[PATCH RFC 06/10] perf,tools: option to set counter read interval

[kan . liang]

From: Kan Liang <kan.liang@xxxxxxxxx>

Add a timer to read counter regularly. Option --counter-read-interval
can be used to set the interval.
Only read counter statistics at the beginning and the end is not enough.
Sometimes, we need fine granularity to do sophisticated analysis. For
example,10-20ms is required to do sophisticated bandwidth analysis.

Signed-off-by: Kan Liang <kan.liang@xxxxxxxxx>
---
 tools/perf/Documentation/perf-record.txt |  8 +++++++
 tools/perf/builtin-record.c              | 37 ++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 2e9ce77..c1d9024 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -308,6 +308,14 @@ This option sets the time out limit. The default value is 500 ms.
 Record context switch events i.e. events of type PERF_RECORD_SWITCH or
 PERF_RECORD_SWITCH_CPU_WIDE.
 
+--counter-read-interval::
+Sets the interval to do counter read regularly. This option is only valid
+with counter read event (:C). This option is disabled by default. It means
+that the event counter can only be read at the beginning and the end.
+This option could be used when we need fine granularity to do sophisticated
+analysis. For example, 10-20ms is required to do sophisticated memory
+bandwidth analysis.
+
 SEE ALSO
 --------
 linkperf:perf-stat[1], linkperf:perf-list[1]
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index cc8fd08..cdc9d3b 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -505,6 +505,14 @@ static void workload_exec_failed_signal(int signo __maybe_unused,
 
 static void snapshot_sig_handler(int sig);
 
+static unsigned int interval;
+struct record *g_rec;
+
+static void perf_read_alarm(int sig __maybe_unused)
+{
+	perf_read_counter(g_rec);
+}
+
 static int __cmd_record(struct record *rec, int argc, const char **argv)
 {
 	int err;
@@ -517,6 +525,9 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 	struct perf_data_file *file = &rec->file;
 	struct perf_session *session;
 	bool disabled = false, draining = false;
+	static timer_t timerid;
+	struct itimerspec timeout;
+	struct sigevent sigevent;
 	int fd;
 
 	rec->progname = argv[0];
@@ -530,6 +541,25 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 	else
 		signal(SIGUSR2, SIG_IGN);
 
+	if (interval) {
+		if (interval < 10) {
+			pr_err("Regular interval for counter read must >= 10 ms.\n");
+			return -1;
+		}
+		signal(SIGALRM, perf_read_alarm);
+		g_rec = rec;
+
+		/* Create a timer. */
+		sigevent.sigev_notify = SIGEV_SIGNAL;
+		sigevent.sigev_signo = SIGALRM;
+		timer_create(CLOCK_REALTIME, &sigevent, &timerid);
+		memset(&timeout, 0, sizeof(timeout));
+		timeout.it_value.tv_sec = interval/1000;
+		timeout.it_interval.tv_sec = interval/1000;
+		timeout.it_value.tv_nsec = (interval % 1000) * 1000000ULL;
+		timeout.it_interval.tv_nsec = (interval % 1000) * 1000000ULL;
+	}
+
 	session = perf_session__new(file, false, tool);
 	if (session == NULL) {
 		pr_err("Perf session creation failed.\n");
@@ -679,6 +709,9 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 	}
 
 	perf_read_counter(rec);
+	if (interval)
+		timer_settime(timerid, 0, &timeout, NULL);
+
 	auxtrace_snapshot_enabled = 1;
 	for (;;) {
 		int hits = rec->samples;
@@ -723,6 +756,8 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 		 */
 		if (done && !disabled && !target__none(&opts->target)) {
 			auxtrace_snapshot_enabled = 0;
+			if (interval)
+				timer_delete(timerid);
 			perf_read_counter(rec);
 			perf_evlist__disable(rec->evlist);
 			disabled = true;
@@ -1132,6 +1167,8 @@ struct option __record_options[] = {
 			"per thread proc mmap processing timeout in ms"),
 	OPT_BOOLEAN(0, "switch-events", &record.opts.record_switch_events,
 		    "Record context switch events"),
+	OPT_UINTEGER(0, "counter-read-interval", &interval,
+			"Read event counter statistics at regular interval in ms (>= 10)"),
 	OPT_END()
 };
 
-- 
1.8.3.1

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