clock: output clock description in metadata

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/lttng-events.c b/lttng-events.c
index 0ef87a8c992a9224b613b218ac1e324b95440a43..6dd3ba4ed19ef1bfb77002c50c1ab90f3714375a 100644 (file)
--- a/lttng-events.c
+++ b/lttng-events.c
@@ -794,8 +794,8 @@ int _lttng_stream_packet_context_declare(struct lttng_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"
@@ -821,11 +821,11 @@ int _lttng_event_header_declare(struct lttng_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"
@@ -834,11 +834,11 @@ int _lttng_event_header_declare(struct lttng_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",
@@ -847,6 +847,33 @@ int _lttng_event_header_declare(struct lttng_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 };
+       unsigned long flags;
+
+       /* Disable interrupts to increase correlation precision. */
+       local_irq_save(flags);
+       monotonic[0] = trace_clock_read64();
+       getnstimeofday(&rts);      
+       monotonic[1] = trace_clock_read64();
+       local_irq_restore(flags);
+
+       offset = (monotonic[0] + monotonic[1]) >> 1;
+       realtime = rts.tv_sec * NSEC_PER_SEC;
+       realtime += rts.tv_nsec;
+       offset = realtime - offset;
+       return offset;
+}
+
 /*
  * Output metadata into this session's metadata buffers.
  */
@@ -910,6 +937,44 @@ int _lttng_session_metadata_statedump(struct lttng_session *session)
        if (ret)
                goto end;
 
+       ret = lttng_metadata_printf(session,
+               "clock {\n"
+               "       name = %s;\n"
+               "       uuid = %s;\n"
+               "       description = \"Monotonic Clock\";\n"
+               "       freq = %llu; /* Frequency, in Hz */\n"
+               "       /* clock value offset from Epoch is: offset * (1/freq) */\n"
+               "       offset = %llu;\n"
+               "};\n\n",
+               "monotonic",
+               trace_clock_uuid(),
+               (unsigned long long) trace_clock_freq(),
+               (unsigned long long) 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 = _lttng_stream_packet_context_declare(session);
        if (ret)
                goto end;

diff --git a/wrapper/trace-clock.h b/wrapper/trace-clock.h
index d2579725e4aaecd38bccc9fb7c5df89b56d455ee..1140b94bcd1de2ae292a5dc9c4f9ffd4653271aa 100644 (file)
--- a/wrapper/trace-clock.h
+++ b/wrapper/trace-clock.h
@@ -44,14 +44,14 @@ static inline u64 trace_clock_read64(void)
        return (u64) trace_clock_monotonic_wrapper();
 }
 
-static inline u64 trace_clock_frequency(void)
+static inline u64 trace_clock_freq(void)
 {
-       return (u64)NSEC_PER_SEC;
+       return (u64) NSEC_PER_SEC;
 }
 
-static inline u32 trace_clock_freq_scale(void)
+static inline const char *trace_clock_uuid(void)
 {
-       return 1;
+       return "CLOCK_MONOTONIC";
 }
 
 static inline int get_trace_clock(void)