[tip:perfcounters/core] perf stat: Add feature to run and measure a command multiple times

tip-bot for Ingo Molnar
2009-06-13T14:51:50Z

Commit-ID: 42202dd56c717f173cd0bf2390249e1bf5cf210b
Gitweb: http://git.kernel.org/tip/42202dd56c717f173cd0bf2390249e1bf5cf210b
Author: Ingo Molnar <mingo@elte.hu>
AuthorDate: Sat, 13 Jun 2009 14:57:28 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Sat, 13 Jun 2009 15:18:57 +0200

perf stat: Add feature to run and measure a command multiple times

Add the --repeat <n> feature to perf stat, which repeats a given
command up to a 100 times, collects the stats and calculates an
average and a stddev.

For example, the following oneliner 'perf stat' command runs hackbench
5 times and prints a tabulated result of all metrics, with averages
and noise levels (in percentage) printed:

aldebaran:~/linux/linux/tools/perf> ./perf stat --repeat 5 ~/hackbench 10
Time: 0.117
Time: 0.108
Time: 0.089
Time: 0.088
Time: 0.100

Performance counter stats for '/home/mingo/hackbench 10' (5 runs):

1243.989586 task-clock-msecs # 10.460 CPUs ( +- 4.720% )
47706 context-switches # 0.038 M/sec ( +- 19.706% )
387 CPU-migrations # 0.000 M/sec ( +- 3.608% )
17793 page-faults # 0.014 M/sec ( +- 0.354% )
3770941606 cycles # 3031.329 M/sec ( +- 4.621% )
1566372416 instructions # 0.415 IPC ( +- 2.703% )
16783421 cache-references # 13.492 M/sec ( +- 5.202% )
7128590 cache-misses # 5.730 M/sec ( +- 7.420% )

0.118924455 seconds time elapsed.

The goal of this feature is to allow the reliance on these accurate
statistics and to know how many times a command has to be repeated
for the noise to go down to an acceptable level.

(The -v option can be used to see a line printed out as each run progresses.)

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
tools/perf/builtin-stat.c | 259 +++++++++++++++++++++++++++++++++-----------
1 files changed, 194 insertions(+), 65 deletions(-)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index c128048..9eb42b1 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -43,6 +43,7 @@
#include "util/parse-events.h"

#include <sys/prctl.h>
+#include <math.h>

static struct perf_counter_attr default_attrs[MAX_COUNTERS] = {

@@ -79,12 +80,34 @@ static const unsigned int default_count[] = {
10000,
};

-static __u64 event_res[MAX_COUNTERS][3];
-static __u64 event_scaled[MAX_COUNTERS];
+#define MAX_RUN 100

-static __u64 runtime_nsecs;
-static __u64 walltime_nsecs;
-static __u64 runtime_cycles;
+static int run_count = 1;
+static int run_idx = 0;
+
+static __u64 event_res[MAX_RUN][MAX_COUNTERS][3];
+static __u64 event_scaled[MAX_RUN][MAX_COUNTERS];
+
+//static __u64 event_hist[MAX_RUN][MAX_COUNTERS][3];
+
+
+static __u64 runtime_nsecs[MAX_RUN];
+static __u64 walltime_nsecs[MAX_RUN];
+static __u64 runtime_cycles[MAX_RUN];
+
+static __u64 event_res_avg[MAX_COUNTERS][3];
+static __u64 event_res_noise[MAX_COUNTERS][3];
+
+static __u64 event_scaled_avg[MAX_COUNTERS];
+
+static __u64 runtime_nsecs_avg;
+static __u64 runtime_nsecs_noise;
+
+static __u64 walltime_nsecs_avg;
+static __u64 walltime_nsecs_noise;
+
+static __u64 runtime_cycles_avg;
+static __u64 runtime_cycles_noise;

static void create_perf_stat_counter(int counter)
{
@@ -140,7 +163,7 @@ static void read_counter(int counter)
int cpu, nv;
int scaled;

