Merge commit '2c789b58062b5bf3bb16ca1654ccf9cf87f3c444' into lttng-luna

[deliverable/tracecompass.git] / org.eclipse.linuxtools.lttng.help / doc / User-Guide.mediawiki

= Overview =

LTTng (Linux Trace Toolkit, next generation) is a highly efficient tracing tool for Linux that can be used to track down kernel and application performance issues as well as troubleshoot problems involving multiple concurrent processes and threads. It consists of a set of kernel modules, daemons - to collect the raw tracing data - and a set of tools to control, visualize and analyze the generated data. It also provides support for user space application instrumentation.

For more information about LTTng, refer to the project [http://lttng.org site]

'''Note''': This User Guide covers the integration of the latest LTTng (v2.0) in Eclipse. The legacy version (v0.x) of both the tracer and the LTTng integration are no longer being maintained.

== About Tracing ==

Tracing is a troubleshooting technique used to understand the behavior of an instrumented application by collecting information on its execution path. A tracer is the software used for tracing. Tracing can be used to troubleshoot a wide range of bugs that are otherwise extremely challenging. These include, for example, performance problems in complex parallel systems or real-time systems.

Tracing is similar to logging: it consists in recording events that happen in a system at selected execution locations. However, compared to logging, it is generally aimed at developers and it usually records low-level events at a high rate. Tracers can typically generate thousands of events per second. The generated traces can easily contain millions of events and have sizes from many megabytes to tens of gigabytes. Tracers must therefore be optimized to handle a lot of data while having a small impact on the system.

Traces may include events from the operating system kernel (IRQ handler entry/exit, system call entry/exit, scheduling activity, network activity, etc). They can also consists of application events (a.k.a UST - User Space Tracing) or a mix of the two.

For the maximum level of detail, tracing events may be viewed like a log file. However, trace analyzers and viewers are available to derive useful information from the raw data. These programs must be specially designed to handle quickly the enormous amount of data a trace may contain.

== LTTng integration ==

The LTTng plug-in for Eclipse provides an Eclipse integration for the control of the LTTng tracer as well as fetching and visualization of the traces produced. It also provides the foundation for user-defined analysis tools.

The LTTng Eclipse plug-in provides the following views:

* ''Project'' - an extension to the standard Eclipse Project view tailored for tracing projects
* ''Control'' - to control the tracer and configure the tracepoints
* ''Events'' - a versatile view that presents the raw events in tabular format with support for searching, filtering and bookmarking
* ''Statistics'' - a view that that provides simple statistics on event occurrences by type
* ''Histogram'' - a view that displays the event density with respect to time in traces

These views can be extended or tailored for specific trace types (e.g. kernel, HW, user app).

At present, the LTTng Eclipse plug-in for Eclipse supports the following kernel-oriented analysis:

* ''Control Flow'' - to visualize processes state transitions
* ''Resources'' - to visualize system resources state transitions

Although the control and fetching parts are targeted at the LTTng tracer, the underlying framework can also be used to process any trace that complies with the ''Common Trace Format'' ([http://www.efficios.com/ctf CTF]). CTF specifies a very efficient and compact binary trace format that is meant to be application-, architecture-, and language-agnostic.

== Features ==

The LTTng Eclipse plug-in has a number of features to allow efficient handling of very large traces (and sets of large traces):

* Support for arbitrarily large traces (larger than available memory)
* Support for correlating multiple time-ordered traces
* Support for zooming down to the nanosecond on any part of a trace or set of traces
* Views synchronization of currently selected time or time range, and window time range
* Efficient searching and filtering of events
* Support for trace bookmarks

There is also support for the integration of non-LTTng trace types:

* Built-in CTF parser
* Dynamic creation of customized parsers (for XML and text traces)

= Installation =

This section describes the installation of the LTTng tracer and the LTTng Eclipse plug-ins as well as their dependencies.

== LTTng Tracer ==

While the Eclipse plug-ins can run on the standard Eclipse platforms (Linux, Mac, Windows), the LTTng tracer and its accompanying tools run on Linux.

The tracer and tools have been available for download in Ubuntu since 12.04. They can easily be installed with the following command:

<pre>
  > sudo apt-get install lttng-tools
</pre>

For other distributions, older Ubuntu distributions, or the latest, bleeding edge LTTng tracer, please refer to the [http://lttng.org/download LTTng website] for installation information.

'''Note''': The LTTng tracer (and accompanying tools) is required only if you want to create your own traces (the usual case). If you intend to simply analyze existing traces then it is not necessary to install the tracer.

== LTTng Eclipse Plug-ins ==

The easiest way to install the LTTng plug-ins for Eclipse is through the Software Updates and Add-ons menu. For information on how to use this menu, refer to this [http://wiki.eclipse.org/Linux_Tools_Project/PluginInstallHelp#Installing_Updates_From_the_Linux_Tools_Update_Site link].

The LTTng plug-ins are structured as a stack of features/plug-ins as following:

* '''CTF''' - A CTF parser that can also be used as a standalone component
** ''Feature'': org.eclipse.linuxtools.ctf
** ''Plug-ins'': org.eclipse.linuxtools.ctf.core, org.eclipse.linuxtools.ctf.parser

* '''TMF''' - ''Tracing and Monitoring Framework'' a framework for generic trace processing
** ''Feature'': org.eclipse.linuxtools.tmf
** ''Plug-ins'': org.eclipse.linuxtools.tmf.core, org.eclipse.linuxtools.tmf.ui

* '''LTTng''' - The wrapper for the LTTng tracer control. Can be used for kernel or application tracing.
** ''Feature'': org.eclipse.linuxtools.lttng2
** ''Plug-ins'': org.eclipse.linuxtools.lttng2.core, org.eclipse.linuxtools.lttng2.ui

* '''LTTng Kernel''' - Analysis components specific to Linux kernel traces
** ''Feature'': org.eclipse.linuxtools.lttng2.kernel
** ''Plug-ins'': org.eclipse.linuxtools.lttng2.kernel.core, org.eclipse.linuxtools.lttng2.kernel.ui

== LTTng Eclipse Dependencies ==

The Eclipse LTTng controls the LTTng tracer through an ''ssh'' connection even if the tracer is running locally (the 'degenerate' case).

Therefore, the target system (where the tracer runs) needs to run an ''ssh'' server as well as ''sftp'' server (for file transfer) to which you have permission to connect.

On the host side (where Eclipse is running), you also need to have Eclipse RSE (Remote System Explorer) installed to handle the SSH connection and transport. The RSE can be installed the standard way (''Help'' > ''Install New Software...'' > ''General Purpose Tools'' > ''Remote System Explorer End-User Runtime'').

== Installation Verification ==

Here are the quick steps to verify that your installation is functional:

* Start Eclipse
* Open the LTTng perspective
* Create a Tracing project
** Right-click in the Project view and select "New Project"
** Enter the name of your project (e.g. "MyLTTngProject")
** The project will be created. It will contain 2 empty folders: "Traces" and "Experiments"
* Import a sample trace
** Right-click on the newly created project "Traces" folder and select "Import..."
** Navigate to the sample LTTng trace that you want to visualize
** Select that trace (check box), select the trace type (e.g. CTF: Kernel Trace), and press "Finish"
** The newly imported trace should appear under the Traces folder
* Visualize the trace
** Expand the Traces folder
** Double-click on the trace
** The trace should load and the views be populated

If an error message is displayed, you might want to double-check that the trace type is correctly set (right-click on the trace and "Select Trace Type...").

Refer to [[#Tracing Perspective | Tracing Perspective]] for detailed description of the views and their usage.

To download sample LTTng traces, go to [http://lttng.org/download]. At the bottom of the page there is a link to some sample LTTng 2.0 kernel traces.

= LTTng =

== Tracing Perspective ==

The '''Tracing''' perspective is part of the '''Tracing and Monitoring Framework (TMF)''' and groups the following views:

* [[#Project_View | Project View]]
* [[#Events_Editor | Events Editor]]
* [[#Histogram_View | Histogram View]]
* [[#Statistics_View   | Statistics View]]

The views are synchronized i.e. selecting an event, a timestamp, a time range, etc will update the other views accordingly.

[[Image:images/TracingPerspective.png]]

The perspective can be opened from the Eclipse Open Perspective dialog ('''Window > Open Perspective... > Other''').

[[Image:images/ShowTracingPerspective.png]]

In addition to these views, the '''Tracing and Monitoring Framework (TMF)''' feature provides a set of generic tracing specific views, such as:

* [[#Colors_View | Colors View]]
* [[#Filters_View | Filters View]]
* [[#Time_Chart_View  | Time Chart View]]
* [[#Environment_Variables_View  | Environment Variables View]]
* [[#State_System_Explorer_View | State System Explorer View]]
* [[#Call_Stack_View | Call Stack View]]

The framework also supports user creation of [[#Custom_Parsers  | Custom Parsers]].

To open one of the above '''Tracing''' views, use the Eclipse Show View dialog ('''Window > Show View > Other...'''). Then select the relevant view from the '''Tracing''' category.

[[Image:images/ShowTracingViews.png]]

Additionally, the '''LTTng''' feature provides an '''LTTng Tracer Control''' functionality. It comes with a dedicated '''Control View'''.

* [[#LTTng_Tracer_Control | LTTng Tracer Control]]

== Project View ==

The project view is the standard Eclipse Project Explorer. '''Tracing''' projects are well integrated in the Eclipse's Common Navigator Framework. The Project Explorer shows '''Tracing''' project with a small "T" decorator in the upper right of the project folder icon.

=== Creating a Tracing Project ===

A new '''Tracing''' project can be created using the New Tracing Project wizard. To create a new '''Tracing'''  select '''File > New > Project...''' from the main menu bar or alternatively form the context-sensitive menu (click with right mouse button in the '''Project Explorer'''.

The first page of project wizard will open.

[[Image:images/NewTracingProjectPage1.png]]

In the list of project categories, expand category '''Tracing''' and select '''Tracing Project''' and the click on '''Next >'''. A second page of the wizard will show. Now enter the a name in the field '''Project Name''', select a location if required and the press on '''Finish'''.

[[Image:images/NewTracingProjectPage2.png]]

A new project will appear in the '''Project Explorer''' view.

[[Image:images/NewProjectExplorer.png]]

Tracing projects have two sub-folders: '''Traces''' which holds the individual traces, and '''Experiments''' which holds sets of traces that we want to correlate.

=== Importing Traces in a Project ===
==== Batch Importing ====
The '''Batch Import Trace Wizard''' allows users to search their media for traces and import multiple traces of varying trace types simultaneously. It also handles name clashes and renaming of traces.

The '''Traces''' folder holds the set of traces available for a tracing project. To import a set of traces to the '''Traces''' folder, one can open the '''Import...''' menu from the '''File''' main menu.

[[Image:images/importImages/importImportMenu.png]]

Then select '''Batch Trace Import'''

[[Image:images/importImages/importMenuSelect.png]]

Or one can select the '''Traces''' folder by double clicking on the project name.

[[Image:images/importImages/importSelectTracingProject.png]]

Then click the right mouse button on the '''Traces''' folder. Then select '''Batch Import...''' menu item in the context-sensitive menu.

[[Image:images/importImages/importBatchImport.png]]

At this point, the '''Batch import wizard''' is opened.

The '''Available trace types''' page is visible. Select a trace type to scan for by clicking an item in trace types tree. If one selects a parent element, the new state will be propagated to the children.

[[Image:images/importImages/importSelectTraceTypeToImport.png]]

When that is done, the warning message will go away and the user can click '''Next >'''.

[[Image:images/importImages/importSelectTraceTypeComplete.png]]

Then select one or more files or directories to scan for traces. The directories added will be recursively scanned, all children files and directories will be scanned. This can be slow depending on the size of the directory to scan.

[[Image:images/importImages/importSelectFilesToScan.png]]

One can add a directory by clicking on '''Add Directory...''' then selecting a directory to import.

[[Image:images/importImages/importSelectedDirectory.png]]

One can also add a file by clicking on '''Add File...''' then selecting a file to import.

[[Image:images/importImages/importAddFile.png]]

Once the files and directories are selected, a background scanner will already start scanning them for potential matches. to select the candidates, click '''Next >'''.

Here the user will see the results of the scan. The list will grow as more files are scanned.
To select a trace to import, first open a trace type.

[[Image:images/importImages/importScan1.png]]

Then select the trace to import.

[[Image:images/importImages/importScan2.png]]

When that is done, typically one can press '''Finish''', and the trace will be imported. They can set the trace to be '''linked''' or '''copied'''. A '''linked''' trace is not copied to the user's workspace, rather, the original file is used. This is useful for traces that are very large and that the user does not want to copy several times. '''Copied''' traces are as their name indicates, copied to the local workspace. This is useful if there is a trace on a network or on some removable media. The user can also specify if the trace should '''overwrite''' the resources in the workspace or not.

