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Date: Mon, 28 Mar 2022 17:59:02 -0300
From: Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To: Ian Rogers <irogers@...gle.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>
CC: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
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>,
Adrian Hunter <adrian.hunter@...el.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,
coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
netdev@...r.kernel.org, bpf@...r.kernel.org,
Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 3/5] perf cpumap: Add intersect function.
On March 28, 2022 5:54:06 PM GMT-03:00, Ian Rogers <irogers@...gle.com> wrote:
>On Mon, Mar 28, 2022 at 1:28 PM Arnaldo Carvalho de Melo
><acme@...nel.org> wrote:
>>
>> Em Sun, Mar 27, 2022 at 11:24:12PM -0700, Ian Rogers escreveu:
>> > The merge function gives the union of two cpu maps. Add an intersect
>> > function which will be used in the next change.
>> >
>> > Signed-off-by: Ian Rogers <irogers@...gle.com>
>> > ---
>> > tools/lib/perf/cpumap.c | 38 ++++++++++++++++++++++++++++
>> > tools/lib/perf/include/perf/cpumap.h | 2 ++
>> > 2 files changed, 40 insertions(+)
>> >
>> > diff --git a/tools/lib/perf/cpumap.c b/tools/lib/perf/cpumap.c
>> > index 953bc50b0e41..56b4d213039f 100644
>> > --- a/tools/lib/perf/cpumap.c
>> > +++ b/tools/lib/perf/cpumap.c
>> > @@ -393,3 +393,41 @@ struct perf_cpu_map *perf_cpu_map__merge(struct perf_cpu_map *orig,
>> > perf_cpu_map__put(orig);
>> > return merged;
>> > }
>> > +
>> > +struct perf_cpu_map *perf_cpu_map__intersect(struct perf_cpu_map *orig,
>> > + struct perf_cpu_map *other)
>> > +{
>> > + struct perf_cpu *tmp_cpus;
>> > + int tmp_len;
>> > + int i, j, k;
>> > + struct perf_cpu_map *merged = NULL;
>> > +
>> > + if (perf_cpu_map__is_subset(other, orig))
>> > + return orig;
>> > + if (perf_cpu_map__is_subset(orig, other)) {
>> > + perf_cpu_map__put(orig);
>>
>> Why this put(orig)?
>
>As with merge, if orig isn't returned then it is put.
For merge I can see it dropping a reference, i.e. get b and merge it into a, after that b was "consumed"
But for intersect?
>
>> > + return perf_cpu_map__get(other);
>>
>> And why the get here and not on the first if?
>
>The first argument orig is either put or returned while the second may
>be returned only if the reference count is incremented. We could
>change the API for merge and intersect to put both arguments, or to
>not put either argument.
>
>Thanks,
>Ian
>
>> > + }
>> > +
>> > + tmp_len = max(orig->nr, other->nr);
>> > + tmp_cpus = malloc(tmp_len * sizeof(struct perf_cpu));
>> > + if (!tmp_cpus)
>> > + return NULL;
>> > +
>> > + i = j = k = 0;
>> > + while (i < orig->nr && j < other->nr) {
>> > + if (orig->map[i].cpu < other->map[j].cpu)
>> > + i++;
>> > + else if (orig->map[i].cpu > other->map[j].cpu)
>> > + j++;
>> > + else {
>> > + j++;
>> > + tmp_cpus[k++] = orig->map[i++];
>> > + }
>> > + }
>> > + if (k)
>> > + merged = cpu_map__trim_new(k, tmp_cpus);
>> > + free(tmp_cpus);
>> > + perf_cpu_map__put(orig);
>> > + return merged;
>> > +}
>> > diff --git a/tools/lib/perf/include/perf/cpumap.h b/tools/lib/perf/include/perf/cpumap.h
>> > index 4a2edbdb5e2b..a2a7216c0b78 100644
>> > --- a/tools/lib/perf/include/perf/cpumap.h
>> > +++ b/tools/lib/perf/include/perf/cpumap.h
>> > @@ -19,6 +19,8 @@ LIBPERF_API struct perf_cpu_map *perf_cpu_map__read(FILE *file);
>> > LIBPERF_API struct perf_cpu_map *perf_cpu_map__get(struct perf_cpu_map *map);
>> > LIBPERF_API struct perf_cpu_map *perf_cpu_map__merge(struct perf_cpu_map *orig,
>> > struct perf_cpu_map *other);
>> > +LIBPERF_API struct perf_cpu_map *perf_cpu_map__intersect(struct perf_cpu_map *orig,
>> > + struct perf_cpu_map *other);
>> > LIBPERF_API void perf_cpu_map__put(struct perf_cpu_map *map);
>> > LIBPERF_API struct perf_cpu perf_cpu_map__cpu(const struct perf_cpu_map *cpus, int idx);
>> > LIBPERF_API int perf_cpu_map__nr(const struct perf_cpu_map *cpus);
>> > --
>> > 2.35.1.1021.g381101b075-goog
>>
>> --
>>
>> - Arnaldo
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