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Documentation: coresight: Document AUX pause and resume

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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
This commit is contained in:
Leo Yan
2025-04-01 19:07:08 +01:00
committed by Suzuki K Poulose
parent 973f47a988
commit 5161890f13
1 changed files with 31 additions and 0 deletions
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Documentation/trace/coresight/coresight-perf.rst
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@@ -78,6 +78,37 @@ enabled like::
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
-----------------------------------------------------------