[PATCH 2/4] perf timechart: Generate backtrace only if needed

[Namhyung Kim <namhyung@kernel.org>]

The backtrace was used by sched-switch and sched-wakeup only.  No need
to call cat_backtrace() in the process_sample_event().  Let's pass NULL
backtrace and generate it from the sched events.

As it needs a pointer to the 'machine', let's save the session in the
timechart struct and use the host machine of the session instead of
passing the pointer to all handlers.  It should be fine to assume the
host machine as timechart command doesn't deal with guest machines and
there's no way to get tracepoints from the guest events.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/perf/builtin-timechart.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/tools/perf/builtin-timechart.c b/tools/perf/builtin-timechart.c
index dafd361ecf9d8cd7..337ae547d008ea0b 100644
--- a/tools/perf/builtin-timechart.c
+++ b/tools/perf/builtin-timechart.c
@@ -56,6 +56,7 @@ struct timechart {
 	struct per_pid		*all_data;
 	struct power_event	*power_events;
 	struct wake_event	*wake_events;
+	struct perf_session	*session;
 	int			proc_num;
 	unsigned int		numcpus;
 	u64			min_freq,	/* Lowest CPU frequency seen */
@@ -578,7 +579,7 @@ typedef int (*tracepoint_handler)(struct timechart *tchart,
 static int process_sample_event(const struct perf_tool *tool,
 				union perf_event *event __maybe_unused,
 				struct perf_sample *sample,
-				struct machine *machine)
+				struct machine *machine __maybe_unused)
 {
 	struct timechart *tchart = container_of(tool, struct timechart, tool);
 	struct evsel *evsel = sample->evsel;
@@ -593,10 +594,8 @@ static int process_sample_event(const struct perf_tool *tool,
 
 	if (evsel->handler != NULL) {
 		tracepoint_handler f = evsel->handler;
-		char *backtrace = cat_backtrace(sample, machine);
 
-		ret = f(tchart, sample, backtrace);
-		free(backtrace);
+		ret = f(tchart, sample, NULL);
 	}
 
 	return ret;
@@ -656,7 +655,10 @@ process_sample_sched_wakeup(struct timechart *tchart,
 			 sample->file_offset, sample->cpu);
 		return -1;
 	}
+
+	backtrace = cat_backtrace(sample, &tchart->session->machines.host);
 	sched_wakeup(tchart, sample->cpu, sample->time, waker, wakee, flags, backtrace);
+	free((char *)backtrace);
 	return 0;
 }
 
@@ -675,8 +677,11 @@ process_sample_sched_switch(struct timechart *tchart,
 			 sample->file_offset, sample->cpu);
 		return -1;
 	}
+
+	backtrace = cat_backtrace(sample, &tchart->session->machines.host);
 	sched_switch(tchart, sample->cpu, sample->time, prev_pid, next_pid,
 		     prev_state, backtrace);
+	free((char *)backtrace);
 	return 0;
 }
 
@@ -1661,6 +1666,7 @@ static int __cmd_timechart(struct timechart *tchart, const char *output_name)
 	if (IS_ERR(session))
 		return PTR_ERR(session);
 
+	tchart->session = session;
 	symbol__init(perf_session__env(session));
 
 	(void)perf_header__process_sections(&session->header,
-- 
2.54.0.1032.g2f8565e1d1-goog