[[Image:images/importImages/importScan3.png]]

One can select several traces also and import them simultaneously. In this case there is a problem, the name of both traces are the same, this is a conflicting name and needs to be resolved.

[[Image:images/importImages/importScan4.png]]

To do so, select one of the conflicting traces, then '''click on its name'''. Then type in a new name.

[[Image:images/importImages/importScan5.png]]

Here the traces shall be copied instead of linked.

[[Image:images/importImages/importScan6.png]]

At this point, press '''Finish''' to import the traces.

If the '''Finish''' button is grayed, or if the user wishes to import to a different project, they need to press '''Next >'''. The user then needs to select a project to import to on the '''options''' page.

[[Image:images/importImages/importOptions.png]]

You will then see the traces in the '''Traces''' folder as shown below and can '''open''' them by '''double-clicking''' on them. For more details on how to open a trace see section [[#Opening_a_Trace_or_Experiment|Opening a Trace or Experiment]].

[[Image:images/importImages/importFinish.png]]

==== Importing ====

The previous way of importing a trace is still available. To access it, simply  select '''Import...''' menu item in the context-sensitive menu.

[[Image:images/ProjectImportTraceAction.png]]

A new display will show for selecting traces to import. By default, it shows the correct destination directory where the traces will be imported to. Now, specify the location of the traces by entering the path directly in the '''Source Directory''' or by browsing the file system (click on button browse). Then select the traces to import in the list of files and folders. Optionally, select the '''Trace Type''' from the drop-down menu, select or deselect the checkboxes for '''Overwrite existing trace without warning''' and '''Create links into workspace'''. When all options are configured, click on '''Finish'''.

Note, that traces of certain types (e.g. LTTng Kernel) are actually a composite of multiple channel traces grouped under a folder. It is the folder that has to be imported.

[[Image:images/ProjectImportTraceDialog.png]]

Upon successful importing the traces will be stored in the '''Traces''' folder. If a trace type was selected in the import dialog, then the corresponding icon will be displayed. If no trace type is selected the unknown icon [[Image:images/unknown_parser.gif]] will be displayed. Linked traces will have a little arrow as decorator on the right bottom corner.

Note that trace type is an extension point of the '''Tracing and Monitoring Framework (TMF)'''. Depending on the which features are loaded, the list of trace types can vary.

=== Selecting a Trace Type ===

If no trace type was selected a trace type as to be associated to a trace before it can be opened. To select a trace type select the relevant trace and click the right mouse button. In the context-sensitive menu, select '''Select Trace Type...''' menu item. A sub-menu will show will all available trace type categories. From the relevant category select the required trace type. The examples, below show how to select the '''Common Trace Format''' types '''LTTng Kernel''' and '''Generic CTF trace'''.

[[Image:images/SelectLTTngKernelTraceType.png]]

[[Image:images/SelectGenericCTFTraceType.png]]

After selecting the trace type, the trace icon will be updated with the corresponding trace type icon.

[[Image:images/ExplorerWithAssociatedTraceType.png]]

=== Creating a Experiment ===

An experiment consists in an arbitrary number of aggregated traces for purpose of correlation. In the degenerate case, an experiment can consist of a single trace. The experiment provides a unified, time-ordered stream of the individual trace events.

To create an experiment, select the folder '''Experiments''' and click the right mouse button. Then select '''New...'''.

[[Image:images/NewExperimentAction.png]]

A new display will open for entering the experiment name. Type the name of the experiment in the text field '''Experiment Name''' and the click on '''OK'''.

[[Image:images/NewExperimentDialog.png]]

=== Selecting Traces for an Experiment ===

After creating an experiment, traces need to be added to the experiment. To select traces for an experiment select the newly create experiment and click the right mouse button. Select '''Select Traces...''' from the context sensitive menu.

[[Image:images/SelectTracesAction.png]]

A new dialog box will open with a list of available traces. Select the traces to add from the list and then click on '''Finish'''.

[[Image:images/SelectTracesDialog.png]]

Now the selected traces will be linked to the experiment and will be shown under the '''Experiments''' folder.

[[Image:images/ExplorerWithExperiment.png]]

Alternatively, traces can be added to an experiment using [[#Drag_and_Drop | Drag and Drop]].

=== Removing Traces from an Experiment ===

To remove one or more traces for an experiment select the trace(s) to remove under the Experiment folder and click the right mouse button. Select '''Remove''' from the context sensitive menu.

[[Image:images/RemoveTracesAction.png]]

After that the selected trace(s) are removed from the experiment. Note that the traces are still in the '''Traces''' folder.

=== Renaming a Trace or Experiment ===

Traces and Experiment can be renamed from the '''Project Explorer''' view. To rename a trace or experiment select the relevant trace and click the right mouse button. Then select '''Rename...''' from the context sensitive menu. The trace or experiment needs to be closed in order to do this operation.

[[Image:images/RenameTraceAction.png]]

A new dialog box will show for entering a new name. Enter a new trace or experiment name respectively in the relevant text field and click on '''OK'''. If the new name already exists the dialog box will show an error and a different name has to be entered.

[[Image:images/RenameTraceDialog.png]]

[[Image:images/RenameExperimentDialog.png]]

After successful renaming the new name will show in the '''Project Explorer'''. In case of a trace all reference links to that trace will be updated too. Note that linked traces only changes the display name, the underlying trace resource will stay the original name.

Note that all supplementary files will be also handled accordingly (see also [[#Deleting Supplementary Files | Deleting Supplementary Files]]).

=== Copying a Trace or Experiment ===

To copy a trace or experiment select the relevant trace or experiment in the '''Project Explorer''' view and click the right mouse button. Then select '''Copy...''' from the context sensitive menu.

[[Image:images/CopyTraceAction.png]]

A new dialog box will show for entering a new name. Enter a new trace or experiment name respectively in the relevant text field and click on '''OK'''. If the new name already exists the dialog box will show an error and a different name has to be entered.

[[Image:images/CopyTraceDialog.png]]

[[Image:images/CopyExperimentDialog.png]]

After successful copy operation the new trace or experiment respectively will show in the '''Project Explorer'''. In case of a linked trace, the copied trace will be a link to the original trace too.

Note that the directory for all supplementary files will be copied, too. (see also [[#Deleting Supplementary Files | Deleting Supplementary Files]]).

=== Deleting a Trace or Experiment ===

To delete a trace or experiment select the relevant trace or experiment in the '''Project Explorer''' view and click the right mouse button. Then select '''Delete...''' from the context sensitive menu. The trace or experiment needs to be closed in order to do this operation.

[[Image:images/DeleteExperimentAction.png]]

A confirmation dialog box will open. To perform the deletion press '''OK''' otherwise select '''Cancel'''.

[[Image:images/DeleteExperimentConfirmationDialog.png]]

After successful operation the selected trace or experiment will be removed from the project. In case of a linked trace only the link will be removed. The actual trace resource remain on the disk.

Note that the directory for all supplementary files will be deleted, too. (see also [[#Deleting Supplementary Files | Deleting Supplementary Files]]).

=== Deleting Supplementary Files ===

Supplementary files are by definition trace specific files that accompany a trace. These file could be temporary files, persistent indexes or any other persistent data files created by the LTTng integration in Eclipse during parsing a trace. For the LTTng 2.0 trace viewer a persistent state history of the Linux Kernel is created and is stored under the name '''stateHistory.ht'''. The statistics for all traces are stored under '''statistics.ht'''. Other state systems may appear in the same folder as more custom views are added.

All supplementary file are hidden from the user and are handled internally by the TMF. However, there is a possibility to delete the supplementary files so that there are recreated when opening a trace.

To delete all supplementary files from a single trace, first, make sure the trace is not opened, then select the relevant trace in the '''Project Explorer''' view and click the right mouse button. Then select the '''Delete Supplementary Files...''' menu item from the context-sensitive menu.

[[Image:images/DeleteSupplementaryFilesAction.png]]

A new dialog box will open with a list of supplementary files. Select the file(s) to delete from the list and press '''OK'''.

[[Image:images/DeleteSupplementaryFilesDialog.png]]

To delete all supplementary files from all traces of a experiment, select the relevant experiment in the '''Project Explorer''' view and click the right mouse button. In the context-sensitive menu select '''Delete Supplementary Files...''' menu item. The experiment and included traces need to be closed in order to do this operation.

A new dialog box will open with a list of supplementary files. Note that the supplementary files are prefixed with the trace name to indicate the trace they belong to. Select the file(s) to delete from the list and press '''OK'''.

[[Image:images/DeleteExpSupplementaryFilesDialog.png]]

=== Opening a Trace or Experiment ===

A trace or experiment can be open by double-clicking the left mouse button on the trace or experiment in the '''Project Explorer''' view. Alternatively, select the trace or experiment in the in the '''Project Explorer''' view and click the right mouse button. Then select '''Open''' menu item of the context-sensitive menu.

[[Image:images/OpenTraceAction.png]]

When opening a trace or experiment all currently open view will be filled which are defined for the corresponding trace type. Additionally, an internal index will be created for fast navigation within a trace. For LTTng 2.0 kernel traces a persistent state history will also be build. This state history will be used in different views to display kernel state information.

=== Drag and Drop ===

Traces can be also be imported to a project by dragging from another tracing project and dropping to the project's trace folder. The trace will be copied and the trace type will be set.

Any resource can be dragged and dropped from a non-tracing project, and any file or folder can be dragged from an external tool, into a tracing project's trace folder. The resource will be copied or imported as a new trace, however the trace type will be unknown and need to be set manually by the user.

To import the trace as a link, use the platform-specific key modifier while dragging the source trace. A link will be created in the target project to the trace's location on the file system.

It is also possible to drop a trace, resource, file or folder into an existing experiment. If the item does not already exist as a trace in the project's trace folder, it will first be copied or imported, then the trace will be added to the experiment.

=== Link with Editor ===

The tracing projects support the feature '''Link With Editor''' of the Project Explorer view. With this feature it is now possible to<br/>
* select a trace element in the Project Explorer view and the corresponding [[#Events_Editor | Events Editor]] will get focus if the relevant trace is open.
* select an [[#Events_Editor | Events Editor]] and the corresponding trace element will be highlighted in the Project Explorer view.

To enable or disable this feature toggle the '''Link With Editor''' button of the Project Explorer view as shown below.

[[Image:images/TMF_LinkWithEditor.png]]

== Events Editor ==

The Events editor shows the basic trace data elements (events) in a tabular format. The editors can be dragged in the editor area so that several traces may be shown side by side. These traces are synchronized by timestamp.

[[Image:images/LTTng2EventsEditor.png]]

The header displays the current trace (or experiment) name.

Being part of the '''Tracing and Monitoring''' Framework, the default table displays the following fields:

* '''Timestamp''': the event timestamp
* '''Source''': the source of the event
* '''Type''': the event type and localization
* '''Reference''' the event reference
* '''Content''': the raw event content

The first row of the table is the header row a.k.a. the Search and Filter row.

The highlighted event is the ''current event'' and is synchronized with the other views. If you select another event, the other views will be updated accordingly. The properties view will display a more detailed view of the selected event.

An event range can be selected by holding the '''Shift''' key while clicking another event or using any of the cursor keys ('''Up'''', '''Down''', '''PageUp''', '''PageDown''', '''Home''', '''End'''). The first and last events in the selection will be used to determine the current selected time range for synchronization with the other views.

[[Image:images/LTTng2EventProperties.png]]

The Events editor can be closed, disposing a trace. When this is done, all the views displaying the information will be updated with the trace data of the next event editor tab. If all the editor tabs are closed, then the views will display their empty states.

=== Searching and Filtering ===

Searching and filtering of events in the table can be performed by entering matching conditions in one or multiple columns in the header row (the first row below the column header).

To toggle between searching and filtering, click on the 'search' ([[Image:images/TmfEventSearch.gif]]) or 'filter' ([[Image:images/TmfEventFilter.gif]]) icon in the header row's left margin, or right-click on the header row and select '''Show Filter Bar''' or '''Show Search Bar''' in the context menu.

To apply a matching condition to a specific column, click on the column's header row cell, type in a [http://download.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html regular expression] and press the '''ENTER''' key. You can also enter a simple text string and it will be automatically be replaced with a 'contains' regular expression.

When matching conditions are applied to two or more columns, all conditions must be met for the event to match (i.e. 'and' behavior).

To clear all matching conditions in the header row, press the '''DEL''' key.

==== Searching ====

When a searching condition is applied to the header row, the table will select the next matching event starting from the top currently displayed event. Wrapping will occur if there is no match until the end of the trace.

All matching events will have a 'search match' icon in their left margin. Non-matching events will be dimmed.

[[Image:images/DefaultTmfEvents-Search.png]]

Pressing the '''ENTER''' key will search and select the next matching event. Pressing the '''SHIFT-ENTER''' key will search and select the previous matching event. Wrapping will occur in both directions.

