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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Date:   Tue, 11 Feb 2020 16:50:41 +0530
From:   kajoljain <kjain@...ux.ibm.com>
To:     Jiri Olsa <jolsa@...hat.com>, Joe Perches <joe@...ches.com>
Cc:     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 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.

Thanks,
Kajol

> 
> hum, I think we already have few of them in perf ;-)
> thanks for the link
> 
> right, that initialization is of course much better, thanks
> 
> jirka
>