linux-kernel - Re: [PATCH 21/22] perf cpumap: Trim the cpu_aggr

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Date:   Mon, 13 Dec 2021 08:11:44 -0800
From:   Ian Rogers <irogers@...gle.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Andi Kleen <ak@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        John Garry <john.garry@...wei.com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        "Paul A . Clarke" <pc@...ibm.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Riccardo Mancini <rickyman7@...il.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Vineet Singh <vineet.singh@...el.com>,
        James Clark <james.clark@....com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, eranian@...gle.com
Subject: Re: [PATCH 21/22] perf cpumap: Trim the cpu_aggr_map

On Sat, Dec 11, 2021 at 11:24 AM Jiri Olsa <jolsa@...hat.com> wrote:
>
> On Tue, Dec 07, 2021 at 06:46:06PM -0800, Ian Rogers wrote:
> > cpu_aggr_map__new removes duplicates, when this happens shrink the
> > array.
> >
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > ---
> >  tools/perf/util/cpumap.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
> > index 8a72ee996722..985c87f1f1ca 100644
> > --- a/tools/perf/util/cpumap.c
> > +++ b/tools/perf/util/cpumap.c
> > @@ -185,7 +185,12 @@ struct cpu_aggr_map *cpu_aggr_map__new(const struct perf_cpu_map *cpus,
> >                       c->nr++;
> >               }
> >       }
> > -
> > +     /* Trim. */
> > +     if (c->nr != cpus->nr) {
> > +             c = realloc(c, sizeof(struct cpu_aggr_map) + sizeof(struct aggr_cpu_id) * c->nr);
> > +             if (!c)
> > +                     return NULL;
> > +     }
>
> curious.. we should do this, but did you detect some big waste in here?

No real size implications, but I was after coaxing address sanitizer
into detecting potential index out of bounds problems.

Thanks,
Ian

> thanks,
> jirka
>
> >       /* ensure we process id in increasing order */
> >       qsort(c->map, c->nr, sizeof(struct aggr_cpu_id), aggr_cpu_id__cmp);
> >
> > --
> > 2.34.1.400.ga245620fadb-goog
> >
>