- count = event_res[counter];
+ count = event_res[run_idx][counter];

count[0] = count[1] = count[2] = 0;

@@ -151,6 +174,8 @@ static void read_counter(int counter)

res = read(fd[cpu][counter], single_count, nv * sizeof(__u64));
assert(res == nv * sizeof(__u64));
+ close(fd[cpu][counter]);
+ fd[cpu][counter] = -1;

count[0] += single_count[0];
if (scale) {
@@ -162,13 +187,13 @@ static void read_counter(int counter)
scaled = 0;
if (scale) {
if (count[2] == 0) {
- event_scaled[counter] = -1;
+ event_scaled[run_idx][counter] = -1;
count[0] = 0;
return;
}

if (count[2] < count[1]) {
- event_scaled[counter] = 1;
+ event_scaled[run_idx][counter] = 1;
count[0] = (unsigned long long)
((double)count[0] * count[1] / count[2] + 0.5);
}
@@ -178,13 +203,62 @@ static void read_counter(int counter)
*/
if (attrs[counter].type == PERF_TYPE_SOFTWARE &&
attrs[counter].config == PERF_COUNT_SW_TASK_CLOCK)
- runtime_nsecs = count[0];
+ runtime_nsecs[run_idx] = count[0];
if (attrs[counter].type == PERF_TYPE_HARDWARE &&
attrs[counter].config == PERF_COUNT_HW_CPU_CYCLES)
- runtime_cycles = count[0];
+ runtime_cycles[run_idx] = count[0];
}

-static void nsec_printout(int counter, __u64 *count)
+static int run_perf_stat(int argc, const char **argv)
+{
+ unsigned long long t0, t1;
+ int status = 0;
+ int counter;
+ int pid;
+
+ if (!system_wide)
+ nr_cpus = 1;
+
+ for (counter = 0; counter < nr_counters; counter++)
+ create_perf_stat_counter(counter);
+
+ /*
+ * Enable counters and exec the command:
+ */
+ t0 = rdclock();
+ prctl(PR_TASK_PERF_COUNTERS_ENABLE);
+
+ if ((pid = fork()) < 0)
+ perror("failed to fork");
+
+ if (!pid) {
+ if (execvp(argv[0], (char **)argv)) {
+ perror(argv[0]);
+ exit(-1);
+ }
+ }
+
+ wait(&status);
+
+ prctl(PR_TASK_PERF_COUNTERS_DISABLE);
+ t1 = rdclock();
+
+ walltime_nsecs[run_idx] = t1 - t0;
+
+ for (counter = 0; counter < nr_counters; counter++)
+ read_counter(counter);
+
+ return WEXITSTATUS(status);
+}
+
+static void print_noise(__u64 *count, __u64 *noise)
+{
+ if (run_count > 1)
+ fprintf(stderr, " ( +- %7.3f%% )",
+ (double)noise[0]/(count[0]+1)*100.0);
+}
+
+static void nsec_printout(int counter, __u64 *count, __u64 *noise)
{
double msecs = (double)count[0] / 1000000;

@@ -193,29 +267,30 @@ static void nsec_printout(int counter, __u64 *count)
if (attrs[counter].type == PERF_TYPE_SOFTWARE &&
attrs[counter].config == PERF_COUNT_SW_TASK_CLOCK) {

- if (walltime_nsecs)
- fprintf(stderr, " # %10.3f CPUs",
- (double)count[0] / (double)walltime_nsecs);
+ if (walltime_nsecs_avg)
+ fprintf(stderr, " # %10.3f CPUs ",
+ (double)count[0] / (double)walltime_nsecs_avg);
}
+ print_noise(count, noise);
}

-static void abs_printout(int counter, __u64 *count)
+static void abs_printout(int counter, __u64 *count, __u64 *noise)
{
fprintf(stderr, " %14Ld %-20s", count[0], event_name(counter));

