From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Sun, 12 Oct 2014 11:46:20 +0000 (+0200)
Subject: clock plugin: increase offset measurement accuracy
X-Git-Tag: v2.7.0-rc1~45
X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=commitdiff_plain;h=6e1b0543ef96dc12ff2bf1ca123a5637064d8c5e

clock plugin: increase offset measurement accuracy

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/src/bin/lttng-sessiond/ust-metadata.c b/src/bin/lttng-sessiond/ust-metadata.c
index b67921ef8..ea5978888 100644
--- a/src/bin/lttng-sessiond/ust-metadata.c
+++ b/src/bin/lttng-sessiond/ust-metadata.c
@@ -38,6 +38,7 @@
 #define max_t(type, a, b)	((type) ((a) > (b) ? (a) : (b)))
 #endif
 
+#define NSEC_PER_SEC			1000000000ULL
 #define NR_CLOCK_OFFSET_SAMPLES		10
 
 struct offset_sample {
@@ -543,10 +544,11 @@ int measure_single_clock_offset(struct offset_sample *sample)
 		return 0;
 	}
 	offset = (monotonic[0] + monotonic[1]) >> 1;
-	realtime = (uint64_t) rts.tv_sec * 1000000000ULL;
-	realtime += rts.tv_nsec;
-	if (tcf != 1000000000ULL) {
-		realtime /= 1000000000ULL / tcf;
+	realtime = (uint64_t) rts.tv_sec * tcf;
+	if (tcf == NSEC_PER_SEC) {
+		realtime += rts.tv_nsec;
+	} else {
+		realtime += (uint64_t) rts.tv_nsec * tcf / NSEC_PER_SEC;
 	}
 	offset = realtime - offset;
 	sample->offset = offset;