Commit 26e1a9bd authored by Tomas Glozar's avatar Tomas Glozar
Browse files

Documentation/rtla: Document --bpf-action option 

Add new option --bpf-action into common_timerlat_options.txt, including
the format in which it takes the BPF program, and a reference to an
example.

Link: https://lore.kernel.org/r/20251126144205.331954-8-tglozar@redhat.com


Signed-off-by: default avatarTomas Glozar <tglozar@redhat.com>
parent 6627556c

Documentation/tools/rtla/common_timerlat_options.txt

+18 −0
Original line number Diff line number Diff line
@@ -65,3 +65,21 @@ 
        Set timerlat to run without workload, waiting for the user to dispatch a per-cpu

        task that waits for a new period on the tracing/osnoise/per_cpu/cpu$ID/timerlat_fd.

        See linux/tools/rtla/example/timerlat_load.py for an example of user-load code.



**--bpf-action** *bpf-program*



        Loads a BPF program from an ELF file and executes it when a latency threshold is exceeded.



        The BPF program must be a valid ELF file loadable with libbpf. The program must contain

        a function named ``action_handler``, stored in an ELF section with the ``tp_`` prefix.

        The prefix is used by libbpf to set BPF program type to BPF_PROG_TYPE_TRACEPOINT.



        The program receives a ``struct trace_event_raw_timerlat_sample`` parameter

        containing timerlat sample data.



        An example is provided in ``tools/tracing/rtla/example/timerlat_bpf_action.c``.

        This example demonstrates how to create a BPF program that prints latency information using

        bpf_trace_printk() when a threshold is exceeded.



        **Note**: BPF actions require BPF support to be available. If BPF is not available

        or disabled, the tool falls back to tracefs mode and BPF actions are not supported.