- if (runtime_cycles &&
+ if (runtime_cycles_avg &&
attrs[counter].type == PERF_TYPE_HARDWARE &&
attrs[counter].config == PERF_COUNT_HW_INSTRUCTIONS) {

- fprintf(stderr, " # %10.3f IPC",
- (double)count[0] / (double)runtime_cycles);
-
- return;
+ fprintf(stderr, " # %10.3f IPC ",
+ (double)count[0] / (double)runtime_cycles_avg);
+ } else {
+ if (runtime_nsecs_avg) {
+ fprintf(stderr, " # %10.3f M/sec",
+ (double)count[0]/runtime_nsecs_avg*1000.0);
+ }
}
-
- if (runtime_nsecs)
- fprintf(stderr, " # %10.3f M/sec",
- (double)count[0]/runtime_nsecs*1000.0);
+ print_noise(count, noise);
}

/*
@@ -223,11 +298,12 @@ static void abs_printout(int counter, __u64 *count)
*/
static void print_counter(int counter)
{
- __u64 *count;
+ __u64 *count, *noise;
int scaled;

- count = event_res[counter];
- scaled = event_scaled[counter];
+ count = event_res_avg[counter];
+ noise = event_res_noise[counter];
+ scaled = event_scaled_avg[counter];

if (scaled == -1) {
fprintf(stderr, " %14s %-20s\n",
@@ -236,9 +312,9 @@ static void print_counter(int counter)
}

if (nsec_counter(counter))
- nsec_printout(counter, count);
+ nsec_printout(counter, count, noise);
else
- abs_printout(counter, count);
+ abs_printout(counter, count, noise);

if (scaled)
fprintf(stderr, " (scaled from %.2f%%)",
@@ -247,43 +323,83 @@ static void print_counter(int counter)
fprintf(stderr, "\n");
}

-static int do_perf_stat(int argc, const char **argv)
+/*
+ * Normalize noise values down to stddev:
+ */
+static void normalize(__u64 *val)
{
- unsigned long long t0, t1;
- int counter;
- int status;
- int pid;
- int i;
-
- if (!system_wide)
- nr_cpus = 1;
+ double res;

- for (counter = 0; counter < nr_counters; counter++)
- create_perf_stat_counter(counter);
+ res = (double)*val / (run_count * sqrt((double)run_count));

- /*
- * Enable counters and exec the command:
- */
- t0 = rdclock();
- prctl(PR_TASK_PERF_COUNTERS_ENABLE);
+ *val = (__u64)res;
+}

- if ((pid = fork()) < 0)
- perror("failed to fork");
+/*
+ * Calculate the averages and noises:
+ */
+static void calc_avg(void)
+{
+ int i, j;
+
+ for (i = 0; i < run_count; i++) {
+ runtime_nsecs_avg += runtime_nsecs[i];
+ walltime_nsecs_avg += walltime_nsecs[i];
+ runtime_cycles_avg += runtime_cycles[i];
+
+ for (j = 0; j < nr_counters; j++) {
+ event_res_avg[j][0] += event_res[i][j][0];
+ event_res_avg[j][1] += event_res[i][j][1];
+ event_res_avg[j][2] += event_res[i][j][2];
+ event_scaled_avg[j] += event_scaled[i][j];
+ }
+ }
+ runtime_nsecs_avg /= run_count;
+ walltime_nsecs_avg /= run_count;
+ runtime_cycles_avg /= run_count;
+
+ for (j = 0; j < nr_counters; j++) {
+ event_res_avg[j][0] /= run_count;
+ event_res_avg[j][1] /= run_count;
+ event_res_avg[j][2] /= run_count;
+ }