Press '''ESC''' to cancel an ongoing search.

Press '''DEL''' to clear the header row and reset all events to normal.

==== Filtering ====

When a filtering condition is entered in the head row, the table will clear all events and fill itself with matching events as they are found from the beginning of the trace.

A status row will be displayed before and after the matching events, dynamically showing how many matching events were found and how many events were processed so far. Once the filtering is completed, the status row icon in the left margin will change from a 'stop' to a 'filter' icon.

[[Image:images/DefaultTmfEvents-Filter.png]]

Press '''ESC''' to stop an ongoing filtering. In this case the status row icon will remain as a 'stop' icon to indicate that not all events were processed.

Press '''DEL''' or right-click on the table and select '''Clear Filters''' from the context menu to clear the header row and remove the filtering. All trace events will be now shown in the table. Note that the currently selected event will remain selected even after the filter is removed.

You can also search on the subset of filtered events by toggling the header row to the Search Bar while a filter is applied. Searching and filtering conditions are independent of each other.

==== Bookmarking ====

Any event of interest can be tagged with a bookmark.

To add a bookmark, double-click the left margin next to an event, or right-click the margin and select '''Add bookmark...'''. Alternatively use the '''Edit''' > '''Add bookmark...''' menu. Edit the bookmark description as desired and press '''OK'''.

The bookmark will be displayed in the left margin, and hovering the mouse over the bookmark icon will display the description in a tooltip.

The bookmark will be added to the '''Bookmarks''' view. In this view the bookmark description can be edited, and the bookmark can be deleted. Double-clicking the bookmark or selecting '''Go to''' from its context menu will open the trace or experiment and go directly to the event that was bookmarked.

To remove a bookmark, double-click its icon, select '''Remove Bookmark''' from the left margin context menu, or select '''Delete''' from the Bookmarks view.

[[Image:images/Bookmarks.png]]

=== Event Source Lookup ===

For CTF traces using specification v1.8.2 or above, information can optionally be embedded in the trace to indicate the source of a trace event. This is accessed through the event context menu by right-clicking on an event in the table.

==== Source Code ====

If a source file is available in the trace for the selected event, the item '''Open Source Code''' is shown in the context menu. Selecting this menu item will attempt to find the source file in all opened projects in the workspace. If multiple candidates exist, a selection dialog will be shown to the user. The selected source file will be opened, at the correct line, in its default language editor. If no candidate is found, an error dialog is shown displaying the source code information.

==== EMF Model ====

If an EMF model URI is available in the trace for the selected event, the item '''Open Model Element''' is shown in the context menu. Selecting this menu item will attempt to open the model file in the project specified in the URI. The model file will be opened in its default model editor. If the model file is not found, an error dialog is shown displaying the URI information.

=== Exporting To Text ===
It is possible to export the content of the trace to a text file based on the columns displayed in the events table. If a filter (see '''[[#Filtering| Filtering]]''') was defined prior exporting only events that match the filter will be exported to the file. To export the trace to text, press the right mouse button on the events table. A context-sensitive menu will show. Select the '''Export To Text...''' menu option. A file locater dialog will open. Fill in the file name and location and then press on '''OK'''. A window with a progress bar will open till the export is finished.

''Note'':  The columns in the text file are separated by tabs.    

== Histogram View ==

The Histogram View displays the trace events distribution with respect to time. When streaming a trace, this view is dynamically updated as the events are received.


[[Image:images/HistogramView.png]]

The '''Hide Lost Events''' toggle button [[Image:images/hide_lost_events.gif]] in the local toolbar allows to hide the bars of lost events. When the button is selected it can be toggled again to show the lost events.

On the top left, there are two data controls:

* '''Current Event (sec)''': Displays the current time or selected time range begin time
* '''Window Span (sec)''': Displays the current time range window size

Both control can be used to modify their respective value. After validation, the other controls and views will be synchronized and updated accordingly.

The large histogram, at the bottom, shows the event distribution over the whole trace or set of traces. It also has a smaller semi-transparent window, with a cross-hair, that shows the currently selected time range window. The time range window can be zoomed in/out by using the mouse wheel. It can also be selected by the mouse and dragged to another region of the trace.

The smaller histogram, on top right, corresponds to the currently selected time range window, a sub-range of the event set. Its size can also be zoomed in/out using the mouse wheel.

The x-axis of each histogram corresponds to the events timestamps. The timestamp of the first and the last event of the respective ranges is displayed. The y-axis of each histogram shows the minimum/maximum number of events in the corresponding histogram bars.

The dashed vertical magenta bar, on the right, shows the position of the last event. The vertical blue bar shows the currently selected time. The current time can be changed by clicking on the histogram. Shift-clicking the histogram will select a time range, in which case there will be vertical blue bars at the begin and end time and the region in between will be shaded.

Hovering the mouse over an histogram bar pops up an information window that displays the start/end time of the corresponding bar as well as the number of events it represents.

In each histogram, the following keys are handled:

* '''Left''': Moves the current event to the previous non-empty bar
* '''Right''': Moves the current event to the next non-empty bar
* '''Home''': Sets the current time to the first histogram bar
* '''End''': Sets the current time to the last non-empty histogram bar

== Statistics View ==

The Statistics View displays the various event counters that are collected when analyzing a trace. The data is organized per trace. To open the Statistics View, select Windows -> Show View -> Other... -> Tracing -> Statistics. A new view will open with the name Statistics. This view shows 3 columns: ''Level'' ''Events total'' and ''Events in selected time range''. After parsing a trace the view will display the number of events per event type in the second column and in the third, the currently selected time range's event type distribution is shown. The cells where the number of events are printed also contain a colored bar that indicates the percentage of the event count in relation to the total number of events. The statistics is collected for the whole trace. This view is part of the '''Tracing and Monitoring Framework (TMF)''' and is generic. It will work for any trace type extensions. For the LTTng 2.0 integration the Statistics view will display statistics as shown below.:

[[Image:images/LTTng2StatisticsView.png]]

By default, the statistics use a state system, therefore will load very quickly once the state system is written to the disk as a supplementary file.

== Colors View ==

[[Image:images/ColorsView.png]]

The Colors view allows the user to define a prioritized list of color settings.

A color setting associates a foreground and background color (used in any events table), and a tick color (used in the Time Chart view), with an event filter.

In an events table, any event row that matches the event filter of a color setting will be displayed with the specified foreground and background colors. If the event matches multiple filters, the color setting with the highest priority will be used.

The same principle applies to the event tick colors in the Time Chart view. If a tick represents many events, the tick color of the highest priority matching event will be used.

Color settings can be inserted, deleted, reordered, imported and exported using the buttons in the Colors view toolbar. Changes to the color settings are applied immediately, and are persisted to disk.

== Filters View ==

[[Image:images/FiltersView.png]]

The Filters view allows the user to define preset filters that can be applied to any events table.

The filters can be more complex than what can be achieved with the filter header row in the events table. The filter is defined in a tree node structure, where the node types can be any of '''EVENTTYPE''', '''AND''', '''OR''', '''CONTAINS''', '''EQUALS''', '''MATCHES''' or '''COMPARE'''. Some nodes types have restrictions on their possible children in the tree.

The '''EVENTTYPE''' node filters against the event type of the trace as defined in a plug-in extension or in a custom parsers. When used, any child node will have its field combo box restricted to the possible fields of that event type.

The '''AND''' node applies the logical ''and'' condition on all of its children. All children conditions must be true for the filter to match. A ''not'' operator can be applied to invert the condition.

The '''OR''' node applies the logical ''or'' condition on all of its children. At least one children condition must be true for the filter to match. A ''not'' operator can be applied to invert the condition.

The '''CONTAINS''' node matches when the specified event ''field'' value contains the specified ''value'' string. A ''not'' operator can be applied to invert the condition. The condition can be case sensitive or insensitive.

The '''EQUALS''' node matches when the specified event ''field'' value equals exactly the specified ''value'' string. A ''not'' operator can be applied to invert the condition. The condition can be case sensitive or insensitive.

The '''MATCHES''' node matches when the specified event ''field'' value matches against the specified ''regular expression''. A ''not'' operator can be applied to invert the condition.

The '''COMPARE''' node matches when the specified event ''field'' value compared with the specified ''value'' gives the specified ''result''. The result can be set to ''smaller than'', ''equal'' or ''greater than''. The type of comparison can be numerical, alphanumerical or based on time stamp. A ''not'' operator can be applied to invert the condition.

Filters can be added, deleted, imported and exported using the buttons in the Filters view toolbar. Changes to the preset filters are only applied and persisted to disk when the '''save filters''' button is pressed.

To apply a saved preset filter in an events table, right-click on the table and select '''Apply preset filter...''' > ''filter name''.

== Time Chart View ==

[[Image:images/TimeChartView.png]]

The Time Chart view allows the user to visualize every open trace in a common time chart. Each trace is display in its own row and ticks are display for every punctual event. As the user zooms using the mouse wheel or by right-clicking and dragging in the time scale, more detailed event data is computed from the traces.

Time synchronization is enabled between the time chart view and other trace viewers such as the events table.

Color settings defined in the Colors view can be used to change the tick color of events displayed in the Time Chart view.

When a search is applied in the events table, the ticks corresponding to matching events in the Time Chart view are decorated with a marker below the tick.

When a bookmark is applied in the events table, the ticks corresponding to the bookmarked event in the Time Chart view is decorated with a bookmark above the tick.

When a filter is applied in the events table, the non-matching ticks are removed from the Time Chart view.

The Time Chart only supports traces that are opened in an editor. The use of an editor is specified in the plug-in extension for that trace type, or is enabled by default for custom traces.

== Environment Variables View ==
A new feature of CTF traces is their ability to store user defined data that is not to be placed in an event. It is generally data that is per-trace specific, such as the tracer version and the trace domain. It will be populated when a trace is loaded if the trace has environment variables. <br>
[[Image:images/LTTng2EnvironmentsView.png]]<br>
The above picture shows a trace loaded that was collected with the '''lttng-modules''' version '''2'''.'''0'''.'''0''' tracer. It is a '''kernel''' trace of the '''3.2.0-18-generic''' '''linux''' kernel.

== State System Explorer View ==

The State System Explorer view allows the user to inspect the state interval values of every attribute of a state system at a particular time.

The view shows a tree of currently selected traces and their registered state system IDs. For each state system the tree structure of attributes is displayed. The attribute name, quark, value, start and end time, and full attribute path are shown for each attribute.

To modify the time of attributes shown in the view, select a different current time in other views that support time synchronization (e.g. event table, histogram view). When a time range is selected, this view uses the begin time.

== Call Stack View ==

The Call Stack view allows the user to visualize the call stack per thread over time, if the application and trace provide this information.

The view shows the call stack information for the currently selected trace.

The table on the left-hand side of the view shows the threads and call stack. The function name, depth, entry and exit time and duration are shown for the call stack at the selected time.

Double-clicking on a function entry in the table will zoom the time graph to the selected function's range of execution.

The time graph on the right-hand side of the view shows the call stack state graphically over time. The function name is visible on each call stack event if size permits. The color of each call stack event is randomly assigned based on the function name, allowing for easy identification of repeated calls to the same function.

Clicking on the time graph will set the current time and consequently update the table with the current call stack information.

Shift-clicking on the time graph will select a time range. When the selection is a time range, the begin time is used to update the stack information.

Double-clicking on a call stack event will zoom the time graph to the selected function's range of execution.

Clicking the '''Select Next Event''' or '''Select Previous Event''' or using the left and right arrows will navigate to the next or previous call stack event, and select the function currently at the top of the call stack.

== Custom Parsers ==

Custom parser wizards allow the user to define their own parsers for text or XML traces. The user defines how the input should be parsed into internal trace events and identifies the event fields that should be created and displayed. Traces created using a custom parser can be correlated with other built-in traces or traces added by plug-in extension.

=== Creating a custom text parser ===

The '''New Custom Text Parser''' wizard can be used to create a custom parser for text logs. It can be launched several ways:

* Select '''File''' &gt; '''New''' &gt; '''Other...''' &gt; '''Tracing''' &gt; '''Custom Text Parser'''
* Open the '''[[#Managing_custom_parsers | Manage Custom Parsers]]''' dialog, select the '''Text''' radio button and click the '''New...''' button

[[Image:images/CustomTextParserInput.png]]

Fill out the first wizard page with the following information:

* '''Log type:''' Enter a name for the custom log entries, which is also the name of the custom parser.
* '''Time Stamp format:''' Enter the date and time pattern that will be used to output the Time Stamp.<br>
Note: information about date and time patterns can be found here: [http://java.sun.com/javase/6/docs/api/java/text/SimpleDateFormat.html]

Click the '''Add next line''', '''Add child line''' or '''Remove line''' buttons to create a new line of input or delete it. For each line of input, enter the following information:

* '''Regular expression:''' Enter a regular expression that should match the input line in the log, using capturing groups to extract the data.<br>
Note: information about date and time patterns can be found here: [http://java.sun.com/javase/6/docs/api/java/util/regex/Pattern.html]

* '''Cardinality:''' Enter the minimum and maximum number of lines matching this line's regular expression that must be found in the log. At least the minimum number of lines must be found before the parser will consider the next line. Child lines will always be considered first.

