X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=doc%2Fman%2Flttng-ust.3;h=380c9fce841305ecfbd4a28314d8c6043d2d2af7;hb=1e3b00595c2cc1abeb3707afd99024b7aead8a25;hp=818ef103ae407498c133ba9e64580595f3b47254;hpb=94c9c48da8ea6424c01d17409cc6788f7ea70450;p=lttng-ust.git diff --git a/doc/man/lttng-ust.3 b/doc/man/lttng-ust.3 index 818ef103..380c9fce 100644 --- a/doc/man/lttng-ust.3 +++ b/doc/man/lttng-ust.3 @@ -1,7 +1,7 @@ .TH "LTTNG-UST" "3" "February 16, 2012" "" "" .SH "NAME" -lttng-ust \(em Linux Trace Toolkit Next Generation User-Space Tracer +lttng-ust \(em Linux Trace Toolkit Next Generation User-Space Tracer 2.x .SH "SYNOPSIS" @@ -12,12 +12,43 @@ Link liblttng-ust.so with applications, following this manpage. .SH "DESCRIPTION" .PP -LTTng-UST, the Linux Trace Toolkit Next Generation Userspace Tracer, is +LTTng-UST, the Linux Trace Toolkit Next Generation Userspace Tracer, is a port of the low-overhead tracing capabilities of the LTTng kernel tracer to user-space. The library "liblttng-ust" enables tracing of applications and libraries. -.SH "USAGE" +.SH "USAGE WITH TRACEF" +.PP +The simplest way to add instrumentation to your code is by far the +tracef() API. To do it, in a nutshell: + +1) #include + +2) /* in your code, use like a printf */ + tracef("my message, this integer %d", 1234); + +3) Link your program against liblttng-ust.so. + +4) Enable UST events when tracing with the following sequence of commands + from lttng-tools: + + lttng create + lttng enable-event -u -a + lttng start + [... run your program ...] + lttng stop + lttng view + +That's it! + +If you want to have more flexibility and control on the event names, +payload typing, etc, you can continue reading on and use the tracepoints +below. "tracef()" is there for quick and dirty ad hoc instrumentation, +whereas tracepoint.h is meant for thorough instrumentation of a code +base to be integrated with an upstream project. +.PP + +.SH "USAGE WITH TRACEPOINT" .PP The simple way to generate the lttng-ust tracepoint probes is to use the lttng-gen-tp(1) tool. See the lttng-gen-tp(1) manpage for explanation. @@ -33,18 +64,22 @@ script, through an example: .nf To create a tracepoint provider, within a build tree similar to -examples/easy-ust installed with lttng-ust documentation, a -sample_component_provider.h for the general layout. This manpage will -focus on the various types that can be recorded into a trace event: +examples/easy-ust installed with lttng-ust documentation, see +sample_component_provider.h for the general layout. You will need to +define TRACEPOINT_CREATE_PROBES before including your tracepoint +provider probe in one source file of your application. See tp.c from +easy-ust for an example of a tracepoint probe source file. This manpage +will focus on the various types that can be recorded into a trace +event: TRACEPOINT_EVENT( /* * provider name, not a variable but a string starting with a - * letter and containing either letters, numbers or underscores. + * letter and containing either letters, numbers or underscores. * Needs to be the same as TRACEPOINT_PROVIDER. Needs to * follow the namespacing guide-lines in lttng/tracepoint.h: - * - * Must be included before include tracepoint provider + * + * Must be included before include tracepoint provider * ex.: project_event * ex.: project_component_event * @@ -59,19 +94,19 @@ TRACEPOINT_EVENT( /* * tracepoint name, same format as sample provider. Does not * need to be declared before. in this case the name is - * "message" + * "message" */ message, /* - * TP_ARGS macro contains the arguments passed for the tracepoint + * TP_ARGS macro contains the arguments passed for the tracepoint * it is in the following format * TP_ARGS(type1, name1, type2, name2, ... type10, name10) - * where there can be from zero to ten elements. - * typeN is the datatype, such as int, struct or double **. + * where there can be from zero to ten elements. + * typeN is the datatype, such as int, struct or double **. * name is the variable name (in "int myInt" the name would be - * myint) + * myint) * TP_ARGS() is valid to mean no arguments * TP_ARGS(void) is valid too */ @@ -80,7 +115,7 @@ TRACEPOINT_EVENT( double, doublearg, float, floatarg), /* - * TP_FIELDS describes how to write the fields of the trace event. + * TP_FIELDS describes how