Re: [PATCH] perf stat: Add hint for SMI cost measurement

Liang, Kan
2019-04-25T13:14:04Z

On 4/25/2019 2:39 AM, Ingo Molnar wrote:
>
> * kan.liang@linux.intel.com <kan.liang@linux.intel.com> wrote:
>
>> +static void smi_env_check(void)
>> +{
>> + char *name;
>> + size_t len;
>> +
>> + if (sysfs__read_str(CPUIDLE_CUR_DRV, &name, &len)) {
>> + pr_warning("Failed to check cstate status.\n");
>
> What a meaningless message. What did we want to do, what happened, and
> why did it fail?
>
>> + return;
>> + }
>> +
>> + if (strncmp(name, "none", 4)) {
>> + pr_warning("Cstate may cause drift between aperf and cycles. "
>> + "Please completely disable cstate, "
>> + "E.g. set idle=poll in grub\n");
>
> Please keep user-visible strings in the same form that the user sees
> them, i.e. in a single line.

To avoid the line over 80 characters, the quoted string was split across
lines in the code. But the string is shown as a single line when it is
output for user.

Are you suggesting to ignore the 80 characters rule when printing
user-visible strings?
Could you please confirm?

Thanks,
Kan

>
> By doing that you'll also note a capitalization error.
>
> Also what does 'Cstate may cause drift' mean? What aspect of cstates
> causes the drift - entering/exiting deeper cstates that are not C0? If so
> then say so.
>
> Thanks,
>
> Ingo
>