perf top: Save and display the drop count stats

Add drop count to 'perf top' headers:

  # perf top --stdio
   PerfTop:    3549 irqs/sec  kernel:51.8%  exact: 100.0% lost: 0/0 drop: 0/0 [4000Hz cycles:ppp],  (all, 8 CPUs)

  # perf top
  Samples: 0  of event 'cycles:ppp', 4000 Hz, Event count (approx.): 0 lost: 0/0 drop: 0/0

The format is: <current period drop>/<total drop>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-2lj87zz8tq9ye1ntax3ulw0n@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-top.c

@@ -1112,8 +1112,11 @@ static int deliver_event(struct ordered_events *qe,
 	struct machine *machine;
 	int ret = -1;
 
-	if (should_drop(qevent, top))
+	if (should_drop(qevent, top)) {
+		top->drop++;
+		top->drop_total++;
 		return 0;
+	}
 
 	ret = perf_evlist__parse_sample(evlist, event, &sample);
 	if (ret) {

tools/perf/ui/browsers/hists.c

@@ -2223,6 +2223,10 @@ static int hists_browser__scnprintf_title(struct hist_browser *browser, char *bf
 				     " lost: %" PRIu64 "/%" PRIu64,
 				     top->lost, top->lost_total);
 
+		printed += scnprintf(bf + printed, size - printed,
+				     " drop: %" PRIu64 "/%" PRIu64,
+				     top->drop, top->drop_total);
+
 		if (top->zero)
 			printed += scnprintf(bf + printed, size - printed, " [z]");
 	}

tools/perf/util/top.c

@@ -46,8 +46,9 @@ size_t perf_top__header_snprintf(struct perf_top *top, char *bf, size_t size)
 							samples_per_sec;
 		ret = SNPRINTF(bf, size,
 			       "   PerfTop:%8.0f irqs/sec  kernel:%4.1f%%"
-			       "  exact: %4.1f%% lost: %" PRIu64 "/%" PRIu64 " [", samples_per_sec,
-			       ksamples_percent, esamples_percent, top->lost, top->lost_total);
+			       "  exact: %4.1f%% lost: %" PRIu64 "/%" PRIu64 " drop: %" PRIu64 "/%" PRIu64 " [",
+			       samples_per_sec, ksamples_percent, esamples_percent,
+			       top->lost, top->lost_total, top->drop, top->drop_total);
 	} else {
 		float us_samples_per_sec = top->us_samples / top->delay_secs;
 		float guest_kernel_samples_per_sec = top->guest_kernel_samples / top->delay_secs;
@@ -113,5 +114,5 @@ void perf_top__reset_sample_counters(struct perf_top *top)
 {
 	top->samples = top->us_samples = top->kernel_samples =
 	top->exact_samples = top->guest_kernel_samples =
-	top->guest_us_samples = top->lost = 0;
+	top->guest_us_samples = top->lost = top->drop = 0;
 }

tools/perf/util/top.h

@@ -22,7 +22,7 @@ struct perf_top {
 	 * Symbols will be added here in perf_event__process_sample and will
 	 * get out after decayed.
 	 */
-	u64		   samples, lost, lost_total;
+	u64		   samples, lost, lost_total, drop, drop_total;
 	u64		   kernel_samples, us_samples;
 	u64		   exact_samples;
 	u64		   guest_us_samples, guest_kernel_samples;