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

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
>

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