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-\author ""
-\author ""
-\end_header
-
-\begin_body
-
-\begin_layout Title
-LTTng Userspace Tracer Manual
-\end_layout
-
-\begin_layout Author
-Pierre-Marc Fournier
-\end_layout
-
-\begin_layout Section
-What is the LTTng Userspace Tracer?
-\end_layout
-
-\begin_layout Subsection
-Overview
-\end_layout
-
-\begin_layout Standard
-The LTTng Userspace Tracer (UST) is a tracing system for userspace applications.
- It is designed to trace efficiently applications that produce events at
- a very high rate.
- UST is derived from LTTng, a tracer for the Linux kernel.
- It has the same trace format.
-\end_layout
-
-\begin_layout Standard
-Users may choose at runtime and even at trace time what instrumentation
- should be activated.
- Custom probes may be used to trace events conditionally.
-\end_layout
-
-\begin_layout Subsection
-Features
-\end_layout
-
-\begin_layout Itemize
-Arbitrary number of channels
-\end_layout
-
-\begin_layout Itemize
-One buffer per process (multiple threads share the same buffer)
-\end_layout
-
-\begin_layout Itemize
-Early process tracing (from the beginning of the main() function)
-\end_layout
-
-\begin_layout Itemize
-Support for custom probes
-\end_layout
-
-\begin_layout Standard
-Still to implement:
-\end_layout
-
-\begin_layout Itemize
-Support for dynamic instrumentation
-\end_layout
-
-\begin_layout Itemize
-Per thread or per CPU buffers
-\end_layout
-
-\begin_layout Standard
-Complementary systems:
-\end_layout
-
-\begin_layout Itemize
-A extension to gdb tracepoints that will allow the tracing of applications
- with dynamic instrumentation is under development.
-\end_layout
-
-\begin_layout Subsection
-Performance
-\end_layout
-
-\begin_layout Section
-Installation
-\end_layout
-
-\begin_layout Subsection
-Obtain the code
-\end_layout
-
-\begin_layout Standard
-To compile UST, you need:
-\end_layout
-
-\begin_layout Itemize
-the UST code
-\end_layout
-
-\begin_layout Itemize
-libkcompat
-\end_layout
-
-\begin_layout Itemize
-liburcu-pmf
-\end_layout
-
-\begin_layout Subsection
-Configure libkcompat
-\end_layout
-
-\begin_layout Standard
-Edit kcompat.h and uncomment the architecture of the target system.
-\end_layout
-
-\begin_layout Subsection
-Configure libust
-\end_layout
-
-\begin_layout Standard
-If the code was obtained through git, first generate a Makefile by running
- autogen.sh.
-\end_layout
-
-\begin_layout Standard
-Then, run ./configure, specifying the directories of liburcu and libkcompat.
- Example:
-\end_layout
-
-\begin_layout Standard
-\begin_inset listings
-inline false
-status open
-
-\begin_layout Plain Layout
-
-./configure --with-urcu=/home/pmf/liburcu-pmf --with-kcompat=/home/pmf/libkcompat
-\end_layout
-
-\end_inset
-
-
-\end_layout
-
-\begin_layout Subsection
-Build liburcu
-\end_layout
-
-\begin_layout Standard
-Go to the liburcu directory and run:
-\end_layout
-
-\begin_layout Standard
-\begin_inset listings
-inline false
-status open
-
-\begin_layout Plain Layout
-
-make
-\end_layout
-
-\end_inset
-
-
-\end_layout
-
-\begin_layout Subsection
-Build ust
-\end_layout
-
-\begin_layout Standard
-Go to the ust directory and run:
-\end_layout
-
-\begin_layout Standard
-\begin_inset listings
-inline false
-status open
-
-\begin_layout Plain Layout
-
-make
-\end_layout
-
-\end_inset
-
-
-\end_layout
-
-\begin_layout Section
-Instrumenting an Application
-\end_layout
-
-\begin_layout Standard
-In order to record a trace of events occurring in a application, the application
- must be instrumented.
- Instrumentation points resemble function calls.
- When the program reaches an instrumentation point, an event is generated.
-\end_layout
-
-\begin_layout Standard
-There are no limitations on the type of code that may be instrumented.
- Multi-threaded programs may be instrumented without problem.
- Signal handlers may be instrumented as well.
-\end_layout
-
-\begin_layout Standard
-There are two APIs to instrument programs: markers and tracepoints.
- Markers are quick to add and are usually used for temporary instrumentation.
