From: Mathieu Desnoyers Date: Wed, 3 Aug 2011 01:12:00 +0000 (-0400) Subject: Commit timestamp guarantees X-Git-Tag: v2.0-pre7~7 X-Git-Url: http://git.liburcu.org/?a=commitdiff_plain;h=fcf745787bc83653284a78ff9846f2d75ca35a65;p=lttng-modules.git Commit timestamp guarantees Signed-off-by: Mathieu Desnoyers --- diff --git a/ltt-ring-buffer-client.h b/ltt-ring-buffer-client.h index 30f0104f..904c42eb 100644 --- a/ltt-ring-buffer-client.h +++ b/ltt-ring-buffer-client.h @@ -22,6 +22,14 @@ * you ever add/remove a field from this header. Packed attribute is not used * because gcc generates poor code on at least powerpc and mips. Don't ever * let gcc add padding between the structure elements. + * + * The guarantee we have with timestamps is that all the events in a + * packet are included (inclusive) within the begin/end timestamps of + * the packet. Another guarantee we have is that the "timestamp begin", + * as well as the event timestamps, are monotonically increasing (never + * decrease) when moving forward in a stream (physically). But this + * guarantee does not apply to "timestamp end", because it is sampled at + * commit time, which is not ordered with respect to space reservation. */ struct packet_header {