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Message-ID: <CAM9d7cjLpE=cKfemsuokc57-5kzezRr3YzqOKZb9Pf4r4-X8+g@mail.gmail.com>
Date: Fri, 11 Sep 2020 12:07:35 +0900
From: Namhyung Kim <namhyung@...nel.org>
To: Ian Rogers <irogers@...gle.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>,
Jiri Olsa <jolsa@...hat.com>, Kajol Jain <kjain@...ux.ibm.com>,
Kan Liang <kan.liang@...ux.intel.com>,
Jin Yao <yao.jin@...ux.intel.com>,
Thomas Richter <tmricht@...ux.ibm.com>,
linux-kernel <linux-kernel@...r.kernel.org>,
Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v3] perf metricgroup: Fix uncore metric expressions
On Fri, Sep 11, 2020 at 3:02 AM Ian Rogers <irogers@...gle.com> wrote:
>
> A metric like DRAM_BW_Use has on SkylakeX events uncore_imc/cas_count_read/
> and uncore_imc/case_count_write/. These events open 6 events per socket
> with pmu names of uncore_imc_[0-5]. The current metric setup code in
> find_evsel_group assumes one ID will map to 1 event to be recorded in
> metric_events. For events with multiple matches, the first event is
> recorded in metric_events (avoiding matching >1 event with the same
> name) and the evlist_used updated so that duplicate events aren't
> removed when the evlist has unused events removed.
>
> Before this change:
> $ /tmp/perf/perf stat -M DRAM_BW_Use -a -- sleep 1
>
> Performance counter stats for 'system wide':
>
> 41.14 MiB uncore_imc/cas_count_read/
> 1,002,614,251 ns duration_time
>
> 1.002614251 seconds time elapsed
>
> After this change:
> $ /tmp/perf/perf stat -M DRAM_BW_Use -a -- sleep 1
>
> Performance counter stats for 'system wide':
>
> 157.47 MiB uncore_imc/cas_count_read/ # 0.00 DRAM_BW_Use
> 126.97 MiB uncore_imc/cas_count_write/
> 1,003,019,728 ns duration_time
>
> v3. cleans up searching for the same event within metric_events to use a
> helper and avoids a redundant search. It uses a continue loop to
> make the search for similarly named events shorter.
> v2. avoids iterating over the whole evlist as suggested by
> namhyung@...nel.org. It also fixes the metric_leader computation
> that was broken in the same commits.
>
> Erroneous duplication introduced in:
> commit 2440689d62e9 ("perf metricgroup: Remove duped metric group events").
>
> Fixes: ded80bda8bc9 ("perf expr: Migrate expr ids table to a hashmap").
> Reported-by: Jin Yao <yao.jin@...ux.intel.com>
> Signed-off-by: Ian Rogers <irogers@...gle.com>
Acked-by: Namhyung Kim <namhyung@...nel.org>
Thanks
Namhyung
> ---
> tools/perf/util/metricgroup.c | 75 ++++++++++++++++++++++++++---------
> 1 file changed, 56 insertions(+), 19 deletions(-)
>
> diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
> index 662f4e8777d5..7b66452cb9f9 100644
> --- a/tools/perf/util/metricgroup.c
> +++ b/tools/perf/util/metricgroup.c
> @@ -149,6 +149,18 @@ static void expr_ids__exit(struct expr_ids *ids)
> free(ids->id[i].id);
> }
>
> +static bool contains_event(struct evsel **metric_events, int num_events,
> + const char *event_name)
> +{
> + int i;
> +
> + for (i = 0; i < num_events; i++) {
> + if (!strcmp(metric_events[i]->name, event_name))
> + return true;
> + }
> + return false;
> +}
> +
> /**
> * Find a group of events in perf_evlist that correspond to those from a parsed
> * metric expression. Note, as find_evsel_group is called in the same order as
> @@ -179,7 +191,11 @@ static struct evsel *find_evsel_group(struct evlist *perf_evlist,
> int i = 0, matched_events = 0, events_to_match;
> const int idnum = (int)hashmap__size(&pctx->ids);
>
> - /* duration_time is grouped separately. */
> + /*
> + * duration_time is always grouped separately, when events are grouped
> + * (ie has_constraint is false) then ignore it in the matching loop and
> + * add it to metric_events at the end.
> + */
> if (!has_constraint &&
> hashmap__find(&pctx->ids, "duration_time", (void **)&val_ptr))
> events_to_match = idnum - 1;
> @@ -206,23 +222,20 @@ static struct evsel *find_evsel_group(struct evlist *perf_evlist,
> sizeof(struct evsel *) * idnum);
> current_leader = ev->leader;
> }
> - if (hashmap__find(&pctx->ids, ev->name, (void **)&val_ptr)) {
> - if (has_constraint) {
> - /*
> - * Events aren't grouped, ensure the same event
> - * isn't matched from two groups.
> - */
> - for (i = 0; i < matched_events; i++) {
> - if (!strcmp(ev->name,
> - metric_events[i]->name)) {
> - break;
> - }
> - }
> - if (i != matched_events)
> - continue;
> - }
> + /*
> + * Check for duplicate events with the same name. For example,
> + * uncore_imc/cas_count_read/ will turn into 6 events per socket
> + * on skylakex. Only the first such event is placed in
> + * metric_events. If events aren't grouped then this also
> + * ensures that the same event in different sibling groups
> + * aren't both added to metric_events.
> + */
> + if (contains_event(metric_events, matched_events, ev->name))
> + continue;
> + /* Does this event belong to the parse context? */
> + if (hashmap__find(&pctx->ids, ev->name, (void **)&val_ptr))
> metric_events[matched_events++] = ev;
> - }
> +
> if (matched_events == events_to_match)
> break;
> }
> @@ -238,7 +251,7 @@ static struct evsel *find_evsel_group(struct evlist *perf_evlist,
> }
>
> if (matched_events != idnum) {
> - /* Not whole match */
> + /* Not a whole match */
> return NULL;
> }
>
> @@ -246,8 +259,32 @@ static struct evsel *find_evsel_group(struct evlist *perf_evlist,
>
> for (i = 0; i < idnum; i++) {
> ev = metric_events[i];
> - ev->metric_leader = ev;
> + /* Don't free the used events. */
> set_bit(ev->idx, evlist_used);
> + /*
> + * The metric leader points to the identically named event in
> + * metric_events.
> + */
> + ev->metric_leader = ev;
> + /*
> + * Mark two events with identical names in the same group (or
> + * globally) as being in use as uncore events may be duplicated
> + * for each pmu. Set the metric leader of such events to be the
> + * event that appears in metric_events.
> + */
> + evlist__for_each_entry_continue(perf_evlist, ev) {
> + /*
> + * If events are grouped then the search can terminate
> + * when then group is left.
> + */
> + if (!has_constraint &&
> + ev->leader != metric_events[i]->leader)
> + break;
> + if (!strcmp(metric_events[i]->name, ev->name)) {
> + set_bit(ev->idx, evlist_used);
> + ev->metric_leader = metric_events[i];
> + }
> + }
> }
>
> return metric_events[0];
> --
> 2.28.0.526.ge36021eeef-goog
>
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