- Tracepoints provide a way to instrument code more cleanly and are suited
- for permanent instrumentation.
-\end_layout
-
-\begin_layout Subsection
-Markers
-\end_layout
-
-\begin_layout Standard
-Markers were ported from the Linux Kernel Markers implementation.
- Therefore, their usage is almost identical.
-\end_layout
-
-\begin_layout Subsubsection
-Inserting Markers
-\end_layout
-
-\begin_layout Standard
-Adding a marker is simply a matter of insert one line in the program.
-\end_layout
-
-\begin_layout Standard
-\begin_inset listings
-inline false
-status open
-
-\begin_layout Plain Layout
-
-#include <marker.h>
-\end_layout
-
-\begin_layout Plain Layout
-
-int main(int argc, char **argv)
-\end_layout
-
-\begin_layout Plain Layout
-
-{
-\end_layout
-
-\begin_layout Plain Layout
-
- int v;
-\end_layout
-
-\begin_layout Plain Layout
-
- char *st;
-\end_layout
-
-\begin_layout Plain Layout
-
-\end_layout
-
-\begin_layout Plain Layout
-
- /* ...
- set values of v and st ...
- */
-\end_layout
-
-\begin_layout Plain Layout
-
-\end_layout
-
-\begin_layout Plain Layout
-
- /* a marker: */
-\end_layout
-
-\begin_layout Plain Layout
-
- trace_mark(main, myevent,
-\begin_inset Quotes eld
-\end_inset
-
-firstarg %d secondarg %s
-\begin_inset Quotes erd
-\end_inset
-
-, v, st);
-\end_layout
-
-\begin_layout Plain Layout
-
-\end_layout
-
-\begin_layout Plain Layout
-
- /* a marker without arguments: */
-\end_layout
-
-\begin_layout Plain Layout
-
- trace_mark(main, myotherevent, MARK_NOARGS);
-\end_layout
-
-\begin_layout Plain Layout
-
-\end_layout
-
-\begin_layout Plain Layout
-
- return 0;
-\end_layout
-
-\begin_layout Plain Layout
-
-}
-\end_layout
-
-\end_inset
-
-
-\end_layout
-
-\begin_layout Standard
-The invocation of the trace_mark() macro requires at least 3 arguments.
- The first, here
-\begin_inset Quotes eld
-\end_inset
-
-main
-\begin_inset Quotes erd
-\end_inset
-
-, is the name of the event category.
- It is also the name of the channel the event will go in.
- The second, here
-\begin_inset Quotes eld
-\end_inset
-
-myevent
-\begin_inset Quotes erd
-\end_inset
-
- is the name of the event.
- The third is a format string that announces the names and the types of
- the event arguments.
- Its format resembles that of a printf() format string; it is described
- thoroughly in Appendix x.
-\end_layout
-
-\begin_layout Standard
-A given Marker may appear more than once in the same program.
- Other Markers may have the same name and a different format string, although
- this might induce some confusion at analysis time.
-\end_layout
-
-\begin_layout Subsubsection
-Registering the Markers
-\end_layout
-
-\begin_layout Standard
-In order to inform to register the Markers present in the module, a macro
- must be inserted at global scope.
- Only one such macro is needed per exacutable or per shared object.
- Adding it more than once, however, is harmless.
-\end_layout
-
-\begin_layout Standard
-\begin_inset listings
-inline false
-status open
-
-\begin_layout Plain Layout
-
-MARKER_LIB;
-\end_layout
-
-\end_inset
-
-
-\end_layout
-
-\begin_layout Subsection
-Tracepoints
-\end_layout
-
-\begin_layout Standard
-The Tracepoints API uses the Markers, but provides a higher-level abstraction.
- Whereas the markers API provides limited type checking, the Tracepoints
- API provides more thorough type checking and discharges from the need to
- insert format strings directly in the code and to have format strings appear
- more than once if a given marker is reused.
-\end_layout
-
-\begin_layout Standard
-A tracepoint in the code looks like this:
-\end_layout
-
-\begin_layout Standard
-\begin_inset listings
-inline false
-status open
-
-\begin_layout Plain Layout
-
-#include <marker.h>
-\end_layout
-
-\begin_layout Plain Layout
-
-\end_layout
-
-\begin_layout Plain Layout
-
-void function()
-\end_layout
-
-\begin_layout Plain Layout
-
-{
-\end_layout
-
-\begin_layout Plain Layout
-
- int v;
-\end_layout
-
-\begin_layout Plain Layout
-
- char *st;
-\end_layout
-
-\begin_layout Plain Layout
-
-\end_layout
-
-\begin_layout Plain Layout
-
- /* ...
