Re: [PATCH 2/4] tracing: add trace_export support for event trace

[tingwei]

On 2020-07-22 00:43, Steven Rostedt wrote:
> On Tue, 21 Jul 2020 12:37:33 -0400
> Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
>
> > On Mon, 20 Jul 2020 10:21:15 +0800
> > Tingwei Zhang <tingwei@xxxxxxxxxxxxxx> wrote:
> >
> > > Only function traces can be exported to other destinations currently.
> > > This patch exports event trace as well.
> > >
> > > Signed-off-by: Tingwei Zhang <tingwei@xxxxxxxxxxxxxx>
> > > ---
> > >  kernel/trace/trace.c | 24 +++++++++++++-----------
> > >  1 file changed, 13 insertions(+), 11 deletions(-)
> > >
> > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> > > index bb62269724d5..aef6330836e2 100644
> > > --- a/kernel/trace/trace.c
> > > +++ b/kernel/trace/trace.c
> > > @@ -2697,17 +2697,6 @@ int tracepoint_printk_sysctl(struct ctl_table
> *table, int write,
> > >  	return ret;
> > >  }
> > >
> > > -void trace_event_buffer_commit(struct trace_event_buffer *fbuffer)
> > > -{
> > > -	if (static_key_false(&tracepoint_printk_key.key))
> > > -		output_printk(fbuffer);
> > > -
> > > -	event_trigger_unlock_commit_regs(fbuffer->trace_file,
> fbuffer->buffer,
> > > -				    fbuffer->event, fbuffer->entry,
> > > -				    fbuffer->flags, fbuffer->pc,
> fbuffer->regs);
> > > -}
> > > -EXPORT_SYMBOL_GPL(trace_event_buffer_commit);
> > > -
> >
> > Please move the ftrace_exports routines up, instead of moving the
> > trace_event_buffer_commit() down. As it fits better where it is (next
> > to the other buffer_commit code).
> >
> > -- Steve
> >
> >
> > >  /*
> > >   * Skip 3:
> > >   *
> > > @@ -2868,6 +2857,19 @@ int unregister_ftrace_export(struct
> > > trace_export *export) }
> > >  EXPORT_SYMBOL_GPL(unregister_ftrace_export);
> > >
> > > +void trace_event_buffer_commit(struct trace_event_buffer *fbuffer)
> > > +{
> > > +	if (static_key_false(&tracepoint_printk_key.key))
> > > +		output_printk(fbuffer);
> > > +
> > > +	if (static_branch_unlikely(&ftrace_exports_enabled))
> > > +		ftrace_exports(fbuffer->event);
>
> I would also recommend making each static branch a separate variable.
> That way you could pick and choose what you want to enable. If you only
> want events, and functions are being traced, it will add a bit of
> overhead to handle the functions to just ignore them.
>
> That is:
>
>  ftrace_exports_enabled, trace_event_exports_enabled,
>  trace_marker_exports_enabled.
>
> -- Steve
That's a good idea.  Let me add that to next revision.

> > > +	event_trigger_unlock_commit_regs(fbuffer->trace_file,
> > > fbuffer->buffer,
> > > +				    fbuffer->event, fbuffer->entry,
> > > +				    fbuffer->flags, fbuffer->pc,
> > > fbuffer->regs); +}
> > > +EXPORT_SYMBOL_GPL(trace_event_buffer_commit);
> > > +
> > >  void
> > >  trace_function(struct trace_array *tr,
> > >  	       unsigned long ip, unsigned long parent_ip, unsigned
> > > long flags,