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

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Message-ID: <20200221130903.GC652992@krava>
Date:   Fri, 21 Feb 2020 14:09:03 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     "Liang, Kan" <kan.liang@...ux.intel.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 Thu, Feb 20, 2020 at 11:14:09AM -0500, Liang, Kan wrote:
> 
> 
> 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.

we use the 'print once' static flags in functions,
so plz keep it inside like WARN_ONCE, or use it directly

jirka