[v2,8/9] trace2: add counter events to perf and event target formats

Commit Message

Jeff Hostetler Dec. 28, 2021, 7:36 p.m. UTC

From: Jeff Hostetler <[e-mail]>

Teach Trace2 "perf" and "event" formats to handle "counter" events
for global counters.  Update the API documentation accordingly.

In a future commit, global counters will be added to the Trace2 API
and it will emit these "counter" events at program exit.

Signed-off-by: Jeff Hostetler <[e-mail]>
---
 Documentation/technical/api-trace2.txt | 19 +++++++++++++++++++
 trace2/tr2_tgt.h                       | 14 ++++++++++++++
 trace2/tr2_tgt_event.c                 | 23 +++++++++++++++++++++++
 trace2/tr2_tgt_normal.c                |  1 +
 trace2/tr2_tgt_perf.c                  | 18 ++++++++++++++++++
 5 files changed, 75 insertions(+)

Patch

diff --git a/Documentation/technical/api-trace2.txt b/Documentation/technical/api-trace2.txt
index 616001bcbb0..bdba0f92280 100644
--- a/Documentation/technical/api-trace2.txt
+++ b/Documentation/technical/api-trace2.txt
@@ -838,6 +838,25 @@  may exceed the "atexit" elapsed time of the program.
 Timer events may represent an individual thread or a summation across
 the entire program.  Summation events will have a unique thread name.
 
+`"counter"`::
+	This event is generated at the end of the program and contains
+	the value of a global counter.
++
+------------
+{
+	"event":"counter",
+	...
+	"name":"test",      # counter name
+	"value":42,         # value of the counter
+}
+------------
++
+A global counter can be incremented throughout the execution of the
+program.  It will be reported in a "counter" event just prior to exit.
++
+Counter events may represent an individual thread or a summation across
+the entire program.  Summation events will have a unique thread name.
+
 == Example Trace2 API Usage
 
 Here is a hypothetical usage of the Trace2 API showing the intended
diff --git a/trace2/tr2_tgt.h b/trace2/tr2_tgt.h
index a41f91d09b5..66f34b9258f 100644
--- a/trace2/tr2_tgt.h
+++ b/trace2/tr2_tgt.h
@@ -120,6 +120,19 @@  typedef void(tr2_tgt_evt_timer_t)(uint64_t us_elapsed_absolute,
 				  uint64_t ns_min_time,
 				  uint64_t ns_max_time);
 
+/*
+ * Item counter event.
+ *
+ * This also does not take a (file,line) pair.
+ *
+ * The thread name is optional.
+ */
+typedef void(tr2_tgt_evt_counter_t)(uint64_t us_elapsed_absolute,
+				    const char *thread_name,
+				    const char *category,
+				    const char *counter_name,
+				    uint64_t value);
+
 /*
  * "vtable" for a TRACE2 target.  Use NULL if a target does not want
  * to emit that message.
@@ -157,6 +170,7 @@  struct tr2_tgt {
 	tr2_tgt_evt_data_json_fl_t              *pfn_data_json_fl;
 	tr2_tgt_evt_printf_va_fl_t              *pfn_printf_va_fl;
 	tr2_tgt_evt_timer_t                     *pfn_timer;
+	tr2_tgt_evt_counter_t                   *pfn_counter;
 };
 /* clang-format on */
 
diff --git a/trace2/tr2_tgt_event.c b/trace2/tr2_tgt_event.c
index fe89e80bb1a..907bff80827 100644
--- a/trace2/tr2_tgt_event.c
+++ b/trace2/tr2_tgt_event.c
@@ -643,6 +643,28 @@  static void fn_timer(uint64_t us_elapsed_absolute,
 	jw_release(&jw);
 }
 
+static void fn_counter(uint64_t us_elapsed_absolute,
+		       const char *thread_name,
+		       const char *category,
+		       const char *counter_name,
+		       uint64_t value)
+{
+	const char *event_name = "counter";
+	struct json_writer jw = JSON_WRITER_INIT;
+	double t_abs = (double)us_elapsed_absolute / 1000000.0;
+
+	jw_object_begin(&jw, 0);
+	event_fmt_prepare(event_name, __FILE__, __LINE__, NULL, &jw, thread_name);
+	jw_object_double(&jw, "t_abs", 6, t_abs);
+	jw_object_string(&jw, "name", counter_name);
+	jw_object_intmax(&jw, "value", value);
+
+	jw_end(&jw);
+
+	tr2_dst_write_line(&tr2dst_event, &jw.json);
+	jw_release(&jw);
+}
+
 struct tr2_tgt tr2_tgt_event = {
 	&tr2dst_event,
 
@@ -675,4 +697,5 @@  struct tr2_tgt tr2_tgt_event = {
 	fn_data_json_fl,
 	NULL, /* printf */
 	fn_timer,
+	fn_counter,
 };
diff --git a/trace2/tr2_tgt_normal.c b/trace2/tr2_tgt_normal.c
index 23a7e78dcaa..1778232f6e9 100644
--- a/trace2/tr2_tgt_normal.c
+++ b/trace2/tr2_tgt_normal.c
@@ -356,4 +356,5 @@  struct tr2_tgt tr2_tgt_normal = {
 	NULL, /* data_json */
 	fn_printf_va_fl,
 	NULL, /* timer */
+	NULL, /* counter */
 };
diff --git a/trace2/tr2_tgt_perf.c b/trace2/tr2_tgt_perf.c
index c07ffad1a32..911cf6e6eab 100644
--- a/trace2/tr2_tgt_perf.c
+++ b/trace2/tr2_tgt_perf.c
@@ -581,6 +581,23 @@  static void fn_timer(uint64_t us_elapsed_absolute,
 	strbuf_release(&buf_payload);
 }
 
+static void fn_counter(uint64_t us_elapsed_absolute,
+		       const char *thread_name,
+		       const char *category,
+		       const char *counter_name,
+		       uint64_t value)
+{
+	const char *event_name = "counter";
+	struct strbuf buf_payload = STRBUF_INIT;
+
+	strbuf_addf(&buf_payload, "name:%s value:%"PRIu64, counter_name, value);
+
+	perf_io_write_fl(__FILE__, __LINE__, event_name, NULL,
+			 &us_elapsed_absolute, NULL,
+			 category, &buf_payload, thread_name);
+	strbuf_release(&buf_payload);
+}
+
 struct tr2_tgt tr2_tgt_perf = {
 	&tr2dst_perf,
 
@@ -613,4 +630,5 @@  struct tr2_tgt tr2_tgt_perf = {
 	fn_data_json_fl,
 	fn_printf_va_fl,
 	fn_timer,
+	fn_counter,
 };