linux-kernel - Re: [PATCH v1 17/23] perf pmus: Prefer perf_pmu__scan over perf_pmus__for_each

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Message-ID: <67147a30-dd5b-35b5-c63e-a838d56b8220@linux.intel.com>
Date:   Sun, 21 May 2023 15:43:53 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Ian Rogers <irogers@...gle.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        John Garry <john.g.garry@...cle.com>,
        Will Deacon <will@...nel.org>,
        James Clark <james.clark@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        Jing Zhang <renyu.zj@...ux.alibaba.com>,
        Ravi Bangoria <ravi.bangoria@....com>,
        Madhavan Srinivasan <maddy@...ux.ibm.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        Ming Wang <wangming01@...ngson.cn>,
        Huacai Chen <chenhuacai@...nel.org>,
        Sandipan Das <sandipan.das@....com>,
        Dmitrii Dolgov <9erthalion6@...il.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Ali Saidi <alisaidi@...zon.com>, Rob Herring <robh@...nel.org>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        Kang Minchul <tegongkang@...il.com>,
        linux-kernel@...r.kernel.org, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v1 17/23] perf pmus: Prefer perf_pmu__scan over
 perf_pmus__for_each_pmu



On 2023-05-17 10:57 a.m., Ian Rogers wrote:
> perf_pmus__for_each_pmu doesn't lazily initialize pmus making its use
> error prone. Just use perf_pmu__scan as this only impacts
> non-performance critical tests.
> 
> Signed-off-by: Ian Rogers <irogers@...gle.com>

Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>

Thanks,
Kan
> ---
>  tools/perf/bench/pmu-scan.c     |  6 ++----
>  tools/perf/tests/event_groups.c |  7 ++-----
>  tools/perf/tests/parse-events.c | 11 ++++-------
>  tools/perf/util/pmus.h          |  2 --
>  4 files changed, 8 insertions(+), 18 deletions(-)
> 
> diff --git a/tools/perf/bench/pmu-scan.c b/tools/perf/bench/pmu-scan.c
> index f0f007843bb8..f4a6c37cbe27 100644
> --- a/tools/perf/bench/pmu-scan.c
> +++ b/tools/perf/bench/pmu-scan.c
> @@ -40,13 +40,11 @@ static struct pmu_scan_result *results;
>  
>  static int save_result(void)
>  {
> -	struct perf_pmu *pmu;
> +	struct perf_pmu *pmu = NULL;
>  	struct list_head *list;
>  	struct pmu_scan_result *r;
>  
> -	perf_pmu__scan(NULL);
> -
> -	perf_pmus__for_each_pmu(pmu) {
> +	while ((pmu = perf_pmu__scan(pmu)) != NULL) {
>  		r = realloc(results, (nr_pmus + 1) * sizeof(*r));
>  		if (r == NULL)
>  			return -ENOMEM;
> diff --git a/tools/perf/tests/event_groups.c b/tools/perf/tests/event_groups.c
> index 029442b4e9c6..3d9a2b524bba 100644
> --- a/tools/perf/tests/event_groups.c
> +++ b/tools/perf/tests/event_groups.c
> @@ -50,13 +50,10 @@ static int event_open(int type, unsigned long config, int group_fd)
>  
>  static int setup_uncore_event(void)
>  {
> -	struct perf_pmu *pmu;
> +	struct perf_pmu *pmu = NULL;
>  	int i, fd;
>  
> -	if (list_empty(&pmus))
> -		perf_pmu__scan(NULL);
> -
> -	perf_pmus__for_each_pmu(pmu) {
> +	while ((pmu = perf_pmu__scan(pmu)) != NULL) {
>  		for (i = 0; i < NR_UNCORE_PMUS; i++) {
>  			if (!strcmp(uncore_pmus[i].name, pmu->name)) {
>  				pr_debug("Using %s for uncore pmu event\n", pmu->name);
> diff --git a/tools/perf/tests/parse-events.c b/tools/perf/tests/parse-events.c
> index 72a10bed84fd..277607ede060 100644
> --- a/tools/perf/tests/parse-events.c
> +++ b/tools/perf/tests/parse-events.c
> @@ -108,11 +108,11 @@ static int test__checkevent_raw(struct evlist *evlist)
>  	TEST_ASSERT_VAL("wrong number of entries", 0 != evlist->core.nr_entries);
>  
>  	perf_evlist__for_each_evsel(&evlist->core, evsel) {
> -		struct perf_pmu *pmu;
> +		struct perf_pmu *pmu = NULL;
>  		bool type_matched = false;
>  
>  		TEST_ASSERT_VAL("wrong config", test_perf_config(evsel, 0x1a));
> -		perf_pmus__for_each_pmu(pmu) {
> +		while ((pmu = perf_pmu__scan(pmu)) != NULL) {
>  			if (pmu->type == evsel->attr.type) {
>  				TEST_ASSERT_VAL("PMU type expected once", !type_matched);
>  				type_matched = true;
> @@ -2243,13 +2243,10 @@ static int test__terms2(struct test_suite *test __maybe_unused, int subtest __ma
>  
>  static int test__pmu_events(struct test_suite *test __maybe_unused, int subtest __maybe_unused)
>  {
> -	struct perf_pmu *pmu;
> +	struct perf_pmu *pmu = NULL;
>  	int ret = TEST_OK;
>  
> -	if (list_empty(&pmus))
> -		perf_pmu__scan(NULL);
> -
> -	perf_pmus__for_each_pmu(pmu) {
> +	while ((pmu = perf_pmu__scan(pmu)) != NULL) {
>  		struct stat st;
>  		char path[PATH_MAX];
>  		struct dirent *ent;
> diff --git a/tools/perf/util/pmus.h b/tools/perf/util/pmus.h
> index d475e2960c10..257de10788e8 100644
> --- a/tools/perf/util/pmus.h
> +++ b/tools/perf/util/pmus.h
> @@ -5,8 +5,6 @@
>  extern struct list_head pmus;
>  struct perf_pmu;
>  
> -#define perf_pmus__for_each_pmu(pmu) list_for_each_entry(pmu, &pmus, list)
> -
>  const struct perf_pmu *perf_pmus__pmu_for_pmu_filter(const char *str);
>  
>  #endif /* __PMUS_H */