From: Nils Carlson Date: Tue, 30 Nov 2010 13:11:23 +0000 (+0100) Subject: Fix info automake and clean doc automake X-Git-Tag: v0.9~1 X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=cf1da69dd47917f75147ab38f6041ad0fe66d952;p=ust.git Fix info automake and clean doc automake Fix so that info is built using automake and also clean up the automake process so that make clean works. Signed-off-by: Nils Carlson Acked-by: Mathieu Desnoyers --- diff --git a/.gitignore b/.gitignore index 4896a47..020c2f4 100644 --- a/.gitignore +++ b/.gitignore @@ -10,6 +10,7 @@ Makefile *.lo Makefile.in *.loT +*.info configure aclocal.m4 autom4te.cache/ diff --git a/configure.ac b/configure.ac index 922e626..4fcd565 100644 --- a/configure.ac +++ b/configure.ac @@ -107,6 +107,8 @@ AC_MSG_RESULT($LIBFORMAT) AC_CONFIG_FILES([ Makefile doc/Makefile + doc/man/Makefile + doc/info/Makefile include/Makefile libust/Makefile tests/Makefile diff --git a/doc/Makefile.am b/doc/Makefile.am index fa769be..37a55ac 100644 --- a/doc/Makefile.am +++ b/doc/Makefile.am @@ -1,2 +1 @@ -EXTRA_DIST = manual man/ustctl.1 man/ustd.1 man/usttrace.1 -man_MANS = man/ustctl.1 man/ustd.1 man/usttrace.1 +SUBDIRS = man info \ No newline at end of file diff --git a/doc/info/Makefile.am b/doc/info/Makefile.am new file mode 100644 index 0000000..93d1896 --- /dev/null +++ b/doc/info/Makefile.am @@ -0,0 +1,2 @@ +EXTRA_DIST = ust.texi +info_TEXINFOS = ust.texi diff --git a/doc/info/ust.texi b/doc/info/ust.texi new file mode 100644 index 0000000..e0565f3 --- /dev/null +++ b/doc/info/ust.texi @@ -0,0 +1,634 @@ +\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 0.5. +@end ifnottex + +@menu +* Overview:: +* Installation:: +* Quick start:: +* Instrumenting an application:: +* Recording a trace:: +* Viewing traces:: +* Performance:: +* Resource Usage:: +* List of environment variables detected by libust:: +* GDB integration:: +@c * Copying:: Your rights and freedoms. +@end menu + +@node Overview +@chapter Overview + +@menu +* What is UST?:: +* License:: +* Supported platforms:: +@end menu + +@node What is UST? +@section What is UST? + +The LTTng Userspace Tracer (UST) is a library accompanied by a set of tools to +trace userspace code. + +Code may be instrumented with either markers or tracepoints. A highly efficient +lockless tracer records these events to a trace buffers. These buffers are reaped +by a deamon which writes trace data to disk. + +High performance is achieved by the use of lockless buffering algorithms, RCU and +per-cpu buffers. In addition, special care is taken to minize cache impact. + +@node License +@section License +The LTTng Userspace Tracer is intended to be linkable to open source software +as well as to proprietary applications. This was accomplished by licensing +the code that needs to be linked to the traced program as @acronym{LGPL}. + +Components licensed as LGPL v2.1: +@itemize @bullet +@item libust +@item libinterfork +@item libustcomm +@end itemize + +Components licensed as GPL v2: +@itemize @bullet +@item ustctl +@item libustcmd +@item ustd +@end itemize + +@node Supported platforms +@section Supported platforms + +UST can currently trace applications running on Linux, on the x86-32, x86-64 +and PowerPC 32 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: @url{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: @url{http://lttng.org/urcu} + +@item +LTTV + +LTTV is a graphical (and text) viewer for LTTng traces. + +Home page: @url{http://lttng.org} + +@end itemize + +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 + +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 inserting one line in the program. + +@example +@verbatim +#include + +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); + + /* another 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 + +DECLARE_TRACE(mychannel_myevent, TP_PROTO(int v, char *st), + TP_ARGS(v, st)); +@end verbatim +@end example + +A third file, here tp.c, contains definitions for the tracepoint. + +@example +@verbatim +#include +#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 +@code{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 ust/mymark 1234 + +# Create a trace +$ ustctl --create-trace 1234 + +# Start tracing +$ ustctl --start-trace 1234 + +# Do things... + +# Stop tracing +$ ustctl --stop-trace 1234 + +# Destroy the trace +$ ustctl --destroy-trace 1234 +@end verbatim +@end example + +For more information about the manual mode, see the ustctl(1) man page. + +@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 the @code{CLONE_VM} flag 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. + +This can be done automatically, 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. + +Alternatively, the program can call @code{ust_before_fork()} before calling +@code{fork()} or @code{clone()} with @code{CLONE_VM}. After the call, +@code{ust_after_fork_parent()} must be called in the parent process and +@code{ust_after_fork_child()} must be called in the child process. + + +@node Tracing programs and libraries that were not linked to libust +@section Tracing programs and libraries that were not linked to libust + +Some programs need to