linux-kernel - Re: [PATCH 1/1] ftrace - add support for tracing_thresh to function

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Date:	Sat, 20 Feb 2010 15:43:04 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Tim Bird <tim.bird@...sony.com>
Cc:	linux kernel <linux-kernel@...r.kernel.org>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH 1/1] ftrace - add support for tracing_thresh to
	function_graph tracer

On Wed, Feb 10, 2010 at 02:52:47PM -0800, Tim Bird wrote:
>  int trace_graph_entry(struct ftrace_graph_ent *trace)
>  {
>  	struct trace_array *tr = graph_array;
> @@ -221,6 +226,10 @@ int trace_graph_entry(struct ftrace_graph_ent *trace)
>  	if (!ftrace_graph_addr(trace->func))
>  		return 0;
>  
> +	/* if tracing duration, only save function exits (omit function entries in log) */
> +	if (tracing_thresh)
> +		return 1;
> +


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.

Thanks.

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