- set values of v and st ...
- */
-\end_layout
-
-\begin_layout Plain Layout
-
-\end_layout
-
-\begin_layout Plain Layout
-
- /* a tracepoint: */
-\end_layout
-
-\begin_layout Plain Layout
-
- trace_main_myevent(v, st);
-\end_layout
-
-\begin_layout Plain Layout
-
-}
-\end_layout
-
-\end_inset
-
-
-\end_layout
-
-\begin_layout Standard
-\begin_inset listings
-inline false
-status open
-
-\begin_layout Plain Layout
-
-DEFINE_TRACE();
-\end_layout
-
-\end_inset
-
-
-\end_layout
-
-\begin_layout Standard
-\begin_inset listings
-inline false
-status open
-
-\begin_layout Plain Layout
-
-TRACEPOINT_LIB;
-\end_layout
-
-\end_inset
-
-
-\end_layout
-
-\begin_layout Subsection
-Compiling the Application
-\end_layout
-
-\begin_layout Standard
-See the
-\begin_inset Quotes eld
-\end_inset
-
-hello
-\begin_inset Quotes erd
-\end_inset
-
- directory for an example application and makefile.
-\end_layout
-
-\begin_layout Itemize
-The compiler must have access to the include path for the libust headers.
-\end_layout
-
-\begin_layout Itemize
-The application should be statically or dynamically linked to libust.
-\end_layout
-
-\begin_layout Section
-Recording a Trace
-\end_layout
-
-\begin_layout Standard
-These preliminary steps need to be done before recording a trace.
-\end_layout
-
-\begin_layout Standard
-\begin_inset listings
-inline false
-status open
-
-\begin_layout Plain Layout
-
-Create the directory for the communication sockets.
- Eventually this should be somewhere in /var.
-\end_layout
-
-\begin_layout Plain Layout
-
-$ mkdir /tmp/socks
-\end_layout
-
-\begin_layout Plain Layout
-
-\end_layout
-
-\begin_layout Plain Layout
-
-Create the directory where ustd will write the trace.
- This will become configurable.
-\end_layout
-
-\begin_layout Plain Layout
-
-$ mkdir /tmp/trace
-\end_layout
-
-\begin_layout Plain Layout
-
-\end_layout
-
-\begin_layout Plain Layout
-
-Start the daemon
-\end_layout
-
-\begin_layout Plain Layout
-
-$ ustd
-\end_layout
-
-\end_inset
-
-
-\end_layout
-
-\begin_layout Subsection
-Basic Recording
-\end_layout
-
-\begin_layout Standard
-Tracing on a running program is controlled with the ust helper program.
- Ust can start the tracing, stop the tracing, enable markers, disable markers
- and list the markers.
- Another program, ustd, is a daemon that collects the trace events and write
- them to a file.
-\end_layout
-
-\begin_layout Standard
-In order to record a trace, the daemon must first be started with the following
- command.
-\end_layout
-
-\begin_layout Standard
-\begin_inset listings
-inline false
-status open
-
-\begin_layout Plain Layout
-
-ustd
-\end_layout
-
-\end_inset
-
-
-\end_layout
-
-\begin_layout Standard
-Markers can be listed with the following command (for PID 1234).
-\end_layout
-
-\begin_layout Standard
-\begin_inset listings
-inline false
-status open
-
-\begin_layout Plain Layout
-
-ust --list-markers 1234
-\end_layout
-
-\end_inset
-
-
-\end_layout
-
-\begin_layout Standard
-A marker can be enabled with the following command (for PID 1234).
-\end_layout
-
-\begin_layout Standard
-\begin_inset listings
-inline false
-status open
-
-\begin_layout Plain Layout
-
-ust --enable-marker ust/mymark 1234
-\end_layout
-
-\end_inset
-
-
-\end_layout
-
-\begin_layout Standard
-Then, the trace can be started.
-\end_layout
-
-\begin_layout Standard
-\begin_inset listings
-inline false
-status open
-
-\begin_layout Plain Layout
-
-ust --start-trace 1234
-\end_layout
-
-\end_inset
-
-
-\end_layout
-
-\begin_layout Standard
-Eventually it can be stopped and destroyed.
