perf evlist: Add --trace-fields option to show trace fields

To use dynamic sort keys, it might be good to add an option to see the
list of field names.

  $ perf evlist -i perf.data.sched
  sched:sched_switch
  sched:sched_stat_wait
  sched:sched_stat_sleep
  sched:sched_stat_iowait
  sched:sched_stat_runtime
  sched:sched_process_fork
  sched:sched_wakeup
  sched:sched_wakeup_new
  sched:sched_migrate_task
  # Tip: use 'perf evlist --trace-fields' to show fields for tracepoint events

  $ perf evlist -i perf.data.sched --trace-fields
  sched:sched_switch: trace_fields: prev_comm,prev_pid,prev_prio,prev_state,next_comm,next_pid,next_prio
  sched:sched_stat_wait: trace_fields: comm,pid,delay
  sched:sched_stat_sleep: trace_fields: comm,pid,delay
  sched:sched_stat_iowait: trace_fields: comm,pid,delay
  sched:sched_stat_runtime: trace_fields: comm,pid,runtime,vruntime
  sched:sched_process_fork: trace_fields: parent_comm,parent_pid,child_comm,child_pid
  sched:sched_wakeup: trace_fields: comm,pid,prio,success,target_cpu
  sched:sched_wakeup_new: trace_fields: comm,pid,prio,success,target_cpu
  sched:sched_migrate_task: trace_fields: comm,pid,prio,orig_cpu,dest_cpu

Committer notes:

For another file, in verbose mode:

  # perf evlist -v --trace-fields
  sched:sched_switch: type: 2, size: 112, config: 0x10b, { sample_period, sample_freq }: 1, sample_type: IP|TID|TIME|CPU|PERIOD|RAW, disabled: 1, inherit: 1, mmap: 1, comm: 1, task: 1, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, trace_fields: prev_comm,prev_pid,prev_prio,prev_state,next_comm,next_pid,next_prio
  #
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1452125549-1511-5-git-send-email-namhyung@kernel.org
[ Replaced 'trace_fields=' with 'trace_fields: ' to make the output consistent in -v mode ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-evlist.txt

@@ -32,6 +32,9 @@ OPTIONS
 --group::
 	Show event group information.
 
+--trace-fields::
+	Show tracepoint field names.
+
 SEE ALSO
 --------
 linkperf:perf-record[1], linkperf:perf-list[1],

tools/perf/builtin-evlist.c

@@ -26,14 +26,22 @@ static int __cmd_evlist(const char *file_name, struct perf_attr_details *details
 		.mode = PERF_DATA_MODE_READ,
 		.force = details->force,
 	};
+	bool has_tracepoint = false;
 
 	session = perf_session__new(&file, 0, NULL);
 	if (session == NULL)
 		return -1;
 
-	evlist__for_each(session->evlist, pos)
+	evlist__for_each(session->evlist, pos) {
 		perf_evsel__fprintf(pos, details, stdout);
 
+		if (pos->attr.type == PERF_TYPE_TRACEPOINT)
+			has_tracepoint = true;
+	}
+
+	if (has_tracepoint && !details->trace_fields)
+		printf("# Tip: use 'perf evlist --trace-fields' to show fields for tracepoint events\n");
+
 	perf_session__delete(session);
 	return 0;
 }
@@ -49,6 +57,7 @@ int cmd_evlist(int argc, const char **argv, const char *prefix __maybe_unused)
 	OPT_BOOLEAN('g', "group", &details.event_group,
 		    "Show event group information"),
 	OPT_BOOLEAN('f', "force", &details.force, "don't complain, do it"),
+	OPT_BOOLEAN(0, "trace-fields", &details.trace_fields, "Show tracepoint fields"),
 	OPT_END()
 	};
 	const char * const evlist_usage[] = {

tools/perf/util/evsel.c

@@ -2298,6 +2298,29 @@ int perf_evsel__fprintf(struct perf_evsel *evsel,
 		printed += comma_fprintf(fp, &first, " %s=%" PRIu64,
 					 term, (u64)evsel->attr.sample_freq);
 	}
+
+	if (details->trace_fields) {
+		struct format_field *field;
+
+		if (evsel->attr.type != PERF_TYPE_TRACEPOINT) {
+			printed += comma_fprintf(fp, &first, " (not a tracepoint)");
+			goto out;
+		}
+
+		field = evsel->tp_format->format.fields;
+		if (field == NULL) {
+			printed += comma_fprintf(fp, &first, " (no trace field)");
+			goto out;
+		}
+
+		printed += comma_fprintf(fp, &first, " trace_fields: %s", field->name);
+
+		field = field->next;
+		while (field) {
+			printed += comma_fprintf(fp, &first, "%s", field->name);
+			field = field->next;
+		}
+	}
 out:
 	fputc('\n', fp);
 	return ++printed;

tools/perf/util/evsel.h

@@ -369,6 +369,7 @@ struct perf_attr_details {
 	bool verbose;
 	bool event_group;
 	bool force;
+	bool trace_fields;
 };
 
 int perf_evsel__fprintf(struct perf_evsel *evsel,