perf intel-pt: Add support for PERF_RECORD_SWITCH

Add support for selecting and processing PERF_RECORD_SWITCH events for
use by Intel PT.  If they are available, they will be used in preference
to sched_switch events.

This enables an unprivileged user to trace multi-threaded or
multi-process workloads with any level of perf_event_paranoid.  However
it depends on kernel support for PERF_RECORD_SWITCH.

Without this patch, tracing a multi-threaded workload will decode
without error but all the data will be attributed to the main thread.

Without this patch, tracing a multi-process workload will result in
decoder errors because the decoder will not know which executable is
executing.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1439458857-30636-3-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 47 insertions, 8 deletions

diff --git a/tools/perf/arch/x86/util/intel-pt.c b/tools/perf/arch/x86/util/intel-pt.c
index 2ca10d796c0b..b02af064f0f9 100644
--- a/tools/perf/arch/x86/util/intel-pt.c
+++ b/tools/perf/arch/x86/util/intel-pt.c
@@ -624,13 +624,49 @@ static int intel_pt_recording_options(struct auxtrace_record *itr,
 	 * threads.
 	 */
 	if (have_timing_info && !cpu_map__empty(cpus)) {
-		err = intel_pt_track_switches(evlist);
-		if (err == -EPERM)
-			pr_debug2("Unable to select sched:sched_switch\n");
-		else if (err)
-			return err;
-		else
-			ptr->have_sched_switch = 1;
+		if (perf_can_record_switch_events()) {
+			bool cpu_wide = !target__none(&opts->target) &&
+					!target__has_task(&opts->target);
+
+			if (!cpu_wide && perf_can_record_cpu_wide()) {
+				struct perf_evsel *switch_evsel;
+
+				err = parse_events(evlist, "dummy:u", NULL);
+				if (err)
+					return err;
+
+				switch_evsel = perf_evlist__last(evlist);
+
+				switch_evsel->attr.freq = 0;
+				switch_evsel->attr.sample_period = 1;
+				switch_evsel->attr.context_switch = 1;
+
+				switch_evsel->system_wide = true;
+				switch_evsel->no_aux_samples = true;
+				switch_evsel->immediate = true;
+
+				perf_evsel__set_sample_bit(switch_evsel, TID);
+				perf_evsel__set_sample_bit(switch_evsel, TIME);
+				perf_evsel__set_sample_bit(switch_evsel, CPU);
+
+				opts->record_switch_events = false;
+				ptr->have_sched_switch = 3;
+			} else {
+				opts->record_switch_events = true;
+				if (cpu_wide)
+					ptr->have_sched_switch = 3;
+				else
+					ptr->have_sched_switch = 2;
+			}
+		} else {
+			err = intel_pt_track_switches(evlist);
+			if (err == -EPERM)
+				pr_debug2("Unable to select sched:sched_switch\n");
+			else if (err)
+				return err;
+			else
+				ptr->have_sched_switch = 1;
+		}
 	}
 
 	if (intel_pt_evsel) {
@@ -663,8 +699,11 @@ static int intel_pt_recording_options(struct auxtrace_record *itr,
 		tracking_evsel->attr.sample_period = 1;
 
 		/* In per-cpu case, always need the time of mmap events etc */
-		if (!cpu_map__empty(cpus))
+		if (!cpu_map__empty(cpus)) {
 			perf_evsel__set_sample_bit(tracking_evsel, TIME);
+			/* And the CPU for switch events */
+			perf_evsel__set_sample_bit(tracking_evsel, CPU);
+		}
 	}
 
 	/*