Re: [PATCH v4 11/11] perf parse-events: Warn when events are regrouped

From: Ian Rogers
Date: Sat Mar 11 2023 - 21:04:38 EST

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On Thu, Mar 9, 2023 at 11:29 PM Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
>
> On 9/03/23 00:59, Ian Rogers wrote:
> > Use if an event is reordered or the number of groups increases to
> > signal that regrouping has happened and warn about it. Disable the
> > warning in the case wild card PMU names are used and for metrics.
>
> The new warning seems to happen no matter what the order
> in some cases e.g.
>
> $ perf record -e branch-misses//u -e cycles:u -- uname
> WARNING: events were regrouped to match PMUs
> Linux
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.004 MB perf.data (11 samples) ]
>
> $ perf record -e cycles:u -e branch-misses//u -- uname
> WARNING: events were regrouped to match PMUs
> Linux
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.005 MB perf.data (16 samples) ]

Thanks Adrian! It is caused by lists of evsels being merged because of
the multiple -e options. There was an assumption idx values would be
sequential and when we merge them this is no longer the case. I added
a fix for v5.

Thanks,
Ian

> >
> > Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> > ---
> > tools/perf/tests/parse-events.c | 2 +-
> > tools/perf/tests/pmu-events.c | 2 +-
> > tools/perf/util/metricgroup.c | 3 ++-
> > tools/perf/util/parse-events.c | 28 ++++++++++++++++++++--------
> > tools/perf/util/parse-events.h | 7 ++++---
> > tools/perf/util/parse-events.y | 1 +
> > 6 files changed, 29 insertions(+), 14 deletions(-)
> >
> > diff --git a/tools/perf/tests/parse-events.c b/tools/perf/tests/parse-events.c
> > index ffa6f0a90741..b1c2f0a20306 100644
> > --- a/tools/perf/tests/parse-events.c
> > +++ b/tools/perf/tests/parse-events.c
> > @@ -2103,7 +2103,7 @@ static int test_event_fake_pmu(const char *str)
> >
> > parse_events_error__init(&err);
> > perf_pmu__test_parse_init();
> > - ret = __parse_events(evlist, str, &err, &perf_pmu__fake);
> > + ret = __parse_events(evlist, str, &err, &perf_pmu__fake, /*warn_if_reordered=*/true);
> > if (ret) {
> > pr_debug("failed to parse event '%s', err %d, str '%s'\n",
> > str, ret, err.str);
> > diff --git a/tools/perf/tests/pmu-events.c b/tools/perf/tests/pmu-events.c
> > index 6ccd413b5983..7f8e86452527 100644
> > --- a/tools/perf/tests/pmu-events.c
> > +++ b/tools/perf/tests/pmu-events.c
> > @@ -785,7 +785,7 @@ static int check_parse_id(const char *id, struct parse_events_error *error,
> > */
> > perf_pmu__test_parse_init();
> > }
> > - ret = __parse_events(evlist, dup, error, fake_pmu);
> > + ret = __parse_events(evlist, dup, error, fake_pmu, /*warn_if_reordered=*/true);
> > free(dup);
> >
> > evlist__delete(evlist);
> > diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
> > index de6dd527a2ba..5783f4c2d1ef 100644
> > --- a/tools/perf/util/metricgroup.c
> > +++ b/tools/perf/util/metricgroup.c
> > @@ -1441,7 +1441,8 @@ static int parse_ids(bool metric_no_merge, struct perf_pmu *fake_pmu,
> > }
> > pr_debug("Parsing metric events '%s'\n", events.buf);
> > parse_events_error__init(&parse_error);
> > - ret = __parse_events(parsed_evlist, events.buf, &parse_error, fake_pmu);
> > + ret = __parse_events(parsed_evlist, events.buf, &parse_error, fake_pmu,
> > + /*warn_if_reordered=*/false);
> > if (ret) {
> > parse_events_error__print(&parse_error, events.buf);
> > goto err_out;
> > diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> > index 9ec3c1dc81e0..4bb28c32b511 100644
> > --- a/tools/perf/util/parse-events.c
> > +++ b/tools/perf/util/parse-events.c
> > @@ -2157,11 +2157,13 @@ static int evlist__cmp(void *state, const struct list_head *l, const struct list
> > return arch_evlist__cmp(lhs, rhs);
> > }
> >
> > -static void parse_events__sort_events_and_fix_groups(struct list_head *list)
> > +static bool parse_events__sort_events_and_fix_groups(struct list_head *list)
> > {
> > int idx = -1;
> > struct evsel *pos, *cur_leader = NULL;
> > struct perf_evsel *cur_leaders_grp = NULL;
> > + bool idx_changed = false;
> > + int orig_num_leaders = 0, num_leaders = 0;
> >
> > /*