-\end_layout
-
-\begin_layout Standard
-\begin_inset listings
-inline false
-status open
-
-\begin_layout Plain Layout
-
-ust --stop-trace 1234
-\end_layout
-
-\begin_layout Plain Layout
-
-ust --destroy-trace 1234
-\end_layout
-
-\end_inset
-
-
-\end_layout
-
-\begin_layout Subsection
-Early Tracing
-\end_layout
-
-\begin_layout Standard
-Sometimes, an application must be traced as soon as it is started.
- In these cases, the Basic Recording method is not satisfactory, as important
- events may be lost before the tracing is started.
-\end_layout
-
-\begin_layout Standard
-By using the Early Tracing method, it is guaranteed that the tracing is
- started when the execution of the main() function of the program starts.
-\end_layout
-
-\begin_layout Standard
-Early Tracing may be enabled by defining the UST_TRACE environment variable
- to a non-empty value when the program starts.
- Additionally, the UST_AUTOPROBE may be set to a non-empty value to automaticall
-y connect all markers to the default probe.
- For example:
-\end_layout
-
-\begin_layout Standard
-\begin_inset listings
-inline false
-status open
-
-\begin_layout Plain Layout
-
-# In another terminal, start the daemon.
-\end_layout
-
-\begin_layout Plain Layout
-
-ustd
-\end_layout
-
-\begin_layout Plain Layout
-
-\end_layout
-
-\begin_layout Plain Layout
-
-# Start
-\begin_inset Quotes eld
-\end_inset
-
-prog
-\begin_inset Quotes erd
-\end_inset
-
- with early tracing.
-\end_layout
-
-\begin_layout Plain Layout
-
-UST_TRACE=1 UST_AUTOPROBE=1 ./prog
-\end_layout
-
-\end_inset
-
-
-\end_layout
-
-\begin_layout Standard
-In order for the trace to be saved, ustd must be running when the traced
- program is started.
-\end_layout
-
-\begin_layout Section
-Viewing and Analyzing the Trace
-\end_layout
-
-\begin_layout Standard
-LTTV may be used for opening the trace.
- If an appropriate time source was used, it may be opened concurrently with
- other application traces and kernel traces.
-\end_layout
-
-\begin_layout Section
-Advanced Concepts
-\end_layout
-
-\begin_layout Subsection
-Using Custom Probes for Conditional Tracing
-\end_layout
-
-\begin_layout Subsection
-Instrumenting Calls to Library Functions without Recompilation
-\end_layout
-
-\begin_layout Standard
-Calls to uninstrumented libraries may be instrumented by creating a wrapper
- library that intercepts calls to the library, trigger an instrumentation
- point.
-\end_layout
-
-\begin_layout Standard
-Such an example can be found in the libmallocwrap directory of the ust code
- package.
-\end_layout
-
-\begin_layout Subsection
-Tracing Programs Without Linking them to the Tracing Library
-\end_layout
-
-\begin_layout Standard
-Programs that were not instrumented nor linked with the tracing libraries
- may still be traced.
- In order to produce events, they must be linked to instrumented libraries
- or use instrumented library wrappers as described in section xx.
-\end_layout
-
-\begin_layout Standard
-\begin_inset listings
-inline false
-status open
-
-\begin_layout Plain Layout
-
-LD_PRELOAD=...
- program
-\end_layout
-
-\end_inset
-
-
-\end_layout
-
-\begin_layout Section
-\start_of_appendix
-Format of Marker Format Strings
-\end_layout
-
-\begin_layout Standard
-The format of Marker format strings is inspired from printf() format strings.
- As with printf(), it is used to indicate to the parsing function the type
- of the arguments that are passed.
- Additionally, format strings indicate the name of each argument and the
- format of that argument in the trace.
- The structure of a typical format string is the following.
-\end_layout
-
-\begin_layout Standard
-\begin_inset listings
-inline false
-status open
-
-\begin_layout Plain Layout
-
-\begin_inset Quotes eld
-\end_inset
-
-field_name1 #tracetype1 %ctype1 field_name2 #tracetype2 %ctype2
-\begin_inset Quotes erd
-\end_inset
-
-
-\end_layout
-
-\end_inset
-
-
-\end_layout
-
-\begin_layout Description
-field_name: The name of the field, as it will be seen when the trace is
- parsed.
-\end_layout
-
-\begin_layout Description
-tracetype: The type of the argument as it will be written in the trace.
-\end_layout
-
-\begin_layout Description
-ctype: The C type of the argument passed to the Marker (this is very similar
- to the %...
- types in a printf() format string)
-\end_layout
-
-\begin_layout Standard
-Both field_name and tracetype are optional.
