[PATCH RFC 16/21] perf intel-pt: Track sideband system-wide when needed

Adrian Hunter
2022-04-22T16:25:59Z

User space tasks can migrate between CPUs, so when tracing selected CPUs,
sideband for all CPUs is still needed. This is in preparation for allowing
system-wide events on all CPUs while the user requested events are on only
user requested CPUs.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
tools/perf/arch/x86/util/intel-pt.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/tools/perf/arch/x86/util/intel-pt.c b/tools/perf/arch/x86/util/intel-pt.c
index e45d64dec57c..62be78bc90b6 100644
--- a/tools/perf/arch/x86/util/intel-pt.c
+++ b/tools/perf/arch/x86/util/intel-pt.c
@@ -864,20 +864,22 @@ static int intel_pt_recording_options(struct auxtrace_record *itr,

/* Add dummy event to keep tracking */
if (opts->full_auxtrace) {
+ bool need_system_wide_tracking;
struct evsel *tracking_evsel;

- err = parse_events(evlist, "dummy:u", NULL);
- if (err)
- return err;
+ /*
+ * User space tasks can migrate between CPUs, so when tracing
+ * selected CPUs, sideband for all CPUs is still needed.
+ */
+ need_system_wide_tracking = evlist->core.has_user_cpus &&
+ !intel_pt_evsel->core.attr.exclude_user;

- tracking_evsel = evlist__last(evlist);
+ tracking_evsel = evlist__add_aux_dummy(evlist, need_system_wide_tracking);
+ if (!tracking_evsel)
+ return -ENOMEM;

evlist__set_tracking_event(evlist, tracking_evsel);

- tracking_evsel->core.attr.freq = 0;
- tracking_evsel->core.attr.sample_period = 1;
-
- tracking_evsel->no_aux_samples = true;
if (need_immediate)
tracking_evsel->immediate = true;

--
2.25.1