document that tracepoint names should ideally not be re-used

[lttng-ust.git] / doc / man / lttng-ust.3

diff --git a/doc/man/lttng-ust.3 b/doc/man/lttng-ust.3
index c6f1935c98a383e4e666ad6962796f0a799ca2f0..08927c64c4a18b60afbb2bc70f12ddb5dc330c51 100644 (file)
--- a/doc/man/lttng-ust.3
+++ b/doc/man/lttng-ust.3
@@ -238,6 +238,10 @@ For instance, add within a function:
 As a call to the tracepoint. It will only be activated when requested by
 lttng(1) through lttng-sessiond(8).
 
+Even though LTTng-UST supports tracepoint() call site duplicates having
+the same provider and event name, it is recommended to use a
+provider event name pair only once within the source code to help
+mapping events back to their call sites when analyzing the trace.
 .fi
 
 .SH "BUILDING/LINKING THE TRACEPOINT PROVIDER"
@@ -304,6 +308,38 @@ LD_PRELOAD=liblttng-ust-fork.so appname).
 
 .fi
 
+.SH "CONTEXT"
+
+.PP
+Context information can be prepended by the tracer before each, or some,
+events. The following context information is supported by LTTng-UST:
+.PP
+
+.PP
+.IP "vtid"
+Virtual thread ID: thread ID as seen from the point of view of the
+process namespace.
+.PP
+
+.PP
+.IP "vpid"
+Virtual process ID: process ID as seen from the point of view of the
+process namespace.
+.PP
+
+.PP
+.IP "procname"
+Thread name, as set by exec() or prctl(). It is recommended that
+programs set their thread name with prctl() before hitting the first
+tracepoint for that thread.
+.PP
+
+.PP
+.IP "pthread_id"
+Pthread identifier. Can be used on architectures where pthread_t maps
+nicely to an unsigned long type.
+.PP
+
 .SH "ENVIRONMENT VARIABLES"
 
 .PP