<u>Important note:</u> The custom parsers identify a log entry when the first line's regular expression matches (Root Line n). Each subsequent text line in the log is attempted to be matched against the regular expression of the parser's input lines in the order that they are defined (Line n.*). Only the first matching input line will be used to process the captured data to be stored in the log entry. When a text line matches a Root Line's regular expression, a new log entry is started.

Click the '''Add group''' or '''Remove group''' buttons to define the data extracted from the capturing groups in the line's regular expression. For each group, enter the following information:

* '''Name combo:''' Select a name for the extracted data:
** '''Time Stamp''': Select this option to identify the time stamp data. The input's data and time pattern must be entered in the format: text box.
** '''Message''': Select this option to identify the main log entry's message. This is usually a group which could have text of greater length.
** '''Other''': Select this option to identify any non-standard data. The name must be entered in the name: text box.

* '''Action combo:''' Select the action to be performed on the extracted data:
** '''Set''': Select this option to overwrite the data for the chosen name when there is a match for this group.
** '''Append''': Select this option to append to the data with the chosen name, if any, when there is a match for this group.
** '''Append with |''' : Select this option to append to the data with the chosen name, if any, when there is a match for this group, using a | separator between matches.

The '''Preview input''' text box can be used to enter any log data that will be processed against the defined custom parser. When the wizard is invoked from a selected log file resource, this input will be automatically filled with the file contents.

The '''Preview:''' text field of each capturing group and of the Time Stamp will be filled from the parsed data of the first matching log entry.

In the '''Preview input''' text box, the matching entries are highlighted with different colors:

* <code><span style="background:#FFFF00">&nbsp;Yellow&nbsp;</span></code> : indicates uncaptured text in a matching line.
* <code><span style="background:#00FF00">&nbsp;Green&nbsp;&nbsp;</span></code> : indicates a captured group in the matching line's regular expression for which a custom parser group is defined. This data will be stored by the custom parser.
* <code><span style="background:#FF00FF">&nbsp;Magenta</span></code> : indicates a captured group in the matching line's regular expression for which there is no custom parser group defined. This data will be lost.
* <code>&nbsp;White&nbsp;&nbsp;</code> : indicates a non-matching line.

The first line of a matching entry is highlighted with darker colors.

By default only the first matching entry will be highlighted. To highlight all matching entries in the preview input data, click the '''Highlight All''' button. This might take a few seconds to process, depending on the input size.

Click the '''Next >''' button to go to the second page of the wizard.

[[Image:images/CustomTextParserOutput.png]]

On this page, the list of default and custom data is shown, along with a preview of the custom parser log table output.

The custom data output can be modified by the following options:

* '''Visibility:''' Select or unselect the checkbox to display the custom data or hide it.

* '''Column order:''' Click '''Move before''' or '''Move after''' to change the display order of custom data.

The table at the bottom of the page shows a preview of the custom parser log table output according to the selected options, using the matching entries of the previous page's '''Preview input''' log data.

Click the '''Finish''' button to close the wizard and save the custom parser.

=== Creating a custom XML parser ===

The '''New Custom XML Parser''' wizard can be used to create a custom parser for XML logs. It can be launched several ways:

* Select '''File''' &gt; '''New''' &gt; '''Other...''' &gt; '''Tracing''' &gt; '''Custom XML Parser'''
* Open the '''[[#Managing_custom_parsers | Manage Custom Parsers]]''' dialog, select the '''XML''' radio button and click the '''New...''' button

[[Image:images/CustomXMLParserInput.png]]

Fill out the first wizard page with the following information:

* '''Log type:''' Enter a name for the custom log entries, which is also the name of the custom parser.
* '''Time Stamp format:''' Enter the date and time pattern that will be used to output the Time Stamp.<br>

Note: information about date and time patterns can be found here: [http://java.sun.com/javase/6/docs/api/java/text/SimpleDateFormat.html]

Click the '''Add document element''' button to create a new document element and enter a name for the root-level document element of the XML file.

Click the '''Add child''' button to create a new element of input to the document element or any other element. For each element, enter the following information:

* '''Element name:''' Enter a name for the element that must match an element of the XML file.
* '''Log entry:''' Select this checkbox to identify an element which represents a log entry. Each element with this name in the XML file will be parsed to a new log entry. At least one log entry element must be identified in the XML document. Log entry elements cannot be nested.
* '''Name combo:''' Select a name for the extracted data:
** '''Ignore''': Select this option to ignore the extracted element's data at this level. It is still possible to extract data from this element's child elements.
** '''Time Stamp''': Select this option to identify the time stamp data. The input's data and time pattern must be entered in the format: text box.
** '''Message''': Select this option to identify the main log entry's message. This is usually an input which could have text of greater length.
** '''Other''': Select this option to identify any non-standard data. The name must be entered in the name: text box. It does not have to match the element name.
* '''Action combo:''' Select the action to be performed on the extracted data:
** '''Set''': Select this option to overwrite the data for the chosen name when there is a match for this element.
** '''Append''': Select this option to append to the data with the chosen name, if any, when there is a match for this element.
** '''Append with |''' : Select this option to append to the data with the chosen name, if any, when there is a match for this element, using a | separator between matches.

Note: An element's extracted data 'value' is a parsed string representation of all its attributes, children elements and their own values. To extract more specific information from an element, ignore its data value and extract the data from one or many of its attributes and children elements.

Click the '''Add attribute''' button to create a new attribute input from the document element or any other element. For each attribute, enter the following information:

* '''Attribute name:''' Enter a name for the attribute that must match an attribute of this element in the XML file.
* '''Name combo:''' Select a name for the extracted data:
** '''Time Stamp''': Select this option to identify the time stamp data. The input's data and time pattern must be entered in the format: text box.
** '''Message''': Select this option to identify the main log entry's message. This is usually an input which could have text of greater length.
** '''Other''': Select this option to identify any non-standard data. The name must be entered in the name: text box. It does not have to match the element name.
* '''Action combo:''' Select the action to be performed on the extracted data:
** '''Set''': Select this option to overwrite the data for the chosen name when there is a match for this element.
** '''Append''': Select this option to append to the data with the chosen name, if any, when there is a match for this element.
** '''Append with |''' : Select this option to append to the data with the chosen name, if any, when there is a match for this element, using a | separator between matches.

Note: A log entry can inherited input data from its parent elements if the data is extracted at a higher level.

Click the '''Feeling lucky''' button to automatically and recursively create child elements and attributes for the current element, according to the XML element data found in the '''Preview input''' text box, if any.

Click the '''Remove element''' or '''Remove attribute''' buttons to remove the extraction of this input data. Take note that all children elements and attributes are also removed.

The '''Preview input''' text box can be used to enter any XML log data that will be processed against the defined custom parser. When the wizard is invoked from a selected log file resource, this input will be automatically filled with the file contents.

The '''Preview:''' text field of each capturing element and attribute and of the Time Stamp will be filled from the parsed data of the first matching log entry. Also, when creating a new child element or attribute, its element or attribute name will be suggested if possible from the preview input data.

Click the '''Next >''' button to go to the second page of the wizard.

[[Image:images/CustomXMLParserOutput.png]]

On this page, the list of default and custom data is shown, along with a preview of the custom parser log table output.

The custom data output can be modified by the following options:

* '''Visibility:''' Select or unselect the checkbox to display the custom data or hide it.
* '''Column order:''' Click '''Move before''' or '''Move before''' to change the display order of custom data.

The table at the bottom of the page shows a preview of the custom parser log table output according to the selected options, using the matching entries of the previous page's '''Preview input''' log data.

Click the '''Finish''' button to close the wizard and save the custom parser.

=== Managing custom parsers ===

The '''Manage Custom Parsers''' dialog is used to manage the list of custom parsers used by the tool. To open the dialog:

* Open the '''Project Explorer''' view.
* Select '''Manage Custom Parsers...''' from the '''Traces''' folder context menu, or from a trace's '''Select Trace Type...''' context sub-menu.

[[Image:images/ManageCustomParsers.png]]

The ordered list of currently defined custom parsers for the selected type is displayed on the left side of the dialog.

To change the type of custom parser to manage, select the '''Text''' or '''XML''' radio button.

The following actions can be performed from this dialog:

* New...

Click the '''New...''' button to launch the '''New Custom Parser''' wizard.

* Edit...

Select a custom parser from the list and click the '''Edit...''' button to launch the '''Edit Custom Parser''' wizard.

* Delete

Select a custom parser from the list and click the '''Delete''' button to remove the custom parser.

* Import...

Click the '''Import...''' button and select a file from the opened file dialog to import all its custom parsers.

* Export...

Select a custom parser from the list, click the '''Export...''' button and enter or select a file in the opened file dialog to export the custom parser. Note that if an existing file containing custom parsers is selected, the custom parser will be appended to the file.

=== Opening a trace using a custom parser ===

Once a custom parser has been created, any [[#Importing Traces in a Project|imported trace]] file can be opened and parsed using it.

To do so:

* Select a trace in the '''Project Explorer''' view
* Right-click the trace and select '''Select Trace Type...''' &gt; '''Custom Text''' or '''Custom XML''' &gt; ''parser name''
* Double-click the trace or right-click it and select '''Open'''

The trace will be opened in an editor showing the events table, and an entry will be added for it in the Time Chart view.

== LTTng Tracer Control ==

The LTTng Tracer Control in Eclipse for the LTTng Tracer toolchain version v2.0 (or later) is done using SSH and requires an SSH server to be running on the remote host. For the SSH connection the SSH implementation of RSE is used. For that a new System Type was defined using the corresponding RSE extension. The functions to control the LTTng tracer (e.g. start and stop), either locally or remotely, are available from a dedicated Control View.

In the following sections the LTTng 2.0 tracer control integration in Eclipse is described. Please refer to the LTTng 2.0 tracer control command line manual for more details and descriptions about all commands and their command line parameters [[#References | References]].

=== Control View ===
To open the Control View, select '''Window->Show View->Other...->LTTng->Control View''.

[[Image:images/LTTngControlView.png]]

==== Creating a New Connection to a Remote Host ====

To connect to a remote host, select the '''New Connection''' button in the Control View.

[[Image:images/LTTngControlViewConnect.png]]

A new display will show for entering the remote host information. A drop down menu will filled with all existing host information which were used before. To enter the host information either select one of the hosts in the drop down menu or enter the host information manually.

[[Image:images/LTTng2NewConnection.png]]

To use an existing connection definition, select the relevant entry in the drop-down menu and then select '''Ok'''.

[[Image:images/LTTng2SelectConnection.png]]

To enter the host information manually select first the button '''Edit connection information'''. Then the text fields '''Connection Name''', '''Host Name''' and '''Port Number''' will be enabled. The '''Host Name''' holds the IP address or DNS name of the remote system. The '''Connection Name''' is the alias name to be displayed in the Control View. The '''Port Number''' is the port number to be used for the IP connection. This parameter is optional and if it is omitted the default port will be used. Enter the relevant information and then select '''Ok'''.

[[Image:images/LTTng2EditConnection.png]]

A new display will show for providing the user name and password. This display only opens if no password had been saved before. Enter user name and password in the '''Enter Password''' dialog box and select '''Ok'''.

[[Image:images/LTTng2EnterPassword.png]]

After pressing '''Ok''' the SSH connection will be established and after successful login the Control View implementation retrieves the LTTng Tracer Control information. This information will be displayed in the Control View in form of a tree structure.

[[Image:images/LTTng2ControlViewFilled.png]]

The top level tree node is the representation of the remote connection (host). The connection name of the connection will be displayed. Depending on the connection state different icons are displayed. If the node is '''CONNECTED''' the icon is shown [[Image:images/Target_connected.gif]], otherwise (states '''CONNECTING''', '''DISCONNNECTING''' or '''DISCONNECTED''' the icon is [[Image:images/Target_disconnected.gif]].

Under the host level two folder groups are located. The first one is the '''Provider''' group. The second one is the '''Sessions''' group.

Under the '''Provider''' group all trace providers are displayed. Trace providers are '''Kernel''' and any user space application that supports UST tracing. Under each provider a corresponding list of events are displayed.

Under the '''Sessions''' group all current sessions will be shown. The level under the sessions show the configured domains. Currently the LTTng 2.0 Tracer Toolchan supports domain '''Kernel''' and '''UST global'''. Under each domain the configured channels will be displayed. The last level is under the channels where the configured events are displayed.

