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);
+                }
         }
 
         /*