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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: Leo Yan <leo.yan@arm.com>
Reviewed-by: James Clark <james.clark@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20250401180708.385396-8-leo.yan@arm.com
authored by
Leo Yan
and committed by
Suzuki K Poulose
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973f47a9
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Documentation/trace/coresight/coresight-perf.rst
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Documentation/trace/coresight/coresight-perf.rst
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Please refer to the kernel configuration help for more information.
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Fine-grained tracing with AUX pause and resume
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----------------------------------------------
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Arm CoreSight may generate a large amount of hardware trace data, which
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will lead to overhead in recording and distract users when reviewing
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profiling result. To mitigate the issue of excessive trace data, Perf
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provides AUX pause and resume functionality for fine-grained tracing.
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The AUX pause and resume can be triggered by associated events. These
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events can be ftrace tracepoints (including static and dynamic
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tracepoints) or PMU events (e.g. CPU PMU cycle event). To create a perf
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session with AUX pause / resume, three configuration terms are
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introduced:
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- "aux-action=start-paused": it is specified for the cs_etm PMU event to
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launch in a paused state.
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- "aux-action=pause": an associated event is specified with this term
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to pause AUX trace.
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- "aux-action=resume": an associated event is specified with this term
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to resume AUX trace.
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Example for triggering AUX pause and resume with ftrace tracepoints::
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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
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Example for triggering AUX pause and resume with PMU event::
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perf record -a -e cs_etm/aux-action=start-paused/k \
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-e cycles/aux-action=pause,period=10000000/ \
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-e cycles/aux-action=resume,period=1050000/ -- sleep 1
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Perf test - Verify kernel and userspace perf CoreSight work
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-----------------------------------------------------------
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