- if (!pid) {
- if (execvp(argv[0], (char **)argv)) {
- perror(argv[0]);
- exit(-1);
+ for (i = 0; i < run_count; i++) {
+ runtime_nsecs_noise +=
+ abs((__s64)(runtime_nsecs[i] - runtime_nsecs_avg));
+ walltime_nsecs_noise +=
+ abs((__s64)(walltime_nsecs[i] - walltime_nsecs_avg));
+ runtime_cycles_noise +=
+ abs((__s64)(runtime_cycles[i] - runtime_cycles_avg));
+
+ for (j = 0; j < nr_counters; j++) {
+ event_res_noise[j][0] +=
+ abs((__s64)(event_res[i][j][0] - event_res_avg[j][0]));
+ event_res_noise[j][1] +=
+ abs((__s64)(event_res[i][j][1] - event_res_avg[j][1]));
+ event_res_noise[j][2] +=
+ abs((__s64)(event_res[i][j][2] - event_res_avg[j][2]));
}
}

- while (wait(&status) >= 0)
- ;
+ normalize(&runtime_nsecs_noise);
+ normalize(&walltime_nsecs_noise);
+ normalize(&runtime_cycles_noise);

- prctl(PR_TASK_PERF_COUNTERS_DISABLE);
- t1 = rdclock();
+ for (j = 0; j < nr_counters; j++) {
+ normalize(&event_res_noise[j][0]);
+ normalize(&event_res_noise[j][1]);
+ normalize(&event_res_noise[j][2]);
+ }
+}
+
+static void print_stat(int argc, const char **argv)
+{
+ int i, counter;
+
+ calc_avg();

- walltime_nsecs = t1 - t0;
+ run_idx = 0;

fflush(stdout);

@@ -293,21 +409,19 @@ static int do_perf_stat(int argc, const char **argv)
for (i = 1; i < argc; i++)
fprintf(stderr, " %s", argv[i]);

- fprintf(stderr, "\':\n");
- fprintf(stderr, "\n");
-
- for (counter = 0; counter < nr_counters; counter++)
- read_counter(counter);
+ fprintf(stderr, "\'");
+ if (run_count > 1)
+ fprintf(stderr, " (%d runs)", run_count);
+ fprintf(stderr, ":\n\n");

for (counter = 0; counter < nr_counters; counter++)
print_counter(counter);

fprintf(stderr, "\n");
- fprintf(stderr, " %14.9f seconds time elapsed.\n", (double)(t1-t0)/1e9);
+ fprintf(stderr, " %14.9f seconds time elapsed.\n",
+ (double)walltime_nsecs_avg/1e9);
fprintf(stderr, "\n");
-
- return 0;
}

static volatile int signr = -1;
@@ -345,11 +459,15 @@ static const struct option options[] = {
"scale/normalize counters"),
OPT_BOOLEAN('v', "verbose", &verbose,
"be more verbose (show counter open errors, etc)"),
+ OPT_INTEGER('r', "repeat", &run_count,
+ "repeat command and print average + stddev (max: 100)"),
OPT_END()
};

int cmd_stat(int argc, const char **argv, const char *prefix)
{
+ int status;
+
page_size = sysconf(_SC_PAGE_SIZE);

memcpy(attrs, default_attrs, sizeof(attrs));
@@ -357,6 +475,8 @@ int cmd_stat(int argc, const char **argv, const char *prefix)
argc = parse_options(argc, argv, options, stat_usage, 0);
if (!argc)
usage_with_options(stat_usage, options);
+ if (run_count <= 0 || run_count > MAX_RUN)
+ usage_with_options(stat_usage, options);

if (!nr_counters)
nr_counters = 8;
@@ -376,5 +496,14 @@ int cmd_stat(int argc, const char **argv, const char *prefix)
signal(SIGALRM, skip_signal);
signal(SIGABRT, skip_signal);

- return do_perf_stat(argc, argv);
+ status = 0;
+ for (run_idx = 0; run_idx < run_count; run_idx++) {
+ if (run_count != 1 && verbose)
+ fprintf(stderr, "[ perf stat: executing run #%d ... ]\n", run_idx+1);
+ status = run_perf_stat(argc, argv);
+ }
+
+ print_stat(argc, argv);
+
+ return status;
}