From b91e5492f9d7ca89919cfe8b0c5b5996263182f7 Mon Sep 17 00:00:00 2001
From: Kan Liang <kan.liang@linux.intel.com>
Date: Thu, 8 Jul 2021 09:03:32 -0700
Subject: [PATCH] perf record: Add a dummy event on hybrid systems to collect
metadata records
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Some symbols may not be resolved if a user only monitors one type of
PMU.
$ sudo perf record -e cpu_atom/branch-instructions/ ./big_small_workload
$ sudo perf report –stdio
# Overhead Command Shared Object Symbol
# ........ ......... ................. .....................
#
28.02% perf-exec [unknown] [.] 0x0000000000401cf6
11.32% perf-exec [unknown] [.] 0x0000000000401d04
10.90% perf-exec [unknown] [.] 0x0000000000401d11
10.61% perf-exec [unknown] [.] 0x0000000000401cfc
To parse symbols the metadata records, e.g., PERF_RECORD_COMM, which are
generated by the kernel, are required.
To decide whether to generate the metadata records, the kernel relies on
the event_filter_match() to filter the unrelated events.
On a hybrid system, event_filter_match() further checks the CPU mask of
the current enabled PMU. If an event is collected on the CPU which
doesn't have an enabled PMU, it's treated as an unrelated event.
The "big_small_workload" is created in a big core, but runs on a small
core. The metadata records are filtered, because the user only monitors
the PMU of the small core. The big core PMU is not enabled.
For a hybrid system, a dummy event is required to generate the complete
side-band events.
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lore.kernel.org/lkml/1625760212-18441-1-git-send-email-kan.liang@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/builtin-record.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index ee2a5cacbdfc8..671a21c9ee4d7 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -891,11 +891,12 @@ static int record__open(struct record *rec)
int rc = 0;
/*
- * For initial_delay or system wide, we need to add a dummy event so
- * that we can track PERF_RECORD_MMAP to cover the delay of waiting or
- * event synthesis.
+ * For initial_delay, system wide or a hybrid system, we need to add a
+ * dummy event so that we can track PERF_RECORD_MMAP to cover the delay
+ * of waiting or event synthesis.
*/
- if (opts->initial_delay || target__has_cpu(&opts->target)) {
+ if (opts->initial_delay || target__has_cpu(&opts->target) ||
+ perf_pmu__has_hybrid()) {
pos = evlist__get_tracking_event(evlist);
if (!evsel__is_dummy_event(pos)) {
/* Set up dummy event. */