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>

diff --git a/tools/perf/util/top.c b/tools/perf/util/top.c
index 54d37a4..f857b51 100644 (file)
--- 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;