perf top: Fix percent output when no samples collected

If there's no sample, kernel and exact percent output at the header
looked like "-nan%".

Tested-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1368497347-9628-3-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 17 insertions, 6 deletions

diff --git a/tools/perf/util/top.c b/tools/perf/util/top.c
index 54d37a4753c5..f857b51b6bde 100644
--- a/tools/perf/util/top.c
+++ b/tools/perf/util/top.c
@@ -23,20 +23,31 @@
 
 size_t perf_top__header_snprintf(struct perf_top *top, char *bf, size_t size)
 {
-        float samples_per_sec = top->samples / top->delay_secs;
-        float ksamples_per_sec = top->kernel_samples / top->delay_secs;
-        float esamples_percent = (100.0 * top->exact_samples) / top->samples;
+        float samples_per_sec;
+        float ksamples_per_sec;
+        float esamples_percent;
         struct perf_record_opts *opts = &top->record_opts;
         struct perf_target *target = &opts->target;
         size_t ret = 0;
 
+        if (top->samples) {
+                samples_per_sec = top->samples / top->delay_secs;
+                ksamples_per_sec = top->kernel_samples / top->delay_secs;
+                esamples_percent = (100.0 * top->exact_samples) / top->samples;
+        } else {
+                samples_per_sec = ksamples_per_sec = esamples_percent = 0.0;
+        }
+
         if (!perf_guest) {
+                float ksamples_percent = 0.0;
+
+                if (samples_per_sec)
+                        ksamples_percent = (100.0 * ksamples_per_sec) /
+                                                        samples_per_sec;
                 ret = SNPRINTF(bf, size,
                                "   PerfTop:%8.0f irqs/sec  kernel:%4.1f%%"
                                "  exact: %4.1f%% [", samples_per_sec,
-                               100.0 - (100.0 * ((samples_per_sec - ksamples_per_sec) /
-                                        samples_per_sec)),
-                                esamples_percent);
+                               ksamples_percent, esamples_percent);
         } 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;