing_features.sample_id_all ? 0 : 1;
 	attr->inherit	    = !opts->no_inherit;
 
+	/*
+	 * If user doesn't explicitly set time option,
+	 * let event attribute decide.
+	 */
+
+	if (!opts->sample_time_set) {
+		if (attr->sample_type & PERF_SAMPLE_TIME)
+			sample_time = true;
+		else
+			sample_time = false;
+	}
+
+	/*
+	 * Event parsing doesn't check the availability
+	 * Clear the bit which event parsing may be set.
+	 * Let following code check and reset if available
+	 *
+	 * Also, the sample size may be caculated mistakenly,
+	 * because event parsing may set the PERF_SAMPLE_TIME.
+	 * Remove the size which add in perf_evsel__init
+	 */
+	if (attr->sample_type & PERF_SAMPLE_TIME) {
+		attr->sample_type &= ~PERF_SAMPLE_TIME;
+		evsel->sample_size -= sizeof(u64);
+	}
+
 	perf_evsel__set_sample_bit(evsel, IP);
 	perf_evsel__set_sample_bit(evsel, TID);
 
@@ -705,14 +732,15 @@ void perf_evsel__config(struct perf_evsel *evsel, struct record_opts *opts)
 	/*
 	 * When the user explicitely disabled time don't force it here.
 	 */
-	if (opts->sample_time &&
+	if (sample_time &&
 	    (!perf_missing_features.sample_id_all &&
 	    (!opts->no_inherit || target__has_cpu(&opts->target) || per_cpu ||
 	     opts->sample_time_set)))
 		perf_evsel__set_sample_bit(evsel, TIME);
 
 	if (opts->raw_samples && !evsel->no_aux_samples) {
-		perf_evsel__set_sample_bit(evsel, TIME);
+		if (sample_time)
+			perf_evsel__set_sample_bit(evsel, TIME);
 		perf_evsel__set_sample_bit(evsel, RAW);
 		perf_evsel__set_sample_bit(evsel, CPU);
 	}
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index a71eeb2..9510047 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -598,6 +598,13 @@ do {									   \
 		 * attr->branch_sample_type = term->val.num;
 		 */
 		break;
+	case PARSE_EVENTS__TERM_TYPE_TIME:
+		CHECK_TYPE_VAL(NUM);
+		if (term->val.num > 1)
+			return -EINVAL;
+		if (term->val.num == 1)
+			attr->sample_type |= PERF_SAMPLE_TIME;
+		 break;
 	case PARSE_EVENTS__TERM_TYPE_NAME:
 		CHECK_TYPE_VAL(STR);
 		break;
diff --git a/tools/perf/util/parse-events.h b/tools/perf/util/parse-events.h
index 131f29b..0d8cae3 100644
--- a/tools/perf/util/parse-events.h
+++ b/tools/perf/util/parse-events.h
@@ -62,6 +62,7 @@ enum {
 	PARSE_EVENTS__TERM_TYPE_NAME,
 	PARSE_EVENTS__TERM_TYPE_SAMPLE_PERIOD,
 	PARSE_EVENTS__TERM_TYPE_BRANCH_SAMPLE_TYPE,
+	PARSE_EVENTS__TERM_TYPE_TIME,
 };
 
 struct parse_events_term {
diff --git a/tools/perf/util/parse-events.l b/tools/perf/util/parse-events.l
index 13cef3c..f542750 100644
--- a/tools/perf/util/parse-events.l
+++ b/tools/perf/util/parse-events.l
@@ -183,6 +183,7 @@ config2			{ return term(yyscanner, PARSE_EVENTS__TERM_TYPE_CONFIG2); }
 name			{ return term(yyscanner, PARSE_EVENTS__TERM_TYPE_NAME); }
 period			{ return term(yyscanner, PARSE_EVENTS__TERM_TYPE_SAMPLE_PERIOD); }
 branch_type		{ return term(yyscanner, PARSE_EVENTS__TERM_TYPE_BRANCH_SAMPLE_TYPE); }
+time			{ return term(yyscanner, PARSE_EVENTS__TERM_TYPE_TIME); }
 ,			{ return ','; }
 "/"			{ BEGIN(INITIAL); return '/'; }
 {name_minus}		{ return str(yyscanner, PE_NAME); }
-- 
1.8.3.1

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