to write the fields of the trace event. * You can put expressions in the "argument expression" area, * typically using the input arguments from TP_ARGS. */ @@ -109,27 +144,34 @@ TRACEPOINT_EVENT( /* * ctf_array: a statically-sized array. * args: (type, field name, argument expression, value) - */ + */ ctf_array(long, arrfield1, values, 3) /* * ctf_array_text: a statically-sized array, printed as * a string. No need to be terminated by a null * character. - */ + * Behavior is undefined if "text" argument is NULL. + */ ctf_array_text(char, arrfield2, text, 10) /* * ctf_sequence: a dynamically-sized array. * args: (type, field name, argument expression, * type of length expression, length expression) - */ + * The "type of length expression" needs to be an + * unsigned type. As a reminder, "unsigned char" should + * be preferred to "char", since the signedness of + * "char" is implementation-defined. + * Behavior is undefined if "text" argument is NULL. + */ ctf_sequence(char, seqfield1, text, size_t, textlen) /* * ctf_sequence_text: a dynamically-sized array, printed * as string. No need to be null-terminated. + * Behavior is undefined if "text" argument is NULL. */ ctf_sequence_text(char, seqfield2, text, size_t, textlen) @@ -137,6 +179,7 @@ TRACEPOINT_EVENT( /* * ctf_string: null-terminated string. * args: (field name, argument expression) + * Behavior is undefined if "text" argument is NULL. */ ctf_string(stringfield, text) @@ -148,6 +191,11 @@ TRACEPOINT_EVENT( ctf_float(double, doublefield, doublearg) ) ) + +There can be an arbitrary number of tracepoint providers within an +application, but they must each have their own provider name. Duplicate +provider names are not allowed. + .fi .SH "ASSIGNING LOGLEVEL TO EVENTS" @@ -160,7 +208,7 @@ following construct: TRACEPOINT_LOGLEVEL(< [com_company_]project[_component] >, < event >, < loglevel_name >) - The first field is the provider name, the second field is the name of +The first field is the provider name, the second field is the name of the tracepoint, and the third field is the loglevel name. A TRACEPOINT_EVENT should be declared prior to the the TRACEPOINT_LOGLEVEL for a given tracepoint name. The TRACEPOINT_PROVIDER must be already @@ -168,56 +216,56 @@ declared before declaring a TRACEPOINT_LOGLEVEL. The loglevels go from 0 to 14. Higher numbers imply the most verbosity (higher event throughput expected. - + Loglevels 0 through 6, and loglevel 14, match syslog(3) loglevels semantic. Loglevels 7 through 13 offer more fine-grained selection of debug information. - + TRACE_EMERG 0 system is unusable - + TRACE_ALERT 1 action must be taken immediately - + TRACE_CRIT 2 critical conditions - + TRACE_ERR 3 error conditions - + TRACE_WARNING 4 warning conditions - + TRACE_NOTICE 5 normal, but significant, condition - + TRACE_INFO 6 informational message - + TRACE_DEBUG_SYSTEM 7 debug information with system-level scope (set of programs) - + TRACE_DEBUG_PROGRAM 8 debug information with program-level scope (set of processes) - + TRACE_DEBUG_PROCESS 9 debug information with process-level scope (set of modules) - + TRACE_DEBUG_MODULE 10 debug information with module (executable/library) scope (set of units) - + TRACE_DEBUG_UNIT 11 debug information with compilation unit scope (set of functions) - + TRACE_DEBUG_FUNCTION 12 debug information with function-level scope - + TRACE_DEBUG_LINE 13 debug information with line-level scope (TRACEPOINT_EVENT default) - + TRACE_DEBUG 14 - debug-level message (trace_printf default) + debug-level message See lttng(1) for information on how to use LTTng-UST loglevels. @@ -238,6 +286,10 @@ For instance, add within a function: As a call to the tracepoint. It will only be activated when requested by lttng(1) through lttng-sessiond(8). +Even though LTTng-UST supports tracepoint() call site duplicates having +the same provider and event name, it is recommended to use a +provider event name pair only once within the source code to help +map events back to their call sites when analyzing the trace. .fi .SH "BUILDING/LINKING THE TRACEPOINT PROVIDER" @@ -260,8 +312,10 @@ carefully: library with "\-llttng-ust". - Include the tracepoint provider header into all C files using the provider. - - Example: - tests/hello/ hello.c tp.c ust_tests_hello.h Makefile.example + - Examples: + - doc/examples/easy-ust/ sample.c sample_component_provider.h tp.c + Makefile + - doc/examples/hello-static-lib/ hello.c tp.c ust_test_hello.h Makefile 2) Compile the Tracepoint Provider separately from the application, using dynamic linking: @@ -276,15 +330,15 @@ carefully: - Link application with "\-ldl". - Set a LD_PRELOAD environment to preload the tracepoint provider shared object before starting the application when tracing is - needed. + needed. Another way is to dlopen the tracepoint probe when needed + by the application. - Example: - - tests/demo/ demo.c tp*.c ust_tests_demo*.h demo-trace + - doc/examples/demo demo.c tp*.c ust_tests_demo*.h demo-trace Makefile - - Note about dlopen() usage: due to locking side-effects due to the - way libc lazily resolves Thread-Local Storage (TLS) symbols when a - library is dlopen'd, linking the tracepoint probe or liblttng-ust - with dlopen() is discouraged. They should be linked with the - application using "\-llibname" or loaded with LD_PRELOAD. + - Note about dlclose() usage: it is not safe to use dlclose on a + provider shared object that is being actively used for tracing due + to a lack of reference counting from lttng-ust to the used shared + object. - Enable instrumentation and control tracing with the "lttng" command from lttng-tools. See lttng-tools doc/quickstart.txt. - Note for C++ support: although an application instrumented with @@ -323,6 +377,13 @@ Virtual process ID: process ID as seen from the point of view of the process namespace. .PP +.PP +.IP "ip" +Instruction pointer: Enables recording of the exact location where a tracepoint +was emitted. Can be used to reverse-lookup the source location that caused the +event to be emitted. +.PP + .PP .IP "procname" Thread name, as set by exec() or prctl(). It is recommended that @@ -336,6 +397,29 @@ Pthread identifier. Can be used on architectures where pthread_t maps nicely to an unsigned long type. .PP +.SH "BASE ADDRESS STATEDUMP" + +.PP +If an application that uses liblttng-ust.so becomes part of a session, +information about its currently loaded shared objects will be traced to the +session at session-enable time. To record this information, the following event +needs to be enabled: +.PP +.IP "ust_baddr_statedump:soinfo" +This event is used to trace a currently loaded shared object. The base address +(where the dynamic linker has placed the shared object) is recorded in the +"baddr" field. The path to the shared object gets recorded in the +"sopath" field (as string). The file size of the loaded object (in +bytes) is recorded to the "size" field and its time of last modification +(in seconds since Epoch) is recorded in the "mtime" field. +.PP +If the event above is enabled, a series of "ust_baddr_statedump:soinfo" +events is recorded at session-enable time. It represents the state of +currently loaded shared objects for the traced process. If this +information gets combined with the lttng-ust-dl(3) instrumentation, all +aspects of dynamic loading that are relevant for symbol and +line number lookup are traced by LTTng. +.PP .SH "ENVIRONMENT VARIABLES" .PP @@ -352,16 +436,33 @@ specified in milliseconds. The value 0 means "don't wait". The value recommended for applications with time constraints on the process startup time. .PP +.IP "LTTNG_UST_WITHOUT_BADDR_STATEDUMP" +Prevent liblttng-ust to perform a base-address statedump on session-enable. +.PP .SH "SEE ALSO" .PP -lttng-gen-tp(1), lttng(1), babeltrace(1), lttng-sessiond(8) +lttng-gen-tp(1), lttng(1), babeltrace(1), lttng-ust-cyg-profile(3), +lttng-ust-dl(3), lttng-sessiond(8) .PP + +.SH "COMPATIBILITY" + +.PP +Older lttng-ust libraries reject more recent, and incompatible, probe +providers. Newer lttng-ust libraries accept older probe providers, even +though some newer features might not be available with those providers. +.PP + .SH "BUGS" .PP -No knows bugs at this point. +LTTng-UST 2.0 and 2.1 lttng-ust libraries do not check for probe +provider version compatibility. This can lead to out-of-bound accesses +when using a more recent probe provider with an older lttng-ust library. +These error only trigger when tracing is active. This issue has been +fixed in LTTng-UST 2.2. If you encounter any issues or usability problem, please report it on our mailing list to help improve this