Each session can be '''ACTIVE''' or '''INACTIVE'''. Active means that tracing has been started, inactive means that the tracing has been stopped. Depending on the state of a session a different icon is displayed. The icon for an active session is [[Image:images/Session_active.gif]]. The icon for an inactive session is [[Image:images/Session_inactive.gif]].

Each channel can be '''ENABLED''' or '''DISABLED'''. An enabled channel means that all configured events of that channel will be traced and a disabled channel won't trace any of its configured events. Different icons are displayed depending on the state of the channel. The icon for an enabled channel is  [[Image:images/Channel.gif]] and the icon for a disabled channel is [[Image:images/Channel_disabled.gif]].

Events within a channel can be in state '''ENABLED''' or '''DISABLED'''. Enabled events are stored in the trace when passed during program execution. Disabled events on the other hand won't be traced. Depending on the state of the event the icons for the event is different. An enabled event has the icon [[Image:images/Event_enabled.gif]] and a disabled event the icon [[Image:images/Event_disabled.gif]].

==== Disconnecting from a Remote Host ====

To disconnect from a remote host, select the host in the Control View and press the '''Disconnect''' button. Alternatively, press the right mouse button. A context-sensitive menu will show. Select the '''Disconnect''' button.

[[Image:images/LTTng2ControlViewDisconnect.png]]

==== Connecting to a Remote Host ====

To connect to a remote host, select the host in the Control View and press the '''Connect''' button. Alternatively, press the right mouse button. A context-sensitive menu will show. Select the '''Connect''' button. This will start the connection process as discribed in [[#Creating a New Connection to a Remote Host | Creating a New Connection to a Remote Host]].

[[Image:images/LTTng2ControlViewConnect.png]]

==== Deleting to a Remote Host Connection ====

To delete a remote host connection, select the host in the Control View and press the '''Delete''' button. Alternatively, press the right mouse button. A context-sensitive menu will show. Select the '''Delete''' button. For that command to be active the connection state has to be '''DISCONNECTED''' and the trace has to be closed.

[[Image:images/LTTng2ControlViewDelete.png]]

==== Creating a Tracing Session ====
To create a tracing session, select the tree node '''Sessions''' and press the right mouse button. Then select the '''Create Session...''' button of the context-sensitive menu.

[[Image:images/LTTng2CreateSessionAction.png]]

A dialog box will open for entering information about the session to be created.

[[Image:images/LTTng2CreateSessionDialog.png]]

Fill in the '''Session Name''' and optionally the '''Session Path''' and press '''Ok'''. Upon successful operation a new session will be created and added under the tree node '''Sessions'''.

==== Creating a Tracing Session With Advanced Options ====
LTTng Tools version v2.1.0 introduces the possibility to configure the trace output location at session creation time. The trace can be stored in the (tracer) local file system or can be transferred over the network.

To create a tracing session and configure the trace output, open the trace session dialog as described in chapter [[#Creating a Tracing Session | Creating a Tracing Session]]. A dialog box will open for entering information about the session to be created.

[[Image:images/LTTng2CreateSessionDialog_Advanced.png]]

The button '''Advanced >>>''' will only show if the remote host has LTTng Tools v2.1.0 installed. To configure the trace output select the '''Advanced >>>''' button. The Dialog box will be shown new fields to configure the trace output location.

[[Image:images/LTTng2CreateSessionDialog_TracePath.png]]

By default, the button '''Use same protocol and address for data and control''' is selected which allows to configure the same '''Protocol''' and '''Address''' for both data URL and control URL.

If button '''Use same protocol and address for data and control''' is selected the '''Protocol''' can be '''net''' for the default network protocol which is TCP (IPv4), '''net6''' for the default network protocol which is TCP (IPv6) and '''file''' for the local file system. For '''net''' and '''net6''' the port can be configured. Enter a value in '''Port''' for data and control URL or keep them empty for the default port to be used. Using '''file''' as protocol no port can be configured and the text fields are disabled.

If button '''Use same protocol and address for data and control''' is not selected the '''Protocol''' can be '''net''' for the default network protocol which is TCP (IPv4), '''net6''' for the default network protocol which is TCP (IPv6), '''tcp''' for the network protocol TCP (IPv4) and '''tcp6''' for the network protocol TCP (IPv6). Note that for '''net''' and '''net6''' always the default port is used and hence the port text fields are disabled. To configure non-default ports use '''tcp''' or '''tcp6'''.

The text field '''Trace Path''' allows for specifying the path relative to the location defined by the '''relayd''' or relative to the location specified by the '''Address''' when using protocol '''file'''. For more information about the '''relayd''' see '''LTTng relayd User Manual''' in chapter [[#References | References]].

To create a session with advanced options, fill in the relevant parameters and press '''Ok'''. Upon successful operation a new session will be created and added under the tree node '''Sessions'''.

==== Creating a Snapshot Tracing Session ====
LTTng Tools version v2.3.0 introduces the possibility to create snapshot tracing sessions. After starting tracing the trace events are not stored on disk or over the network. They are only transfered to disk or over the network when the user records a snapshot. To create such a snapshot session, open the trace session dialog as described in chapter [[#Creating a Tracing Session | Creating a Tracing Session]].

[[Image:images/LTTng2CreateSessionDialog_Snapshot.png]]

Fill in all necessary information, select checkbox for '''Snapshot Mode''' and press '''Ok'''. By default, the location for the snapshot output will be on the host where the host is located.

Refer to chapter [[#Recording a Snapshot | Recording a Snapshot]] for how to create a snapshot.

==== Enabling Channels - General ====

Enabling channels can be done using a session tree node when the domain hasn't be created in the session or, alternatively on a domain tree node of a session in case the domain is already available.

==== Enabling Channels On Session Level ====

To enable a channel, select the tree node of the relevant session and press the right mouse button. Then select the '''Enable Channel...''' button of the context-sensitive menu.

[[Image:images/LTTng2CreateChannelAction.png]]

A dialog box will open for entering information about the channel to be created.

[[Image:images/LTTng2CreateChannelDialog.png]]

By default the domain '''Kernel''' is selected. To create a UST channel, select '''UST''' under the domain section. The label <Default> in any text box indicates that the default value of the tracer will be configured. To initialize the dialog box press button '''Default'''.

If required update the following channel information and then press '''Ok'''.

* '''Channel Name''': The name of the channel.
* '''Sub Buffer size''': The size of the sub-buffers of the channel (in bytes).
* '''Number of Sub Buffers''': The number of sub-buffers of the channel.
* '''Switch Timer Interval''': The switch timer interval.
* '''Read Timer Interval''': The read timer interval.
* '''Discard Mode''': '''Overwrite''' events in buffer or '''Discard''' new events when buffer is full.

Upon successful operation, the requested domain will be created under the session tree node as well as the requested channel will be added under the domain. The channel will be '''ENABLED'''.

==== Configuring Trace File Rotation ====

Since LTTng Tools v2.2.0 it is possible to set the maximum size of trace files and the maximum number of them. These options are located in the same dialog box that is used for enabling channels.

[[Image:images/LTTng2CreateChannelDialogFileRotation.png]]

* '''Maximum size of trace files''': The maximum size of trace files
* '''Maximum number of trace files''': The maximum number of trace files

==== Configuring per UID and per PID Buffers (UST only) ====

Since LTTng Tools v2.2.0 it is possible to configure the type of buffers for '''UST''' application. It is now possible to choose between per '''UID''' buffers (per user ID) and per '''PID''' buffers (per process ID) using the dialog box for enabling channels.

[[Image:images/LTTng2CreateChannelDialogPerUIDBuffers.png]]

* '''Per PID buffers''': To activate the per PID buffers option for UST channels
* '''Per UID buffers''': To activate the per UID buffers option for UST channels

If no buffer type is selected then the default value of the tracer will be configured.

Note that '''Global shared buffers''' is only for kernel channel and is pre-selected when '''Kernel''' is selected in the dalog box.

==== Configuring Periodical Flush for metadata Channel ====

Since LTTng Tools v2.2.0 it is possible to configure periodical flush for the metadata channel. To set this, use the checkbox '''Configure metadata channel''' then fill the switch timer interval.

[[Image:images/LTTng2CreateChannelDialogMetadataFlush.png]]

==== Enabling Channels On Domain Level ====

Once a domain is available, channels can be enabled directly using the domain. To enable a channel under an existing domain, select the tree node of the relevant domain and press the right mouse button. Then select the '''Enable Channel...''' button of the context-sensitive menu.

[[Image:images/LTTng2CreateChannelOnDomainAction.png]]

The dialog box for enabling channel will open for entering information about the channel to be created. Note that the domain is pre-selected and cannot be changed. Fill the relevant information and press '''Ok'''.

==== Enabling and Disabling Channels ====

To disable one or more enabled channels, select the tree nodes of the relevant channels and press the right mouse button. Then select the '''Disable Channel''' menu item of the context-sensitive menu.

[[Image:images/LTTng2DisableChannelAction.png]]

Upon successful operation, the selected channels will be '''DISABLED''' and the icons for the channels will be updated.

To enable one or more disabled channels, select the tree nodes of the relevant channels and press the right mouse button. Then select the '''Enable Channel''' menu item of the context-sensitive menu.

[[Image:images/LTTng2EnableChannelAction.png]]

Upon successful operation, the selected channels will be '''ENABLED''' and the icons for the channels will be updated.

==== Enabling Events - General ====

Enabling events can be done using different levels in the tree node. It can be done on the session, domain level and channel level. For the case of session or domain, i.e. when no specific channels is assigned then enabling of events is done on the default channel with the name '''channel0''' which created, if not already exists, by the LTTng tracer control on the server side.

==== Enabling Kernel Events On Session Level ====

To enable events, select the tree node of the relevant session and press the right mouse button. Then select the '''Enable Event (default channel)...''' button of the context-sensitive menu.

[[Image:images/LTTng2EventOnSessionAction.png]]

A dialog box will open for entering information about events to be enabled.

[[Image:images/LTTng2EventOnSessionDialog.png]]

By default the domain '''Kernel''' is selected and the kernel specific data sections are created. From this dialog box kernel '''Tracepoint''' events, '''System calls (Syscall)''', a '''Dynamic Probe''' or a '''Dynamic Function entry/return''' probe can be enabled. Note that events of one of these types at a time can be enabled.

To enable '''Tracepoint''' events, first select the corresponding '''Select''' button, then select either all tracepoins (select '''All''') or select selectively one or more tracepoints in the displayed tree of tracepoints and finally press '''Ok'''.

[[Image:images/LTTng2TracepointEventsDialog.png]]

Upon successful operation, the domain '''Kernel''' will be created in the tree (if neccessary), the default channel with name "channel0" will be added under the domain (if necessary) as well as all requested events of type '''TRACEPOINT''' under the channel. The channel and events will be '''ENABLED'''.

[[Image:images/LTTng2EnabledKernelTracepoints.png]]

To enable all '''Syscalls''', select the corresponding '''Select''' button and press '''Ok'''.

[[Image:images/LTTng2SyscallsDialog.png]]

Upon successful operation, the event with the name '''syscalls''' and event type '''SYSCALL''' will be added under the default channel (channel0). If necessary the domain '''Kernel''' and the channel '''channel0''' will be created.

[[Image:images/LTTng2EnabledKernelSyscalls.png]]

To enable a '''Dynamic Probe''' event, select the corresponding '''Select''' button, fill the '''Event Name''' and '''Probe''' fields and press '''Ok'''. Note that the probe can be an address, symbol or a symbol+offset where the address and offset can be octal (0NNN...), decimal (NNN...) or hexadecimal (0xNNN...).

[[Image:images/LTTng2ProbeEventDialog.png]]

Upon successful operation, the dynamic probe event with the given name and event type '''PROBE''' will be added under the default channel (channel0). If necessary the domain '''Kernel''' and the channel '''channel0''' will be created.

[[Image:images/LTTng2EnabledKernelProbeEvent.png]]

To enable a '''Dynamic Function entry/return Probe''' event, select the corresponding '''Select''' button, fill the '''Event Name''' and '''Function''' fields and press '''Ok'''. Note that the funtion probe can be an address, symbol or a symbol+offset where the address and offset can be octal (0NNN...), decimal (NNN...) or hexadecimal (0xNNN...).

[[Image:images/LTTng2FunctionEventDialog.png]]

Upon successful operation, the dynamic function probe event with the given name and event type '''PROBE''' will be added under the default channel (channel0). If necessary the domain '''Kernel''' and the channel '''channel0''' will be created.

[[Image:images/LTTng2EnabledFunctionProbeEvent.png]]

==== Enabling UST Events On Session Level ====

For enabling UST events, first open the enable events dialog as described in section [[#Enabling Kernel Events On Session Level | Enabling Kernel Events On Session Level]] and select domain '''UST'''.

To enable '''Tracepoint''' events, first select the corresponding '''Select''' button, then select either all tracepoins (select '''All''') or select selectively one or more tracepoints in the displayed tree of tracepoints and finally press '''Ok'''.

