Re: [PATCH] perf stat: Ensure group is defined on top of the same cpu mask

[Jiri Olsa <jolsa@redhat.com>]

On Sun, May 31, 2020 at 05:04:47PM -0700, Ian Rogers wrote:
> On Sun, May 31, 2020 at 9:22 AM Jiri Olsa <jolsa@kernel.org> wrote:
> >
> > Jin Yao reported the issue (and posted first versions of this change)
> > with groups being defined over events with different cpu mask.
> >
> > This causes assert aborts in get_group_fd, like:
> >
> >   # perf stat -M "C2_Pkg_Residency" -a -- sleep 1
> >   perf: util/evsel.c:1464: get_group_fd: Assertion `!(fd == -1)' failed.
> >   Aborted
> >
> > All the events in the group have to be defined over the same
> > cpus so the group_fd can be found for every leader/member pair.
> >
> > Adding check to ensure this condition is met and removing the
> > group (with warning) if we detect mixed cpus, like:
> >
> >   $ sudo perf stat -e '{power/energy-cores/,cycles},{instructions,power/energy-cores/}'
> >   WARNING: event cpu maps do not match, disabling group:
> >     anon group { power/energy-cores/, cycles }
> >     anon group { instructions, power/energy-cores/ }
> 
> This is really cool! I wonder if there is a better wording for 'event
> cpu maps' ? It may be useful to list what the cpu maps are for the
> events as a diagnostic aid.

right, something like this in verbose mode?
it display cpu maps of events that did not match

[root@krava perf]# ./perf stat -e '{cycles,power/energy-cores/}' -v
WARNING: group events cpu maps do not match, disabling group:
  anon group { cycles, power/energy-cores/ }
     cycles: 0-7
     power/energy-cores/: 0

jirka

> 
> Thanks,
> Ian
> 
> > Fixes: 6a4bb04caacc8 ("perf tools: Enable grouping logic for parsed events")
> > Co-developed-by: Jin Yao <yao.jin@linux.intel.com>
> > Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >  tools/perf/builtin-stat.c | 51 +++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 51 insertions(+)
> >
> > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> > index b2b79aa161dd..512a41363d07 100644
> > --- a/tools/perf/builtin-stat.c
> > +++ b/tools/perf/builtin-stat.c
> > @@ -190,6 +190,55 @@ static struct perf_stat_config stat_config = {
> >         .big_num                = true,
> >  };
> >
> > +static bool cpus_map_matched(struct evsel *a, struct evsel *b)
> > +{
> > +       if (!a->core.cpus && !b->core.cpus)
> > +               return true;
> > +
> > +       if (!a->core.cpus || !b->core.cpus)
> > +               return false;
> > +
> > +       if (a->core.cpus->nr != b->core.cpus->nr)
> > +               return false;
> > +
> > +       for (int i = 0; i < a->core.cpus->nr; i++) {
> > +               if (a->core.cpus->map[i] != b->core.cpus->map[i])
> > +                       return false;
> > +       }
> > +
> > +       return true;
> > +}
> > +
> > +static void evlist__check_cpu_maps(struct evlist *evlist)
> > +{
> > +       struct evsel *evsel, *pos, *leader;
> > +       char buf[1024];
> > +
> > +       evlist__for_each_entry(evlist, evsel) {
> > +               leader = evsel->leader;
> > +
> > +               /* Check that leader matches cpus with each member. */
> > +               if (leader == evsel)
> > +                       continue;
> > +               if (cpus_map_matched(leader, evsel))
> > +                       continue;
> > +
> > +               /*
> > +                * If there's mismatch display dismantle the
> > +                * group and warn user.
> > +                */
> > +               WARN_ONCE(1, "WARNING: group events cpu maps do not match, disabling group:\n");
> > +               evsel__group_desc(leader, buf, sizeof(buf));
> > +               pr_warning("  %s\n", buf);
> > +
> > +               for_each_group_evsel(pos, leader) {
> > +                       pos->leader = pos;
> > +                       pos->core.nr_members = 0;
> > +               }
> > +               evsel->leader->core.nr_members = 0;
> > +       }
> > +}
> > +
> >  static inline void diff_timespec(struct timespec *r, struct timespec *a,
> >                                  struct timespec *b)
> >  {
> > @@ -1962,6 +2011,8 @@ int cmd_stat(int argc, const char **argv)
> >         } else if (argc && !strncmp(argv[0], "rep", 3))
> >                 return __cmd_report(argc, argv);
> >
> > +       evlist__check_cpu_maps(evsel_list);
> > +
> >         interval = stat_config.interval;
> >         timeout = stat_config.timeout;
> >
> > --
> > 2.25.4
> >
>