- These are all valid format strings:
-\end_layout
-
-\begin_layout Standard
-\begin_inset listings
-inline false
-status open
-
-\begin_layout Plain Layout
-
-\end_layout
-
-\end_inset
-
-
-\end_layout
-
-\begin_layout Subsection
-tracetype
-\end_layout
-
-\begin_layout Standard
-A typical Marker format string looks like this:
-\end_layout
-
-\begin_layout Standard
-The serialization format string supports the basic printf format strings.
-\end_layout
-
-\begin_layout Standard
-In addition, it defines new formats that can be used to serialize more
-\end_layout
-
-\begin_layout Standard
-complex/non portable data structures.
-\end_layout
-
-\begin_layout Standard
-Typical use:
-\end_layout
-
-\begin_layout Standard
-field_name %ctype
-\end_layout
-
-\begin_layout Standard
-field_name #tracetype %ctype
-\end_layout
-
-\begin_layout Standard
-field_name #tracetype %ctype1 %ctype2 ...
-\end_layout
-
-\begin_layout Standard
-A conversion is performed between format string types supported by GCC and
-\end_layout
-
-\begin_layout Standard
-the trace type requested.
- GCC type is used to perform type checking on format
-\end_layout
-
-\begin_layout Standard
-strings.
- Trace type is used to specify the exact binary representation
-\end_layout
-
-\begin_layout Standard
-in the trace.
- A mapping is done between one or more GCC types to one trace
-\end_layout
-
-\begin_layout Standard
-type.
- Sign extension, if required by the conversion, is performed following
-\end_layout
-
-\begin_layout Standard
-the trace type.
-\end_layout
-
-\begin_layout Standard
-If a gcc format is not declared with a trace format, the gcc format is
-\end_layout
-
-\begin_layout Standard
-also used as binary representation in the trace.
-\end_layout
-
-\begin_layout Standard
-Strings are supported with %s.
-\end_layout
-
-\begin_layout Standard
-A single tracetype (sequence) can take multiple c types as parameter.
-\end_layout
-
-\begin_layout Standard
-c types:
-\end_layout
-
-\begin_layout Standard
-see printf(3).
-\end_layout
-
-\begin_layout Standard
-Note: to write a uint32_t in a trace, the following expression is recommended
-\end_layout
-
-\begin_layout Standard
-si it can be portable:
-\end_layout
-
-\begin_layout Standard
-("#4u%lu", (unsigned long)var)
-\end_layout
-
-\begin_layout Standard
-trace types:
-\end_layout
-
-\begin_layout Standard
-Serialization specific formats :
-\end_layout
-
-\begin_layout Standard
-Fixed size integers
-\end_layout
-
-\begin_layout Standard
-#1u writes uint8_t
-\end_layout
-
-\begin_layout Standard
-#2u writes uint16_t
-\end_layout
-
-\begin_layout Standard
-#4u writes uint32_t
-\end_layout
-
-\begin_layout Standard
-#8u writes uint64_t
-\end_layout
-
-\begin_layout Standard
-#1d writes int8_t
-\end_layout
-
-\begin_layout Standard
-#2d writes int16_t
-\end_layout
-
-\begin_layout Standard
-#4d writes int32_t
-\end_layout
-
-\begin_layout Standard
-#8d writes int64_t
-\end_layout
-
-\begin_layout Standard
-i.e.:
-\end_layout
-
-\begin_layout Standard
-#1u%lu #2u%lu #4d%lu #8d%lu #llu%hu #d%lu
-\end_layout
-
-\begin_layout Standard
-* Attributes:
-\end_layout
-
-\begin_layout Standard
-n: (for network byte order)
-\end_layout
-
-\begin_layout Standard
-#ntracetype%ctype
-\end_layout
-
-\begin_layout Standard
-is written in the trace in network byte order.
-\end_layout
-
-\begin_layout Standard
-i.e.: #bn4u%lu, #n%lu, #b%u
-\end_layout
-
-\begin_layout Standard
-TODO (eventually)
-\end_layout
-
-\begin_layout Standard
-Variable length sequence
-\end_layout
-
-\begin_layout Standard
-#a #tracetype1 #tracetype2 %array_ptr %elem_size %num_elems
-\end_layout
-
-\begin_layout Standard
-In the trace:
-\end_layout
-
-\begin_layout Standard
-#a specifies that this is a sequence
-\end_layout
-
-\begin_layout Standard
-#tracetype1 is the type of elements in the sequence
-\end_layout
-
-\begin_layout Standard
-#tracetype2 is the type of the element count
-\end_layout
-
-\begin_layout Standard
-GCC input:
-\end_layout
-
-\begin_layout Standard
-array_ptr is a pointer to an array that contains members of size
-\end_layout
-
-\begin_layout Standard
-elem_size.
