realtime:documentation:howto:tools:rtla
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realtime:documentation:howto:tools:rtla [2025/12/04 14:13] tglozar Add section on tuning options |
realtime:documentation:howto:tools:rtla [2025/12/11 12:39] (current) tglozar [Calling into external tooling] Add link to rtla with perf processor trace tutorial |
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| * //--deepest-idle-state <n>// - limits the deepest allowed idle state via cpuidle interface, only on CPUs where measurement is running, unlike --dma-latency, which affects all CPUs. | * //--deepest-idle-state <n>// - limits the deepest allowed idle state via cpuidle interface, only on CPUs where measurement is running, unlike --dma-latency, which affects all CPUs. | ||
| + | Setting the deepest idle state instead of DMA latency helps with power consumption, but might lead to increased latencies on some systems. | ||
| ===== Events ===== | ===== Events ===== | ||
| - | Arguments to enable common events for automatic and trace options: | + | All **rtla** tools include //latency source auto-analysis//, enabled with //-a <us>// option, which takes the duration of a latency in microseconds for rtla to stop tracing at. Auto-analysis uses tracepoints to capture thread and IRQ interference to the real-time workload, which are collected, processed, and finally formatted and printed at the end of the measurement. |
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| + | If auto-analysis is not enough to determine the cause of the latency, additional tracepoints may be enabled using the //-e <event_name>// option. Arguments to enable common events for automatic and trace options: | ||
| ''<nowiki> | ''<nowiki> | ||
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| grep 1 /sys/kernel/debug/tracing/instances/ /sys/kernel/debug/tracing/events/ -R --include enable | grep 1 /sys/kernel/debug/tracing/instances/ /sys/kernel/debug/tracing/events/ -R --include enable | ||
| </nowiki>'' | </nowiki>'' | ||
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| + | To be able to see captured events after the end of the rtla run, trace output has to be enabled using the //--trace/-t// option, unless -a is used, which enables //-t// automatically. | ||
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| + | ===== Calling into external tooling ===== | ||
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| + | Since version 6.17, **rtla** supports integrating external tools into latency measurement by the means of //actions//. Actions can run a command or send a signal to a process whenever tracing is stopped on latency threshold set with //-T/-i/-a// (for timerlat; //-s/-S/-a// for osnoise), or at the end of tracing. A special action resumes tracing after stop, if requested. | ||
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| + | External tooling might be used in cases where rtla's tracefs-based diagnostics are insufficient. See the rtla manpages for how to use actions. One specific use of actions is covered in the tutorial, [[realtime:documentation:howto:tools:rtla:processor_trace|Using rtla with perf processor trace]]. | ||
| ===== More Information ===== | ===== More Information ===== | ||
realtime/documentation/howto/tools/rtla.1764857589.txt.gz · Last modified: 2025/12/04 14:13 by tglozar
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