Re: [PATCH 2/2] trace-cmd: Add ftrace options with fgraph retval option

[Jianfeng Wang <jianfeng.w.wang@oracle.com>]

On 5/16/24 5:53 PM, Steven Rostedt wrote:
> 
> Finally got the time to look at these patches ;-)
> 
> On Mon, 15 Apr 2024 08:49:21 -0700
> Jianfeng Wang <jianfeng.w.wang@oracle.com> wrote:
> 
>> +++ b/lib/trace-cmd/trace-ftrace.c
>> @@ -23,6 +23,12 @@ struct tep_plugin_option trace_ftrace_options[] = {
>>  		.description =
>>  		"Show the depth of each entry",
>>  	},
>> +	{
>> +		.name = "retval",
>> +		.plugin_alias = "fgraph",
>> +		.description =
>> +		"Print function retval at function exit in function graph",
>> +	},
> 
> Honestly, I don't think this should be an option. Or if it is, it
> should be default on. If the retval exists in the trace, it should just
> be printed. Why ask the user to show it when they spent the time to
> enable it in the recording?
> 
> Thanks!
> 
> -- Steve
> 

Thanks for your response!

I make it a default-off option because the feature changes the output format of
the 'trace-cmd report'. So to be on the safe side, keep the original format by
default. Also, the kernel has options (i.e., options/funcgraph-retval and
options/funcgraph-retval-hex) to enable printing functions' retval in trace.log

From my point of view, I'd like to see the retval on by default. If you are
okay, I'd like to make it default on and add an option to display retval in hex.

>>  	{
>>  		.name = NULL,
>>  	}