linux-kernel - Re: [PATCH 13/19] perf ftrace: add option '-b/--buffer-size' to set per-cpu buffer size

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Date:   Wed, 20 May 2020 18:08:14 -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 13/19] perf ftrace: add option '-b/--buffer-size' to set
 per-cpu buffer size

Em Sun, May 10, 2020 at 11:06:22PM +0800, Changbin Du escreveu:
> This adds an option '-b/--buffer-size' to allow us set the size of per-cpu
> tracing buffer.

-m
 
> Signed-off-by: Changbin Du <changbin.du@...il.com>
> ---
>  tools/perf/builtin-ftrace.c | 45 ++++++++++++++++++++++++++++---------
>  1 file changed, 35 insertions(+), 10 deletions(-)
> 
> diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> index 8fd95c109fe8..a93fbdac6aa4 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -47,6 +47,7 @@ struct perf_ftrace {
>  	bool			long_info;
>  	unsigned		tracing_thresh;
>  	bool			trace_children;
> +	unsigned		buffer_size_kb;
>  };
>  
>  struct filter_entry {
> @@ -187,6 +188,17 @@ static int read_tracing_file_to_stdout(const char *name)
>  	return ret;
>  }
>  
> +static int write_tracing_file_int(const char *name, int value)
> +{
> +	char buf[16];
> +
> +	snprintf(buf, sizeof(buf), "%d", value);
> +	if (write_tracing_file(name, buf) < 0)
> +		return -1;
> +
> +	return 0;
> +}
> +
>  static int reset_tracing_cpu(void);
>  static void reset_tracing_filters(void);
>  
> @@ -360,8 +372,6 @@ static void reset_tracing_filters(void)
>  
>  static int set_tracing_depth(struct perf_ftrace *ftrace)
>  {
> -	char buf[16];
> -
>  	if (ftrace->graph_depth == 0)
>  		return 0;
>  
> @@ -370,9 +380,7 @@ static int set_tracing_depth(struct perf_ftrace *ftrace)
>  		return -1;
>  	}
>  
> -	snprintf(buf, sizeof(buf), "%d", ftrace->graph_depth);
> -
> -	if (write_tracing_file("max_graph_depth", buf) < 0)
> +	if (write_tracing_file_int("max_graph_depth", ftrace->graph_depth) < 0)
>  		return -1;
>  
>  	return 0;
> @@ -419,14 +427,10 @@ static int set_tracing_long_info(struct perf_ftrace *ftrace)
>  
>  static int set_tracing_thresh(struct perf_ftrace *ftrace)
>  {
> -	char buf[16];
> -
>  	if (ftrace->tracing_thresh == 0)
>  		return 0;
>  
> -	snprintf(buf, sizeof(buf), "%d", ftrace->tracing_thresh);
> -
> -	if (write_tracing_file("tracing_thresh", buf) < 0)
> +	if (write_tracing_file_int("tracing_thresh", ftrace->tracing_thresh) < 0)
>  		return -1;
>  
>  	return 0;
> @@ -454,6 +458,20 @@ static int set_tracing_trace_children(struct perf_ftrace *ftrace)
>  	return 0;
>  }
>  
> +static int set_tracing_buffer_size_kb(struct perf_ftrace *ftrace)
> +{
> +	int ret;
> +
> +	if (ftrace->buffer_size_kb == 0)
> +		return 0;
> +
> +	ret = write_tracing_file_int("buffer_size_kb", ftrace->buffer_size_kb);
> +	if (ret < 0)
> +		return ret;
> +
> +	return 0;
> +}
> +
>  static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
>  {
>  	char *trace_file;
> @@ -557,6 +575,11 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
>  		goto out_reset;
>  	}
>  
> +	if (set_tracing_buffer_size_kb(ftrace) < 0) {
> +		pr_err("failed to set tracing per-cpu buffer size\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;
> @@ -706,6 +729,8 @@ int cmd_ftrace(int argc, const char **argv)
>  		     "Only show functions of which the duration is greater than <n>µs"),
>  	OPT_BOOLEAN(0, "trace-children", &ftrace.trace_children,
>  		    "Trace children processes"),
> +	OPT_UINTEGER('b', "buffer-size", &ftrace.buffer_size_kb,
> +		     "size of per cpu buffer in kb"),
>  	OPT_END()
>  	};
>  
> -- 
> 2.25.1
> 

-- 

- Arnaldo