> > * Compute index to insert ungrouped events at. Place them where the
> > @@ -2170,11 +2172,11 @@ static void parse_events__sort_events_and_fix_groups(struct list_head *list)
> > list_for_each_entry(pos, list, core.node) {
> > const struct evsel *pos_leader = evsel__leader(pos);
> >
> > - if (pos != pos_leader || pos->core.nr_members > 1)
> > - continue;
> > + if (pos == pos_leader)
> > + orig_num_leaders++;
> >
> > - idx = pos->core.idx;
> > - break;
> > + if (idx == -1 && pos == pos_leader && pos->core.nr_members < 2)
> > + idx = pos->core.idx;
> > }
> >
> > /* Sort events. */
> > @@ -2192,6 +2194,8 @@ static void parse_events__sort_events_and_fix_groups(struct list_head *list)
> > bool force_grouped = arch_evsel__must_be_in_group(pos);
> >
> > /* Reset index and nr_members. */
> > + if (pos->core.idx != idx)
> > + idx_changed = true;
> > pos->core.idx = idx++;
> > pos->core.nr_members = 0;
> >
> > @@ -2225,12 +2229,18 @@ static void parse_events__sort_events_and_fix_groups(struct list_head *list)
> > }
> > }
> > list_for_each_entry(pos, list, core.node) {
> > - pos->core.leader->nr_members++;
> > + struct evsel *pos_leader = evsel__leader(pos);
> > +
> > + if (pos == pos_leader)
> > + num_leaders++;
> > + pos_leader->core.nr_members++;
> > }
> > + return idx_changed || num_leaders != orig_num_leaders;
> > }
> >
> > int __parse_events(struct evlist *evlist, const char *str,
> > - struct parse_events_error *err, struct perf_pmu *fake_pmu)
> > + struct parse_events_error *err, struct perf_pmu *fake_pmu,
> > + bool warn_if_reordered)
> > {
> > struct parse_events_state parse_state = {
> > .list = LIST_HEAD_INIT(parse_state.list),
> > @@ -2250,7 +2260,9 @@ int __parse_events(struct evlist *evlist, const char *str,
> > return -1;
> > }
> >
> > - parse_events__sort_events_and_fix_groups(&parse_state.list);
> > + if (parse_events__sort_events_and_fix_groups(&parse_state.list) &&
> > + warn_if_reordered && !parse_state.wild_card_pmus)
> > + pr_warning("WARNING: events were regrouped to match PMUs\n");
> >
> > /*
> > * Add list to the evlist even with errors to allow callers to clean up.
> > diff --git a/tools/perf/util/parse-events.h b/tools/perf/util/parse-events.h
> > index 767ad1729228..46204c1a7916 100644
> > --- a/tools/perf/util/parse-events.h
> > +++ b/tools/perf/util/parse-events.h
> > @@ -26,13 +26,13 @@ int parse_events_option(const struct option *opt, const char *str, int unset);
> > int parse_events_option_new_evlist(const struct option *opt, const char *str, int unset);
> > __attribute__((nonnull(1, 2, 3)))
> > int __parse_events(struct evlist *evlist, const char *str, struct parse_events_error *error,
> > - struct perf_pmu *fake_pmu);
> > + struct perf_pmu *fake_pmu, bool warn_if_reordered);
> >
> > -__attribute__((nonnull))
> > +__attribute__((nonnull(1, 2, 3)))
> > static inline int parse_events(struct evlist *evlist, const char *str,
> > struct parse_events_error *err)
> > {
> > - return __parse_events(evlist, str, err, NULL);
> > + return __parse_events(evlist, str, err, /*fake_pmu=*/NULL, /*warn_if_reordered=*/true);
> > }
> >
> > int parse_event(struct evlist *evlist, const char *str);
> > @@ -128,6 +128,7 @@ struct parse_events_state {
> > int stoken;
> > struct perf_pmu *fake_pmu;
> > char *hybrid_pmu_name;
> > + bool wild_card_pmus;
> > };
> >
> > void parse_events__shrink_config_terms(void);
> > diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
> > index 3a04602d2982..4488443e506e 100644
> > --- a/tools/perf/util/parse-events.y
> > +++ b/tools/perf/util/parse-events.y
> > @@ -323,6 +323,7 @@ event_pmu_name opt_pmu_config
> > if (!parse_events_add_pmu(_parse_state, list, pmu->name, terms,
> > /*auto_merge_stats=*/true)) {
> > ok++;
> > + parse_state->wild_card_pmus = true;
> > }
> > parse_events_terms__delete(terms);
> > }
>

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Previous message: Jarkko Sakkinen: "Re: [PATCH v3] tpm: disable hwrng for fTPM on some AMD designs"
In reply to: Adrian Hunter: "Re: [PATCH v4 11/11] perf parse-events: Warn when events are regrouped"
Next in thread: Liang, Kan: "Re: [PATCH v4 00/11] Better fixes for grouping of events"
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