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

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Date:   Thu, 25 Apr 2019 15:05:32 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     acme@...hat.com, mingo@...hat.com, linux-kernel@...r.kernel.org,
        jolsa@...hat.com, namhyung@...il.com, lgoncalv@...hat.com,
        ak@...ux.intel.com
Subject: Re: [PATCH] perf stat: Add hint for SMI cost measurement



On 4/25/2019 1:47 PM, Ingo Molnar wrote:
> 
> * Liang, Kan <kan.liang@...ux.intel.com> wrote:
> 
>>
>>
>> On 4/25/2019 2:39 AM, Ingo Molnar wrote:
>>>
>>> * kan.liang@...ux.intel.com <kan.liang@...ux.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?
> 
> What I'd suggest is split it up into multiple messages, or shorten the
> message. Small violations of col80 for user visible strings is fine (up
> to 100-120 columns I guess), but if the string is longer it's a clear
> sign that the syslog message it too long to begin ...
> 

Sure, I will update the messages and send out V2.

Thanks,
Kan