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70165c78e3
Document both --on-threshold and --on-end, with examples. Cc: John Kacur <jkacur@redhat.com> Cc: Luis Goncalves <lgoncalv@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Chang Yin <cyin@redhat.com> Cc: Costa Shulyupin <costa.shul@redhat.com> Cc: Crystal Wood <crwood@redhat.com> Cc: Gabriele Monaco <gmonaco@redhat.com> Link: https://lore.kernel.org/20250626123405.1496931-10-tglozar@redhat.com Signed-off-by: Tomas Glozar <tglozar@redhat.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
121 lines
4.4 KiB
ReStructuredText
121 lines
4.4 KiB
ReStructuredText
**-a**, **--auto** *us*
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Set the automatic trace mode. This mode sets some commonly used options
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while debugging the system. It is equivalent to use **-T** *us* **-s** *us*
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**-t**. By default, *timerlat* tracer uses FIFO:95 for *timerlat* threads,
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thus equilavent to **-P** *f:95*.
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**-p**, **--period** *us*
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Set the *timerlat* tracer period in microseconds.
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**-i**, **--irq** *us*
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Stop trace if the *IRQ* latency is higher than the argument in us.
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**-T**, **--thread** *us*
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Stop trace if the *Thread* latency is higher than the argument in us.
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**-s**, **--stack** *us*
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Save the stack trace at the *IRQ* if a *Thread* latency is higher than the
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argument in us.
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**-t**, **--trace** \[*file*]
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Save the stopped trace to [*file|timerlat_trace.txt*].
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**--dma-latency** *us*
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Set the /dev/cpu_dma_latency to *us*, aiming to bound exit from idle latencies.
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*cyclictest* sets this value to *0* by default, use **--dma-latency** *0* to have
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similar results.
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**--deepest-idle-state** *n*
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Disable idle states higher than *n* for cpus that are running timerlat threads to
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reduce exit from idle latencies. If *n* is -1, all idle states are disabled.
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On exit from timerlat, the idle state setting is restored to its original state
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before running timerlat.
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Requires rtla to be built with libcpupower.
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**-k**, **--kernel-threads**
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Use timerlat kernel-space threads, in contrast of **-u**.
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**-u**, **--user-threads**
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Set timerlat to run without a workload, and then dispatches user-space workloads
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to wait on the timerlat_fd. Once the workload is awakes, it goes to sleep again
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adding so the measurement for the kernel-to-user and user-to-kernel to the tracer
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output. **--user-threads** will be used unless the user specify **-k**.
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**-U**, **--user-load**
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Set timerlat to run without workload, waiting for the user to dispatch a per-cpu
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task that waits for a new period on the tracing/osnoise/per_cpu/cpu$ID/timerlat_fd.
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See linux/tools/rtla/sample/timerlat_load.py for an example of user-load code.
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**--on-threshold** *action*
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Defines an action to be executed when tracing is stopped on a latency threshold
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specified by **-i/--irq** or **-T/--thread**.
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Multiple --on-threshold actions may be specified, and they will be executed in
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the order they are provided. If any action fails, subsequent actions in the list
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will not be executed.
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Supported actions are:
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- *trace[,file=<filename>]*
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Saves trace output, optionally taking a filename. Alternative to -t/--trace.
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Note that nlike -t/--trace, specifying this multiple times will result in
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the trace being saved multiple times.
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- *signal,num=<sig>,pid=<pid>*
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Sends signal to process. "parent" might be specified in place of pid to target
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the parent process of rtla.
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- *shell,command=<command>*
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Execute shell command.
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- *continue*
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Continue tracing after actions are executed instead of stopping.
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Example:
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$ rtla timerlat -T 20 --on-threshold trace
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--on-threshold shell,command="grep ipi_send timerlat_trace.txt"
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--on-threshold signal,num=2,pid=parent
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This will save a trace with the default filename "timerlat_trace.txt", print its
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lines that contain the text "ipi_send" on standard output, and send signal 2
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(SIGINT) to the parent process.
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Performance Considerations:
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For time-sensitive actions, it is recommended to run **rtla timerlat** with BPF
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support and RT priority. Note that due to implementational limitations, actions
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might be delayed up to one second after tracing is stopped if BPF mode is not
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available or disabled.
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**--on-end** *action*
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Defines an action to be executed at the end of **rtla timerlat** tracing.
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Multiple --on-end actions can be specified, and they will be executed in the order
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they are provided. If any action fails, subsequent actions in the list will not be
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executed.
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See the documentation for **--on-threshold** for the list of supported actions, with
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the exception that *continue* has no effect.
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Example:
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$ rtla timerlat -d 5s --on-end trace
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This runs rtla timerlat with default options and save trace output at the end.
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