Re: [PATCH v2 2/2] trace-cmd: Add ftrace options for the fgraph retval feature

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

On 7/17/24 11:50 AM, Steven Rostedt wrote:
> On Tue, 21 May 2024 14:37:30 -0700
> Jianfeng Wang <jianfeng.w.wang@oracle.com> wrote:
> 
>> Add two internal options for fgraph: fgraph:retval-skip and
>> fgraph:retval-hex. By default, trace-cmd will print each function's
>> return value at the function_graph exit point, if the kernel supports
>> the fgraph-retval feature. If users want to skip the output of
>> functions' return values, then set fgraph:retval-skip. Alternatively,
>> users can set fgraph:retval-hex to force the return values to be
>> printed in hex format.
>>
>> Here are example commands:
>>> trace-cmd report -O fgraph:retval-skip
>>> trace-cmd report -O fgraph:retval-hex  
> 
> I would like to see a -O fgraph:retval-dec
> 
> As by default most is shown in hex, having an option to do that would
> be great.
> 
> -- Steve
> 
> 

Hi Steve,

Sorry, I am confused about this.

Do you suggesting adding one more option fgraph:retval-dec or
replacing fgraph:retval-hex with fgraph:retval-dec (and making the hex
format as the default)?

Currently, the patch prints return values in decimal by default
(without any input), while users can specify fgraph:retval-hex to let
numbers printed in hex.

Thanks for your comments.

Best,
-Jianfeng

>>
>> Signed-off-by: Jianfeng Wang <jianfeng.w.wang@oracle.com>
>> ---
>>  lib/trace-cmd/trace-ftrace.c | 22 ++++++++++++++++++----
>>  1 file changed, 18 insertions(+), 4 deletions(-)
>>
>> diff --git a/lib/trace-cmd/trace-ftrace.c b/lib/trace-cmd/trace-ftrace.c
>> index 2b4e49a5..d2378833 100644
>> --- a/lib/trace-cmd/trace-ftrace.c
>> +++ b/lib/trace-cmd/trace-ftrace.c
>> @@ -26,6 +26,18 @@ struct tep_plugin_option trace_ftrace_options[] = {
>>  		.description =
>>  		"Show the depth of each entry",
>>  	},
>> +	{
>> +		.name = "retval-skip",
>> +		.plugin_alias = "fgraph",
>> +		.description =
>> +		"Skip printing function retval in function graph",
>> +	},
>> +	{
>> +		.name = "retval-hex",
>> +		.plugin_alias = "fgraph",
>> +		.description =
>> +		"Print function retval in hex at function exit in function graph",
>> +	},
>>  	{
>>  		.name = NULL,
>>  	}
>> @@ -33,6 +45,8 @@ struct tep_plugin_option trace_ftrace_options[] = {
>>  
>>  static struct tep_plugin_option *fgraph_tail = &trace_ftrace_options[0];
>>  static struct tep_plugin_option *fgraph_depth = &trace_ftrace_options[1];
>> +static struct tep_plugin_option *fgraph_retval_skip = &trace_ftrace_options[2];
>> +static struct tep_plugin_option *fgraph_retval_hex = &trace_ftrace_options[3];
>>  
>>  static int find_ret_event(struct tracecmd_ftrace *finfo, struct tep_handle *pevent)
>>  {
>> @@ -235,8 +249,8 @@ print_graph_entry_leaf(struct trace_seq *s,
>>  		ret = trace_seq_printf(s, " (%lld)", depth);
>>  
>>  	/* Return Value */
>> -	if (ret && fgraph_retval_supported) {
>> -		if (!IS_LINUX_ERR_VALUE(retval))
>> +	if (ret && fgraph_retval_supported && !fgraph_retval_skip->set) {
>> +		if (fgraph_retval_hex->set || !IS_LINUX_ERR_VALUE(retval))
>>  			ret = trace_seq_printf(s, " (ret=0x%llx)", retval);
>>  		else
>>  			ret = trace_seq_printf(s, " (ret=%lld)", retval);
>> @@ -385,8 +399,8 @@ fgraph_ret_handler(struct trace_seq *s, struct tep_record *record,
>>  		trace_seq_printf(s, " (%lld)", depth);
>>  
>>  	/* Return Value */
>> -	if (fgraph_retval_supported) {
>> -		if (!IS_LINUX_ERR_VALUE(retval))
>> +	if (fgraph_retval_supported && !fgraph_retval_skip->set) {
>> +		if (fgraph_retval_hex->set || !IS_LINUX_ERR_VALUE(retval))
>>  			trace_seq_printf(s, " (ret=0x%llx)", retval);
>>  		else
>>  			trace_seq_printf(s, " (ret=%lld)", retval);
>