be traced even though they were not linked to libust +either because they were not instrumented or because it was not practical. + +An executable that is not instrumented can still yield interesting traces when +at least one of its dynamic libraries is instrumented. It is also possible to +trace certain function calls by intercepting them with a specially crafted +library that is linked with @env{LD_PRELOAD} at program start. + +In any case, a program that was not linked to libust at compile time must be +linked to it at run time with @env{LD_PRELOAD}. This can be accomplished with +@command{usttrace}'s @option{-l} option. It can also be done by setting the +@env{LD_PRELOAD} environment variable on the command line. For example: + +@example +@verbatim +# Run ls with usttrace, LD_PRELOAD'ing libust +# (assuming one of the libraries used by ls is instrumented). +$ usttrace -l ls + +# Run ls, manually adding the LD_PRELOAD. +$ LD_PRELOAD=/usr/local/lib/libust.so.0 ls +@end verbatim +@end example + + +@node Performance +@chapter Performance + +Todo. + +@node Viewing traces +@chapter Viewing traces + +Traces may be viewed with LTTV. An example of command for launching LTTV is +given in the quickstart. + +@menu +* Viewing multiple traces:: +* Combined kernel-userspace tracing:: +@end menu + +@node Viewing multiple traces +@section Viewing multiple traces + +When tracing multi-process applications or several applications simultaneously, +more than one trace will be obtained. LTTV can open and display all these +traces simultaneously. + +@node Combined kernel-userspace tracing +@section Combined kernel-userspace tracing + +In addition to multiple userspace traces, LTTV can open a kernel trace recorded +with the LTTng kernel tracer. This provides events that enable the rendering of +the Control Flow View and the Resource View. + +When doing so, it is necessary to use the same time source for the kernel +tracer as well as the userspace tracer. Currently, the recommended method is to +use the timestamp counter for both. The TSC can however only be used on architectures +where it is synchronized across cores. + +@node Resource Usage +@chapter Resource Usage + +The purpose of this section is to give an overview of the resource usage of libust. For +a developer, knowing this can be important: because libust is linked with applications, it +needs to share some resources with it. Some applications may make some assumptions that are in +conflict with libust's usage of resources. + +In practice however, libust is designed to be transparent and is compatible +with the vast majority of applications. This means no changes are required in +the application (or library) being linked to libust. + +Libust is initialized by a constructor, which by definition runs before the +@code{main()} function of the application starts. This constructor creates a +thread called the @emph{listener thread}. The listener thread initializes a +named socket and waits for connections for ustd or ustctl. + +Libust-specific code may: +@itemize @bullet +@item use @code{malloc()} and @code{free()} +@item map shared memory segment in the process adress space +@item intercept some library calls, specifically @code{fork()} and @code{clone()} +@item do interprocess communication with the daemon or ustctl +@item create and open named sockets + +@end itemize + +It will not: +@itemize @bullet +@item handle any signal (all signals are blocked in the listener thread) +@item change any process-wide setting that could confuse the application +@end itemize + +@node List of environment variables detected by libust +@appendix List of environment variables detected by libust + +The behavior of tracing can be influenced by setting special environment +variables in the environment of the traced application. This section +describes these variables. + +@itemize @bullet + +@item +@env{UST_TRACE} + +If set to 1, start tracing as soon as the program starts. Tracing is +guaranteed to be started by the time the @code{main()} function starts. + +@item +@env{UST_AUTOPROBE} + +If set to @code{1}, enable all markers by the time the @code{main()} function starts. + +@item +@env{UST_AUTOCOLLECT} + +If set to @code{0}, disable notification of daemon on trace start. Useful for +performance tests. + +@item +@env{UST_OVERWRITE} + +If set to @code{1}, enable overwriting of buffers on overrun. + +@item +@env{UST_SUBBUF_NUM} + +If set, defines the default number of subbuffers per buffer. + +@item +@env{UST_SUBBUF_SIZE} + +If set, defines the default size of subbuffers, in bytes. + +@end itemize + +@node GDB integration +@appendix GDB integration + +GDB, the GNU Debugger, can use UST markers as GDB tracepoints (note GDB has its +own concept of tracepoint). This feature is called GDB Static Tracepoints. When +a GDB tracepoint is hit, GDB collects the marker arguments, as well as the +state of the registers. + +In UST, support for GDB integration is not compiled in by default because of +the cost of saving registers when a marker is hit. To enable it, run the +@command{./configure} script with the @code{-DCONFIG_UST_GDB_INTEGRATION} flag +in the @env{CFLAGS} environment