From 28b120498f554e2478806c27f7bf7ab295f3ffdf Mon Sep 17 00:00:00 2001
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Thu, 26 Jan 2012 21:32:03 -0500
Subject: [PATCH] clock: add clock description to metadata

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
 liblttng-ust/clock.h      | 14 +++++--
 liblttng-ust/ltt-events.c | 78 ++++++++++++++++++++++++++++++++++++---
 2 files changed, 83 insertions(+), 9 deletions(-)

diff --git a/liblttng-ust/clock.h b/liblttng-ust/clock.h
index 23294d2b..95e3e43b 100644
--- a/liblttng-ust/clock.h
+++ b/liblttng-ust/clock.h
@@ -34,7 +34,8 @@
 
 /* Choosing correct trace clock */
 
-static __inline__ uint64_t trace_clock_read64(void)
+static __inline__
+uint64_t trace_clock_read64(void)
 {
 	struct timespec ts;
 
@@ -42,9 +43,16 @@ static __inline__ uint64_t trace_clock_read64(void)
 	return ((uint64_t) ts.tv_sec * 1000000000ULL) + ts.tv_nsec;
 }
 
-static __inline__ uint32_t trace_clock_freq_scale(void)
+static __inline__
+uint64_t trace_clock_freq(void)
 {
-	return 1;
+	return 1000000000ULL;
+}
+
+static __inline__
+const char *trace_clock_uuid(void)
+{
+	return "CLOCK_MONOTONIC";
 }
 
 #endif /* _UST_CLOCK_H */
diff --git a/liblttng-ust/ltt-events.c b/liblttng-ust/ltt-events.c
index 9751089c..7d2dc31a 100644
--- a/liblttng-ust/ltt-events.c
+++ b/liblttng-ust/ltt-events.c
@@ -20,6 +20,9 @@
 #include <sys/ipc.h>
 #include <stdint.h>
 #include <stddef.h>
+#include <inttypes.h>
+#include <time.h>
+#include "clock.h"
 
 #include <urcu-bp.h>
 #include <urcu/compiler.h>
@@ -987,8 +990,8 @@ int _ltt_stream_packet_context_declare(struct ltt_session *session)
 {
 	return lttng_metadata_printf(session,
 		"struct packet_context {\n"
-		"	uint64_t timestamp_begin;\n"
-		"	uint64_t timestamp_end;\n"
+		"	uint64_clock_monotonic_t timestamp_begin;\n"
+		"	uint64_clock_monotonic_t timestamp_end;\n"
 		"	uint32_t events_discarded;\n"
 		"	uint32_t content_size;\n"
 		"	uint32_t packet_size;\n"
@@ -1014,11 +1017,11 @@ int _ltt_event_header_declare(struct ltt_session *session)
 	"	enum : uint5_t { compact = 0 ... 30, extended = 31 } id;\n"
 	"	variant <id> {\n"
 	"		struct {\n"
-	"			uint27_t timestamp;\n"
+	"			uint27_clock_monotonic_t timestamp;\n"
 	"		} compact;\n"
 	"		struct {\n"
 	"			uint32_t id;\n"
-	"			uint64_t timestamp;\n"
+	"			uint64_clock_monotonic_t timestamp;\n"
 	"		} extended;\n"
 	"	} v;\n"
 	"} align(%u);\n"
@@ -1027,11 +1030,11 @@ int _ltt_event_header_declare(struct ltt_session *session)
 	"	enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id;\n"
 	"	variant <id> {\n"
 	"		struct {\n"
-	"			uint32_t timestamp;\n"
+	"			uint32_clock_monotonic_t timestamp;\n"
 	"		} compact;\n"
 	"		struct {\n"
 	"			uint32_t id;\n"
-	"			uint64_t timestamp;\n"
+	"			uint64_clock_monotonic_t timestamp;\n"
 	"		} extended;\n"
 	"	} v;\n"
 	"} align(%u);\n\n",
@@ -1040,6 +1043,31 @@ int _ltt_event_header_declare(struct ltt_session *session)
 	);
 }
 
+/*
+ * Approximation of NTP time of day to clock monotonic correlation,
+ * taken at start of trace.
+ * Yes, this is only an approximation. Yes, we can (and will) do better
+ * in future versions.
+ */
+static
+uint64_t measure_clock_offset(void)
+{
+	uint64_t offset, monotonic[2], realtime;
+	struct timespec rts = { 0, 0 };
+	int ret;
+
+	monotonic[0] = trace_clock_read64();
+	ret = clock_gettime(CLOCK_REALTIME, &rts);	
+	if (ret < 0)
+		return 0;
+	monotonic[1] = trace_clock_read64();
+	offset = (monotonic[0] + monotonic[1]) >> 1;
+	realtime = rts.tv_sec * 1000000000ULL;
+	realtime += rts.tv_nsec;
+	offset = realtime - offset;
+	return offset;
+}
+
 /*
  * Output metadata into this session's metadata buffers.
  */
@@ -1103,6 +1131,44 @@ int _ltt_session_metadata_statedump(struct ltt_session *session)
 	if (ret)
 		goto end;
 
+	ret = lttng_metadata_printf(session,
+		"clock {\n"
+		"	name = %s;\n"
+		"	uuid = %s;\n"
+		"	description = \"Monotonic Clock\";\n"
+		"	freq = %" PRIu64 "; /* Frequency, in Hz */\n"
+		"	/* clock value offset from Epoch is: offset * (1/freq) */\n"
+		"	offset = %" PRIu64 ";\n"
+		"};\n\n",
+		"monotonic",
+		trace_clock_uuid(),
+		trace_clock_freq(),
+		measure_clock_offset()
+		);
+	if (ret)
+		goto end;
+
+	ret = lttng_metadata_printf(session,
+		"typealias integer {\n"
+		"	size = 27; align = 1; signed = false;\n"
+		"	map = clock.monotonic.value;\n"
+		"} := uint27_clock_monotonic_t;\n"
+		"\n"
+		"typealias integer {\n"
+		"	size = 32; align = %u; signed = false;\n"
+		"	map = clock.monotonic.value;\n"
+		"} := uint32_clock_monotonic_t;\n"
+		"\n"
+		"typealias integer {\n"
+		"	size = 64; align = %u; signed = false;\n"
+		"	map = clock.monotonic.value;\n"
+		"} := uint64_clock_monotonic_t;\n\n",
+		lttng_alignof(uint32_t) * CHAR_BIT,
+		lttng_alignof(uint64_t) * CHAR_BIT
+		);
+	if (ret)
+		goto end;
+
 	ret = _ltt_stream_packet_context_declare(session);
 	if (ret)
 		goto end;
-- 
2.34.1