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DateMon, 22 Feb 2010 19:17:08 +0100
FromFrederic Weisbecker <>
SubjectRe: [PATCH 1/1] ftrace - add support for tracing_thresh to function_graph tracer
On Mon, Feb 22, 2010 at 09:57:43AM -0500, Steven Rostedt wrote:
> On Sat, 2010-02-20 at 15:43 +0100, Frederic Weisbecker wrote:
> >
> > Instead of having yet another check here, may be should we
> > have a dedicated stub trace_graph_entry?
> >
> >
> >
> > > @@ -254,6 +263,10 @@ static void __trace_graph_return(struct trace_array *tr,
> > > if (unlikely(__this_cpu_read(per_cpu_var(ftrace_cpu_disabled))))
> > > return;
> > >
> > > + if (tracing_thresh &&
> > > + (trace->rettime - trace->calltime < tracing_thresh))
> > > + return;
> > > +
> >
> >
> >
> > And perhaps we can do the same for the return handler?
> > We could have a trace_graph_return_threshold that
> > performs the above check and then relies on trace_graph_return.
>
> So you mean to register a different type of function to the graph tracer
> if trace_thresh is enabled? That does sound like a better idea.


Yeah, this is going to optimize both types of tracing. And I would
also like to prevent from adding new checks in the common graph
tracing if possible. User's cpus and cachelines deserve better :)



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