linux-kernel - Re: [PATCH v4 3/4] perf-stat: introduce config stat.bpf-counter-events

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Date:   Tue, 20 Apr 2021 21:21:32 +0000
From:   Song Liu <songliubraving@...com>
To:     Jiri Olsa <jolsa@...hat.com>
CC:     Song Liu <song@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>,
        "acme@...nel.org" <acme@...nel.org>,
        "acme@...hat.com" <acme@...hat.com>,
        "namhyung@...nel.org" <namhyung@...nel.org>,
        "jolsa@...nel.org" <jolsa@...nel.org>
Subject: Re: [PATCH v4 3/4] perf-stat: introduce config
 stat.bpf-counter-events



> On Apr 20, 2021, at 10:31 AM, Jiri Olsa <jolsa@...hat.com> wrote:
> 
> On Mon, Apr 19, 2021 at 01:36:48PM -0700, Song Liu wrote:
> 
> SNIP
> 
>> 	if (stat_config.initial_delay < 0) {
>> @@ -784,11 +790,11 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
>> 	if (affinity__setup(&affinity) < 0)
>> 		return -1;
>> 
>> -	if (target__has_bpf(&target)) {
>> -		evlist__for_each_entry(evsel_list, counter) {
>> -			if (bpf_counter__load(counter, &target))
>> -				return -1;
>> -		}
>> +	evlist__for_each_entry(evsel_list, counter) {
>> +		if (bpf_counter__load(counter, &target))
>> +			return -1;
>> +		if (!evsel__is_bpf(counter))
>> +			all_counters_use_bpf = false;
> 
> could be done in bpf_counter__load, check below:
> 
>> 	}
>> 
>> 	evlist__for_each_cpu (evsel_list, i, cpu) {
>> diff --git a/tools/perf/util/bpf_counter.c b/tools/perf/util/bpf_counter.c
>> index 5de991ab46af9..33b1888103dfa 100644
>> --- a/tools/perf/util/bpf_counter.c
>> +++ b/tools/perf/util/bpf_counter.c
>> @@ -790,7 +790,8 @@ int bpf_counter__load(struct evsel *evsel, struct target *target)
>> {
>> 	if (target->bpf_str)
>> 		evsel->bpf_counter_ops = &bpf_program_profiler_ops;
>> -	else if (target->use_bpf)
>> +	else if (target->use_bpf ||
>> +		 evsel__match_bpf_counter_events(evsel->name))
>> 		evsel->bpf_counter_ops = &bperf_ops;
> 
> with:
> 	else
> 		all_counters_use_bpf = false;
> 
> I was also thinking of oving it to evlist, but it's sat specific,
> so I think it's good as static.. thanks for changing the implementation

Hmm... then we need to somehow make all_counters_use_bpf visible in
bpf_counter.c, which won't be very clean. Also, since this is stat 
specific, I guess it is better to keep it inside builtin-stat.c?
The runtime overhead should be minimal. 

Thanks,
Song