~~~~~~~~~~~~~~~~~~~~
If an application that uses `liblttng-ust` becomes part of a tracing
session, information about its currently loaded shared objects, their
-build IDs, and their debug link informations are emitted as events
+build IDs, and their debug link information are emitted as events
by the tracer.
The following LTTng-UST state dump events exist and must be enabled
+
This event has no fields.
-`lttng_ust_statedump:soinfo`::
- Emitted when information about a currently loaded shared object is
- found.
+`lttng_ust_statedump:bin_info`::
+ Emitted when information about a currently loaded executable or
+ shared object is found.
+
Fields:
+
[options="header"]
-|==============================================================
+|==================================================================
| Field name | Description
-| `baddr` | Base address of loaded library
-| `memsz` | Size of loaded library in memory
-| `sopath` | Path to loaded library file
-|==============================================================
+| `baddr` | Base address of loaded executable
+| `memsz` | Size of loaded executable in memory
+| `path` | Path to loaded executable file
+| `is_pic` | Whether the executable is
+ position-independent code
+|==================================================================
`lttng_ust_statedump:build_id`::
Emitted when a build ID is found in a currently loaded shared
cc -o app tp.o app.o -llttng-ust -ldl
-------------------------------------
+Using the man:lttng(1) tool, create an LTTng tracing session, enable
+all the events of this tracepoint provider, and start tracing:
+
+[role="term"]
+----------------------------------------------
+lttng create my-session
+lttng enable-event --userspace 'my_provider:*'
+lttng start
+----------------------------------------------
+
+You may also enable specific events:
+
+[role="term"]
+----------------------------------------------------------
+lttng enable-event --userspace my_provider:big_event
+lttng enable-event --userspace my_provider:event_instance2
+----------------------------------------------------------
+
+Run the application:
+
+[role="term"]
+--------------------
+./app some arguments
+--------------------
+
+Stop the current tracing session and inspect the recorded events:
+
+[role="term"]
+----------
+lttng stop
+lttng view
+----------
+
Tracepoint provider header file
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
ENVIRONMENT VARIABLES
---------------------
-`LTTNG_UST_DEBUG`::
- Activate `liblttng-ust` debug and error output.
-
-`LTTNG_UST_REGISTER_TIMEOUT`::
- Specify how long the applications should wait for the
- _registration done_ session daemon command before proceeding to
- execute the main program (milliseconds).
+`LTTNG_HOME`::
+ Alternative user's home directory. This variable is useful when the
+ user running the instrumented application has a non-writable home
+ directory.
+
-The value 0 means _do not wait_. The value -1 means _wait forever_.
-Setting this environment variable to 0 is recommended for applications
-with time constraints on the process startup time.
+Unix sockets used for the communication between `liblttng-ust` and the
+LTTng session and consumer daemons (part of the LTTng-tools project)
+are located in a specific directory under `$LTTNG_HOME` (or `$HOME` if
+`$LTTNG_HOME` is not set).
+
+`LTTNG_UST_BLOCKING_RETRY_TIMEOUT`::
+ Maximum duration (milliseconds) to retry event tracing when
+ there's no space left for the event record in the sub-buffer.
++
+--
+`0` (default)::
+ Never block the application.
+
+Positive value::
+ Block the application for the specified number of milliseconds. If
+ there's no space left after this duration, discard the event
+ record.
+
+Negative value::
+ Block the application until there's space left for the event record.
+--
+
-Default: 3000.
+This option can be useful in workloads generating very large trace data
+throughput, where blocking the application is an acceptable trade-off to
+prevent discarding event records.
++
+WARNING: Setting this environment variable to a non-zero value may
+significantly affect application timings.
-`LTTNG_UST_WITHOUT_BADDR_STATEDUMP`::
- Prevent `liblttng-ust` from performing a base address state dump
- (see the <<state-dump,LTTng-UST state dump>> section above).
+`LTTNG_UST_CLOCK_PLUGIN`::
+ Path to the shared object which acts as the clock override plugin.
+ An example of such a plugin can be found in the LTTng-UST
+ documentation under
+ https://github.com/lttng/lttng-ust/tree/master/doc/examples/clock-override[`examples/clock-override`].
+
+`LTTNG_UST_DEBUG`::
+ Activates `liblttng-ust`'s debug and error output if set to `1`.
`LTTNG_UST_GETCPU_PLUGIN`::
Path to the shared object which acts as the `getcpu()` override
documentation under
https://github.com/lttng/lttng-ust/tree/master/doc/examples/getcpu-override[`examples/getcpu-override`].
-`LTTNG_UST_CLOCK_PLUGIN`::
- Path to the shared object which acts as the clock override plugin.
- An example of such a plugin can be found in the LTTng-UST
- documentation under
- https://github.com/lttng/lttng-ust/tree/master/doc/examples/clock-override[`examples/clock-override`].
+`LTTNG_UST_REGISTER_TIMEOUT`::
+ Waiting time for the _registration done_ session daemon command
+ before proceeding to execute the main program (milliseconds).
++
+The value `0` means _do not wait_. The value `-1` means _wait forever_.
+Setting this environment variable to `0` is recommended for applications
+with time constraints on the process startup time.
++
+Default: {lttng_ust_register_timeout}.
+
+`LTTNG_UST_BLOCKING_RETRY_TIMEOUT`::
+ Maximum time during which event tracing retry is attempted on buffer
+ full condition (millliseconds). Setting this environment to non-zero
+ value effectively blocks the application on buffer full condition.
+ Setting this environment variable to non-zero values may
+ significantly affect application timings. Setting this to a negative
+ value may block the application indefinitely if there is no consumer
+ emptying the ring buffer. The delay between retry attempts is the
+ minimum between the specified timeout value and 100ms. This option
+ can be useful in workloads generating very large trace data
+ throughput, where blocking the application is an acceptable
+ trade-off to not discard events. _Use with caution_.
++
+The value `0` means _do not retry_. The value `-1` means _retry forever_.
+Value > `0` means a maximum timeout of the given value.
++
+Default: {lttng_ust_blocking_retry_timeout}.
+
+`LTTNG_UST_WITHOUT_BADDR_STATEDUMP`::
+ Prevents `liblttng-ust` from performing a base address state dump
+ (see the <<state-dump,LTTng-UST state dump>> section above) if
+ set to `1`.
include::common-footer.txt[]
projects / lttng-ust.git / blobdiff