Commit 5161890f authored by Leo Yan's avatar Leo Yan Committed by Suzuki K Poulose
Browse files

Documentation: coresight: Document AUX pause and resume 



This adds description for AUX pause and resume.  It gives introduction
for what's AUX pause and resume and records usage examples.

Signed-off-by: default avatarLeo Yan <leo.yan@arm.com>
Reviewed-by: default avatarJames Clark <james.clark@linaro.org>
Signed-off-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20250401180708.385396-8-leo.yan@arm.com
parent 973f47a9

Documentation/trace/coresight/coresight-perf.rst

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Please refer to the kernel configuration help for more information.



Fine-grained tracing with AUX pause and resume

----------------------------------------------



Arm CoreSight may generate a large amount of hardware trace data, which

will lead to overhead in recording and distract users when reviewing

profiling result. To mitigate the issue of excessive trace data, Perf

provides AUX pause and resume functionality for fine-grained tracing.



The AUX pause and resume can be triggered by associated events. These

events can be ftrace tracepoints (including static and dynamic

tracepoints) or PMU events (e.g. CPU PMU cycle event). To create a perf

session with AUX pause / resume, three configuration terms are

introduced:



- "aux-action=start-paused": it is specified for the cs_etm PMU event to

  launch in a paused state.

- "aux-action=pause": an associated event is specified with this term

  to pause AUX trace.

- "aux-action=resume": an associated event is specified with this term

  to resume AUX trace.



Example for triggering AUX pause and resume with ftrace tracepoints::



  perf record -e cs_etm/aux-action=start-paused/k,syscalls:sys_enter_openat/aux-action=resume/,syscalls:sys_exit_openat/aux-action=pause/ ls



Example for triggering AUX pause and resume with PMU event::



  perf record -a -e cs_etm/aux-action=start-paused/k \

        -e cycles/aux-action=pause,period=10000000/ \

        -e cycles/aux-action=resume,period=1050000/ -- sleep 1



Perf test - Verify kernel and userspace perf CoreSight work

-----------------------------------------------------------