Re: [PATCH v3 2/7] rtla/timerlat: Add --bpf-action option

[Tomas Glozar]

po 3. 11. 2025 v 15:45 odesílatel Wander Lairson Costa
<wan...@redhat.com> napsal:
> >
> > Executing additional BPF code on latency threshold overflow allows doing
> > doing low-latency and in-kernel troubleshooting of the cause of the
>
> typo: double "doing"
>

Thanks, I'll fix that :)

> > --- a/tools/tracing/rtla/src/timerlat.c
> > +++ b/tools/tracing/rtla/src/timerlat.c
> > @@ -48,6 +48,17 @@ timerlat_apply_config(struct osnoise_tool *tool, struct 
> > timerlat_params *params)
> >               }
> >       }
> >
> > +     /* Check if BPF action program is requested but BPF is not available 
> > */
> > +     if (params->bpf_action_program) {
> > +             if (params->mode == TRACING_MODE_TRACEFS) {
> > +                     err_msg("BPF actions are not supported in 
> > tracefs-only mode\n");
>
> I would just emit a warning to the user and proceed ignoring the bpf action 
> argument.
>

I believe if the user explicitly requests BPF actions to be used,
measurement should not proceed without the action. Imagine someone
setting --bpf-action in an automated test, expecting it to report
something. But the action never fires, because they do not notice they
are running an old kernel that does not support this.

The user can always restart/reconfigure RTLA to skip the option.

Tomas