perf_counter tools: Sample and display frequency adjustment changes

To allow the debugging of frequency-adjusting counters, sample
those adjustments and display them in perf report -D.
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Documentation/perf_counter/builtin-record.c

@@ -347,7 +347,7 @@ static void create_counter(int counter, int cpu, pid_t pid)
 	memset(&attr, 0, sizeof(attr));
 	attr.config		= event_id[counter];
 	attr.sample_period	= event_count[counter];
-	attr.sample_type	= PERF_SAMPLE_IP | PERF_SAMPLE_TID;
+	attr.sample_type	= PERF_SAMPLE_IP | PERF_SAMPLE_TID | PERF_SAMPLE_PERIOD;
 	attr.freq		= freq;
 	attr.mmap		= track;
 	attr.comm		= track;

Documentation/perf_counter/builtin-report.c

@@ -69,12 +69,20 @@ struct fork_event {
 	__u32 pid, ppid;
 };
 
+struct period_event {
+	struct perf_event_header header;
+	__u64 time;
+	__u64 id;
+	__u64 sample_period;
+};
+
 typedef union event_union {
 	struct perf_event_header	header;
 	struct ip_event			ip;
 	struct mmap_event		mmap;
 	struct comm_event		comm;
 	struct fork_event		fork;
+	struct period_event		period;
 } event_t;
 
 static LIST_HEAD(dsos);
@@ -1052,6 +1060,19 @@ process_fork_event(event_t *event, unsigned long offset, unsigned long head)
 	return 0;
 }
 
+static int
+process_period_event(event_t *event, unsigned long offset, unsigned long head)
+{
+	dprintf("%p [%p]: PERF_EVENT_PERIOD: time:%Ld, id:%Ld: period:%Ld\n",
+		(void *)(offset + head),
+		(void *)(long)(event->header.size),
+		event->period.time,
+		event->period.id,
+		event->period.sample_period);
+
+	return 0;
+}
+
 static int
 process_event(event_t *event, unsigned long offset, unsigned long head)
 {
@@ -1068,11 +1089,12 @@ process_event(event_t *event, unsigned long offset, unsigned long head)
 	case PERF_EVENT_FORK:
 		return process_fork_event(event, offset, head);
 
+	case PERF_EVENT_PERIOD:
+		return process_period_event(event, offset, head);
 	/*
 	 * We dont process them right now but they are fine:
 	 */
 
-	case PERF_EVENT_PERIOD:
 	case PERF_EVENT_THROTTLE:
 	case PERF_EVENT_UNTHROTTLE:
 		return 0;
@@ -1157,6 +1179,11 @@ static int __cmd_report(void)
 
 	size = event->header.size;
 
+	dprintf("%p [%p]: event: %d\n",
+			(void *)(offset + head),
+			(void *)(long)event->header.size,
+			event->header.type);
+
 	if (!size || process_event(event, offset, head) < 0) {
 
 		dprintf("%p [%p]: skipping unknown header type: %d\n",