variable. For example: + +@example +@verbatim + +CFLAGS=-DCONFIG_UST_GDB_INTEGRATION ./configure + +@end verbatim +@end example + +As of this writing, GDB Static Tracepoints have been submitted +(@url{http://sourceware.org/ml/gdb-patches/2010-06/msg00592.html}) to the GDB +mailing list. + +GDB integration is currently only supported on x86-32 and x86-64. + +@bye diff --git a/doc/man/Makefile.am b/doc/man/Makefile.am new file mode 100644 index 0000000..7e18b8e --- /dev/null +++ b/doc/man/Makefile.am @@ -0,0 +1,2 @@ +EXTRA_DIST = ustctl.1 ustd.1 usttrace.1 +man_MANS = ustctl.1 ustd.1 usttrace.1 diff --git a/doc/manual/.gitignore b/doc/manual/.gitignore deleted file mode 100644 index 2460008..0000000 --- a/doc/manual/.gitignore +++ /dev/null @@ -1 +0,0 @@ -!Makefile diff --git a/doc/manual/Makefile b/doc/manual/Makefile deleted file mode 100644 index 62a430f..0000000 --- a/doc/manual/Makefile +++ /dev/null @@ -1,4 +0,0 @@ -all: ust.html - -ust.html: manual.texinfo - makeinfo --html --no-split manual.texinfo diff --git a/doc/manual/manual.texinfo b/doc/manual/manual.texinfo deleted file mode 100644 index e0565f3..0000000 --- a/doc/manual/manual.texinfo +++ /dev/null @@ -1,634 +0,0 @@ -\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 0.5. -@end ifnottex - -@menu -* Overview:: -* Installation:: -* Quick start:: -* Instrumenting an application:: -* Recording a trace:: -* Viewing traces:: -* Performance:: -* Resource Usage:: -* List of environment variables detected by libust:: -* GDB integration:: -@c * Copying:: Your rights and freedoms. -@end menu - -@node Overview -@chapter Overview - -@menu -* What is UST?:: -* License:: -* Supported platforms:: -@end menu - -@node What is UST? -@section What is UST? - -The LTTng Userspace Tracer (UST) is a library accompanied by a set of tools to -trace userspace code. - -Code may be instrumented with either markers or tracepoints. A highly efficient -lockless tracer records these events to a trace buffers. These buffers are reaped -by a deamon which writes trace data to disk. - -High performance is achieved by the use of lockless buffering algorithms, RCU and -per-cpu buffers. In addition, special care is taken to minize cache impact. - -@node License -@section License -The LTTng Userspace Tracer is intended to be linkable to open source software -as well as to proprietary applications. This was accomplished by licensing -the code that needs to be linked to the traced program as @acronym{LGPL}. - -Components licensed as LGPL v2.1: -@itemize @bullet -@item libust -@item libinterfork -@item libustcomm -@end itemize - -Components licensed as GPL v2: -@itemize @bullet -@item ustctl -@item libustcmd -@item ustd -@end itemize - -@node Supported platforms -@section Supported platforms - -UST can currently trace applications running on Linux, on the x86-32, x86-64 -and PowerPC 32 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: @url{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: @url{http://lttng.org/urcu} - -@item -LTTV - -LTTV is a graphical (and text) viewer for LTTng traces. - -Home page: @url{http://lttng.org} - -@end itemize - -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 - -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 inserting one line in the program. - -@example -@verbatim -#include - -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); - - /* another 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 - -DECLARE_TRACE(mychannel_myevent, TP_PROTO(int v, char *st), - TP_ARGS(v, st)); -@end verbatim -@end example - -A third file, here tp.c, contains definitions for the tracepoint. - -@example -@verbatim -#include -#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 -@code{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 ust/mymark 1234 - -# Create a trace -$ ustctl --create-trace 1234 - -# Start tracing -$ ustctl --start-trace 1234 - -# Do things... - -# Stop tracing -$ ustctl --stop-trace 1234 - -# Destroy the trace -$ ustctl --destroy-trace 1234 -@end verbatim -@end example - -For more information about the manual mode, see the ustctl(1) man page. - -@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 the @code{CLONE_VM} flag 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. - -This can be done automatically, 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. - -Alternatively, the program can call @code{ust_before_fork()} before calling -@code{fork()} or @code{clone()} with @code{CLONE_VM}. After the call, -@code{ust_after_fork_parent()} must be called in the parent process and -@code{ust_after_fork_child()} must be called in the child process. - - -@node Tracing programs and libraries that were not linked to libust -@section Tracing programs and libraries that were not linked to libust - -Some programs need to be traced even though they were not linked to libust -either because they were not instrumented or because it was not practical. - -An executable that is not instrumented can still yield interesting traces when -at least one of its dynamic libraries is instrumented. It is also possible to -trace certain function calls by intercepting them with a specially crafted -library that is linked with @env{LD_PRELOAD} at program start. - -In any case, a program that was not linked to libust at compile time must be -linked to it at run time with @env{LD_PRELOAD}. This can be accomplished with -@command{usttrace}'s @option{-l} option. It can also be done by setting the -@env{LD_PRELOAD} environment variable on the command line. For example: - -@example -@verbatim -# Run ls with usttrace, LD_PRELOAD'ing libust -# (assuming one of the libraries used by ls is instrumented). -$ usttrace -l ls - -# Run ls, manually adding the LD_PRELOAD. -$ LD_PRELOAD=/usr/local/lib/libust.so.0 ls -@end verbatim -@end example - - -@node Performance -@chapter Performance - -Todo. - -@node Viewing traces -@chapter Viewing traces - -Traces may be viewed with LTTV. An example of command for launching LTTV is -given in the quickstart. - -@menu -* Viewing multiple traces:: -* Combined kernel-userspace tracing:: -@end menu - -@node Viewing multiple traces -@section Viewing multiple traces - -When tracing multi-process applications or several applications simultaneously, -more than one trace will be obtained. LTTV can open and display all these -traces simultaneously. - -@node Combined kernel-userspace tracing -@section Combined kernel-userspace tracing - -In addition to multiple userspace traces, LTTV can open a kernel trace recorded -with the LTTng kernel tracer. This provides events that enable the rendering of -the Control Flow View and the Resource View. - -When doing so, it is necessary to use the same time source for the kernel -tracer as well as the userspace tracer. Currently, the recommended method is to -use the timestamp counter for both. The TSC can however only be used on architectures -where it is synchronized across cores. - -@node Resource Usage -@chapter Resource Usage - -The purpose of this section is to give an overview of the resource usage of libust. For -a developer, knowing this can be important: because libust is linked with applications, it -needs to share some resources with it. Some applications may make some assumptions that are in -conflict with libust's usage of resources. - -In practice however, libust is designed to be transparent and is compatible -with the vast majority of applications. This means no changes are required in -the application (or library) being linked to libust. - -Libust is initialized by a constructor, which by definition runs before the -@code{main()} function of the application starts. This constructor creates a -thread called the @emph{listener thread}. The listener thread initializes a -named socket and waits for connections for ustd or ustctl. - -Libust-specific code may: -@itemize @bullet -@item use @code{malloc()} and @code{free()} -@item map shared memory segment in the process adress space -@item intercept some library calls, specifically @code{fork()} and @code{clone()} -@item do interprocess communication with the daemon or ustctl -@item create and open named sockets - -@end itemize - -It will not: -@itemize @bullet -@item handle any signal (all signals are blocked in the listener thread) -@item change any process-wide setting that could confuse the application -@end itemize - -@node List of environment variables detected by libust -@appendix List of environment variables detected by libust - -The behavior of tracing can be influenced by setting special environment -variables in the environment of the traced application. This section -describes these variables. - -@itemize @bullet - -@item -@env{UST_TRACE} - -If set to 1, start tracing as soon as the program starts. Tracing is -guaranteed to be started by the time the @code{main()} function starts. - -@item -@env{UST_AUTOPROBE} - -If set to @code{1}, enable all markers by the time the @code{main()} function starts. - -@item -@env{UST_AUTOCOLLECT} - -If set to @code{0}, disable notification of daemon on trace start. Useful for -performance tests. - -@item -@env{UST_OVERWRITE} - -If set to @code{1}, enable overwriting of buffers on overrun. - -@item -@env{UST_SUBBUF_NUM} - -If set, defines the default number of subbuffers per buffer. - -@item -@env{UST_SUBBUF_SIZE} - -If set, defines the default size of subbuffers, in bytes. - -@end itemize - -@node GDB integration -@appendix GDB integration - -GDB, the GNU Debugger, can use UST markers as GDB tracepoints (note GDB has its -own concept of tracepoint). This feature is called GDB Static Tracepoints. When -a GDB tracepoint is hit, GDB collects the marker arguments, as well as the -state of the registers. - -In UST, support for GDB integration is not compiled in by default because of -the cost of saving registers when a marker is hit. To enable it, run the -@command{./configure} script with the @code{-DCONFIG_UST_GDB_INTEGRATION} flag -in the @env{CFLAGS} environment variable. For example: - -@example -@verbatim - -CFLAGS=-DCONFIG_UST_GDB_INTEGRATION ./configure - -@end verbatim -@end example - -As of this writing, GDB Static Tracepoints have been submitted -(@url{http://sourceware.org/ml/gdb-patches/2010-06/msg00592.html}) to the GDB -mailing list. - -GDB integration is currently only supported on x86-32 and x86-64. - -@bye