Re: [PATCH 3/4] perf parse-events: Don't move slots event when no topdwon metrics event

Mi, Dapeng
2024-07-03T02:51:41Z

On 7/3/2024 2:03 AM, Liang, Kan wrote:
>
> On 2024-07-02 6:40 p.m., Dapeng Mi wrote:
>> Currently the helper arch_evlist__cmp() would unconditionally move slots
>> event to be the leader event even though there is no topdown metrics
>> event in the group.
>>
>> perf stat -e "{instructions,slots}" -C 0 sleep 1
>> WARNING: events were regrouped to match PMUs
>>
>> Performance counter stats for 'CPU(s) 0':
>>
>> 27,581,148 slots
>> 8,390,827 instructions
>>
>> 1.045546595 seconds time elapsed
>>
>> This is an overkill. It's not necessary to move slots event as the leader
>> event if there is no topdown metrics event.
>>
>> Thus only regroup events when there are both topdown slots and metrics
>> events in a group.
>>
>> Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
>> ---
>> tools/perf/arch/x86/util/evlist.c | 6 ++++--
>> tools/perf/util/evlist.h | 7 ++++++-
>> tools/perf/util/parse-events.c | 35 ++++++++++++++++++-------------
>> 3 files changed, 31 insertions(+), 17 deletions(-)
>>
>> diff --git a/tools/perf/arch/x86/util/evlist.c b/tools/perf/arch/x86/util/evlist.c
>> index 7215c7c7b435..a1e78be6ebd1 100644
>> --- a/tools/perf/arch/x86/util/evlist.c
>> +++ b/tools/perf/arch/x86/util/evlist.c
>> @@ -73,9 +73,11 @@ int arch_evlist__add_default_attrs(struct evlist *evlist,
>> return ___evlist__add_default_attrs(evlist, attrs, nr_attrs);
>> }
>>
>> -int arch_evlist__cmp(const struct evsel *lhs, const struct evsel *rhs)
>> +int arch_evlist__cmp(const struct evsel *lhs, const struct evsel *rhs, void *priv)
>> {
>> - if (topdown_sys_has_perf_metrics() &&
>> + struct sort_priv *_priv = priv;
>> +
>> + if (topdown_sys_has_perf_metrics() && _priv->topdown_metrics_in_group &&
>> (arch_evsel__must_be_in_group(lhs) || arch_evsel__must_be_in_group(rhs))) {
>> /* Ensure the topdown slots comes first. */
>> if (strcasestr(lhs->name, "slots") && !strcasestr(lhs->name, "uops_retired.slots"))
>> diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
>> index cb91dc9117a2..14c858dcf5a2 100644
>> --- a/tools/perf/util/evlist.h
>> +++ b/tools/perf/util/evlist.h
>> @@ -89,6 +89,11 @@ struct evsel_str_handler {
>> void *handler;
>> };
>>
>> +struct sort_priv {
>> + int force_grouped_idx;
>> + bool topdown_metrics_in_group;
> The topdown metrics should be only available in some Intel platforms. I
> don't think we want to add such platform-specific variable in the
> generic code.
>
> The current code just re-order the events, not re-group. So it doesn't
> impact the result accuracy.
> So the issue is just an annoying WARNING, right?
>
> It seems the issue has been there for more than 1 year. No complaints
> except for one internal test case, which can be easily fixed.
> Considering the complexity of the fix, I guess we may leave it as is.

I was also hesitating on whether posting the patch. Not sure if other tools
depends on the events output order. If not, it's just an annoying WARNING.
But I think there should no other tools depending on it as you said no any
complaints on this.

I would drop this patch in next version.

