linux-kernel - Re: [PATCH 0/2] tracing: Add a way to have custom events in the tracefs directory

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Date:   Wed, 2 Mar 2022 11:00:27 -0500
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Tom Zanussi <zanussi@...nel.org>
Subject: Re: [PATCH 0/2] tracing: Add a way to have custom events in the
 tracefs directory

On Tue, Mar 1, 2022 at 10:28 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> We would like to have in production a way to record sched wakeups and
> sched switch, and be able to save the information in a small file
> with as much available as possible. Currently the wake up and sched switch
> events are 36 and 64 bytes each (plus a 4 byte ring buffer event header).
>
> By having a custom module tap into the sched switch and waking trace points
> we can bring those events down to 16 and 14 bytes respectively.
>
> Steven Rostedt (Google) (2):
>       tracing: Allow custom events to be added to the tracefs directory
>       tracing: Add sample code for custom trace events

Great! I will test these out / review it in the coming week or so.

Thanks!

- Joel

>
> ----
>  kernel/trace/trace_events.c               |   2 +
>  samples/Kconfig                           |   8 +-
>  samples/Makefile                          |   1 +
>  samples/trace_events/Makefile             |   2 +
>  samples/trace_events/trace_custom_sched.c | 280 ++++++++++++++++++++++++++++++
>  5 files changed, 292 insertions(+), 1 deletion(-)
>  create mode 100644 samples/trace_events/trace_custom_sched.c