linux-kernel - [PATCH V2 2/2] perf parse-events: Do not break up AUX event group

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Date:   Mon,  8 May 2023 12:39:52 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org
Subject: [PATCH V2 2/2] perf parse-events: Do not break up AUX event group

Do not assume which events may have a PMU name, allowing the logic to
keep an AUX event group together.

Example:

 Before:

    $ perf record --no-bpf-event -c 10 -e '{intel_pt//,tlb_flush.stlb_any/aux-sample-size=8192/pp}:u' -- sleep 0.1
    WARNING: events were regrouped to match PMUs
    Cannot add AUX area sampling to a group leader

 After:

    $ perf record --no-bpf-event -c 10 -e '{intel_pt//,tlb_flush.stlb_any/aux-sample-size=8192/pp}:u' -- sleep 0.1
    [ perf record: Woken up 1 times to write data ]
    [ perf record: Captured and wrote 0.078 MB perf.data ]
    $ perf script -F-dso,+addr | grep -C5 tlb_flush.stlb_any | head -11
    sleep 20444 [003]  7939.510243:  1  branches:uH:  7f5350cc82a2 dl_main+0x9a2 => 7f5350cb38f0 _dl_add_to_namespace_list+0x0
    sleep 20444 [003]  7939.510243:  1  branches:uH:  7f5350cb3908 _dl_add_to_namespace_list+0x18 => 7f5350cbb080 rtld_mutex_dummy+0x0
    sleep 20444 [003]  7939.510243:  1  branches:uH:  7f5350cc8350 dl_main+0xa50 => 0 [unknown]
    sleep 20444 [003]  7939.510244:  1  branches:uH:  7f5350cc83ca dl_main+0xaca => 7f5350caeb60 _dl_process_pt_gnu_property+0x0
    sleep 20444 [003]  7939.510245:  1  branches:uH:  7f5350caeb60 _dl_process_pt_gnu_property+0x0 => 0 [unknown]
    sleep 20444  7939.510245:       10 tlb_flush.stlb_any/aux-sample-size=8192/pp: 0 7f5350caeb60 _dl_process_pt_gnu_property+0x0
    sleep 20444 [003]  7939.510254:  1  branches:uH:  7f5350cc87fe dl_main+0xefe => 7f5350ccd240 strcmp+0x0
    sleep 20444 [003]  7939.510254:  1  branches:uH:  7f5350cc8862 dl_main+0xf62 => 0 [unknown]
    sleep 20444 [003]  7939.510255:  1  branches:uH:  7f5350cc9cdc dl_main+0x23dc => 0 [unknown]
    sleep 20444 [003]  7939.510257:  1  branches:uH:  7f5350cc89f6 dl_main+0x10f6 => 7f5350cb9530 _dl_setup_hash+0x0
    sleep 20444 [003]  7939.510257:  1  branches:uH:  7f5350cc8a2d dl_main+0x112d => 7f5350cb3990 _dl_new_object+0x0

Suggested-by: Ian Rogers <irogers@...gle.com>
Fixes: 347c2f0a0988 ("perf parse-events: Sort and group parsed events")
Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
---
 tools/perf/util/evsel.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index e18752fd9245..9fdcde5471df 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -828,11 +828,9 @@ bool evsel__name_is(struct evsel *evsel, const char *name)
 
 const char *evsel__group_pmu_name(const struct evsel *evsel)
 {
-	struct evsel *leader, *pos;
+	struct evsel *leader = evsel__leader(evsel);
+	struct evsel *pos;
 
-	/* If the pmu_name is set use it. pmu_name isn't set for CPU and software events. */
-	if (evsel->pmu_name)
-		return evsel->pmu_name;
 	/*
 	 * Software events may be in a group with other uncore PMU events. Use
 	 * the pmu_name of the first non-software event to avoid breaking the
@@ -841,7 +839,6 @@ const char *evsel__group_pmu_name(const struct evsel *evsel)
 	 * Aux event leaders, like intel_pt, expect a group with events from
 	 * other PMUs, so substitute the AUX event's PMU in this case.
 	 */
-	leader  = evsel__leader(evsel);
 	if (evsel->core.attr.type == PERF_TYPE_SOFTWARE || evsel__is_aux_event(leader)) {
 		/* Starting with the leader, find the first event with a named PMU. */
 		for_each_group_evsel(pos, leader) {
@@ -850,7 +847,7 @@ const char *evsel__group_pmu_name(const struct evsel *evsel)
 		}
 	}
 
-	return "cpu";
+	return evsel->pmu_name ?: "cpu";
 }
 
 const char *evsel__metric_id(const struct evsel *evsel)
-- 
2.34.1