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Date:   Tue, 12 Dec 2023 15:06:39 +0000
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Subject: Re: [PATCH v1 06/14] libperf cpumap: Add any, empty and min helpers
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To:     Ian Rogers <irogers@google.com>
References: <20231129060211.1890454-1-irogers@google.com>
 <20231129060211.1890454-7-irogers@google.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Mike Leach <mike.leach@linaro.org>,
        Leo Yan <leo.yan@linaro.org>,
        John Garry <john.g.garry@oracle.com>,
        Will Deacon <will@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Darren Hart <dvhart@infradead.org>,
        Davidlohr Bueso <dave@stgolabs.net>,
        =?UTF-8?Q?Andr=c3=a9_Almeida?= <andrealmeid@igalia.com>,
        Kan Liang <kan.liang@linux.intel.com>,
        K Prateek Nayak <kprateek.nayak@amd.com>,
        Sean Christopherson <seanjc@google.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Kajol Jain <kjain@linux.ibm.com>,
        Athira Rajeev <atrajeev@linux.vnet.ibm.com>,
        Andrew Jones <ajones@ventanamicro.com>,
        Alexandre Ghiti <alexghiti@rivosinc.com>,
        Atish Patra <atishp@rivosinc.com>,
        "Steinar H. Gunderson" <sesse@google.com>,
        Yang Jihong <yangjihong1@huawei.com>,
        Yang Li <yang.lee@linux.alibaba.com>,
        Changbin Du <changbin.du@huawei.com>,
        Sandipan Das <sandipan.das@amd.com>,
        Ravi Bangoria <ravi.bangoria@amd.com>,
        Paran Lee <p4ranlee@gmail.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Huacai Chen <chenhuacai@kernel.org>,
        Yanteng Si <siyanteng@loongson.cn>,
        linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
        coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org,
        bpf@vger.kernel.org
From:   James Clark <james.clark@arm.com>
In-Reply-To: <20231129060211.1890454-7-irogers@google.com>
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On 29/11/2023 06:02, Ian Rogers wrote:
> Additional helpers to better replace
> perf_cpu_map__has_any_cpu_or_is_empty.
> 
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/lib/perf/cpumap.c              | 27 +++++++++++++++++++++++++++
>  tools/lib/perf/include/perf/cpumap.h | 16 ++++++++++++++++
>  tools/lib/perf/libperf.map           |  4 ++++
>  3 files changed, 47 insertions(+)
> 
> diff --git a/tools/lib/perf/cpumap.c b/tools/lib/perf/cpumap.c
> index 49fc98e16514..7403819da8fd 100644
> --- a/tools/lib/perf/cpumap.c
> +++ b/tools/lib/perf/cpumap.c
> @@ -316,6 +316,19 @@ bool perf_cpu_map__has_any_cpu_or_is_empty(const struct perf_cpu_map *map)
>  	return map ? __perf_cpu_map__cpu(map, 0).cpu == -1 : true;
>  }
>  
> +bool perf_cpu_map__is_any_cpu_or_is_empty(const struct perf_cpu_map *map)
> +{
> +	if (!map)
> +		return true;
> +
> +	return __perf_cpu_map__nr(map) == 1 && __perf_cpu_map__cpu(map, 0).cpu == -1;
> +}

I'm struggling to understand the relevance of the difference between
has_any and is_any I see that there is a slight difference, but could it
not be refactored out so we only need one?

Do you ever get an 'any' map that has more than 1 entry? It's quite a
subtle difference that is_any returns false if the first one is 'any'
but then there are subsequent entries. Whereas has_any would return
true. I'm not sure if future readers would be able to appreciate that.

I see has_any is only used twice, both on evlist->all_cpus. Is there
something about that member that means it could have a map that has an
'any' mixed with CPUs? Wouldn't that have the same result as a normal
'any' anyway?

> +
> +bool perf_cpu_map__is_empty(const struct perf_cpu_map *map)
> +{
> +	return map == NULL;
> +}
> +
>  int perf_cpu_map__idx(const struct perf_cpu_map *cpus, struct perf_cpu cpu)
>  {
>  	int low, high;
> @@ -372,6 +385,20 @@ bool perf_cpu_map__has_any_cpu(const struct perf_cpu_map *map)
>  	return map && __perf_cpu_map__cpu(map, 0).cpu == -1;
>  }
>  
> +struct perf_cpu perf_cpu_map__min(const struct perf_cpu_map *map)
> +{
> +	struct perf_cpu cpu, result = {
> +		.cpu = -1
> +	};
> +	int idx;
> +
> +	perf_cpu_map__for_each_cpu_skip_any(cpu, idx, map) {
> +		result = cpu;
> +		break;
> +	}
> +	return result;
> +}
> +
>  struct perf_cpu perf_cpu_map__max(const struct perf_cpu_map *map)
>  {
>  	struct perf_cpu result = {
> diff --git a/tools/lib/perf/include/perf/cpumap.h b/tools/lib/perf/include/perf/cpumap.h
> index dbe0a7352b64..523e4348fc96 100644
> --- a/tools/lib/perf/include/perf/cpumap.h
> +++ b/tools/lib/perf/include/perf/cpumap.h
> @@ -50,6 +50,22 @@ LIBPERF_API int perf_cpu_map__nr(const struct perf_cpu_map *cpus);
>   * perf_cpu_map__has_any_cpu_or_is_empty - is map either empty or has the "any CPU"/dummy value.
>   */
>  LIBPERF_API bool perf_cpu_map__has_any_cpu_or_is_empty(const struct perf_cpu_map *map);
> +/**
> + * perf_cpu_map__is_any_cpu_or_is_empty - is map either empty or the "any CPU"/dummy value.
> + */
> +LIBPERF_API bool perf_cpu_map__is_any_cpu_or_is_empty(const struct perf_cpu_map *map);
> +/**
> + * perf_cpu_map__is_empty - does the map contain no values and it doesn't
> + *                          contain the special "any CPU"/dummy value.
> + */
> +LIBPERF_API bool perf_cpu_map__is_empty(const struct perf_cpu_map *map);
> +/**
> + * perf_cpu_map__min - the minimum CPU value or -1 if empty or just the "any CPU"/dummy value.
> + */
> +LIBPERF_API struct perf_cpu perf_cpu_map__min(const struct perf_cpu_map *map);
> +/**
> + * perf_cpu_map__max - the maximum CPU value or -1 if empty or just the "any CPU"/dummy value.
> + */
>  LIBPERF_API struct perf_cpu perf_cpu_map__max(const struct perf_cpu_map *map);
>  LIBPERF_API bool perf_cpu_map__has(const struct perf_cpu_map *map, struct perf_cpu cpu);
>  LIBPERF_API bool perf_cpu_map__equal(const struct perf_cpu_map *lhs,
> diff --git a/tools/lib/perf/libperf.map b/tools/lib/perf/libperf.map
> index 10b3f3722642..2aa79b696032 100644
> --- a/tools/lib/perf/libperf.map
> +++ b/tools/lib/perf/libperf.map
> @@ -10,6 +10,10 @@ LIBPERF_0.0.1 {
>  		perf_cpu_map__nr;
>  		perf_cpu_map__cpu;
>  		perf_cpu_map__has_any_cpu_or_is_empty;
> +		perf_cpu_map__is_any_cpu_or_is_empty;
> +		perf_cpu_map__is_empty;
> +		perf_cpu_map__has_any_cpu;
> +		perf_cpu_map__min;
>  		perf_cpu_map__max;
>  		perf_cpu_map__has;
>  		perf_thread_map__new_array;