-\end_layout
-
-\begin_layout Standard
-num_elems is the number of elements in the array.
-\end_layout
-
-\begin_layout Standard
-i.e.: #a #lu #lu %p %lu %u
-\end_layout
-
-\begin_layout Standard
-Callback
-\end_layout
-
-\begin_layout Standard
-#k callback (taken from the probe data)
-\end_layout
-
-\begin_layout Standard
-The following % arguments are exepected by the callback
-\end_layout
-
-\begin_layout Standard
-i.e.: #a #lu #lu #k %p
-\end_layout
-
-\begin_layout Standard
-Note: No conversion is done from floats to integers, nor from integers to
-\end_layout
-
-\begin_layout Standard
-floats between c types and trace types.
- float conversion from double to float
-\end_layout
-
-\begin_layout Standard
-or from float to double is also not supported.
-\end_layout
-
-\begin_layout Section
-Environment variables
-\end_layout
-
-\begin_layout Standard
-The following environment variables change the behavior of libust.
-\end_layout
-
-\begin_layout Description
-UST_TRACE When defined, automatically enables tracing.
-\end_layout
-
-\begin_layout Description
-UST_AUTOPROBE When value is 1, enable all markers automatically.
- When value is a regular expression, enable all markers whose name matches
- the regular expression.
-\end_layout
-
-\begin_layout Description
-UST_DAEMON_SOCKET If not set, the default location of the daemon socket
- is used.
- If set, the value is used as path to the ustd socket.
-\end_layout
-
-\end_body
-\end_document
--- /dev/null
+\input texinfo @c -*-texinfo-*-
+@c %**start of header
+@setfilename ust.info
+@settitle LTTng Userspace Tracer (UST) Manual
+@c %**end of header
+
+@copying
+This manual is for program, version version.
+
+Copyright @copyright{} copyright-owner.
+
+@quotation
+Permission is granted to ...
+@end quotation
+@end copying
+
+@titlepage
+@title LTTng Userspace Tracer (UST) Manual
+@c @subtitle subtitle-if-any
+@c @subtitle second-subtitle
+@c @author author
+
+@c The following two commands
+@c start the copyright page.
+@c @page
+@c @vskip 0pt plus 1filll
+@c @insertcopying
+
+@c Published by ...
+@end titlepage
+
+@c So the toc is printed at the start.
+@contents
+
+@ifnottex
+@node Top
+@top LTTng Userspace Tracer
+
+This manual is for UST 0.1.
+@end ifnottex
+
+@menu
+* Overview::
+* Installation::
+* Quick start::
+* Instrumenting an application::
+* Recording a trace::
+* Viewing traces::
+* Performance::
+@c * Copying:: Your rights and freedoms.
+@end menu
+
+@node Overview
+@chapter Overview
+
+@menu
+* Supported platforms::
+@end menu
+
+@node Supported platforms
+@section Supported platforms
+
+UST can currently trace applications running on Linux, on the x86-32 and x86-64 architectures.
+
+@node Installation
+@chapter Installation
+
+The LTTng userspace tracer is a library and a set of userspace tools.
+
+The following packages are required:
+
+@itemize @bullet
+@item
+ust
+
+This contains the tracing library, the ustd daemon, trace control tools
+and other helper tools.
+
+Repository: http://git.dorsal.polymtl.ca
+
+@item
+libkcompat
+
+This is a library that contains a userspace port of some kernel APIs.
+
+Repository: http://git.dorsal.polymtl.ca
+
+@item
+liburcu
+
+This is the userspace read-copy update library by Mathieu Desnoyers.
+
+Available in Debian as package liburcu-dev.
+
+Home page: http://lttng.org/?q=node/18
+
+@item
+LTTV
+
+LTTV is a graphical (and text) viewer for LTTng traces.
+
+Home page: http://lttng.org
+
+@end itemize
+
+Libkcompat and liburcu should be installed first. UST may then be compiled
+and installed. LTTV has no dependency on the other packages; it may therefore
+be installed on a system which does not have UST installed.
+
+Refer to the README in each of these packages for installation instructions.
+
+@c @menu
+@c @end menu
+
+@node Quick start
+@chapter Quick start
+
+First, instrument a program with a marker.
