perf stat: Move stats related code to util/stat.c

Then, the code can be shared between kvm events and perf stat.

Signed-off-by: Xiao Guangrong <[e-mail]>
[ Dong Hao <[e-mail]>: rebase it on acme's git tree ]
Signed-off-by: Dong Hao <[e-mail]>
Cc: Avi Kivity <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: [e-mail]
Cc: Marcelo Tosatti <[e-mail]>
Cc: Runzhen Wang <[e-mail]>
Cc: Xiao Guangrong <[e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/Makefile

···
 LIB_OBJS += $(OUTPUT)util/rblist.o
 LIB_OBJS += $(OUTPUT)util/intlist.o
 LIB_OBJS += $(OUTPUT)util/vdso.o
+LIB_OBJS += $(OUTPUT)util/stat.o
 
 LIB_OBJS += $(OUTPUT)ui/helpline.o
 LIB_OBJS += $(OUTPUT)ui/hist.o

tools/perf/builtin-stat.c

···
 #include "util/evsel.h"
 #include "util/debug.h"
 #include "util/color.h"
+#include "util/stat.h"
 #include "util/header.h"
 #include "util/cpumap.h"
 #include "util/thread.h"
 #include "util/thread_map.h"
 
 #include <sys/prctl.h>
-#include <math.h>
 #include <locale.h>
 
 #define DEFAULT_SEPARATOR	" "
···
 
 static volatile int done = 0;
 
-struct stats
-{
-	double n, mean, M2;
-};
-
 struct perf_stat {
 	struct stats	  res_stats[3];
 };
···
 {
 	free(evsel->priv);
 	evsel->priv = NULL;
-}
-
-static void update_stats(struct stats *stats, u64 val)
-{
-	double delta;
-
-	stats->n++;
-	delta = val - stats->mean;
-	stats->mean += delta / stats->n;
-	stats->M2 += delta*(val - stats->mean);
-}
-
-static double avg_stats(struct stats *stats)
-{
-	return stats->mean;
-}
-
-/*
- * 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 variance, variance_mean;
-
-	if (!stats->n)
-		return 0.0;
-
-	variance = stats->M2 / (stats->n - 1);
-	variance_mean = variance / stats->n;
-
-	return sqrt(variance_mean);
 }
 
 static struct stats runtime_nsecs_stats[MAX_NR_CPUS];
···
 
 static void print_noise_pct(double total, double avg)
 {
-	double pct = 0.0;
-
-	if (avg)
-		pct = 100.0*total/avg;
+	double pct = rel_stddev_stats(total, avg);
 
 	if (csv_output)
 		fprintf(output, "%s%.2f%%", csv_sep, pct);

tools/perf/util/stat.c

···
+#include <math.h>
+
+#include "stat.h"
+
+void update_stats(struct stats *stats, u64 val)
+{
+	double delta;
+
+	stats->n++;
+	delta = val - stats->mean;
+	stats->mean += delta / stats->n;
+	stats->M2 += delta*(val - stats->mean);
+}
+
+double avg_stats(struct stats *stats)
+{
+	return stats->mean;
+}
+
+/*
+ * 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)
+ *
+ */
+double stddev_stats(struct stats *stats)
+{
+	double variance, variance_mean;
+
+	if (!stats->n)
+		return 0.0;
+
+	variance = stats->M2 / (stats->n - 1);
+	variance_mean = variance / stats->n;
+
+	return sqrt(variance_mean);
+}
+
+double rel_stddev_stats(double stddev, double avg)
+{
+	double pct = 0.0;
+
+	if (avg)
+		pct = 100.0 * stddev/avg;
+
+	return pct;
+}

tools/perf/util/stat.h

···
+#ifndef __PERF_STATS_H
+#define __PERF_STATS_H
+
+#include "types.h"
+
+struct stats
+{
+	double n, mean, M2;
+};
+
+void update_stats(struct stats *stats, u64 val);
+double avg_stats(struct stats *stats);
+double stddev_stats(struct stats *stats);
+double rel_stddev_stats(double stddev, double avg);
+
+#endif