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

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Date:   Tue, 18 Jul 2023 17:18:35 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Andi Kleen <ak@...ux.intel.com>,
        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@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1 2/3] perf parse-events: When fixing group leaders always
 set the leader

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@...gle.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