+
+@example
+@verbatim
+
+#include <ust/marker.h>
+
+int main(int argc, char **argv)
+{
+ int v;
+ char *st;
+
+ /* ... set values of v and st ... */
+
+ /* a marker: */
+ trace_mark(ust, myevent, "firstarg %d secondarg %s", v, st);
+
+ /* a marker without arguments: */
+ trace_mark(ust, myotherevent, MARK_NOARGS);
+
+ return 0;
+}
+
+@end verbatim
+@end example
+
+Then compile it in the regular way, linking it with libust. For example:
+
+@example
+gcc -o foo -lust foo.c
+@end example
+
+Run the program with @command{usttrace}. The @command{usttrace} output says where the trace
+was written.
+
+@example
+usttrace ./foo
+@end example
+
+Finally, open the trace in LTTV.
+
+@example
+lttv-gui -t /path/to/trace
+@end example
+
+The trace can also be dumped as text in the console:
+
+@example
+lttv -m textDump -t /path/to/trace
+@end example
+
+@node Instrumenting an application
+@chapter Instrumenting an application
+
+In order to record a trace of events occurring in a application, the
+application must be instrumented. Instrumentation points resemble function
+calls. When the program reaches an instrumentation point, an event is
+generated.
+
+There are no limitations on the type of code that may be instrumented.
+Multi-threaded programs may be instrumented without problem. Signal handlers
+may be instrumented as well.
+
+There are two APIs to instrument programs: markers and tracepoints. Markers are
+quick to add and are usually used for temporary instrumentation. Tracepoints
+provide a way to instrument code more cleanly and are suited for permanent
+instrumentation.
+
+In addition to executable programs, shared libraries may also be instrumented
+with the methods described in this chapter.
+
+@menu
+* Markers::
+* Tracepoints::
+@end menu
+
+@node Markers
+@section Markers
+
+Adding a marker is simply a matter of insert one line in the program.
+
+@example
+@verbatim
+#include <ust/marker.h>
+
+int main(int argc, char **argv)
+{
+ int v;
+ char *st;
+
+ /* ... set values of v and st ... */
+
+ /* a marker: */
+ trace_mark(main, myevent, "firstarg %d secondarg %s", v, st);
+
+ /* a marker without arguments: */
+ trace_mark(main, myotherevent, MARK_NOARGS);
+
+ return 0;
+}
+@end verbatim
+@end example
+
+The invocation of the trace_mark() macro requires at least 3 arguments. The
+first, here "main", is the name of the event category. It is also the name of
+the channel the event will go in. The second, here "myevent" is the name of the
+event. The third is a format string that announces the names and the types of
+the event arguments. Its format resembles that of a printf() format string; it
+is described thoroughly in Appendix x.
+
+A given Marker may appear more than once in the same program. Other Markers may
+have the same name and a different format string, although this might induce
+some confusion at analysis time.
+
+@node Tracepoints
+@section Tracepoints
+
+The Tracepoints API uses the Markers, but provides a higher-level abstraction.
+Whereas the markers API provides limited type checking, the Tracepoints API
+provides more thorough type checking and discharges from the need to insert
+format strings directly in the code and to have format strings appear more than
+once if a given marker is reused.
+
+@quotation Note Although this example uses @emph{mychannel} as the channel, the
+only channel name currently supported with early tracing is @strong{ust}. The
+@command{usttrace} tool always uses the early tracing mode. When using manual
+mode without early tracing, any channel name may be used. @end quotation
+
+A function instrumented with a tracepoint looks like this:
+
+@example
+@verbatim
+#include "tp.h"
+
+void function()
+{
+ int v;
+ char *st;
+
+ /* ... set values of v and st ... */
+
+ /* a tracepoint: */
+ trace_mychannel_myevent(v, st);
+}
+@end verbatim
+@end example
+
+Another file, here tp.h, contains declarations for the tracepoint.
+
+@example
+@verbatim
+#include <ust/tracepoint.h>
+
+DECLARE_TRACE(mychannel_myevent, TPPROTO(int v, char *st),
+ TPARGS(v, st));
+@end verbatim
+@end example
+
+A third file, here tp.c, contains definitions for the tracepoint.
+
+@example
+@verbatim
+#include <ust/marker.h>
+#include "tp.h"
+
+DEFINE_TRACE(mychannel_myevent);
+
+void mychannel_myevent_probe(int v, char *st)
+{
+ trace_mark(mychannel, myevent, "v %d st %s", v, st);
+}
+
+static void __attribute__((constructor)) init()
+{
+ register_trace_mychannel_myevent(mychannel_myevent_probe);
+}
+@end verbatim
+@end example
+
+Here, tp.h and tp.c could contain declarations and definitions for other
+tracepoints. The constructor would contain other register_* calls.
