[PATCH v2 0/9] rtla/timerlat: Support actions on threshold and on end

Tomas Glozar
2025-06-26T12:36:08Z

This series adds a feature that allows to user to specify certain
kinds of "actions" to be executed at one of two places in the rtla
measurement: when tracing is stopped on latency threshold, and at the
end of tracing.

Two new options are added: --on-threshold, and --on-end, taking
the action as an argument. For example:

$ rtla timerlat hist -T 10 \
--on-threshold shell,command="echo Threshold"
--on-end shell,command="echo Tracing stopped"

will print "Threshold" if a thread latency higher than 10 microseconds
is reached, and "Tracing stopped" always at the end.

The list of possible actions is extensible and is covered in
the commit messages. Later, a documentation patch series will be sent
with clear explanation of every action and its syntax.

Notably, a special action "continue" resumes tracing. For example:

$ rtla timerlat hist -T 100 \
--on-threshold shell,command="echo Threshold" \
--on-threshold continue -d 10s

will print "Threshold" as many times as tracing is stopped after
thread latency reaches 100us.

The feature was inspired by a case where collecting perf data on rtla
latency overflow was required, which can be done by sending a signal
to the perf process.

Example of this with Intel PT aux buffer:

$ perf record --cpu 0 -e intel_pt// -S -- rtla timerlat top -q -T 100 \
-c 0 --on-threshold signal,pid=parent,num=12 --on-theshold continue

In general, the feature is aiming to allow integration with external
tooling. To implement even more flexibility, passing context to the
shell through environmental variables, or even an entire scripting
language with access to the rtla internals can be implemented if
needed.

Changes since v1:
- Dropped short options on suggestion from Arnaldo.
- Added documentation.

Tomas Glozar (9):
rtla/timerlat: Introduce enum timerlat_tracing_mode
rtla/timerlat: Add action on threshold feature
rtla/timerlat_bpf: Allow resuming tracing
rtla/timerlat: Add continue action
rtla/timerlat: Add action on end feature
rtla/tests: Check rtla output with grep
rtla/tests: Add tests for actions
rtla/tests: Limit duration to maximum of 10s
Documentation/rtla: Add actions feature

.../tools/rtla/common_timerlat_options.rst | 64 +++++
tools/tracing/rtla/src/Build | 1 +
tools/tracing/rtla/src/actions.c | 260 ++++++++++++++++++
tools/tracing/rtla/src/actions.h | 52 ++++
tools/tracing/rtla/src/timerlat.bpf.c | 13 +-
tools/tracing/rtla/src/timerlat.c | 24 +-
tools/tracing/rtla/src/timerlat.h | 24 +-
tools/tracing/rtla/src/timerlat_bpf.c | 13 +
tools/tracing/rtla/src/timerlat_bpf.h | 3 +
tools/tracing/rtla/src/timerlat_hist.c | 140 +++++++---
tools/tracing/rtla/src/timerlat_top.c | 165 +++++++----
tools/tracing/rtla/tests/engine.sh | 21 +-
tools/tracing/rtla/tests/hwnoise.t | 8 +-
tools/tracing/rtla/tests/osnoise.t | 4 +-
tools/tracing/rtla/tests/timerlat.t | 36 ++-
15 files changed, 712 insertions(+), 116 deletions(-)
create mode 100644 tools/tracing/rtla/src/actions.c
create mode 100644 tools/tracing/rtla/src/actions.h

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2.49.0