Re: [RFC][PATCH] tracing: Allow creating instances with specified system events

Daniel Wagner
2023-11-28T08:47:03Z

On Mon, Nov 27, 2023 at 05:50:21PM -0500, Steven Rostedt wrote:
> On Mon, 27 Nov 2023 17:41:08 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
> > From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
> >
> > A trace instance may only need to enable specific events. As the eventfs
> > directory of an instance currently creates all events which adds overhead,
> > allow internal instances to be created with just the events in systems
> > that they care about. This currently only deals with systems and not
> > individual events, but this should bring down the overhead of creating
> > instances for specific use cases quite bit.
>
> This change log is not very good. I didn't actually state what was done :-p
>
> Anyway, function trace_array_get_by_name() has an added parameter "systems"
> (and I forgot to update its kerneldoc). This parameter is a string of
> comma, or space, or commas and spaces deliminators of event system names.
> If it's not NULL, then it will only create the event system directories of
> those event systems that match the systems parameter.
>
> That is:
>
> trace_array_get_by_name("qla2xxx", "qla");
>
> Will create an instance called "qla2xxx" and only have "qla" system events
> in it.

Makes sense to me. The qla2xxx driver is interested only in its own
trace events. This should be fine, at least as far I understand it.