From: Philippe Proulx Date: Mon, 16 Nov 2015 17:40:31 +0000 (-0500) Subject: doc/man: create lttng-enable-event(1) and update/fix content X-Git-Tag: v2.8.0-rc1~35 X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=commitdiff_plain;h=e9b06e2bf2e5b0e8627e0944cc2f087eebc52e98 doc/man: create lttng-enable-event(1) and update/fix content Signed-off-by: Philippe Proulx Signed-off-by: Jérémie Galarneau --- diff --git a/doc/man/Makefile.am b/doc/man/Makefile.am index 316e28950..44631298d 100644 --- a/doc/man/Makefile.am +++ b/doc/man/Makefile.am @@ -27,7 +27,8 @@ MAN1_NAMES = \ lttng-untrack \ lttng-status \ lttng-help \ - lttng-snapshot + lttng-snapshot \ + lttng-enable-event MAN3_NAMES = MAN8_NAMES = MAN1_NO_ASCIIDOC_NAMES = lttng-crash diff --git a/doc/man/lttng-enable-event.1.txt b/doc/man/lttng-enable-event.1.txt new file mode 100644 index 000000000..4d88bdb1b --- /dev/null +++ b/doc/man/lttng-enable-event.1.txt @@ -0,0 +1,436 @@ +lttng-enable-event(1) +===================== + + +NAME +---- +lttng-enable-event - Create or enable LTTng event rules + + +SYNOPSIS +-------- +Create or enable Linux kernel event rules: + +[verse] +*lttng* ['GENERAL OPTIONS'] *enable-event* option:--kernel + [option:--probe='SOURCE' | option:--function='SOURCE' | option:--syscall] + [option:--filter='EXPR'] [option:--session='SESSION'] + [option:--channel='CHANNEL'] 'EVENT'[,'EVENT']... + +Create or enable an "all" Linux kernel event rule: + +[verse] +*lttng* ['GENERAL OPTIONS'] *enable-event* option:--kernel option:--all [option:--syscall] + [option:--filter='EXPR'] [option:--session='SESSION'] [option:--channel='CHANNEL'] + +Create or enable application event rules: + +[verse] +*lttng* ['GENERAL OPTIONS'] *enable-event* + (option:--userspace | option:--jul | option:--log4j | option:--python) + [option:--filter='EXPR'] [option:--exclude='EVENT'[,'EVENT']...] + [option:--loglevel='LOGLEVEL' | option:--loglevel-only='LOGLEVEL'] + [option:--session='SESSION'] [option:--channel='CHANNEL'] (option:--all | 'EVENT'[,'EVENT']...) + + +DESCRIPTION +----------- +The `lttng enable-event` command can create a new event rule, or enable +one or more existing and disabled ones. + +An event rule created by `lttng enable-event` is a set of conditions +that must be satisfied in order for an actual event to be emitted by +an LTTng tracer when the execution of an application or the Linux kernel +reaches an event source (tracepoint, system call, dynamic probe). +Event sources can be listed with the linklttng:lttng-list(1) command. + +The linklttng:lttng-disable-event(1) command can be used to disable +existing event rules. + +Event rules are always assigned to a channel when they are created. If +the option:--channel option is omitted, a default channel named +`channel0` is used (and created automatically if it does not exist for +the specified domain in the selected tracing session). + +If the option:--session option is omitted, the chosen channel is picked +from the current tracing session. + +Events can be enabled while tracing is active +(use linklttng:lttng-start(1) to make a tracing session active). + + +Event source types +~~~~~~~~~~~~~~~~~~ +Four types of event sources are available in the Linux kernel tracing +domain (option:--kernel option): + +Tracepoint (option:--tracepoint option; default):: + A Linux kernel tracepoint, that is, a static instrumentation point + placed in the kernel source code. Standard tracepoints are designed + and placed in the source code by developers and record useful + payload fields. + +Dynamic probe (option:--probe option):: + A Linux kernel kprobe, that is, an instrumentation point placed + dynamically in the compiled kernel code. Dynamic probe events do not + record any payload field. + +Function probe (option:--function option):: + A Linux kernel kretprobe, that is, two instrumentation points placed + dynamically where a function is entered and where it returns in the + compiled kernel code. Function probe events do not record any + payload field. + +System call (option:--syscall option):: + A Linux kernel system call. Two instrumentation points are + statically placed where a system call function is entered and where + it returns in the compiled kernel code. System call event sources + record useful payload fields. + +The application tracing domains (option:--userspace, option:--jul, +option:--log4j, or option:--python options) only support tracepoints. +In the cases of the JUL, Apache log4j, and Python domains, the event +names correspond to _logger_ names. + + +Understanding event rule conditions +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +When creating an event rule with `lttng enable-event`, conditions are +specified using options. The logical conjunction (logical AND) of all +those conditions must be true when an event source is reached by an +application or by the Linux kernel in order for an actual event +to be emitted by an LTTng tracer. + +Any condition that is not explicitly specified on creation is considered +a _don't care_. + +For example, consider the following commands: + +---------------------------------------------------------------- +lttng enable-event --userspace hello:world +lttng enable-event --userspace hello:world --loglevel=TRACE_INFO +---------------------------------------------------------------- + +Here, two event rules are created. The first one has a single condition: +the tracepoint name must match `hello:world`. The second one has two +conditions: + +* The tracepoint name must match `hello:world`, _and_ +* The tracepoint's defined log level must be at least as severe as + the `TRACE_INFO` level. + +In this case, the second event rule is pointless because the first one +is more general: it does not care about the tracepoint's log level. +If an event source matching both event rules is reached by the +application's execution, only one event is emitted. + +The available conditions for the Linux kernel domain are: + +* Tracepoint/system call name ('EVENT' argument with + option:--tracepoint or option:--syscall options) or + dynamic probe/function name/address + (option:--probe or option:--function option's argument) which must + match event source's equivalent. ++ +Wildcard using the `*` character are supported _at the end_ of +tracepoint and system call names. + +* Filter expression (option:--filter option) executed against the + dynamic values of event fields at execution time that must evaluate + to true. See the <> section + below for more information. + +The available conditions for the application domains are: + +* Tracepoint name ('EVENT' with option:--tracepoint option) which must + match event source's equivalent. ++ +Wildcard using the `*` character are supported _at the end_ of +tracepoint names. When creating an event rule with a tracepoint name +containing a wildcard, specific tracepoint names can be excluded from +the match using the option:--exclude option. + +* Filter expression (option:--filter option) executed against the + dynamic values of event fields at execution time that must evaluate + to true. See the <> section + below for more information. +* Event's log level that must be at least as severe as a given + log level (option:--loglevel option) or match exactly a given log + level (option:--loglevel-only option). + +When using `lttng enable-event` with a set of conditions that does not +currently exist for the chosen tracing session, domain, and channel, +a new event rule is created. Otherwise, the existing event rule is +enabled if it is currently disabled +(see linklttng:lttng-disable-event(1)). + +The option:--all option can be used alongside the option:--tracepoint +or option:--syscall options. When this option is used, no 'EVENT' +argument must be specified. This option defines a single event rule +matching _all_ the possible events of a given tracing domain for the +chosen channel and tracing session. It is the equivalent of an 'EVENT' +argument named `*` (wildcard). + + +[[filter-syntax]] +Filter expression syntax +~~~~~~~~~~~~~~~~~~~~~~~~ +Filter expressions can be specified with the option:--filter option +when creating a new event rule. If the filter expression evaluates +to true when executed against the dynamic values of an event's fields +when tracing, the filtering condition passes. + +The filter expression syntax is very similar to C language conditional +expressions (expressions that can be evaluated by an `if` statement). + +The following logical operators are supported: + +[width="40%",options="header"] +|===================================== +| Name | Syntax +| Logical negation (NOT) | `!a` +| Logical conjunction (AND) | `a && b` +| Logical disjunction (OR) | `a \|\| b` +|===================================== + +The following comparison operators/relational operators are supported: + +[width="40%",options="header"] +|==================================== +| Name | Syntax +| Equal to | `a == b` +| Not equal to | `a != b` +| Greater than | `a > b` +| Less than | `a < b` +| Greater than or equal to | `a >= b` +| Less than or equal to | `a <= b` +|==================================== + +The arithmetic and bitwise operators are :not: supported. + +The precedence table of the operators above is the same as the one of +the C language. Parentheses are supported to bypass this. + +The dynamic value of an event field is read by using its name as +a C identifier. + +The dynamic value of a statically-known context field is read by +prefixing its name with `$ctx.`. Statically-known context fields are +context fields added to channels without the `$app.` prefix using the +linklttng:lttng-add-context(1) command. + +The dynamic value of an application-specific context field is read by +prefixing its name with `$app.` (follows the format used to add such a +context field with the linklttng:lttng-add-context(1) command). + +When a comparison includes a non existent event field, the whole filter +expression evaluates to false (the event is discarded). + +C integer and floating point number constants are supported, as well as +literal strings between double quotes (`"`). Literal strings can contain +a wildcard character (`*`) at the end to match more than one string. +This wildcard can be escaped using `\\*`. + +LTTng-UST enumeration fields can be compared to integer values (fields +or constants). + +NOTE: Although it is possible to filter the process ID of an event when +the `pid` context has been added to its channel using, for example, +`$ctx.pid == 2832`, it is recommended to use the PID tracker