linux-kernel - Re: [PATCH v5 4/6] perf cpumap: Handle dummy maps as empty in subset

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Message-ID: <b94f3863-c690-e0f7-5cde-18fbf24143e5@intel.com>
Date:   Tue, 3 May 2022 10:43:27 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Ian Rogers <irogers@...gle.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>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Kajol Jain <kjain@...ux.ibm.com>,
        James Clark <james.clark@....com>,
        German Gomez <german.gomez@....com>,
        Riccardo Mancini <rickyman7@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Alexey Bayduraev <alexey.v.bayduraev@...ux.intel.com>,
        Alexander Antonov <alexander.antonov@...ux.intel.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v5 4/6] perf cpumap: Handle dummy maps as empty in subset

On 3/05/22 07:17, Ian Rogers wrote:
> perf_cpu_map__empty is true for empty and dummy maps. Make is_subset
> respect that.

As I wrote before, I am not keen on this because it prevents -1, as a
valid 3rd parameter to perf_event_open(), from being represented
in merged evsel cpu maps.

Why do you want this?

> 
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/lib/perf/cpumap.c   |  4 ++--
>  tools/perf/tests/cpumap.c | 10 +++++++++-
>  2 files changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/lib/perf/cpumap.c b/tools/lib/perf/cpumap.c
> index 384d5e076ee4..9c83675788c2 100644
> --- a/tools/lib/perf/cpumap.c
> +++ b/tools/lib/perf/cpumap.c
> @@ -322,9 +322,9 @@ struct perf_cpu perf_cpu_map__max(struct perf_cpu_map *map)
>  /** Is 'b' a subset of 'a'. */
>  bool perf_cpu_map__is_subset(const struct perf_cpu_map *a, const struct perf_cpu_map *b)
>  {
> -	if (a == b || !b)
> +	if (a == b || perf_cpu_map__empty(b))
>  		return true;
> -	if (!a || b->nr > a->nr)
> +	if (perf_cpu_map__empty(a) || b->nr > a->nr)
>  		return false;
>  
>  	for (int i = 0, j = 0; i < a->nr; i++) {
> diff --git a/tools/perf/tests/cpumap.c b/tools/perf/tests/cpumap.c
> index f94929ebb54b..d52b58395385 100644
> --- a/tools/perf/tests/cpumap.c
> +++ b/tools/perf/tests/cpumap.c
> @@ -128,13 +128,21 @@ static int test__cpu_map_merge(struct test_suite *test __maybe_unused, int subte
>  	struct perf_cpu_map *a = perf_cpu_map__new("4,2,1");
>  	struct perf_cpu_map *b = perf_cpu_map__new("4,5,7");
>  	struct perf_cpu_map *c = perf_cpu_map__merge(a, b);
> +	struct perf_cpu_map *d = perf_cpu_map__dummy_new();
> +	struct perf_cpu_map *e = perf_cpu_map__merge(b, d);
>  	char buf[100];
>  
>  	TEST_ASSERT_VAL("failed to merge map: bad nr", perf_cpu_map__nr(c) == 5);
>  	cpu_map__snprint(c, buf, sizeof(buf));
>  	TEST_ASSERT_VAL("failed to merge map: bad result", !strcmp(buf, "1-2,4-5,7"));
> -	perf_cpu_map__put(b);
> +
> +	TEST_ASSERT_VAL("failed to merge map: bad nr", perf_cpu_map__nr(e) == 3);
> +	cpu_map__snprint(e, buf, sizeof(buf));
> +	TEST_ASSERT_VAL("failed to merge map: bad result", !strcmp(buf, "4-5,7"));
> +
>  	perf_cpu_map__put(c);
> +	perf_cpu_map__put(d);
> +	perf_cpu_map__put(e);
>  	return 0;
>  }
>