Re: [PATCH 2/2] trace-cmd: Add an option to set saved_cmdlines_size

[Steven Rostedt <rostedt@goodmis.org>]

On Thu,  7 Nov 2019 10:51:06 +0000
vincent.donnefort@arm.com wrote:

> From: Vincent Donnefort <vincent.donnefort@arm.com>
> 
> The tracing file saved_cmdlines_size allows setting the number of entries
> that saved_cmdlines will contain. The latter is then dumped into the
> trace.dat file to map PIDs with comm. The default value is 128.
> 
> Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
> 
> diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c
> index 7260d27..a4e10a4 100644
> --- a/tracecmd/trace-record.c
> +++ b/tracecmd/trace-record.c
> @@ -229,6 +229,7 @@ struct common_record_context {
>  	int topt;
>  	int do_child;
>  	int run_command;
> +	int saved_cmdlines_size;
>  };
>  
>  static void add_reset_file(const char *file, const char *val, int prio)
> @@ -1810,6 +1811,39 @@ static void set_options(void)
>  	}
>  }
>  
> +static void set_saved_cmdlines_size(struct common_record_context *ctx)
> +{
> +	char *path, *str;
> +	int fd, len, ret;
> +
> +	if (!ctx->saved_cmdlines_size)
> +		return;
> +
> +	path = tracecmd_get_tracing_file("saved_cmdlines_size");
> +	if (!path)
> +		goto err;
> +
> +	reset_save_file(path, RESET_DEFAULT_PRIO);
> +
> +	fd = open(path, O_WRONLY);
> +	tracecmd_put_tracing_file(path);
> +	if (fd < 0)
> +		goto err;
> +
> +	len = asprintf(&str, "%d", ctx->saved_cmdlines_size);
> +	if (len < 0)
> +		die("%s couldn't allocate memory", __func__);
> +
> +	if (write(fd, str, len) > 0)
> +		ret = 0;
> +
> +	close(fd);
> +	free(str);
> +err:
> +	if (ret)
> +		warning("Couldn't set saved_cmdlines_size");
> +}
> +
>  static int trace_check_file_exists(struct buffer_instance *instance, char *file)
>  {
>  	struct stat st;
> @@ -5480,7 +5514,7 @@ static void parse_record_options(int argc,
>  		if (IS_EXTRACT(ctx))
>  			opts = "+haf:Fp:co:O:sr:g:l:n:P:N:tb:B:ksiT";
>  		else
> -			opts = "+hae:f:FA:p:cC:dDGo:O:s:r:vg:l:n:P:N:tb:R:B:ksSiTm:M:H:q";
> +			opts = "+hae:f:FA:p:cC:dDGo:O:s:r:vg:l:n:P:N:tb:R:B:kK:sSiTm:M:H:qK";
>  		c = getopt_long (argc-1, argv+1, opts, long_options, &option_index);
>  		if (c == -1)
>  			break;
> @@ -5741,6 +5775,9 @@ static void parse_record_options(int argc,
>  		case 'k':
>  			keep = 1;
>  			break;
> +		case 'K':
> +			ctx->saved_cmdlines_size = atoi(optarg);
> +			break;

Perhaps we should make this a long variable --cmdline-size(?), and not
yet give it a short option. 

>  		case 'i':
>  			ignore_event_not_found = 1;
>  			break;
> @@ -5990,6 +6027,7 @@ static void record_trace(int argc, char **argv,
>  			enable_events(instance);
>  	}
>  
> +	set_saved_cmdlines_size(ctx);
>  	set_buffer_size();
>  	update_plugins(type);
>  	set_options();
> diff --git a/tracecmd/trace-usage.c b/tracecmd/trace-usage.c
> index b5788f7..ddfb480 100644
> --- a/tracecmd/trace-usage.c
> +++ b/tracecmd/trace-usage.c
> @@ -47,6 +47,7 @@ static struct usage_help usage_help[] = {
>  		"          -b change kernel buffersize (in kilobytes per CPU)\n"
>  		"          -B create sub buffer and following events will be enabled here\n"
>  		"          -k do not reset the buffers after tracing.\n"
> +		"          -K change kernel saved_cmdlines_size\n"

We would also want to update the man pages too.

Thanks!

-- Steve

>  		"          -i do not fail if an event is not found\n"
>  		"          -q print no output to the screen\n"
>  		"          --quiet print no output to the screen\n"