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.
+--
++
+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_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/getcpu-override[`examples/getcpu-override`].
-`LTTNG_UST_LOADED`::
- Set internally by `liblttng-ust`'s constructor. Can be used by
- applications to detect if lttng-ust is loaded, even if liblttng-ust
- is not directly linked by the application. This environment
- variable stays set across fork and exec, so an application could
- observe this environment variable being set if a parent process had
- lttng-ust loaded when issuing fork, even if this application does
- not have lttng-ust in its address space.
-
`LTTNG_UST_REGISTER_TIMEOUT`::
Waiting time for the _registration done_ session daemon command
before proceeding to execute the main program (milliseconds).
+
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