+
+@node Recording a trace
+@chapter Recording a trace
+
+@menu
+* Using @command{usttrace}::
+* Setting up the recording manually::
+* Using early tracing::
+* Crash recovery::
+* Tracing across @code{fork()} and @code{clone()}::
+* Tracing programs and libraries that were not linked to libust::
+@end menu
+
+@node Using @command{usttrace}
+@section Using @command{usttrace}
+
+The simplest way to record a trace is to use the @command{usttrace} script. An
+example is given in the quickstart above.
+
+The @command{usttrace} script automatically:
+@itemize @bullet
+@item creates a daemon
+@item enables all markers
+@item runs the command specified on the command line
+@item after the command ends, prints the location where the trace was saved
+@end itemize
+
+Each subdirectory of the save location contains the trace of one process that
+was generated by the command. The name of a subdirectory consists in the the PID
+of the process, followed by the timestamp of its creation.
+
+The save location also contains logs of the tracing.
+
+When using @command{usttrace}, the early tracing is always active, which means
+that the tracing is guaranteed to be started by the time the process enters its
+main() function.
+
+Several @command{usttrace}'s may be run simultaneously without risk of
+conflict. This facilitates the use of the tracer by idependent users on a
+system. Each instance of @command{usttrace} starts its own daemon which
+collects the events of the processes it creates.
+
+@node Setting up the recording manually
+@section Setting up the recording manually
+
+Instead of using @command{usttrace}, a trace may be recorded on an already
+running process.
+
+First the daemon must be started.
+
+@example
+@verbatim
+# Make sure the directory for the communication sockets exists.
+$ mkdir /tmp/ustsocks
+
+# Make sure the directory where ustd will write the trace exists.
+$ mkdir /tmp/trace
+
+# Start the daemon
+$ ustd
+
+# We assume the program we want to trace is already running and that
+# it has pid 1234.
+
+# List the available markers
+$ ustctl --list-markers 1234
+# A column indicates 0 for an inactive marker and 1 for an active marker.
+
+# Enable a marker
+$ ustctl --enable-marker 1234 ust/mymark
+
+# Create a trace
+$ ustctl --create-trace 1234
+
+# Start tracing
+$ ustctl --start-trace 1234
+
+# Do things...
+
+# Stop tracing
+$ ustctl --stop-trace 1234
+@end verbatim
+@end example
+
+@node Using early tracing
+@section Using early tracing
+
+Early tracing consists in starting the tracing as early as possible in the
+program, so no events are lost between program start and the point where the
+command to start the tracing is given. When using early tracing, it is
+guaranteed that by the time the traced program enters its @code{main()}
+function, the tracing will be started.
+
+When using @command{usttrace}, the early tracing is always active.
+
+When using the manual mode (@command{ustctl}), early tracing is enabled using
+environment variables. Setting @env{UST_TRACE} to @code{1}, enables early
+tracing, while setting @env{UST_AUTOPROBE} to @code{1} enables all markers
+automatically.
+
+
+@node Crash recovery
+@section Crash recovery
+
+When a process being traced crashes, the daemon is able to recover all the
+events in its buffers that were successfully commited. This is possible because
+the buffers are in a shared memory segment which remains available to the
+daemon even after the termination of the traced process.
+
+@node Tracing across @code{fork()} and @code{clone()}
+@section Tracing across @code{fork()} and @code{clone()}
+
+Tracing across @code{clone()} when @code{CLONE_VM} is specified is supported
+without any particular action.
+
+When @code{clone()} is called without @code{CLONE_VM} or @code{fork()} is
+called, a new address space is created and the tracer must be notified to
+create new buffers for it. @strong{TODO: specify how to do it.}
+
+This can be done automatically (for @code{fork()} only for now), by
+@env{LD_PRELOAD}'ing @file{libinterfork.so}. This library intercepts calls to
+@code{fork()} and informs the tracer it is being called. When using
+@command{usttrace}, this is accomplied by specifying the @option{-f} command
+line argument.
+
+@node Tracing programs and libraries that were not linked to libust
+@section Tracing programs and libraries that were not linked to libust
+
+Todo.
+
+@node Performance
+@chapter Performance
+
+Todo.
+
+@node Viewing traces
+@chapter Viewing traces
+
+@bye
projects / ust.git / commitdiff
