perf report: Support forced leader feature in pipe mode

Stephane reported a problem with forced leader in pipe mode, where
report does not force the group output. The reason is that we don't
force the leader in pipe mode.

This patch adds HEADER_LAST_FEATURE mark to have a point where we have
all events and features received, and force the group if requested.

  $ perf record --group -e '{cycles, instructions}' -o - kill | perf report -i - --group

  SNIP

  #         Overhead  Command  Shared Object     Symbol
  # ................  .......  ................  .......................
  #
      28.36%   0.00%  kill     libc-2.25.so      [.] __unregister_atfork
      26.32%   0.00%  kill     libc-2.25.so      [.] _dl_addr
      26.10%   0.00%  kill     ld-2.25.so        [.] _dl_relocate_object
      17.32%   0.00%  kill     ld-2.25.so        [.] __tunables_init
       1.70%   0.01%  kill     [unknown]         [k] 0xffffffffafa01a40
       0.20%   0.00%  kill     ld-2.25.so        [.] _start
       0.00%  48.77%  kill     ld-2.25.so        [.] do_lookup_x
       0.00%  42.97%  kill     libc-2.25.so      [.] _IO_getline
       0.00%   6.35%  kill     ld-2.25.so        [.] strcmp
       0.00%   1.71%  kill     ld-2.25.so        [.] _dl_sysdep_start
       0.00%   0.19%  kill     ld-2.25.so        [.] _dl_start

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Stephane Eranian <eranian@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180314092205.23291-2-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-report.c

@@ -68,6 +68,7 @@ struct report {
 	bool			header;
 	bool			header_only;
 	bool			nonany_branch_mode;
+	bool			group_set;
 	int			max_stack;
 	struct perf_read_values	show_threads_values;
 	const char		*pretty_printing_style;
@@ -193,6 +194,45 @@ out:
 	return err;
 }
 
+/*
+ * Events in data file are not collect in groups, but we still want
+ * the group display. Set the artificial group and set the leader's
+ * forced_leader flag to notify the display code.
+ */
+static void setup_forced_leader(struct report *report,
+				struct perf_evlist *evlist)
+{
+	if (report->group_set && !evlist->nr_groups) {
+		struct perf_evsel *leader = perf_evlist__first(evlist);
+
+		perf_evlist__set_leader(evlist);
+		leader->forced_leader = true;
+	}
+}
+
+static int process_feature_event(struct perf_tool *tool,
+				 union perf_event *event,
+				 struct perf_session *session __maybe_unused)
+{
+	struct report *rep = container_of(tool, struct report, tool);
+
+	if (event->feat.feat_id < HEADER_LAST_FEATURE)
+		return perf_event__process_feature(tool, event, session);
+
+	if (event->feat.feat_id != HEADER_LAST_FEATURE) {
+		pr_err("failed: wrong feature ID: %" PRIu64 "\n",
+		       event->feat.feat_id);
+		return -1;
+	}
+
+	/*
+	 * All features are received, we can force the
+	 * group if needed.
+	 */
+	setup_forced_leader(rep, session->evlist);
+	return 0;
+}
+
 static int process_sample_event(struct perf_tool *tool,
 				union perf_event *event,
 				struct perf_sample *sample,
@@ -940,7 +980,6 @@ int cmd_report(int argc, const char **argv)
 		"perf report [<options>]",
 		NULL
 	};
-	bool group_set = false;
 	struct report report = {
 		.tool = {
 			.sample		 = process_sample_event,
@@ -958,7 +997,7 @@ int cmd_report(int argc, const char **argv)
 			.id_index	 = perf_event__process_id_index,
 			.auxtrace_info	 = perf_event__process_auxtrace_info,
 			.auxtrace	 = perf_event__process_auxtrace,
-			.feature	 = perf_event__process_feature,
+			.feature	 = process_feature_event,
 			.ordered_events	 = true,
 			.ordering_requires_timestamps = true,
 		},
@@ -1060,7 +1099,7 @@ int cmd_report(int argc, const char **argv)
 		   "Specify disassembler style (e.g. -M intel for intel syntax)"),
 	OPT_BOOLEAN(0, "show-total-period", &symbol_conf.show_total_period,
 		    "Show a column with the sum of periods"),
-	OPT_BOOLEAN_SET(0, "group", &symbol_conf.event_group, &group_set,
+	OPT_BOOLEAN_SET(0, "group", &symbol_conf.event_group, &report.group_set,
 		    "Show event group information together"),
 	OPT_CALLBACK_NOOPT('b', "branch-stack", &branch_mode, "",
 		    "use branch records for per branch histogram filling",
@@ -1177,17 +1216,7 @@ repeat:
 	has_br_stack = perf_header__has_feat(&session->header,
 					     HEADER_BRANCH_STACK);
 
-	/*
-	 * Events in data file are not collect in groups, but we still want
-	 * the group display. Set the artificial group and set the leader's
-	 * forced_leader flag to notify the display code.
-	 */
-	if (group_set && !session->evlist->nr_groups) {
-		struct perf_evsel *leader = perf_evlist__first(session->evlist);
-
-		perf_evlist__set_leader(session->evlist);
-		leader->forced_leader = true;
-	}
+	setup_forced_leader(&report, session->evlist);
 
 	if (itrace_synth_opts.last_branch)
 		has_br_stack = true;

tools/perf/util/header.c

@@ -3415,8 +3415,17 @@ int perf_event__synthesize_features(struct perf_tool *tool,
 			return ret;
 		}
 	}
+
+	/* Send HEADER_LAST_FEATURE mark. */
+	fe = ff.buf;
+	fe->feat_id     = HEADER_LAST_FEATURE;
+	fe->header.type = PERF_RECORD_HEADER_FEATURE;
+	fe->header.size = sizeof(*fe);
+
+	ret = process(tool, ff.buf, NULL, NULL);
+
 	free(ff.buf);
-	return 0;
+	return ret;
 }
 
 int perf_event__process_feature(struct perf_tool *tool,