[PATCH v1 2/3] perf parse-events: When fixing group leaders always set the leader

[Ian Rogers <irogers@google.com>]

The evsel grouping fix iterates over evsels tracking the leader group
and the current position's group, updating the current position's
leader if an evsel is being forced into a group or groups
changed. However, groups changing isn't a sufficient condition as
sorting may have reordered events and the leader may no longer come
first. For this reason update all leaders whenever they disagree.

This change breaks certain Icelake+ metrics due to bugs in the
kernel. For example, tma_l3_bound with threshold enabled tries to
program the events:

{topdown-retiring,slots,CYCLE_ACTIVITY.STALLS_L2_MISS,topdown-fe-bound,EXE_ACTIVITY.BOUND_ON_STORES,EXE_ACTIVITY.1_PORTS_UTIL,topdown-be-bound,cpu/INT_MISC.RECOVERY_CYCLES,cmask=1,edge/,CYCLE_ACTIVITY.STALLS_L3_MISS,CPU_CLK_UNHALTED.THREAD,CYCLE_ACTIVITY.STALLS_MEM_ANY,EXE_ACTIVITY.2_PORTS_UTIL,CYCLE_ACTIVITY.STALLS_TOTAL,topdown-bad-spec}:W

fixing the perf metric event order gives:

{slots,topdown-retiring,topdown-fe-bound,topdown-be-bound,topdown-bad-spec,CYCLE_ACTIVITY.STALLS_L2_MISS,EXE_ACTIVITY.BOUND_ON_STORES,EXE_ACTIVITY.1_PORTS_UTIL,cpu/INT_MISC.RECOVERY_CYCLES,cmask=1,edge/,CYCLE_ACTIVITY.STALLS_L3_MISS,CPU_CLK_UNHALTED.THREAD,CYCLE_ACTIVITY.STALLS_MEM_ANY,EXE_ACTIVITY.2_PORTS_UTIL,CYCLE_ACTIVITY.STALLS_TOTAL}:W

Both of these return "<not counted>" for all events, whilst they work
with the group removed respecting that the perf metric events must
still be grouped. A vendor events update will need to add
METRIC_NO_GROUP to these metrics to workaround the kernel PMU driver
issue.

Fixes: a90cc5a9eeab ("perf evsel: Don't let evsel__group_pmu_name() traverse unsorted group")
Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/parse-events.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index f10760ac1781..4a36ce60c7dd 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -2181,7 +2181,7 @@ static int 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);
 		const char *pos_pmu_name = pos->group_pmu_name;
-		const char *cur_leader_pmu_name, *pos_leader_pmu_name;
+		const char *cur_leader_pmu_name;
 		bool pos_force_grouped = arch_evsel__must_be_in_group(pos);
 
 		/* Reset index and nr_members. */
@@ -2215,13 +2215,8 @@ static int parse_events__sort_events_and_fix_groups(struct list_head *list)
 			 */
 			cur_leader_force_grouped = pos_force_grouped;
 		}
-		pos_leader_pmu_name = pos_leader->group_pmu_name;
-		if (strcmp(pos_leader_pmu_name, pos_pmu_name) || pos_force_grouped) {
-			/*
-			 * Event's PMU differs from its leader's. Groups can't
-			 * span PMUs, so update leader from the group/PMU
-			 * tracker.
-			 */
+		if (pos_leader != cur_leader) {
+			/* The leader changed so update it. */
 			evsel__set_leader(pos, cur_leader);
 		}
 	}
-- 
2.41.0.487.g6d72f3e995-goog