diff options
authorKan Liang <>2021-07-08 09:03:32 -0700
committerArnaldo Carvalho de Melo <>2021-07-09 14:04:32 -0300
commitb91e5492f9d7ca89919cfe8b0c5b5996263182f7 (patch)
parent5f148e7c6ad7f6e693a459a1df741db47a5ab82e (diff)
perf record: Add a dummy event on hybrid systems to collect metadata records
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 <> Acked-by: Namhyung Kim <> Cc: Jin Yao <> Cc: Jiri Olsa <> Link: Signed-off-by: Arnaldo Carvalho de Melo <>
1 files changed, 5 insertions, 4 deletions
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index ee2a5cacbdfc..671a21c9ee4d 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. */