[PATCH v1 3/8] perf stat: introduce control descriptors and --ctl-fd[-ack] options

[Alexey Budankov]

Introduce control file descriptors and --ctl-fd[-ack] options to pass
control descriptors from command line. Extend --delay option with -1
value to start collection in paused mode to be resumed later by resume
command provided via control file descriptor.

Signed-off-by: Alexey Budankov <alexey.budankov@xxxxxxxxxxxxxxx>
---
 tools/perf/builtin-stat.c | 28 ++++++++++++++++++++++++----
 tools/perf/util/evlist.h  |  3 +++
 tools/perf/util/stat.h    |  4 +++-
 3 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index ec053dc1e35c..0a1b79fd3f48 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -187,6 +187,8 @@ static struct perf_stat_config stat_config = {
 	.metric_only_len	= METRIC_ONLY_LEN,
 	.walltime_nsecs_stats	= &walltime_nsecs_stats,
 	.big_num		= true,
+	.ctl_fd			= -1,
+	.ctl_fd_ack		= -1
 };
 
 static inline void diff_timespec(struct timespec *r, struct timespec *a,
@@ -373,16 +375,26 @@ static void process_interval(void)
 
 static void enable_counters(void)
 {
-	if (stat_config.initial_delay)
+	if (stat_config.initial_delay < 0) {
+		pr_info(PERF_EVLIST__PAUSED_MSG);
+		return;
+	}
+
+	if (stat_config.initial_delay > 0) {
+		pr_info(PERF_EVLIST__PAUSED_MSG);
 		usleep(stat_config.initial_delay * USEC_PER_MSEC);
+	}
 
 	/*
 	 * We need to enable counters only if:
 	 * - we don't have tracee (attaching to task or cpu)
 	 * - we have initial delay configured
 	 */
-	if (!target__none(&target) || stat_config.initial_delay)
+	if (!target__none(&target) || stat_config.initial_delay) {
 		evlist__enable(evsel_list);
+		if (stat_config.initial_delay > 0)
+			pr_info(PERF_EVLIST__RESUMED_MSG);
+	}
 }
 
 static void disable_counters(void)
@@ -912,8 +924,8 @@ static struct option stat_options[] = {
 		     "aggregate counts per thread", AGGR_THREAD),
 	OPT_SET_UINT(0, "per-node", &stat_config.aggr_mode,
 		     "aggregate counts per numa node", AGGR_NODE),
-	OPT_UINTEGER('D', "delay", &stat_config.initial_delay,
-		     "ms to wait before starting measurement after program start"),
+	OPT_INTEGER('D', "delay", &stat_config.initial_delay,
+		     "ms to wait before starting measurement after program start (-1: start paused"),
 	OPT_CALLBACK_NOOPT(0, "metric-only", &stat_config.metric_only, NULL,
 			"Only print computed metrics. No raw values", enable_metric_only),
 	OPT_BOOLEAN(0, "topdown", &topdown_run,
@@ -933,6 +945,10 @@ static struct option stat_options[] = {
 		    "Use with 'percore' event qualifier to show the event "
 		    "counts of one hardware thread by sum up total hardware "
 		    "threads of same physical core"),
+	OPT_INTEGER(0, "ctl-fd", &stat_config.ctl_fd,
+		    "Listen on fd descriptor for command to control measurement ('r': resume, 'p': pause)"),
+	OPT_INTEGER(0, "ctl-fd-ack", &stat_config.ctl_fd_ack,
+		    "Send control command completion ('a') to fd ack descriptor"),
 	OPT_END()
 };
 
@@ -2129,6 +2145,8 @@ int cmd_stat(int argc, const char **argv)
 	signal(SIGALRM, skip_signal);
 	signal(SIGABRT, skip_signal);
 
+	perf_evlist__initialize_ctlfd(evsel_list, stat_config.ctl_fd, stat_config.ctl_fd_ack);
+
 	status = 0;
 	for (run_idx = 0; forever || run_idx < stat_config.run_count; run_idx++) {
 		if (stat_config.run_count != 1 && verbose > 0)
@@ -2148,6 +2166,8 @@ int cmd_stat(int argc, const char **argv)
 	if (!forever && status != -1 && !interval)
 		print_counters(NULL, argc, argv);
 
+	perf_evlist__finalize_ctlfd(evsel_list);
+
 	if (STAT_RECORD) {
 		/*
 		 * We synthesize the kernel mmap record just so that older tools
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index a94b2993fafc..c91368483074 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -369,6 +369,9 @@ enum evlist_ctl_cmd {
 	CTL_CMD_ACK = 'a'
 };
 
+#define PERF_EVLIST__RESUMED_MSG "Monitoring resumed\n"
+#define PERF_EVLIST__PAUSED_MSG  "Monitoring paused\n"
+
 int perf_evlist__initialize_ctlfd(struct evlist *evlist, int ctl_fd, int ctl_fd_ack);
 int perf_evlist__finalize_ctlfd(struct evlist *evlist);
 int perf_evlist__ctlfd_process(struct evlist *evlist, enum evlist_ctl_cmd *cmd);
diff --git a/tools/perf/util/stat.h b/tools/perf/util/stat.h
index b4fdfaa7f2c0..0b0fa3a2cde2 100644
--- a/tools/perf/util/stat.h
+++ b/tools/perf/util/stat.h
@@ -113,7 +113,7 @@ struct perf_stat_config {
 	FILE			*output;
 	unsigned int		 interval;
 	unsigned int		 timeout;
-	unsigned int		 initial_delay;
+	int			 initial_delay;
 	unsigned int		 unit_width;
 	unsigned int		 metric_only_len;
 	int			 times;
@@ -130,6 +130,8 @@ struct perf_stat_config {
 	struct perf_cpu_map		*cpus_aggr_map;
 	u64			*walltime_run;
 	struct rblist		 metric_events;
+	int			 ctl_fd;
+	int			 ctl_fd_ack;
 };
 
 void update_stats(struct stats *stats, u64 val);
-- 
2.24.1