1.. |threshold| replace:: **-a/--auto**, **-i/--irq**, or **-T/--thread** 2.. |thresharg| replace:: -T 3.. |tracer| replace:: timerlat 4 5.. |actionsperf| replace:: 6 For time-sensitive actions, it is recommended to run **rtla timerlat** with BPF 7 support and RT priority. Note that due to implementational limitations, actions 8 might be delayed up to one second after tracing is stopped if BPF mode is not 9 available or disabled. 10 11**-a**, **--auto** *us* 12 13 Set the automatic trace mode. This mode sets some commonly used options 14 while debugging the system. It is equivalent to use **-T** *us* **-s** *us* 15 **-t**. By default, *timerlat* tracer uses FIFO:95 for *timerlat* threads, 16 thus equivalent to **-P** *f:95*. 17 18**-p**, **--period** *us* 19 20 Set the *timerlat* tracer period in microseconds. 21 22**-i**, **--irq** *us* 23 24 Stop trace if the *IRQ* latency is higher than the argument in us. 25 26**-T**, **--thread** *us* 27 28 Stop trace if the *Thread* latency is higher than the argument in us. 29 30**-s**, **--stack** *us* 31 32 Save the stack trace at the *IRQ* if a *Thread* latency is higher than the 33 argument in us. 34 35**-t**, **--trace** \[*file*] 36 37 Save the stopped trace to [*file|timerlat_trace.txt*]. 38 39**--dma-latency** *us* 40 Set the /dev/cpu_dma_latency to *us*, aiming to bound exit from idle latencies. 41 *cyclictest* sets this value to *0* by default, use **--dma-latency** *0* to have 42 similar results. 43 44**--deepest-idle-state** *n* 45 Disable idle states higher than *n* for cpus that are running timerlat threads to 46 reduce exit from idle latencies. If *n* is -1, all idle states are disabled. 47 On exit from timerlat, the idle state setting is restored to its original state 48 before running timerlat. 49 50 Requires rtla to be built with libcpupower. 51 52**-k**, **--kernel-threads** 53 54 Use timerlat kernel-space threads, in contrast of **-u**. 55 56**-u**, **--user-threads** 57 58 Set timerlat to run without a workload, and then dispatches user-space workloads 59 to wait on the timerlat_fd. Once the workload is awakened, it goes to sleep again 60 adding so the measurement for the kernel-to-user and user-to-kernel to the tracer 61 output. **--user-threads** will be used unless the user specify **-k**. 62 63**-U**, **--user-load** 64 65 Set timerlat to run without workload, waiting for the user to dispatch a per-cpu 66 task that waits for a new period on the tracing/osnoise/per_cpu/cpu$ID/timerlat_fd. 67 See linux/tools/rtla/example/timerlat_load.py for an example of user-load code. 68 69**--bpf-action** *bpf-program* 70 71 Loads a BPF program from an ELF file and executes it when a latency threshold is exceeded. 72 73 The BPF program must be a valid ELF file loadable with libbpf. The program must contain 74 a function named ``action_handler``, stored in an ELF section with the ``tp_`` prefix. 75 The prefix is used by libbpf to set BPF program type to BPF_PROG_TYPE_TRACEPOINT. 76 77 The program receives a ``struct trace_event_raw_timerlat_sample`` parameter 78 containing timerlat sample data. 79 80 An example is provided in ``tools/tracing/rtla/example/timerlat_bpf_action.c``. 81 This example demonstrates how to create a BPF program that prints latency information using 82 bpf_trace_printk() when a threshold is exceeded. 83 84 **Note**: BPF actions require BPF support to be available. If BPF is not available 85 or disabled, the tool falls back to tracefs mode and BPF actions are not supported. 86