[PATCH v2 9/9] Documentation/rtla: Add actions feature

Tomas Glozar
2025-06-26T12:36:41Z

Document both --on-threshold and --on-end, with examples.

Signed-off-by: Tomas Glozar <tglozar@redhat.com>
---
.../tools/rtla/common_timerlat_options.rst | 64 +++++++++++++++++++
1 file changed, 64 insertions(+)

diff --git a/Documentation/tools/rtla/common_timerlat_options.rst b/Documentation/tools/rtla/common_timerlat_options.rst
index 10dc802f8d65..7854368f1827 100644
--- a/Documentation/tools/rtla/common_timerlat_options.rst
+++ b/Documentation/tools/rtla/common_timerlat_options.rst
@@ -55,3 +55,67 @@
Set timerlat to run without workload, waiting for the user to dispatch a per-cpu
task that waits for a new period on the tracing/osnoise/per_cpu/cpu$ID/timerlat_fd.
See linux/tools/rtla/sample/timerlat_load.py for an example of user-load code.
+
+**--on-threshold** *action*
+
+ Defines an action to be executed when tracing is stopped on a latency threshold
+ specified by **-i/--irq** or **-T/--thread**.
+
+ Multiple --on-threshold actions may be specified, and they will be executed in
+ the order they are provided. If any action fails, subsequent actions in the list
+ will not be executed.
+
+ Supported actions are:
+
+ - *trace[,file=<filename>]*
+
+ Saves trace output, optionally taking a filename. Alternative to -t/--trace.
+ Note that nlike -t/--trace, specifying this multiple times will result in
+ the trace being saved multiple times.
+
+ - *signal,num=<sig>,pid=<pid>*
+
+ Sends signal to process. "parent" might be specified in place of pid to target
+ the parent process of rtla.
+
+ - *shell,command=<command>*
+
+ Execute shell command.
+
+ - *continue*
+
+ Continue tracing after actions are executed instead of stopping.
+
+ Example:
+
+ $ rtla timerlat -T 20 --on-threshold trace
+ --on-threshold shell,command="grep ipi_send timerlat_trace.txt"
+ --on-threshold signal,num=2,pid=parent
+
+ This will save a trace with the default filename "timerlat_trace.txt", print its
+ lines that contain the text "ipi_send" on standard output, and send signal 2
+ (SIGINT) to the parent process.
+
+ Performance Considerations:
+
+ For time-sensitive actions, it is recommended to run **rtla timerlat** with BPF
+ support and RT priority. Note that due to implementational limitations, actions
+ might be delayed up to one second after tracing is stopped if BPF mode is not
+ available or disabled.
+
+**--on-end** *action*
+
+ Defines an action to be executed at the end of **rtla timerlat** tracing.
+
+ Multiple --on-end actions can be specified, and they will be executed in the order
+ they are provided. If any action fails, subsequent actions in the list will not be
+ executed.
+
+ See the documentation for **--on-threshold** for the list of supported actions, with
+ the exception that *continue* has no effect.
+
+ Example:
+
+ $ rtla timerlat -d 5s --on-end trace
+
+ This runs rtla timerlat with default options and save trace output at the end.
--
2.49.0