linux-kernel - Re: [PATCH v2 6/6] perf cpumap: Add range data encoding

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Message-ID: <CAP-5=fVczMiasS15UovH8kzOaNw=TC_adeqjC+xBzv8jVJ3DTQ@mail.gmail.com>
Date:   Thu, 4 Aug 2022 12:30:53 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Jiri Olsa <olsajiri@...il.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        James Clark <james.clark@....com>,
        Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Riccardo Mancini <rickyman7@...il.com>,
        German Gomez <german.gomez@....com>,
        Colin Ian King <colin.king@...el.com>,
        Song Liu <songliubraving@...com>,
        Dave Marchevsky <davemarchevsky@...com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        Alexey Bayduraev <alexey.v.bayduraev@...ux.intel.com>,
        Leo Yan <leo.yan@...aro.org>, linux-perf-users@...r.kernel.org,
        linux-kernel@...r.kernel.org, Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v2 6/6] perf cpumap: Add range data encoding

On Sun, Jul 31, 2022 at 5:39 AM Jiri Olsa <olsajiri@...il.com> wrote:
>
> On Tue, Jun 14, 2022 at 07:33:53AM -0700, Ian Rogers wrote:
>
> SNIP
>
> > +     event = cpu_map_data__alloc(&syn_data, sizeof(struct perf_event_header));
> >       if (!event)
> >               return NULL;
> >
> > +     syn_data.data = &event->data;
> >       event->header.type = PERF_RECORD_CPU_MAP;
> > -     event->header.size = size;
> > -     event->data.type   = type;
> > -
> > -     cpu_map_data__synthesize(&event->data, map, type, max);
> > +     event->header.size = syn_data.size;
> > +     cpu_map_data__synthesize(&syn_data);
> >       return event;
> >  }
> >
> > +
> >  int perf_event__synthesize_cpu_map(struct perf_tool *tool,
> >                                  const struct perf_cpu_map *map,
> >                                  perf_event__handler_t process,
> > @@ -1891,24 +1894,20 @@ int perf_event__synthesize_event_update_name(struct perf_tool *tool, struct evse
> >  int perf_event__synthesize_event_update_cpus(struct perf_tool *tool, struct evsel *evsel,
> >                                            perf_event__handler_t process)
> >  {
> > -     size_t size = sizeof(struct perf_event_header) + sizeof(u64) + sizeof(u64);
> > +     struct synthesize_cpu_map_data syn_data = { .map = evsel->core.own_cpus };
> >       struct perf_record_event_update *ev;
> > -     int max, err;
> > -     u16 type;
> > -
> > -     if (!evsel->core.own_cpus)
> > -             return 0;
>
> all seems fine, just looks like we no longer do this check,
> might not be needed anymore, as that changed in past

This function is called in a test and in this file. The caller already
does this test and so the check is redundant plus a little confusing:
https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/tree/tools/perf/util/synthetic-events.c?h=perf/core#n2062
As you say, it wasn't needed any more and so I removed it.

Thanks,
Ian

> thanks,
> jirka
>
> > +     int err;
> >
> > -     ev = cpu_map_data__alloc(evsel->core.own_cpus, &size, &type, &max);
> > +     ev = cpu_map_data__alloc(&syn_data, sizeof(struct perf_event_header) + 2 * sizeof(u64));
> >       if (!ev)
> >               return -ENOMEM;
> >
> > +     syn_data.data = &ev->cpus.cpus;
> >       ev->header.type = PERF_RECORD_EVENT_UPDATE;
> > -     ev->header.size = (u16)size;
> > +     ev->header.size = (u16)syn_data.size;
> >       ev->type        = PERF_EVENT_UPDATE__CPUS;
> >       ev->id          = evsel->core.id[0];
> > -
> > -     cpu_map_data__synthesize(&ev->cpus.cpus, evsel->core.own_cpus, type, max);
> > +     cpu_map_data__synthesize(&syn_data);
> >
> >       err = process(tool, (union perf_event *)ev, NULL, NULL);
> >       free(ev);
> > --
> > 2.36.1.476.g0c4daa206d-goog
> >