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Date: Mon, 28 Mar 2022 14:25:21 -0700
From: Ian Rogers <irogers@...gle.com>
To: Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
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 Mon, Mar 28, 2022 at 2:00 PM Arnaldo Carvalho de Melo
<arnaldo.melo@...il.com> wrote:
>
>
>
> 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?
The current use case is the intersect of all online CPUs with the
merge of all CPU maps from evsels. So we can generally just reuse
all_cpus, or the common case of both maps contain every CPU. I think
the pattern makes code like:
evlist->cpus = perf_cpu_map__intersect(evlist->cpus, other);
not quite as messy, as without the put you need:
tmp = perf_cpu_map__intersect(evlist->cpus, other);
perf_cpu_map__put(evlist->cpus);
evlist->cpus = tmp;
I'm somewhat agnostic on what the API should be, but it'd be nice if
merge and intersect behaved in a similar way.
Thanks,
Ian
> >
> >> > + 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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