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Date: Mon, 28 Mar 2022 17:56:07 -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 2/5] perf cpumap: More cpu map reuse by merge. On March 28, 2022 5:50:21 PM GMT-03:00, Ian Rogers <irogers@...gle.com> wrote: >On Mon, Mar 28, 2022 at 1:26 PM Arnaldo Carvalho de Melo ><acme@...nel.org> wrote: >> >> Em Sun, Mar 27, 2022 at 11:24:11PM -0700, Ian Rogers escreveu: >> > perf_cpu_map__merge will reuse one of its arguments if they are equal or >> > the other argument is NULL. The arguments could be reused if it is known >> > one set of values is a subset of the other. For example, a map of 0-1 >> > and a map of just 0 when merged yields the map of 0-1. Currently a new >> > map is created rather than adding a reference count to the original 0-1 >> > map. >> > >> > Signed-off-by: Ian Rogers <irogers@...gle.com> >> > --- >> > tools/lib/perf/cpumap.c | 38 ++++++++++++++++++++++++++++---------- >> > 1 file changed, 28 insertions(+), 10 deletions(-) >> > >> > diff --git a/tools/lib/perf/cpumap.c b/tools/lib/perf/cpumap.c >> > index ee66760f1e63..953bc50b0e41 100644 >> > --- a/tools/lib/perf/cpumap.c >> > +++ b/tools/lib/perf/cpumap.c >> > @@ -319,6 +319,29 @@ struct perf_cpu perf_cpu_map__max(struct perf_cpu_map *map) >> > return map->nr > 0 ? map->map[map->nr - 1] : result; >> > } >> > >> > +/** Is 'b' a subset of 'a'. */ >> > +static bool perf_cpu_map__is_subset(const struct perf_cpu_map *a, >> > + const struct perf_cpu_map *b) >> > +{ >> > + int i, j; >> > + >> > + if (a == b || !b) >> > + return true; >> > + if (!a || b->nr > a->nr) >> > + return false; >> > + j = 0; >> > + for (i = 0; i < a->nr; i++) { >> >> Since the kernel bumped the minimum gcc version to one that supports >> declaring loop variables locally and that perf has been using this since >> forever: >> >> ⬢[acme@...lbox perf]$ grep -r '(int [[:alpha:]] = 0;' tools/perf >> tools/perf/util/block-info.c: for (int i = 0; i < nr_hpps; i++) >> tools/perf/util/block-info.c: for (int i = 0; i < nr_hpps; i++) { >> tools/perf/util/block-info.c: for (int i = 0; i < nr_reps; i++) >> tools/perf/util/stream.c: for (int i = 0; i < nr_evsel; i++) >> tools/perf/util/stream.c: for (int i = 0; i < nr_evsel; i++) { >> tools/perf/util/stream.c: for (int i = 0; i < els->nr_evsel; i++) { >> tools/perf/util/stream.c: for (int i = 0; i < es_pair->nr_streams; i++) { >> tools/perf/util/stream.c: for (int i = 0; i < es_base->nr_streams; i++) { >> tools/perf/util/cpumap.c: for (int j = 0; j < c->nr; j++) { >> tools/perf/util/mem-events.c: for (int j = 0; j < PERF_MEM_EVENTS__MAX; j++) { >> tools/perf/util/header.c: for (int i = 0; i < ff->ph->env.nr_hybrid_cpc_nodes; i++) { >> tools/perf/builtin-diff.c: for (int i = 0; i < num; i++) >> tools/perf/builtin-diff.c: for (int i = 0; i < pair->block_info->num; i++) { >> tools/perf/builtin-stat.c: for (int i = 0; i < perf_cpu_map__nr(a->core.cpus); i++) { >> ⬢[acme@...lbox perf]$ >> >> And this builds on all my test containers, please use: >> >> for (int i = 0, j = 0; i < a->nr; i++) >> >> In this case to make the source code more compact. > >Ack. We still need to declare 'j' and it is a bit weird to declare j >before i. Fwiw, Making.config has the CORE_CFLAGS set to gnu99, but >declaring in the loop is clearly valid in c99. > >> > + if (a->map[i].cpu > b->map[j].cpu) >> > + return false; >> > + if (a->map[i].cpu == b->map[j].cpu) { >> > + j++; >> > + if (j == b->nr) >> > + return true; >> >> Ok, as its guaranteed that cpu_maps are ordered. >> >> > + } >> > + } >> > + return false; >> > +} >> > + >> > /* >> > * Merge two cpumaps >> > * >> > @@ -335,17 +358,12 @@ struct perf_cpu_map *perf_cpu_map__merge(struct perf_cpu_map *orig, >> > int i, j, k; >> > struct perf_cpu_map *merged; >> > >> > - if (!orig && !other) >> > - return NULL; >> > - if (!orig) { >> > - perf_cpu_map__get(other); >> > - return other; >> > - } >> > - if (!other) >> > - return orig; >> > - if (orig->nr == other->nr && >> > - !memcmp(orig->map, other->map, orig->nr * sizeof(struct perf_cpu))) >> > + if (perf_cpu_map__is_subset(orig, other)) >> > return orig; >> >> Can't we have first the introduction of perf_cpu_map__is_subset() and >> then another patch that gets the refcount, i.e. the four lines below? > >I believe that will fail as it'd be an unused static function warning >and werror. I thought that it seemed useful enough not to be a static, even if we don't at first export it, i.e. keep it as internal to libperf > >Thanks, >Ian > >> > + if (perf_cpu_map__is_subset(other, orig)) { >> > + perf_cpu_map__put(orig); >> > + return perf_cpu_map__get(other); >> > + } >> > >> > tmp_len = orig->nr + other->nr; >> > tmp_cpus = malloc(tmp_len * sizeof(struct perf_cpu)); >> > -- >> > 2.35.1.1021.g381101b075-goog >> >> -- >> >> - Arnaldo
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