linux-kernel - Re: [PATCH 12/19] perf ftrace: add support for tracing children processes

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Date:   Wed, 20 May 2020 18:07:57 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Changbin Du <changbin.du@...il.com>
Cc:     Jiri Olsa <jolsa@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 12/19] perf ftrace: add support for tracing children
 processes

Em Sun, May 10, 2020 at 11:06:21PM +0800, Changbin Du escreveu:
> This adds an option '--trace-children' to allow us trace children
> processes spawned by our target.

--inherit

- Arnaldo
 
> Signed-off-by: Changbin Du <changbin.du@...il.com>
> ---
>  tools/perf/builtin-ftrace.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> index ab76ba66bd9e..8fd95c109fe8 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -46,6 +46,7 @@ struct perf_ftrace {
>  	bool			funcgraph_tail;
>  	bool			long_info;
>  	unsigned		tracing_thresh;
> +	bool			trace_children;
>  };
>  
>  struct filter_entry {
> @@ -200,6 +201,7 @@ static void reset_tracing_options(struct perf_ftrace *ftrace __maybe_unused)
>  	write_tracing_option_file("irq-info", "0");
>  	write_tracing_option_file("userstacktrace", "0");
>  	write_tracing_option_file("sym-userobj", "0");
> +	write_tracing_option_file("function-fork", "0");
>  }
>  
>  static int reset_tracing_files(struct perf_ftrace *ftrace __maybe_unused)
> @@ -441,6 +443,17 @@ static int set_tracing_funcgraph_tail(struct perf_ftrace *ftrace)
>  	return 0;
>  }
>  
> +static int set_tracing_trace_children(struct perf_ftrace *ftrace)
> +{
> +	if (!ftrace->trace_children)
> +		return 0;
> +
> +	if (write_tracing_option_file("function-fork", "1") < 0)
> +		return -1;
> +
> +	return 0;
> +}
> +
>  static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
>  {
>  	char *trace_file;
> @@ -539,6 +552,11 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
>  		goto out_reset;
>  	}
>  
> +	if (set_tracing_trace_children(ftrace) < 0) {
> +		pr_err("failed to set tracing option function-fork\n");
> +		goto out_reset;
> +	}
> +
>  	if (write_tracing_file("current_tracer", ftrace->tracer) < 0) {
>  		pr_err("failed to set current_tracer to %s\n", ftrace->tracer);
>  		goto out_reset;
> @@ -686,6 +704,8 @@ int cmd_ftrace(int argc, const char **argv)
>  		    "Show process names, PIDs, timestamps, irq-info if available"),
>  	OPT_UINTEGER(0, "tracing-thresh", &ftrace.tracing_thresh,
>  		     "Only show functions of which the duration is greater than <n>µs"),
> +	OPT_BOOLEAN(0, "trace-children", &ftrace.trace_children,
> +		    "Trace children processes"),
>  	OPT_END()
>  	};
>  
> -- 
> 2.25.1
> 

-- 

- Arnaldo