[PATCH v2 04/11] perf stat: extend -D,--delay option with -1 value

[Alexey Budankov]

Extend -D,--delay option with -1 value to start monitoring with
events disabled to be enabled later by enable command provided
via control file descriptor.

Signed-off-by: Alexey Budankov <alexey.budankov@xxxxxxxxxxxxxxx>
---
 tools/perf/builtin-stat.c | 18 ++++++++++++++----
 tools/perf/util/evlist.h  |  3 +++
 tools/perf/util/stat.h    |  2 +-
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 9775b0905146..bda777ca0420 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -383,16 +383,26 @@ static bool print_interval_and_stop(struct perf_stat_config *config, int *times)
 
 static void enable_counters(void)
 {
-	if (stat_config.initial_delay)
+	if (stat_config.initial_delay < 0) {
+		pr_info(PERF_EVLIST__DISABLED_MSG);
+		return;
+	}
+
+	if (stat_config.initial_delay > 0) {
+		pr_info(PERF_EVLIST__DISABLED_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__ENABLED_MSG);
+	}
 }
 
 static void disable_counters(void)
@@ -929,8 +939,8 @@ 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 with events disabled"),
 	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,
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 84386850c290..874ecf068ac9 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -366,6 +366,9 @@ enum evlist_ctl_cmd {
 	CTL_CMD_ACK = 'a'
 };
 
+#define PERF_EVLIST__ENABLED_MSG "Events enabled\n"
+#define PERF_EVLIST__DISABLED_MSG "Events disabled\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..027b9dcd902f 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;
-- 
2.24.1