[PATCH v2 3/3] perf metricgroup: Fix uncore metric expressions

[Ian Rogers <irogers@google.com>]

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

v2. avoids iterating over the whole evlist as suggested by
    namhyung@kernel.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@linux.intel.com>
Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/metricgroup.c | 45 ++++++++++++++++++++++++++++++++---
 1 file changed, 42 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
index 662f4e8777d5..79080de9217d 100644
--- a/tools/perf/util/metricgroup.c
+++ b/tools/perf/util/metricgroup.c
@@ -206,6 +206,18 @@ static struct evsel *find_evsel_group(struct evlist *perf_evlist,
 				sizeof(struct evsel *) * idnum);
 			current_leader = ev->leader;
 		}
+		/*
+		 * 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.
+		 */
+		for (i = 0; i < matched_events; i++) {
+			if (!strcmp(metric_events[i]->name, ev->name))
+				break;
+		}
+		if (i != matched_events)
+			continue;
 		if (hashmap__find(&pctx->ids, ev->name, (void **)&val_ptr)) {
 			if (has_constraint) {
 				/*
@@ -245,9 +257,36 @@ static struct evsel *find_evsel_group(struct evlist *perf_evlist,
 	metric_events[idnum] = NULL;
 
 	for (i = 0; i < idnum; i++) {
-		ev = metric_events[i];
-		ev->metric_leader = ev;
-		set_bit(ev->idx, evlist_used);
+		/* Don't free used events. */
+		set_bit(metric_events[i]->idx, evlist_used);
+		/*
+		 * The metric leader points to the identically named event in
+		 * metric_events.
+		 */
+		metric_events[i]->metric_leader = metric_events[i];
+		/*
+		 * 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 to be the event that
+		 * appears in metric_events.
+		 */
+		if (!has_constraint) {
+			for_each_group_evsel(ev, metric_events[i]->leader) {
+				if (ev != metric_events[i] &&
+				    !strcmp(metric_events[i]->name, ev->name)) {
+					set_bit(ev->idx, evlist_used);
+					ev->metric_leader = metric_events[i];
+				}
+			}
+		} else {
+			evlist__for_each_entry(perf_evlist, ev) {
+				if (ev != metric_events[i] &&
+				    !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