perf hists: Print number of samples, not the period sum

So that we match the header where we state the number of events with the
"Samples" column when using 'perf report -n/--show-nr-samples':

 [root@emilia ~]# perf record -a sleep 1
 [ perf record: Woken up 1 times to write data ]
 [ perf record: Captured and wrote 0.111 MB perf.data (~4860 samples) ]
 [root@emilia ~]# perf report --stdio --show-nr-samples
 # Events: 11  cycles
 #
 # Overhead  Samples        Command       Shared Object                        Symbol
 # ........ ..........  ...........  ..................  ............................
 #
     16.65%          1        sleep  [kernel.kallsyms]   [k] unmap_vmas
     16.10%          1         perf  libpthread-2.12.so  [.] __pthread_cleanup_push_defer
     15.79%          2         perf  [kernel.kallsyms]   [k] format_decode
     12.88%          1  kworker/1:2  [kernel.kallsyms]   [k] cache_reap
     10.69%          1      swapper  [kernel.kallsyms]   [k] _raw_spin_lock
      7.55%          1        sleep  [kernel.kallsyms]   [k] prepare_exec_creds
      6.00%          1         perf  [jbd2]              [k] start_this_handle
      5.29%          1         perf  [kernel.kallsyms]   [k] seq_read
      4.75%          1         perf  [kernel.kallsyms]   [k] get_pid_task
      4.30%          1         perf  [kernel.kallsyms]   [k] _raw_spin_unlock_irqrestore

 #
 # (For a higher level overview, try: perf report --sort comm,dso)
 #
 [root@emilia ~]#

Reported-by: Stephane Eranian <eranian@google.com>
Acked-by: Stephane Eranian <eranian@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/hist.c

@@ -591,6 +591,7 @@ int hist_entry__snprintf(struct hist_entry *self, char *s, size_t size,
 {
 	struct sort_entry *se;
 	u64 period, total, period_sys, period_us, period_guest_sys, period_guest_us;
+	u64 nr_events;
 	const char *sep = symbol_conf.field_sep;
 	int ret;
 
@@ -599,6 +600,7 @@ int hist_entry__snprintf(struct hist_entry *self, char *s, size_t size,
 
 	if (pair_hists) {
 		period = self->pair ? self->pair->period : 0;
+		nr_events = self->pair ? self->pair->nr_events : 0;
 		total = pair_hists->stats.total_period;
 		period_sys = self->pair ? self->pair->period_sys : 0;
 		period_us = self->pair ? self->pair->period_us : 0;
@@ -606,6 +608,7 @@ int hist_entry__snprintf(struct hist_entry *self, char *s, size_t size,
 		period_guest_us = self->pair ? self->pair->period_guest_us : 0;
 	} else {
 		period = self->period;
+		nr_events = self->nr_events;
 		total = session_total;
 		period_sys = self->period_sys;
 		period_us = self->period_us;
@@ -646,9 +649,9 @@ int hist_entry__snprintf(struct hist_entry *self, char *s, size_t size,
 
 	if (symbol_conf.show_nr_samples) {
 		if (sep)
-			ret += snprintf(s + ret, size - ret, "%c%" PRIu64, *sep, period);
+			ret += snprintf(s + ret, size - ret, "%c%" PRIu64, *sep, nr_events);
 		else
-			ret += snprintf(s + ret, size - ret, "%11" PRIu64, period);
+			ret += snprintf(s + ret, size - ret, "%11" PRIu64, nr_events);
 	}
 
 	if (pair_hists) {