[[Image:images/LTTng2UstTracepointEventsDialog.png]]

Upon successful operation, the domain '''UST global''' will be created in the tree (if neccessary), the default channel with name "channel0" will be added under the domain (if necessary) as well as all requested events under the channel. The channel and events will be '''ENABLED'''. Note that for the case that '''All''' tracepoints were selected the wildcard '''*''' is used which will be shown in the Control View as below.

[[Image:images/LTTng2EnabledAllUstTracepoints.png]]

For UST it is possible to enable '''Tracepoint''' events using a wildcard. To enable '''Tracepoint''' events with a wildcard, select first the corresponding '''Select''' button, fill the '''Wildcard''' field and press '''Ok'''.

[[Image:images/LTTng2UstWildcardEventsDialog.png]]

Upon successful operation, the event with the given wildcard and event type '''TRACEPOINT''' will be added under the default channel (channel0). If necessary the domain '''UST global''' and the channel '''channel0''' will be created.

[[Image:images/LTTng2EnabledUstWildcardEvents.png]]

For UST it is possible to enable '''Tracepoint''' events using log levels. To enable '''Tracepoint''' events using log levels, select first the corresponding '''Select''' button, select a log level from the drop down menu, fill in the relevant information (see below) and press '''Ok'''.

* '''Event Name''': Name to display
* '''loglevel''': To specify if a range of log levels (0 to selected log level) shall be configured
* '''loglevel-only''': To specify that only the specified log level shall be configured

[[Image:images/LTTng2UstLoglevelEventsDialog.png]]

Upon successful operation, the event with the given event name and event type '''TRACEPOINT''' will be added under the default channel (channel0). If necessary the domain '''UST global''' and the channel '''channel0''' will be created.

[[Image:images/LTTng2EnabledUstLoglevelEvents.png]]

==== Enabling Events On Domain Level ====

Kernel events can also be enabled on the domain level. For that select the relevant domain tree node, click the right mouse button and the select '''Enable Event (default channel)...'''. A new dialog box will open for providing information about the events to be enabled. Depending on the domain, '''Kernel''' or '''UST global''', the domain specifc fields are shown and the domain selector is preselected and read-only.

[[Image:images/LTTng2EventOnDomainAction.png]]

To enable events for domain '''Kernel''' follow the instructions in section [[#Enabling Kernel Events On Session Level | Enabling Kernel Events On Session Level]], for domain '''UST global''' [[#Enabling UST Events On Session Level | Enabling UST Events On Session Level]].

When enabling events on the domain level, the events will be add to the default channel '''channel0'''. This channel will be created by on the server side if neccessary.

==== Enabling Events On Channel Level ====

Kernel events can also be enabled on the channel level. If necessary, create a channel as described in sections [[#Enabling Channels On Session Level | Creating Channels On Session Level]] or [[#Enabling Channels On Domain Level | Creating Channels On Domain Level]].

Then select the relevant channel tree node, click the right mouse button and the select '''Enable Event...'''. A new dialog box will open for providing information about the events to be enabled. Depending on the domain, '''Kernel''' or '''UST global''', the domain specifc fields are shown and the domain selector is preselected and read-only.

[[Image:images/LTTng2EventOnChannelAction.png]]

To enable events for domain '''Kernel''' follow the instructions in section [[#Enabling Kernel Events On Session Level | Enabling Kernel Events On Session Level]], for domain '''UST global''' [[#Enabling UST Events On Session Level | Enabling UST Events On Session Level]].

When enabling events on the channel level, the events will be add to the selected channel.

==== Enabling and Disabling Events ====

To disable one or more enabled events, select the tree nodes of the relevant events and click the right mouse button. Then select '''Disable Event''' menu item in the context-sensitive menu.

[[Image:images/LTTng2DisableEventAction.png]]

Upon successful operation, the selected events will be '''DISABLED''' and the icons for these events will be updated.

To enable one or more disabled events, select the tree nodes of the relevant events and press the right mouse button. Then select the '''Enable Event''' menu item of the context-sensitive menu.

[[Image:images/LTTng2EnableEventAction.png]]

Upon successful operation, the selected events will be '''ENABLED''' and the icons for these events will be updated.

'''Note''': There is currently a limitation for kernel event of type '''SYSCALL'''. This kernel event can not be disabled. An error will appear when trying to disable this type of event. A work-around for that is to have the syscall event in a separate channel and disable the channel instead of the event.

==== Enabling Tracepoint Events From Provider ====

It is possible to enable events of type '''Tracepoint''' directly from the providers and assign the enabled event to a session and channel. Before doing that a session has to be created as described in section [[#Creating a Tracing Session | Creating a Tracing Session]]. Also, if other than default channel '''channel0''' is required, create a channel as described in sections [[#Enabling Channels On Session Level | Creating Channels On Session Level]] or [[#Enabling Channels On Domain Level | Creating Channels On Domain Level]].

To assign tracepoint events to a session and channel, select the events to be enabled under the provider (e.g. provider '''Kernel'''), click right mouse button and then select '''Enable Event...''' menu item from the context sensitive menu.

[[Image:images/LTTng2AssignEventAction.png]]

A new display will open for defining the session and channel.

[[Image:images/LTTng2AssignEventDialog.png]]

Select a session from the '''Session List''' drop-down menu, a channel from the '''Channel List''' drop-down menu and the press '''Ok'''. Upon successful operation, the selected events will be added to the selected session and channel of the domain that the selected provider belongs to. In case that there was no channel available, the domain and the default channel '''channel0''' will be created for corresponding session. The newly added events will be '''ENABLED'''.

[[Image:images/LTTng2AssignedEvents.png]]

==== Configuring Filter Expression On UST Event Fields ====

Since LTTng Tools v2.1.0 it is possible to configure a filter expression on UST event fields. To configure a filter expression on UST event fields, open the enable event dialog as described in chapters [[#Enabling UST Events On Session Level | Enabling UST Events On Session Level]], [[#Enabling Events On Domain Level | Enabling Events On Domain Level]] or [[#Enabling Events On Channel Level | Enabling Events On Channel Level]], select UST if needed, select the relevant '''Tracepoint''' event(s) and enter the filter expression in the '''Filter Expression''' text field.

[[Image:images/LTTng2EnableEventWithFilter.png]]

Alternatively, open the dialog box for assigning events to a session and channel described in [[#Enabling Tracepoint Events From Provider | Enabling Tracepoint Events From Provider]] (for UST providers) and enter the filter expression in the '''Filter Expression''' text field.

[[Image:images/LTTng2AssignEventDialogWithFilter.png]]

For the syntax of the filter expression refer to the '''LTTng Tracer Control Command Line Tool User Manual''' of chapter [[#References |References]].

==== Adding Contexts to Channels and Events of a Domain ====

It is possible to add contexts to channels and events. Adding contexts on channels and events from the domain level, will enable the specified contexts to all channels of the domain and all their events. To add contexts on the domain level, select a domain, click right mouse button on a domain tree node (e.g. provider '''Kernel''') and select the menu item '''Add Context...''' from the context-sensitive menu.

[[Image:images/LTTng2AddContextOnDomainAction.png]]

A new display will open for selecting one or more contexts to add.

[[Image:images/LTTng2AddContextDialog.png]]

The tree shows all available context that can be added. Select one or more context and the press '''Ok'''. Upon successful operation, the selected context will be added to all channels and their events of the selected domain.

'''Note''': The LTTng UST tracer only supports  contexts '''procname''', '''pthread_id''', '''vpid''' '''vtid'''. Adding any other contexts in the UST domina will fail.

==== Adding Contexts to All Events of a Channel ====

Adding contexts on channels and events from the channel level, will enable the specified contexts to all events of the selected channel. To add contexts on the channel level, select a channel, click right mouse button on a channel tree node and select the menu item '''Add Context...''' from the context-sensitive menu.

[[Image:images/LTTng2AddContextOnChannelAction.png]]

A new display will open for selecting one or more contexts to add. Select one or more contexts as described in chapter [[#Adding Contexts to Channels and Events of a Domain | Adding Contexts to Channels and Events of a Domain]]. Upon successful operation, the selected context will be added to all channels and their events of the selected domain. '''Note''' that the LTTng 2.0 tracer control on the remote host doesn't provide a way to retrieve added contexts. Hence it's not possible to display the context information in the GUI.

==== Adding Contexts to an Event of a Specific Channel ====

Adding contexts to an event of a channel is only available in LTTng Tools versions v2.0.0-2.1.x. The menu option won't be visible for LTTng Tools version v2.2.0 or later. To add contexts on an event select an event of a channel, click right mouse button on the corresponding event tree node and select the menu item '''Add Context...''' from the context-sensitive menu.

[[Image:images/LTTng2AddContextToEventsAction.png]]

A new display will open for selecting one or more contexts to add. Select one or more contexts as described in chapter [[#Adding Contexts to Channels and Events of a Domain | Adding Contexts to Channels and Events of a Domain]]. Upon successful operation, the selected context will be added to the selected event.

==== Start Tracing ====

To start tracing, select one or more sessions to start in the Control View and press the '''Start''' button. Alternatively, press the right mouse button on the session tree nodes. A context-sensitive menu will show. Then select the '''Start''' menu item.

[[Image:images/LTTng2StartTracingAction.png]]

Upon successful operation, the tracing session will be '''ACTIVE''' and the icon of the session will be updated.

==== Recording a Snapshot ====

LTTng Tools version v2.3.0 introduces the possibility to create snapshot tracing sessions. After creating a snapshot session (see [[#Creating a Snapshot Tracing Session | Creating a Snapshot Tracing Session]]) and starting tracing (see [[#Start Tracing | Start Tracing]]) it possible to record snapshots. To record a snapshot select one or more sessions and press the '''Record Snapshot''' button. Alternatively, press the right mouse button on the session tree nodes. A context-sensitive menu will show. Then select the '''Recored Snapshot''' menu item.

[[Image:images/LTTng2RecordSnapshotAction.png]]

This action can be executed many times. It is possible to import the recorded snpshots to a tracing project. The trace session might be '''ACTIVE''' or '''INACTIVE''' for that. Refer to section [[#Importing Session Traces to a Tracing Project | Importing Session Traces to a Tracing Project]] on how to import a trace to a tracing project.

==== Stop Tracing ====

To stop tracing, select one or more sessions to stop in the Control View and press the '''Stop''' button. Alternatively, click the right mouse button on the session tree node. A context-sensitive menu will show. Then select the '''Stop''' menu item.

[[Image:images/LTTng2StopTracingAction.png]]

Upon successful operation, the tracing session will be '''INACTIVE''' and the icon of the session will be updated.

==== Destroying a Tracing Session ====

To destroy a tracing session, select one or more sessions to destroy in the Control View and press the '''Destroy''' button. Alternatively, click the right mouse button on the session tree node. A context-sensitive menu will show. Then select the '''Destroy...''' menu item. Note that the session has to be '''INACTIVE''' for this operation.

[[Image:images/LTTng2DestroySessionAction.png]]

A confirmation dialog box will open. Click on '''Ok''' to destroy the session otherwise click on '''Cancel'''.

[[Image:images/LTTng2DestroyConfirmationDialog.png]]

Upon successful operation, the tracing session will be destroyed and removed from the tree.

==== Refreshing the Node Information ====

To refresh the remote host information, select any node in the tree of the Control View and press the '''Refresh''' button. Alternatively, click the right mouse button on any tree node. A context-sensitive menu will show. Then select the '''Refresh''' menu item.

[[Image:images/LTTng2RefreshAction.png]]

Upon successful operation, the tree in the Control View will be refreshed with the remote host configuration.

==== Quantifing LTTng overhead (Calibrate) ====

The LTTng calibrate command can be used to find out the combined average overhead of the LTTng tracer and the instrumentation mechanisms used. For now, the only calibration implemented is that of the kernel function
instrumentation (kretprobes). To run the calibrate command, select the a domain (e.g. '''Kernel'''), click the right mouse button on the domain tree node. A context-sensitive menu will show. Select the '''Calibrate''' menu item.

[[Image:images/LTTng2CalibrateAction.png]]

Upon successful operation, the calibrate command is executed and relevant information is stored in the trace. Note: that the trace has to be active so that to command as any effect.

==== Importing Session Traces to a Tracing Project ====

To import traces from a tracing session, select the relevant session and click on the '''Import''' Button. Alternatively, click the right mouse button on the session tree node and select the menu item '''Import...''' from the context-sensitive menu.

[[Image:images/LTTng2ImportAction.png]]

A new display will open for selecting the traces to import.

