From c31d469f3734b0d60786deb2be9dafb3225755c3 Mon Sep 17 00:00:00 2001 From: David Goulet Date: Wed, 15 Jan 2020 10:55:07 -0500 Subject: trace: Comments and configure fix Signed-off-by: David Goulet --- src/lib/trace/events.h | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) (limited to 'src/lib/trace/events.h') diff --git a/src/lib/trace/events.h b/src/lib/trace/events.h index 8cc0136b09..4a8078bf34 100644 --- a/src/lib/trace/events.h +++ b/src/lib/trace/events.h @@ -9,7 +9,30 @@ #ifndef TOR_LIB_TRACE_EVENTS_H #define TOR_LIB_TRACE_EVENTS_H -/* XXX: DOCDOC once framework is stable. */ +/* + * A tracepoint signature is defined as follow: + * + * tor_trace(, , ...) + * + * If tracing is enabled, the tor_trace() macro is mapped to all possible + * instrumentations (defined below). Each instrumentation type MUST define a + * top level macro (TOR_TRACE_) so it can be inserted into each + * tracepoint. + * + * In case no tracing is enabled (HAVE_TRACING), tracepoints are NOP and thus + * have no execution cost. + * + * Currently, three types of instrumentation are supported: + * + * log-debug: Every tracepoints is mapped to a log_debug() statement. + * + * User Statically-Defined Tracing (USDT): Probes that can be used with perf, + * dtrace, SystemTap, DTrace and BPF Compiler Collection (BCC). + * + * LTTng-UST: Probes for the LTTng Userspace Tracer. If USDT interface + * (sdt.h) is available, the USDT probes are also generated by LTTng thus + * enabling this instrumentation provides both probes. + */ #ifdef HAVE_TRACING -- cgit v1.2.3-54-g00ecf