>
> Thanks,
> Kan
>> +};
>> +
>> struct evlist *evlist__new(void);
>> struct evlist *evlist__new_default(void);
>> struct evlist *evlist__new_dummy(void);
>> @@ -112,7 +117,7 @@ int arch_evlist__add_default_attrs(struct evlist *evlist,
>> #define evlist__add_default_attrs(evlist, array) \
>> arch_evlist__add_default_attrs(evlist, array, ARRAY_SIZE(array))
>>
>> -int arch_evlist__cmp(const struct evsel *lhs, const struct evsel *rhs);
>> +int arch_evlist__cmp(const struct evsel *lhs, const struct evsel *rhs, void *priv);
>>
>> int evlist__add_dummy(struct evlist *evlist);
>> struct evsel *evlist__add_aux_dummy(struct evlist *evlist, bool system_wide);
>> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
>> index 6ed0f9c5581d..a3f7173a7ae2 100644
>> --- a/tools/perf/util/parse-events.c
>> +++ b/tools/perf/util/parse-events.c
>> @@ -1962,19 +1962,21 @@ static int evsel__compute_group_pmu_name(struct evsel *evsel,
>> return evsel->group_pmu_name ? 0 : -ENOMEM;
>> }
>>
>> -__weak int arch_evlist__cmp(const struct evsel *lhs, const struct evsel *rhs)
>> +__weak int arch_evlist__cmp(const struct evsel *lhs, const struct evsel *rhs,
>> + void *priv __maybe_unused)
>> {
>> /* Order by insertion index. */
>> return lhs->core.idx - rhs->core.idx;
>> }
>>
>> -static int evlist__cmp(void *_fg_idx, const struct list_head *l, const struct list_head *r)
>> +static int evlist__cmp(void *_sort_priv, const struct list_head *l, const struct list_head *r)
>> {
>> const struct perf_evsel *lhs_core = container_of(l, struct perf_evsel, node);
>> const struct evsel *lhs = container_of(lhs_core, struct evsel, core);
>> const struct perf_evsel *rhs_core = container_of(r, struct perf_evsel, node);
>> const struct evsel *rhs = container_of(rhs_core, struct evsel, core);
>> - int *force_grouped_idx = _fg_idx;
>> + struct sort_priv *sort_priv = _sort_priv;
>> + int force_grouped_idx = sort_priv->force_grouped_idx;
>> int lhs_sort_idx, rhs_sort_idx, ret;
>> const char *lhs_pmu_name, *rhs_pmu_name;
>> bool lhs_has_group, rhs_has_group;
>> @@ -1992,8 +1994,8 @@ static int evlist__cmp(void *_fg_idx, const struct list_head *l, const struct li
>> lhs_sort_idx = lhs_core->leader->idx;
>> } else {
>> lhs_has_group = false;
>> - lhs_sort_idx = *force_grouped_idx != -1 && arch_evsel__must_be_in_group(lhs)
>> - ? *force_grouped_idx
>> + lhs_sort_idx = force_grouped_idx != -1 && arch_evsel__must_be_in_group(lhs)
>> + ? force_grouped_idx
>> : lhs_core->idx;
>> }
>> if (rhs_core->leader != rhs_core || rhs_core->nr_members > 1) {
>> @@ -2001,8 +2003,8 @@ static int evlist__cmp(void *_fg_idx, const struct list_head *l, const struct li
>> rhs_sort_idx = rhs_core->leader->idx;
>> } else {
>> rhs_has_group = false;
>> - rhs_sort_idx = *force_grouped_idx != -1 && arch_evsel__must_be_in_group(rhs)
>> - ? *force_grouped_idx
>> + rhs_sort_idx = force_grouped_idx != -1 && arch_evsel__must_be_in_group(rhs)
>> + ? force_grouped_idx
>> : rhs_core->idx;
>> }
>>
>> @@ -2019,16 +2021,17 @@ static int evlist__cmp(void *_fg_idx, const struct list_head *l, const struct li
>> }
>>
>> /* Architecture specific sorting. */
>> - return arch_evlist__cmp(lhs, rhs);
>> + return arch_evlist__cmp(lhs, rhs, _sort_priv);
>> }
>>
>> static int parse_events__sort_events_and_fix_groups(struct list_head *list)
>> {
>> - int idx = 0, force_grouped_idx = -1;
>> struct evsel *pos, *cur_leader = NULL;
>> struct perf_evsel *cur_leaders_grp = NULL;
>> bool idx_changed = false, cur_leader_force_grouped = false;
>> int orig_num_leaders = 0, num_leaders = 0;
>> + struct sort_priv sort_priv = {-1, false};
>> + int idx = 0;
>> int ret;
>>
>> /*
>> @@ -2053,13 +2056,17 @@ static int parse_events__sort_events_and_fix_groups(struct list_head *list)
>> pos->core.idx = idx++;
>>
>> /* Remember an index to sort all forced grouped events together to. */
>> - if (force_grouped_idx == -1 && pos == pos_leader && pos->core.nr_members < 2 &&
>> - arch_evsel__must_be_in_group(pos))
>> - force_grouped_idx = pos->core.idx;
>> + if (sort_priv.force_grouped_idx == -1 && pos == pos_leader &&
>> + pos->core.nr_members < 2 && arch_evsel__must_be_in_group(pos))
>> + sort_priv.force_grouped_idx = pos->core.idx;
>> +
>> + if (!sort_priv.topdown_metrics_in_group &&
>> + strcasestr(pos->name, "topdown"))
>> + sort_priv.topdown_metrics_in_group = true;
>> }
>>
>> /* Sort events. */
>> - list_sort(&force_grouped_idx, list, evlist__cmp);
>> + list_sort(&sort_priv, list, evlist__cmp);
>>
>> /*
>> * Recompute groups, splitting for PMUs and adding groups for events
>> @@ -2070,7 +2077,7 @@ static int parse_events__sort_events_and_fix_groups(struct list_head *list)
>> const struct evsel *pos_leader = evsel__leader(pos);
>> const char *pos_pmu_name = pos->group_pmu_name;
>> const char *cur_leader_pmu_name;
>> - bool pos_force_grouped = force_grouped_idx != -1 &&
>> + bool pos_force_grouped = sort_priv.force_grouped_idx != -1 &&
>> arch_evsel__must_be_in_group(pos);
>>
>> /* Reset index and nr_members. */