diff options
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/perf/builtin-stat.c | 25 |
1 files changed, 19 insertions, 6 deletions
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c index 9c6377f7152..e9424fa7242 100644 --- a/tools/perf/builtin-stat.c +++ b/tools/perf/builtin-stat.c @@ -75,7 +75,7 @@ static int null_run = 0; static int fd[MAX_NR_CPUS][MAX_COUNTERS]; static u64 event_res[MAX_COUNTERS][3]; -static u64 event_scaled[MAX_COUNTERS]; +static int event_scaled[MAX_COUNTERS]; struct stats { @@ -97,17 +97,31 @@ static double avg_stats(struct stats *stats) } /* - * stddev = sqrt(1/N (\Sum n_i^2) - avg(n)^2) + * http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance + * + * (\Sum n_i^2) - ((\Sum n_i)^2)/n + * s^2 ------------------------------- + * n - 1 + * + * http://en.wikipedia.org/wiki/Stddev + * + * The std dev of the mean is related to the std dev by: + * + * s + * s_mean = ------- + * sqrt(n) + * */ static double stddev_stats(struct stats *stats) { double avg = stats->sum / run_count; + double variance = (stats->sum_sq - stats->sum*avg)/(run_count - 1); + double variance_mean = variance / run_count; - return sqrt(stats->sum_sq/run_count - avg*avg); + return sqrt(variance_mean); } struct stats event_res_stats[MAX_COUNTERS][3]; -struct stats event_scaled_stats[MAX_COUNTERS]; struct stats runtime_nsecs_stats; struct stats walltime_nsecs_stats; struct stats runtime_cycles_stats; @@ -343,11 +357,10 @@ static void abs_printout(int counter, double avg, double stddev) static void print_counter(int counter) { double avg, stddev; - int scaled; + int scaled = event_scaled[counter]; avg = avg_stats(&event_res_stats[counter][0]); stddev = stddev_stats(&event_res_stats[counter][0]); - scaled = avg_stats(&event_scaled_stats[counter]); if (scaled == -1) { fprintf(stderr, " %14s %-24s\n", |