The LTTng Documentation
=======================
Philippe Proulx <pproulx@efficios.com>
-v2.8, 14 March 2017
+v2.8, 24 July 2017
include::../common/copyright.txt[]
+include::../common/warning-not-maintained.txt[]
+
+
include::../common/welcome.txt[]
[[installing-lttng]]
== Installation
+include::../common/warning-installation-outdated.txt[]
+
**LTTng** is a set of software <<plumbing,components>> which interact to
<<instrumenting,instrument>> the Linux kernel and user applications, and
to <<controlling-tracing,control tracing>> (start and stop
.Java and Python application instrumentation and tracing
====
If you need to instrument and trace <<java-application,Java
-applications>> on openSUSE, you need to build and install
+applications>> on Fedora, you need to build and install
LTTng-UST{nbsp}{revision} <<building-from-source,from source>> and pass
the `--enable-java-agent-jul`, `--enable-java-agent-log4j`, or
`--enable-java-agent-all` options to the `configure` script, depending
on which Java logging framework you use.
If you need to instrument and trace <<python-application,Python
-applications>> on openSUSE, you need to build and install
+applications>> on Fedora, you need to build and install
LTTng-UST{nbsp}{revision} from source and pass the
`--enable-python-agent` option to the `configure` script.
====
.Java and Python application instrumentation and tracing
====
If you need to instrument and trace <<java-application,Java
-applications>> on openSUSE, you need to build and install
+applications>> on Yocto/OpenEmbedded, you need to build and install
LTTng-UST{nbsp}{revision} <<building-from-source,from source>> and pass
the `--enable-java-agent-jul`, `--enable-java-agent-log4j`, or
`--enable-java-agent-all` options to the `configure` script, depending
on which Java logging framework you use.
If you need to instrument and trace <<python-application,Python
-applications>> on openSUSE, you need to build and install
+applications>> on Yocto/OpenEmbedded, you need to build and install
LTTng-UST{nbsp}{revision} from source and pass the
`--enable-python-agent` option to the `configure` script.
====
discard mode, the tracer only discards the event record that doesn't
fit.
-In discard mode, LTTng increments a count of lost event records when
-an event record is lost and saves this count to the trace. In
-overwrite mode, LTTng keeps no information when it overwrites a
-sub-buffer before consuming it.
+In discard mode, LTTng increments a count of lost event records when an
+event record is lost and saves this count to the trace. In overwrite
+mode, since LTTng 2.8, LTTng increments a count of lost sub-buffers when
+a sub-buffer is lost and saves this count to the trace. In this mode,
+the exact number of lost event records in those lost sub-buffers is not
+saved to the trace. Trace analyses can use the trace's saved discarded
+event record and sub-buffer counts to decide whether or not to perform
+the analyses even if trace data is known to be missing.
There are a few ways to decrease your probability of losing event
records.
An **event** is the consequence of the execution of an _instrumentation
point_, like a tracepoint that you manually place in some source code,
or a Linux kernel KProbe. An event is said to _occur_ at a specific
-time. Different actions can be taken upon the occurance of an event,
+time. Different actions can be taken upon the occurrence of an event,
like record the event's payload to a buffer.
An **event record** is the representation of an event in a sub-buffer. A
* **LTTng-tools**: Libraries and command-line interface to
control tracing sessions.
** <<lttng-sessiond,Session daemon>> (man:lttng-sessiond(8)).
-** <<lttng-consumerd,Consumer daemon>> (man:lttng-consumerd(8)).
+** <<lttng-consumerd,Consumer daemon>> (cmd:lttng-consumerd).
** <<lttng-relayd,Relay daemon>> (man:lttng-relayd(8)).
** <<liblttng-ctl-lttng,Tracing control library>> (`liblttng-ctl`).
** <<lttng-cli,Tracing control command-line tool>> (man:lttng(1)).
.The consumer daemon.
image::plumbing-consumerd.png[]
-The _consumer daemon_, man:lttng-consumerd(8), is a daemon which shares
+The _consumer daemon_, cmd:lttng-consumerd, is a daemon which shares
ring buffers with user applications or with the LTTng kernel modules to
collect trace data and send it to some location (on disk or to a
<<lttng-relayd,relay daemon>> over the network). The consumer daemon
.PIDs 3, 7, 10, and 13 are removed from the whitelist.
image::track-1-4-15-16.png[]
-LTTng can track all possible PIDs again using the opt:track(1):--all
-option:
+LTTng can track all possible PIDs again using the
+opt:lttng-track(1):--all option:
[role="term"]
----
or a Linux kernel KProbe.
+
An event is said to _occur_ at a specific time. Different actions can
-be taken upon the occurance of an event, like record the event's payload
+be taken upon the occurrence of an event, like record the event's payload
to a sub-buffer.
<<channel-overwrite-mode-vs-discard-mode,event loss mode>>::