[[Image:images/LTTng2ImportDialog.png]]

By default all traces are selected. A default project with the name '''Remote''' is selected which will be created if necessary. Update the list of traces to be imported, if necessary, by selecting and deselecting the relevant traces in the tree viewer. Use buttons '''Select All''' or '''Deselect All''' to select or deselect all traces. Also if needed, change the tracing project from the '''Available Projects''' combo box. Select the Overwrite button ('''Overwrite existing trace without warning''') if required. Then press button '''Ok'''. Upon successful import operation the selected traces will be stored in the '''Traces''' directory of the specified tracing project. For '''Kernel''' traces the trace type '''LTTng Kernel''' and for '''UST''' traces the trace type '''Generic CTF Trace''' will be set. From the '''Project Explorer''' view, the trace can be analyzed further.

'''Note''': The trace will be imported with a name constructed with information about session, whether it is a kernel or ust trace, ust buffer type (per UID or per PID) and snapshot details. 

'''Note''': If the overwrite button ('''Overwrite existing trace without warning''') was not selected and a trace with the same name of a trace to be imported already exists in the project, then a new confirmation dialog box will open.

[[Image:images/LTTng2ImportOverwriteConfirmationDialog.png]]

To Overwrite select the '''Overwrite''' Button and press '''Ok'''.

If the existing trace should not be overwritten select, then select the '''Rename''' option of the confirmation dialog box above, enter a new name and then press '''Ok'''.

[[Image:images/LTTng2ImportRenameDialog.png]]

==== Importing Network Traces to a Tracing Project ====

Since LTTng Tools v2.1.0 it is possible to store traces over the network. To import network traces, execute the '''Import''' action as described in chapter [[#Importing Session Traces to a Tracing Project|Importing Session Traces to a Tracing Project]]. For network traces the '''Batch Import Trace Wizard''' will be displayed. Follow the instructions in chapter [[#Batch Importing|Batch Importing]] to import the network traces of the current session. 

=== Properties View ===

The Control View provides property information of selected tree component. Depending on the selected tree component different properties are displayed in the property view. For example, when selecting the node level the property view will be filled as followed:

[[Image:images/LTTng2PropertyView.png]]

'''List of properties''':

* '''Host''' Properties
** '''Connection Name''': The alias name to be displayed in the Control View.
** '''Host Name''': The IP address or DNS name of the remote system.
** '''State''': The state of the connection ('''CONNECTED''', '''CONNECTING''', '''DISCONNNECTING''' or '''DISCONNECTED''').
* '''Kernel Provider''' Properties
** '''Provider Name''': The name of the provider.
* '''UST Provider''' Properties
** '''Provider Name''': The name of the provider.
** '''Process ID''': The process ID of the provider.
* '''Event''' Properties (Provider)
** '''Event Name''': The name of the event.
** '''Event Type''': The event type ('''TRACEPOINT''' only).
** '''Fields''': Shows a list of fields defined for the selected event. (UST only, since support for LTTng Tools v2.1.0)
** '''Log Level''': The log level of the event.
* '''Session''' Properties
** '''Session Name''': The name of the Session.
** '''Session Path''': The path on the remote host where the traces will be stored. (Not shown for snapshot sessions).
** '''State''': The state of the session ('''ACTIVE''' or '''INACTIVE''')
** '''Snapshot ID''': The snapshot ID. (Only shown for snapshot sessions).
** '''Snapshot Name''': The name of the snapshot output configuration. (Only shown for snapshot sessions).
** '''Snapshot Path''': The path where the snapshot session is located. (Only shown for snapshot sessions).
* '''Domain''' Properties
** '''Domain Name''': The name of the domain.
** '''Buffer Type''': The buffer type of the domain.
* '''Channel''' Properties
** '''Channel Name''': The name of the channel.
** '''Number of Sub Buffers''': The number of sub-buffers of the channel.
** '''Output type''': The output type for the trace (e.g. ''splice()'' or ''mmap()'')
** '''Overwrite Mode''': The channel overwrite mode ('''true''' for overwrite mode, '''false''' for discard)
** '''Read Timer Interval''': The read timer interval.
** '''State''': The channel state ('''ENABLED''' or '''DISABLED''')
** '''Sub Buffer size''': The size of the sub-buffers of the channel (in bytes).
** '''Switch Timer Interval''': The switch timer interval.
* '''Event''' Properties (Channel)
** '''Event Name''': The name of the event.
** '''Event Type''': The event type ('''TRACEPOINT''', '''SYSCALL''' or '''PROBE''').
** '''Log Level''': The log level of the event.
** '''State''': The Event state ('''ENABLED''' or '''DISABLED''')
** '''Filter''': Shows '''with filter''' if a filter expression is configured else property '''Filter''' is omitted. (since support for LTTng Tools v2.1.0)

=== LTTng Tracer Control Preferences ===

Serveral LTTng 2.0 tracer control preferences exists which can be configured. To configure these preferences, select '''Window->Preferences''' from the top level menu. The preference display will open. Then select '''Tracing->LTTng Tracer Control Preferences'''. This preferences page allows the user to specify the tracing group of the user and to specify the command execution timeout as well as it allows the user to configure the logging of LTTng 2.0 tracer control commands and results to a file.

[[Image:images/LTTng2Preferences.png]]

To change the tracing group of the user which will be specified on each command line, enter the new group name in the '''Tracing Group''' text field and click button '''OK'''. The default tracing group is '''tracing''' and can be restored by pressing the '''Restore Defaults''' button.

[[Image:images/LTTng2PreferencesGroup.png]]

To configure logging of trace control commands and the corresponding command result to a file, selected the button  '''Logging'''. To append to an existing log file, select the '''Append''' button. Deselect the '''Append''' button to overwrite any existing log file. It's possible to specify a verbose level. There are 3 levels with inceasing verbosity from '''Level 1''' to '''Level 3'''. To change the verbosity level, select the relevant level or select '''None'''. If '''None''' is selected only commands and command results are logged. Then press on button '''OK'''. The log file will be stored in the users home directory with the name ''lttng_tracer_control.log''. The name and location cannot be changed. To reset to default preferences, click on the button '''Restore Defaults'''.

[[Image:images/LTTng2PreferencesLogging.png]]

To configure the LTTng command execution timeout, enter a timeout value into the text field '''Command Timeout (in seconds)''' and press on button '''OK'''. To reset to the default value of 15 seconds, click on the button '''Restore Defaults'''.

[[Image:images/LTTng2PreferencesTimeout.png]]

= LTTng Kernel Analysis =

Historically, LTTng was developped to trace the Linux kernel and, over time, a number of kernel-oriented analysis views were developped and organized in a perspective.

This section presents a description of the LTTng Kernel Perspective.

== LTTng Kernel Perspective ==

The '''LTTng Kernel''' perspective is built upon the [[#Tracing_Perspective | Tracing Perspective]], re-organizes them slightly and adds the following views:

* [[#Control_Flow_View | Control Flow View]] - to visualize processes state transitions
* [[#Resources_View | Resources View]] - to visualize system resources state transitions


[[Image:images/LTTngKernelPerspective.png]]


The perspective can be opened from the Eclipse Open Perspective dialog ('''Window > Open Perspective... > Other''').


[[Image:images/OpenLTTngKernelPerspective.png]]

== Control Flow View ==

The '''''Control Flow''''' view is a LTTng-specific view that shows per-process events graphically. To enable it, select ''Control Flow'' under ''LTTng'' within the ''Show View'' window ('''Window''' -> '''Show View''' -> '''Other...'''):

[[Image:images/Cfv_show_view.png]]

You should get something like this:

[[Image:images/Cfv_global.png]]

The view is divided into the following important sections: '''process tree and information''', '''control flow''' and the '''toolbar'''.

The following sections provide detailed information for each part of the Control Flow View.

=== Process tree and information ===

Processes are organized as a tree within this view. This way, child and parent processes are easy to identify.

[[Image:images/Cfv_process_tree.png]]

The layout is based on the states computed from the trace events.

A given process may be shown at different places within the tree since the nodes are '''unique (TID, birth time) couples'''. This means that if process B of parent A dies, you'll still see it in the tree. If process A forks process B again, it will be shown as a different node since it won't have the same birth time (and probably not the same TID). This has the advantage that the tree, once loaded, never changes: horizontal scrolling within the [[#Control flow|control flow]] remains possible.

The TID column shows the process node's '''thread ID''' and the PTID column shows its '''parent thread ID''' (nothing is shown if the process has no parent).

=== Control flow ===

This part of the Control Flow View is probably the most interesting one. Using the mouse, you can navigate through the trace (go left, right) and zoom on a specific region to inspect its details.

The colored bars you see represent '''states''' for the associated process node. When a process state changes in time, so does the color. For state '''SYSCALL''' the name of the system call is displayed in the state bar. States colors legend is available through a [[#Toolbar|toolbar button]]:

[[Image:images/Cfv_legend.png]]

This dark yellow is what you'll see most of the time since scheduling puts processes on hold while others run.

The vertical blue line with T1 above it is the '''current selection indicator'''. When a time range is selected, the region between the begin and end time of the selection will be shaded and two lines with T1 and T2 above will be displayed. The time stamps corresponding to T1, T2 and their delta are shown in the status line when the mouse is hovering over the control flow.

Arrows can be displayed that follow the execution of each CPU across processes. The arrows indicate when the scheduler switches from one process to another for a given CPU. The CPU being followed is indicated on the state tooltip. When the scheduler switches to and from the idle process, the arrow skips to the next process which executes on the CPU after the idle process. Note that an appropriate zoom level is required for all arrows to be displayed.

The display of arrows is optional and can be toggled using the '''Hide Arrows''' toolbar button. It is also possible to follow a CPU's execution across state changes and the scheduler's process switching using the '''Follow CPU Forward/Backward''' toolbar buttons.

==== Using the mouse ====

The states flow is usable with the mouse. The following actions are set:

* '''left-click''': select a time or time range begin time
* '''Shift-left-click''': select a time range end time
* '''left-drag horizontally''': select a time range or change the time range begin or end time
* '''middle-drag or Ctrl-left-drag horizontally''': pan left or right
* '''right-drag horizontally''': [[#Zoom region|zoom region]]
* '''click on a colored bar''': the associated process node is selected and the current time indicator is moved where the click happened
* '''mouse wheel up/down''': zoom in or out
* '''drag the time ruler horizontally''': zoom in or out with fixed start time
* '''double-click the time ruler''': reset zoom to full range

When the current time indicator is changed (when clicking in the states flow), all the other views are '''synchronized'''. For example, the [[#LTTng_Kernel_Events_Editor|Events Editor]] will show the event matching the current time indicator. The reverse behaviour is also implemented: selecting an event within the Events View will update the Control Flow View current time indicator.

==== Incomplete regions ====

You'll notice '''small dots''' over the colored bars at some places:

[[Image:images/Cfv_small_dots.png]]

Those dots mean the underlying region is '''incomplete''': there's not enough pixels to view all the events. In other words, you have to zoom in.

When zooming in, small dots start to disappear:

[[Image:images/Cfv_zoom.png]]

When no dots are left, you are viewing '''all the events and states''' within that region.

==== Zoom region ====

To zoom in on a specific region, '''right-click and drag''' in order to draw a time range:

[[Image:images/Cfv_zoom_region.png]]

The states flow horizontal space will only show the selected region.

==== Tooltips ====

Hover the cursor over a colored bar and a '''tooltip''' will pop up:

[[Image:images/Cfv_tooltip.png]]

The tooltip indicates:

* the process name
* the pointed state name
* the CPU (if applicable)
* the system call name (if applicable)
* the pointed state date and start/stop times
* the pointed state duration (seconds)

=== Toolbar ===

The Control Flow View '''toolbar''', located at the top right of the view, has shortcut buttons to perform common actions:

{|
| [[Image:images/filter_items.gif]]
| Show View Filter
| Opens the process filter dialog
|-
| [[Image:images/show_legend.gif]]
| Show Legend
| Displays the states legend
|-
| [[Image:images/home_nav.gif]]
| Reset the Time Scale to Default
| Resets the zoom window to the full range
|-
| [[Image:images/prev_event.gif]]
| Select Previous Event
| Selects the previous state for the selected process
|-
| [[Image:images/next_event.gif]]
| Select Next Event
| Selects the next state for the selected process
|-
| [[Image:images/prev_menu.gif]]
| Select Previous Process
| Selects the previous process
|-
| [[Image:images/next_menu.gif]]
| Select Next Process
| Selects the next process
|-
| [[Image:images/zoomin_nav.gif]]
| Zoom In
| Zooms in on the selection by 50%
|-
| [[Image:images/zoomout_nav.gif]]
| Zoom Out
| Zooms out on the selection by 50%
|-
| [[Image:images/hide_arrows.gif]]
| Hide Arrows
| Toggles the display of arrows on or off
|-
| [[Image:images/follow_arrow_bwd.gif]]
| Follow CPU Backward
| Selects the previous state following CPU execution across processes
|-
| [[Image:images/follow_arrow_fwd.gif]]
| Follow CPU Forward
| Selects the next state following CPU execution across processes
|}

== Resources View ==

This view is specific to kernel trace. To open it, go in '''Window''' -> '''Show View''' -> '''Other...''' and select '''LTTng/Resources''' in the list.

