Fix: handle clock offset with frequency different from 1GHz

[babeltrace.git] / lib / trace-collection.c

diff --git a/lib/trace-collection.c b/lib/trace-collection.c
index 9bc5b1fcc8b0ecc543dd65b7a67734f4c44c8968..1c78f280fe0bcb128d3da85dbdfdf5a0e5daa6b4 100644 (file)
--- a/lib/trace-collection.c
+++ b/lib/trace-collection.c
@@ -24,6 +24,7 @@
 #include <babeltrace/ctf-text/types.h>
 #include <babeltrace/trace-collection.h>
 #include <babeltrace/ctf-ir/metadata.h>        /* for clocks */
+#include <babeltrace/clock-internal.h>
 
 #include <inttypes.h>
 
@@ -63,6 +64,19 @@ static void check_clock_match(gpointer key, gpointer value, gpointer user_data)
        }
 }
 
+/*
+ * Note: if using a frequency different from 1GHz for clock->offset, it
+ * is recommended to express the seconds in offset_s, otherwise there
+ * will be a loss of precision caused by the limited size of the double
+ * mantissa.
+ */
+static
+uint64_t clock_offset_ns(struct ctf_clock *clock)
+{
+       return clock->offset_s * 1000000000ULL
+                       + clock_cycles_to_ns(clock, clock->offset);
+}
+
 static void clock_add(gpointer key, gpointer value, gpointer user_data)
 {
        struct clock_match *clock_match = user_data;
@@ -88,8 +102,7 @@ static void clock_add(gpointer key, gpointer value, gpointer user_data)
                                fprintf(stderr, "[error] Only CTF traces with a single clock description are supported by this babeltrace version.\n");
                        }
                        if (!clock_match->tc->offset_nr) {
-                               clock_match->tc->offset_first =
-                                       (t_clock->offset_s * 1000000000ULL) + t_clock->offset;
+                               clock_match->tc->offset_first = clock_offset_ns(t_clock);
                                clock_match->tc->delta_offset_first_sum = 0;
                                clock_match->tc->offset_nr++;
                                clock_match->tc->single_clock_offset_avg =
@@ -105,23 +118,18 @@ static void clock_add(gpointer key, gpointer value, gpointer user_data)
                         * Check that the offsets match. If not, warn
                         * the user that we do an arbitrary choice.
                         */
-                       diff_ns = tc_clock->offset_s;
-                       diff_ns -= t_clock->offset_s;
-                       diff_ns *= 1000000000ULL;
-                       diff_ns += tc_clock->offset;
-                       diff_ns -= t_clock->offset;
+                       diff_ns = clock_offset_ns(tc_clock) - clock_offset_ns(t_clock);
                        printf_debug("Clock \"%s\" offset between traces has a delta of %" PRIu64 " ns.",
                                g_quark_to_string(tc_clock->name),
                                diff_ns < 0 ? -diff_ns : diff_ns);
-                       if (diff_ns > 10000) {
+                       if (diff_ns > 10000 || diff_ns < -10000) {
                                fprintf(stderr, "[warning] Clock \"%s\" offset differs between traces (delta %" PRIu64 " ns). Using average.\n",
                                        g_quark_to_string(tc_clock->name),
                                        diff_ns < 0 ? -diff_ns : diff_ns);
                        }
                        /* Compute average */
                        clock_match->tc->delta_offset_first_sum +=
-                               (t_clock->offset_s * 1000000000ULL) + t_clock->offset
-                               - clock_match->tc->offset_first;
+                               clock_offset_ns(t_clock) - clock_match->tc->offset_first;
                        clock_match->tc->offset_nr++;
                        clock_match->tc->single_clock_offset_avg =
                                clock_match->tc->offset_first