instead, +which is much more efficient (see linklttng:lttng-track(1)). + +Examples: + +---------------------------- +msg_id == 23 && size >= 2048 +---------------------------- + +------------------------------------------------- +$ctx.procname == "lttng*" && (!flag || poel < 34) +------------------------------------------------- + +--------------------------------------------------------- +$app.my_provider:my_context == 17.34e9 || some_enum >= 14 +--------------------------------------------------------- + + +[[log-levels]] +Log levels +~~~~~~~~~~ +Tracepoints and log statements in applications have an attached log +level. Application event rules can contain a _log level_ condition. + +With the option:--loglevel option, the event source's log level must +be at least as severe as the option's argument. With the +option:--loglevel-only option, the event source's log level must match +the option's argument. + +The available log levels are: + +User space domain (option:--userspace option):: + Shortcuts such as `system` are allowed. ++ +* `TRACE_EMERG` (0) +* `TRACE_ALERT` (1) +* `TRACE_CRIT` (2) +* `TRACE_ERR` (3) +* `TRACE_WARNING` (4) +* `TRACE_NOTICE` (5) +* `TRACE_INFO` (6) +* `TRACE_DEBUG_SYSTEM` (7) +* `TRACE_DEBUG_PROGRAM` (8) +* `TRACE_DEBUG_PROCESS` (9) +* `TRACE_DEBUG_MODULE` (10) +* `TRACE_DEBUG_UNIT` (11) +* `TRACE_DEBUG_FUNCTION` (12) +* `TRACE_DEBUG_LINE` (13) +* `TRACE_DEBUG` (14) + +`java.util.logging` domain (option:--jul option):: + Shortcuts such as `severe` are allowed. ++ +* `JUL_OFF` (`INT32_MAX`) +* `JUL_SEVERE` (1000) +* `JUL_WARNING` (900) +* `JUL_INFO` (800) +* `JUL_CONFIG` (700) +* `JUL_FINE` (500) +* `JUL_FINER` (400) +* `JUL_FINEST` (300) +* `JUL_ALL` (`INT32_MIN`) + +Apache log4j domain (option:--log4j option):: + Shortcuts such as `severe` are allowed. ++ +* `LOG4J_OFF` (`INT32_MAX`) +* `LOG4J_FATAL` (50000) +* `LOG4J_ERROR` (40000) +* `LOG4J_WARN` (30000) +* `LOG4J_INFO` (20000) +* `LOG4J_DEBUG` (10000) +* `LOG4J_TRACE` (5000) +* `LOG4J_ALL` (`INT32_MIN`) + +Python domain (option:--python option):: + Shortcuts such as `critical` are allowed. ++ +* `PYTHON_CRITICAL` (50) +* `PYTHON_ERROR` (40) +* `PYTHON_WARNING` (30) +* `PYTHON_INFO` (20) +* `PYTHON_DEBUG` (10) +* `PYTHON_NOTSET` (0) + + +include::common-cmd-options-head.txt[] + + +Domain +~~~~~~ +One of: + +option:-j, option:--jul:: + Create or enable event rules in the `java.util.logging` + (JUL) domain. + +option:-k, option:--kernel:: + Create or enable event rules in the Linux kernel domain. + +option:-l, option:--log4j:: + Create or enable event rules in the Apache log4j domain. + +option:-p, option:--python:: + Create or enable event rules in the Python domain. + +option:-u, option:--userspace:: + Create or enable event rules in the user space domain. + + +Target +~~~~~~ +option:-c, option:--channel='CHANNEL':: + Create or enable event rules in the channel named 'CHANNEL' instead + of the default channel name `channel0`. + +option:-s, option:--session='SESSION':: + Create or enable event rules in the tracing session named 'SESSION' + instead of the current tracing session. + + +Event source type +~~~~~~~~~~~~~~~~~ +One of: + +option:--function='SOURCE':: + Linux kernel kretprobe. Only available with the option:--kernel + domain option. 'SOURCE' is one of: ++ +* Function address (`0x` prefix supported) +* Function symbol +* Function symbol and offset (`SYMBOL+OFFSET` format) + +option:--probe='SOURCE':: + Linux kernel kprobe. Only available with the option:--kernel + domain option. 'SOURCE' is one of: ++ +* Address (`0x` prefix supported) +* Symbol +* Symbol and offset (`SYMBOL+OFFSET` format) + +option:--syscall:: + Linux kernel system call. Only available with the option:--kernel + domain option. + +option:--tracepoint:: + Linux kernel or application tracepoint (default). + + +Log level +~~~~~~~~~ +One of: + +option:--loglevel='LOGLEVEL':: + Add log level condition to the event rule: the event source's + defined log level must be at least as severe as 'LOGLEVEL'. + See the <> section above for the available + log levels. Only available with application domains. + +option:--loglevel-only='LOGLEVEL':: + Add log level condition to the event rule: the event source's + defined log level must match 'LOGLEVEL'. See the + <> section above for the available log + levels. Only available with application domains. + + +Filtering and exclusion +~~~~~~~~~~~~~~~~~~~~~~~ +option:-x, option:--exclude='EVENT'[,'EVENT']...:: + Exclude events named 'EVENT' from the event rule. This option + can be used when the command's 'EVENT' argument contains a wildcard + (`*`) to exclude specific names. Only available with application + domains. + +option:-f, option:--filter='EXPR':: + Add filter expression condition to the event rule. Expression 'EXPR' + must evaluate to true when executed against the dynamic values of + event fields. See the <> + section above for more information. + + +Shortcuts +~~~~~~~~~ +option:-a, option:--all:: + Equivalent to an 'EVENT' argument named `*` (wildcard) when also + using the option:--tracepoint (default) or option:--syscall option. + + +include::common-cmd-help-options.txt[] + + +include::common-cmd-footer.txt[] + + +SEE ALSO +-------- +linklttng:lttng-disable-event(1), +linklttng:lttng(1)