linux-kernel - Re: [PATCH v3] tools/perf/metricgroup: Fix printing event names of metric group with multiple events incase of overlapping events

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Message-ID: <20200211134145.GA93194@krava>
Date:   Tue, 11 Feb 2020 14:41:45 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     kajoljain <kjain@...ux.ibm.com>
Cc:     Joe Perches <joe@...ches.com>, acme@...nel.org,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Jiri Olsa <jolsa@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jin Yao <yao.jin@...ux.intel.com>,
        Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>,
        Anju T Sudhakar <anju@...ux.vnet.ibm.com>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Subject: Re: [PATCH v3] tools/perf/metricgroup: Fix printing event names of
 metric group with multiple events incase of overlapping events

On Tue, Feb 11, 2020 at 04:50:41PM +0530, kajoljain wrote:
> 
> 
> On 2/10/20 5:41 PM, Jiri Olsa wrote:
> > On Thu, Feb 06, 2020 at 10:58:12AM -0800, Joe Perches wrote:
> >> On Thu, 2020-02-06 at 19:45 +0100, Jiri Olsa wrote:
> >>> On Fri, Jan 31, 2020 at 10:55:22AM +0530, Kajol Jain wrote:
> >>>
> >>> SNIP
> >>>
> >>>>  				ev->metric_leader = metric_events[i];
> >>>>  			}
> >>>> +			j++;
> >>>>  		}
> >>>> +		ev = metric_events[i];
> >>>> +		evlist_used[ev->idx] = true;
> >>>>  	}
> >>>>  
> >>>>  	return metric_events[0];
> >>>> @@ -160,6 +161,9 @@ static int metricgroup__setup_events(struct list_head *groups,
> >>>>  	int ret = 0;
> >>>>  	struct egroup *eg;
> >>>>  	struct evsel *evsel;
> >>>> +	bool evlist_used[perf_evlist->core.nr_entries];
> >>>> +
> >>>> +	memset(evlist_used, 0, perf_evlist->core.nr_entries);
> >>>
> >>> I know I posted this in the previous email, but are we sure bool
> >>> is always 1 byte?  would sizeod(evlist_used) be safer?
> 
> 
> Hi jiri,
>      Yes you are right. We should use 'evlist_used' size itself.
> 
> >>>
> >>> other than that it looks ok
> >>>
> >>> Andi, you're ok with this?
> >>
> >> stack declarations of variable length arrays are not
> >> a good thing.
> >>
> >> https://lwn.net/Articles/749089/
> >>
> >> and
> >>
> >> 	bool evlist_used[perf_evlist->core.nr_entries] = {};
> 
> 
> I am planning to use calloc and free that memory later in function 'metricgroup__setup_events'.
> Something like this. 
> 
> 
> +       bool *evlist_used;
> +
> +       evlist_used = (bool *)calloc(perf_evlist->core.nr_entries,
> +                                    sizeof(bool));
> +       if (!evlist_used) {
> +               ret = -ENOMEM;
> +               break;
> +       }
> 
> Please let me know if its looking fine.

I'm also ok with the array on the stack, but I don't mind
this change as well

thanks,
jirka