[PATCH] perf record/arm-spe: Override attr->sample_period for non-libpfm4 events

From: German Gomez
Date: Fri Jan 14 2022 - 16:21:25 EST


A previous commit preventing attr->sample_period values from being
overridden in pfm events changed a related behaviour in arm_spe.

Before this patch:
perf record -c 10000 -e arm_spe_0// -- sleep 1

Would not yield an SPE event with period=10000, because the arm-spe code
initializes sample_period to a non-0 value, so the "-c 10000" is ignored.

This patch restores the previous behaviour for non-libpfm4 events.

Reported-by: Chase Conklin <chase.conklin@xxxxxxx>
Fixes: ae5dcc8abe31 (“perf record: Prevent override of attr->sample_period for libpfm4 events”)
Signed-off-by: German Gomez <german.gomez@xxxxxxx>
---
tools/perf/util/evsel.c | 25 +++++++++++++++++--------
1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index a59fb2ecb84e..86ab038f020f 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1065,6 +1065,17 @@ void __weak arch_evsel__fixup_new_cycles(struct perf_event_attr *attr __maybe_un
{
}

+static void evsel__set_default_freq_period(struct record_opts *opts,
+ struct perf_event_attr *attr)
+{
+ if (opts->freq) {
+ attr->freq = 1;
+ attr->sample_freq = opts->freq;
+ } else {
+ attr->sample_period = opts->default_interval;
+ }
+}
+
/*
* The enable_on_exec/disabled value strategy:
*
@@ -1131,14 +1142,12 @@ void evsel__config(struct evsel *evsel, struct record_opts *opts,
* We default some events to have a default interval. But keep
* it a weak assumption overridable by the user.
*/
- if (!attr->sample_period) {
- if (opts->freq) {
- attr->freq = 1;
- attr->sample_freq = opts->freq;
- } else {
- attr->sample_period = opts->default_interval;
- }
- }
+ if ((evsel->is_libpfm_event && !attr->sample_period) ||
+ (!evsel->is_libpfm_event && (!attr->sample_period ||
+ opts->user_freq != UINT_MAX ||
+ opts->user_interval != ULLONG_MAX)))
+ evsel__set_default_freq_period(opts, attr);
+
/*
* If attr->freq was set (here or earlier), ask for period
* to be sampled.
--
2.25.1