linux-kernel - Re: [PATCH 4/5] perf metricgroup: Support metric constraint

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Date:   Thu, 20 Feb 2020 11:14:09 -0500
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     acme@...nel.org, mingo@...hat.com, peterz@...radead.org,
        linux-kernel@...r.kernel.org, mark.rutland@....com,
        namhyung@...nel.org, ravi.bangoria@...ux.ibm.com,
        yao.jin@...ux.intel.com, ak@...ux.intel.com
Subject: Re: [PATCH 4/5] perf metricgroup: Support metric constraint



On 2/20/2020 6:35 AM, Jiri Olsa wrote:
> On Wed, Feb 19, 2020 at 11:08:39AM -0800, kan.liang@...ux.intel.com wrote:
> 
> SNIP
> 
>> +static bool violate_nmi_constraint;
>> +
>> +static bool metricgroup__has_constraint(struct pmu_event *pe)
>> +{
>> +	if (!pe->metric_constraint)
>> +		return false;
>> +
>> +	if (!strcmp(pe->metric_constraint, "NO_NMI_WATCHDOG") &&
>> +	    sysctl__nmi_watchdog_enabled()) {
>> +		pr_warning("Splitting metric group %s into standalone metrics.\n",
>> +			   pe->metric_name);
>> +		violate_nmi_constraint = true;
> 
> no static flags plz.. can't you just print that rest of the warning in here?
>

Because we only want to print the NMI watchdog warning once.
If there are more than one metric groups with constraint, the warning 
may be printed several times. For example,
   $ perf stat -M Page_Walks_Utilization,Page_Walks_Utilization
   Splitting metric group Page_Walks_Utilization into standalone metrics.
   Try disabling the NMI watchdog to comply NO_NMI_WATCHDOG metric 
constraint:
       echo 0 > /proc/sys/kernel/nmi_watchdog
       perf stat ...
       echo 1 > /proc/sys/kernel/nmi_watchdog
   Splitting metric group Page_Walks_Utilization into standalone metrics.
   Try disabling the NMI watchdog to comply NO_NMI_WATCHDOG metric 
constraint:
       echo 0 > /proc/sys/kernel/nmi_watchdog
       perf stat ...
       echo 1 > /proc/sys/kernel/nmi_watchdog
Is it OK?

If it's OK, I think we can remove the flag.

Thanks,
Kan

> jirka
> 
>> +		return true;
>> +	}
>> +
>> +	return false;
>> +}
>> +
>>   static int metricgroup__add_metric(const char *metric, struct strbuf *events,
>>   				   struct list_head *group_list)
>>   {
>> @@ -460,7 +490,10 @@ static int metricgroup__add_metric(const char *metric, struct strbuf *events,
>>   			if (events->len > 0)
>>   				strbuf_addf(events, ",");
>>   
>> -			metricgroup__add_metric_weak_group(events, ids, idnum);
>> +			if (metricgroup__has_constraint(pe))
>> +				metricgroup__add_metric_non_group(events, ids, idnum);
>> +			else
>> +				metricgroup__add_metric_weak_group(events, ids, idnum);
>>   
>>   			eg = malloc(sizeof(struct egroup));
>>   			if (!eg) {
>> @@ -544,6 +577,13 @@ int metricgroup__parse_groups(const struct option *opt,
>>   	strbuf_release(&extra_events);
>>   	ret = metricgroup__setup_events(&group_list, perf_evlist,
>>   					metric_events);
>> +
>> +	if (violate_nmi_constraint) {
>> +		pr_warning("Try disabling the NMI watchdog to comply NO_NMI_WATCHDOG metric constraint:\n"
>> +			   "    echo 0 > /proc/sys/kernel/nmi_watchdog\n"
>> +			   "    perf stat ...\n"
>> +			   "    echo 1 > /proc/sys/kernel/nmi_watchdog\n");
>> +	}
>>   out:
>>   	metricgroup__free_egroups(&group_list);
>>   	return ret;
>> -- 
>> 2.7.4
>>
>