[PATCH 40/41] perf intel-pt: Improve sync_switch by processing PERF_RECORD_SWITCH* in events

Arnaldo Carvalho de Melo
2019-05-29T13:39:34Z

From: Adrian Hunter <adrian.hunter@intel.com>

sync_switch is a facility to synchronize decoding more closely with the
point in the kernel when the context actually switched.

Improve it by processing "context switch in" events.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20190412113830.4126-8-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/intel-pt.c | 40 +++++++++++++++++++++++++++++++++++++-
1 file changed, 39 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
index 03b1da6d1da4..6aaba1146fc8 100644
--- a/tools/perf/util/intel-pt.c
+++ b/tools/perf/util/intel-pt.c
@@ -1914,6 +1914,44 @@ static int intel_pt_process_switch(struct intel_pt *pt,
return machine__set_current_tid(pt->machine, cpu, -1, tid);
}

+static int intel_pt_context_switch_in(struct intel_pt *pt,
+ struct perf_sample *sample)
+{
+ pid_t pid = sample->pid;
+ pid_t tid = sample->tid;
+ int cpu = sample->cpu;
+
+ if (pt->sync_switch) {
+ struct intel_pt_queue *ptq;
+
+ ptq = intel_pt_cpu_to_ptq(pt, cpu);
+ if (ptq && ptq->sync_switch) {
+ ptq->next_tid = -1;
+ switch (ptq->switch_state) {
+ case INTEL_PT_SS_NOT_TRACING:
+ case INTEL_PT_SS_UNKNOWN:
+ case INTEL_PT_SS_TRACING:
+ break;
+ case INTEL_PT_SS_EXPECTING_SWITCH_EVENT:
+ case INTEL_PT_SS_EXPECTING_SWITCH_IP:
+ ptq->switch_state = INTEL_PT_SS_TRACING;
+ break;
+ default:
+ break;
+ }
+ }
+ }
+
+ /*
+ * If the current tid has not been updated yet, ensure it is now that
+ * a "switch in" event has occurred.
+ */
+ if (machine__get_current_tid(pt->machine, cpu) == tid)
+ return 0;
+
+ return machine__set_current_tid(pt->machine, cpu, pid, tid);
+}
+
static int intel_pt_context_switch(struct intel_pt *pt, union perf_event *event,
struct perf_sample *sample)
{
@@ -1925,7 +1963,7 @@ static int intel_pt_context_switch(struct intel_pt *pt, union perf_event *event,

if (pt->have_sched_switch == 3) {
if (!out)
- return 0;
+ return intel_pt_context_switch_in(pt, sample);
if (event->header.type != PERF_RECORD_SWITCH_CPU_WIDE) {
pr_err("Expecting CPU-wide context switch event\n");
return -EINVAL;
--
2.20.1