[[Image:images/Rv_example.png| Example of resources view with all trace points and syscalls enabled]]

This view shows the state of system resources i.e. if changes occured during the trace either on '''CPUs''', '''IRQs''' or '''soft IRQs''', it will appear in this view. The left side of the view present a list of resources that are affected by at least one event of the trace. The right side illustrate the state in which each resource is at some point in time. For state '''USERMODE''' it also prints the process name in the state bar. For state '''SYSCALL''' the name of the system call is
displayed in the state region.

Just like other views, according to which trace points and system calls are activated, the content of this view may change from one trace to another.

Each state are represented by one color so it is faster to say what is happening.

[[Image:images/Rv_legend.png|Color for each state]]

To go through the state of a resource, you first have to select the resource and the timestamp that interest you. For the latter, you can pick some time before the interesting part of the trace.

[[Image:images/RV_infobox1.png|Shows the state of an IRQ]]

Then, by selecting '''Next Event''', it will show the next state transition and the event that occured at this time.

[[Image:images/RV_infobox2.png|Shows the next state of the IRQ]]

This view is also synchronized with the others : [[#Histogram_View | Histogram View]], [[#LTTng_Kernel_Events_Editor | Events Editor]], [[#Control_Flow_View | Control Flow View]], etc.

=== Navigation ===

See Control Flow View's '''[[#Using_the_mouse|Using the mouse]]''' and '''[[#Zoom_region|Zoom region]]'''.

=== Incomplete regions ===

See Control Flow View's '''[[#Incomplete_regions|Incomplete regions]]'''.

=== Toolbar ===

The Resources View '''toolbar''', located at the top right of the view, has shortcut buttons to perform common actions:

{|
| [[Image:images/show_legend.gif]]
| Show Legend
| Displays the states legend
|-
| [[Image:images/home_nav.gif]]
| Reset the Time Scale to Default
| Resets the zoom window to the full range
|-
| [[Image:images/prev_event.gif]]
| Select Previous Event
| Selects the previous state for the selected resource
|-
| [[Image:images/next_event.gif]]
| Select Next Event
| Selects the next state for the selected resource
|-
| [[Image:images/prev_menu.gif]]
| Select Previous Resource
| Selects the previous resource
|-
| [[Image:images/next_menu.gif]]
| Select Next Resource
| Selects the next resource
|-
| [[Image:images/zoomin_nav.gif]]
| Zoom In
| Zooms in on the selection by 50%
|-
| [[Image:images/zoomout_nav.gif]]
| Zoom Out
| Zooms out on the selection by 50%
|}

== LTTng Kernel Events Editor ==

The LTTng Kernel Events editor '''is''' the plain TMF [[#Events_Editor | Events Editor]], except that it provides its own specialized viewer to replace the standard one. In short, it has exactly the same behaviour but the layout is slightly different:

* '''Timestamp''': the event timestamp
* '''Channel''': the event channel (data collector)
* '''Event Type''': the event type (or kernel marker)
* '''Content''': the raw event content


[[Image:images/LTTng2EventsEditor.png]]

= Trace synchronization =

It is possible to synchronize traces from different machines so that they have the same time reference. Events from the reference trace will have the same timestamps as usual, but the events from traces synchronized with the first one will have their timestamps transformed according to the formula obtained after synchronization.

== Obtain synchronizable traces ==

To synchronize traces from different machines, they need to exchange packets through the network and have events enabled such that the data can be matched from one trace to the other. For now, only TCP packets can be matched between two traces.

LTTng traces that can be synchronized are obtained using one of two methods (both methods are compatible):

=== LTTng-module network tracepoint with complete data ===

The tracepoints '''net_dev_queue''' and '''netif_receive_skb''' will be used for synchronization. Both tracepoints are available in lttng-modules since version 2.2, but they do not contain sufficient data to be used to synchronize traces.

An experimental branch introduces this extra data: lttng-modules will need to be compiled by hand.

Obtain the source code for the experimental lttng-modules

    # git clone git://git.dorsal.polymtl.ca/~gbastien/lttng-modules.git
    # cd lttng-modules

Checkout the ''net_data_experimental'' branch, compile and install lttng-modules as per the lttng-modules documentation

    # git checkout net_data_experimental
    # make
    # sudo make modules_install
    # sudo depmod -a

This experimental branch adds IP, IPv6 and TCP header data to the tracepoints. Packets received and sent with other protocols do not have this extra header data, but all packets are captured.

=== LTTng-modules addons kernel module with dynamic tracepoints ===

This method adds dynamic instrumentation on TCP packets via extra kernel modules. Only TCP packets are captured.

Obtain the source code, along with lttng-modules

    # git clone https://github.com/giraldeau/lttng-modules.git
    # cd lttng-modules

Checkout the addons branch, compile and install lttng-modules as per the lttng-modules documentation. The ''make'' command will fail at first with a message about the unset SYSMAP variable. Instructions on how to generate a System.map are mentioned in the error message.

    # git checkout addons
    # make
    # (follow the instructions to obtain the System.map file and set the SYSMAP variable)
    # make
    # sudo make modules_install
    # sudo depmod -a

The lttng-addons modules must be inserted manually for the TCP tracepoints to be made available.

    # sudo modprobe lttng-addons
    # sudo modprobe lttng-probe-addons

The following tracepoints will be available

    # sudo lttng list -k
    Kernel events:
    -------------
      ...
      inet_sock_create (loglevel: TRACE_EMERG (0)) (type: tracepoint)
      inet_sock_delete (loglevel: TRACE_EMERG (0)) (type: tracepoint)
      inet_sock_clone (loglevel: TRACE_EMERG (0)) (type: tracepoint)
      inet_accept (loglevel: TRACE_EMERG (0)) (type: tracepoint)
      inet_connect (loglevel: TRACE_EMERG (0)) (type: tracepoint)
      inet_sock_local_in (loglevel: TRACE_EMERG (0)) (type: tracepoint)
      inet_sock_local_out (loglevel: TRACE_EMERG (0)) (type: tracepoint)
      ...

The ones used for trace synchronization are '''inet_sock_local_in''' and '''inet_sock_local_out'''.

== Synchronize traces in TMF ==

In order to synchronize traces, create a new experiment and select all traces that need to be synchronized. Right-click on the experiment and select '''Synchronize traces'''. For each trace whose time needs to be transformed, a new trace named as the original but followed by a '_' will be created with the transformed timestamps, and the original trace will be replaced in the experiment. The original trace can still be accessed under the '''Traces''' folder.

[[Image:images/Sync_menu.png| Right-click synchronize traces to perform the trace synchronization]]

When opening the experiment now, all the views will be synchronized. The following screenshot presents the differences in the filtered Control Flow View before and after the time synchronization.

[[Image:images/Sync_cfv.png| Example of Control Flow View before and after trace synchronization]]

Information on the quality of the synchronization, the timestamp transformation formula and some synchronization statistics can be visualized in the '''Synchronization''' view. To open the '''Synchronization''' view, use the Eclipse Show View dialog ('''Window''' -> '''Show View''' -> '''Other...'''). Then select '''Synchronization''' under '''Tracing'''.

[[Image:images/Sync_view.png| Example of Synchronization view]]

= Timestamp formatting =

Most views that show timestamps are displayed in the same time format. The unified timestamp format can be changed in the Preferences page. To get to that page, click on '''Window''' -> '''Preferences''' -> '''Tracing''' -> '''Time Format'''. Then a window will show the time format preferences.

[[Image:images/TmfTimestampFormatPage.png]]

The preference page has several subsections:

* '''Current Format''' a format string generated by the page
* '''Sample Display''' an example of a timestamp formatted with the '''Current Format''' string.
* '''Time Zone''' the time zone to use when displaying the time. The value '''Local time''' corresponds to the local, system-configured, time zone.
* '''Data and Time format''' how to format the date (days/months/years) and the time (hours/minutes/seconds)
* '''Sub-second format''' how much precision is shown for the sub-second units
* '''Date delimiter''' the character used to delimit the date units such as months and years
* '''Time delimiter''' the character to separate super-second time units such as seconds and minutes
* '''Sub-Second Delimiter''' the character to separate the sub-second groups such as milliseconds and nanoseconds
* '''Restore Defaults''' restores the system settings
* '''Apply''' apply changes

This will update all the displayed timestamps.

= Limitations =

* When parsing text traces, the timestamps are assumed to be in the local time zone. This means that when combining it to CTF binary traces, there could be offsets by a few hours depending on where the traces were taken and where they were read.
* LTTng Tools v2.1.0 introduced the command line options ''--no-consumer'' and ''--disable-consumer'' for session creation as well as the commands ''enable-consumer'' and ''disable-consumer''. The LTTng Tracer Control in Eclipse doesn't support these options and commands because they will obsolete in LTTng Tools v2.2.0 and because the procedure for session creation offers already all relevant advanced parameters.

= How to use LTTng to diagnose problems =

LTTng is a tracer, it will give an enormous amount of information about the system it is running on. This means it can solve many types of problems.

The following are examples of problems that can be solved with a tracer.

== Random stutters ==

Bob is running a computer program and it stutters periodically every 2 minutes. The CPU load is relatively low and Bob isn't running low on RAM.

He decides to trace his complete system for 10 minutes. He opens the LTTng view in eclipse. From the control, he creates a session and enables all kernel tracepoints.

He now has a 10 GB trace file. He imports the trace to his viewer and loads it up.

A cursory look at the histogram bar on the bottom show relatively even event distribution, there are no interesting spikes, so he will have to dig deeper to find the issue. If he had seen a spike every 2 minutes, there would be strong chances this would be the first thing to investigate as it would imply a lot of kernel activity at the same period as his glitch, this would have been a path to investigate.

As Bob suspects that he may be having some hardware raising IRQs or some other hardware based issue and adding delays. He looks at the ressource view and doesn't see anything abnormal.

Bob did note an exact second one glitch occured: 11:58:03. He zooms into the time range or 11:58:02-11:58:04 using the histogram.He is happy to see the time is human readable local wall clock time and no longer in "nanseconds since the last reboot". <br>In the resource view, once again, he sees many soft irqs being raised at the same time, around the time his gui would freeze. He changes views and looks at the control flow view at that time and sees a process spending a lot of time in the kernel: FooMonitor- his temperature monitoring software.

At this point he closes FooMonitor and notices the bug dissapeared. He could call it a day but he wants to see what was causing the system to freeze. He cannot justify closing a piece of software without understanding the issue. It may be a conflict that HIS software is causing after all.

The system freezes around the time this program is running. He clicks on the process in the control flow view and looks at the corresponding events in the detailed events view. He sees: open - read - close repeated hundreds of times on the same file. The file being read was /dev/HWmonitor. He sends a report to the FooMonitor team and warns his team that FooMonitor was glitching their performance.

The FooMonitor team finds that they were calling a system bus call that would halt a cpu while reading the temperature so that the core would not induce an 0.1 degree error in the reading, by disabling this feature, they improve their software and stop the glitches from occurring on their custommer's machine. They also optimize their code to open the file read and clone it once.

By using system wide kernel tracing, even without deep kernel knowledge Bob was able to isolate a bug in a rogue piece of software in his system.

== Slow I/O ==

Alice is running her server. She noticed that one of her nodes was slowing down, and wasn't sure why, upon reading the trace she noticed that her time between a block request and complete was around 10ms.

This is abnormal, normally her server handles IOs in under 100us, since they are quite local.

She walks up to the server and hears the hard drive thrashing, This prompts her to look up in the events view the sectors being read in the block complete requests. There are her requests interleaved with other ones at the opposite side of the hard drive.

She sees the tracer writing but there is another process that is writing to the server disk non stop. She looks in the control flow view and sees that there's a program from another fellow engineer, "Wally" that is writing in his home in a loop "All work and no play makes Jack a dull boy.".

Alice kills the program, and immediately the server speeds up. She then goes to discuss this with Wally and implements strict hard disk quotas on the server.

= References =

* [http://www.eclipse.org/linuxtools/projectPages/lttng/ Linux Tools - LTTng integration]
* [http://www.lttng.org/ LTTng project]
* [http://lttng.org/files/doc/man-pages/man1/lttng.1.html LTTng Tracer Control Command Line Tool User Manual]
* [http://lttng.org/files/doc/man-pages/man8/lttng-relayd.8.html LTTng relayd User Manual]
* [http://wiki.eclipse.org/Linux_Tools_Project/TMF/User_Guide TMF User Guide]

= Updating This Document =

This document is maintained in a collaborative wiki.  If you wish to update or modify this document please visit [http://wiki.eclipse.org/index.php/Linux_Tools_Project/LTTng2/User_Guide http://wiki.eclipse.org/Linux_Tools_Project/LTTng2/User_Guide]