linux-kernel - Re: [PATCH v3 3/4] perf-stat: introduce config stat.bpf-counter-events

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Message-ID: <C55B43CE-0909-4322-89DB-143A300871A6@fb.com>
Date:   Mon, 19 Apr 2021 20:27:14 +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 v3 3/4] perf-stat: introduce config
 stat.bpf-counter-events



> On Apr 19, 2021, at 7:26 AM, Jiri Olsa <jolsa@...hat.com> wrote:
> 
> On Fri, Apr 16, 2021 at 03:13:24PM -0700, Song Liu wrote:
> 
> SNIP
> 
>> +/*
>> + * Returns:
>> + *     0   if all events use BPF;
>> + *     1   if some events do NOT use BPF;
>> + *     < 0 on errors;
>> + */
>> static int read_bpf_map_counters(void)
>> {
>> +	bool has_none_bpf_events = false;
>> 	struct evsel *counter;
>> 	int err;
>> 
>> 	evlist__for_each_entry(evsel_list, counter) {
>> +		if (!evsel__is_bpf(counter)) {
>> +			has_none_bpf_events = true;
>> +			continue;
>> +		}
>> 		err = bpf_counter__read(counter);
>> 		if (err)
>> 			return err;
>> 	}
>> -	return 0;
>> +	return has_none_bpf_events ? 1 : 0;
>> }
>> 
>> static void read_counters(struct timespec *rs)
>> @@ -442,9 +455,10 @@ static void read_counters(struct timespec *rs)
>> 	int err;
>> 
>> 	if (!stat_config.stop_read_counter) {
>> -		if (target__has_bpf(&target))
>> -			err = read_bpf_map_counters();
>> -		else
>> +		err = read_bpf_map_counters();
>> +		if (err < 0)
>> +			return;
>> +		if (err)
>> 			err = read_affinity_counters(rs);
> 
> this part is confusing for me.. I understand we don't want to enter
> read_affinity_counters when there's no bpf counter, so we don't set
> affinities in vain.. but there must be better way ;-)
> 
>> diff --git a/tools/perf/util/bpf_counter.c b/tools/perf/util/bpf_counter.c
>> index 5de991ab46af9..3189b63714371 100644
>> --- a/tools/perf/util/bpf_counter.c
>> +++ b/tools/perf/util/bpf_counter.c
>> @@ -792,6 +792,8 @@ int bpf_counter__load(struct evsel *evsel, struct target *target)
>> 		evsel->bpf_counter_ops = &bpf_program_profiler_ops;
>> 	else if (target->use_bpf)
>> 		evsel->bpf_counter_ops = &bperf_ops;
>> +	else if (evsel__match_bpf_counter_events(evsel->name))
>> +		evsel->bpf_counter_ops = &bperf_ops;
> 
> please put this with the target->use_bpf check,
> it seems like it's another thing

Thanks for the review. Fixing these in v4. 

Song