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SubjectRe: [PATCH v2 2/4] perf ftrace: Add ftrace.tracer config option
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On 01/31/2017 10:15 PM, Arnaldo Carvalho de Melo wrote:
> Em Tue, Jan 31, 2017 at 09:46:28AM -0300, Arnaldo Carvalho de Melo escreveu:
>> Also you are silently ignoring any unknown variable in this section, so
>> if someone has this:
>>
>> cat ~/.perfconfig
>>
>> [ftrace]
>>
>> trace = function
>>
>>
>> I.e. forgets the 'r', it will keep using the current default,
>> "function_graph" till the user checks the config and adds that missing
>> 'r'...
>>
>> I haven't changed this because I think this is so common that we should
>> instead have a different error return for those config callbacks that
>> will tell perf_config() to say something like:
>>
>> "unknown variable %s.%s\n", section_name, variable_name
>
> So I read a bit more the config code and ended up with this:
>
> static int perf_ftrace_config(const char *var, const char *value, void *cb)
> {
> struct perf_ftrace *ftrace = cb;
>
> if (prefixcmp(var, "ftrace."))
> return 0;
>
> if (strcmp(var, "ftrace.tracer"))
> return -1;
>
> if (!strcmp(value, "function_graph") ||
> !strcmp(value, "function")) {
> ftrace->tracer = value;
> return 0;
> }
>
> pr_err("Please select \"function_graph\" (default) or \"function\"\n");
> return -1;
> }
>
> I.e. it will ignore variables for other sections and will stop at an unknown
> variable or value for ftrace.tracer:
>
> [root@jouet ~]# cat ~/.perfconfig
> [ftrace]
> trace = function
> [root@jouet ~]# perf ftrace usleep 1
> Error: wrong config key-value pair ftrace.trace=function
> [root@jouet ~]# cat ~/.perfconfig
> [ftrace]
> tracer = functin
> [root@jouet ~]# perf ftrace usleep 1
> Please select "function_graph" (default) or "function"
> Error: wrong config key-value pair ftrace.tracer=functin
> [root@jouet ~]# cat ~/.perfconfig
> [ftrace]
> tracer = function
> [root@jouet ~]# perf ftrace usleep 1 | head -5
> <idle>-0 [000] d... 3855.820847: switch_mm_irqs_off <-__schedule
> <...>-18550 [000] d... 3855.820849: finish_task_switch <-__schedule
> <...>-18550 [000] d... 3855.820851: smp_irq_work_interrupt <-irq_work_interrupt
> <...>-18550 [000] d... 3855.820851: irq_enter <-smp_irq_work_interrupt
> <...>-18550 [000] d... 3855.820851: rcu_irq_enter <-irq_enter
> [root@jouet ~]#
>

This is great!! I agonized about error message for
each other cases as above! But I think this is more precise than my patch!

Thanks,
Taeung

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