1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Benchmark scanning sysfs files for PMU information.
4 *
5 * Copyright 2023 Google LLC.
6 */
7#include <errno.h>
8#include <stdio.h>
9#include "bench.h"
10#include "util/debug.h"
11#include "util/pmu.h"
12#include "util/pmus.h"
13#include "util/stat.h"
14#include <linux/atomic.h>
15#include <linux/err.h>
16#include <linux/time64.h>
17#include <subcmd/parse-options.h>
18
19static unsigned int iterations = 100;
20
21struct pmu_scan_result {
22 char *name;
23 int nr_aliases;
24 int nr_formats;
25 int nr_caps;
26 bool is_core;
27};
28
29static const struct option options[] = {
30 OPT_UINTEGER('i', "iterations", &iterations,
31 "Number of iterations used to compute average"),
32 OPT_END()
33};
34
35static const char *const bench_usage[] = {
36 "perf bench internals pmu-scan <options>",
37 NULL
38};
39
40static int nr_pmus;
41static struct pmu_scan_result *results;
42
43static int save_result(void)
44{
45 struct perf_pmu *pmu = NULL;
46 struct list_head *list;
47 struct pmu_scan_result *r;
48
49 while ((pmu = perf_pmus__scan(pmu)) != NULL) {
50 r = realloc(results, (nr_pmus + 1) * sizeof(*r));
51 if (r == NULL)
52 return -ENOMEM;
53
54 results = r;
55 r = results + nr_pmus;
56
57 r->name = strdup(pmu->name);
58 r->is_core = pmu->is_core;
59 r->nr_caps = pmu->nr_caps;
60
61 r->nr_aliases = perf_pmu__num_events(pmu);
62
63 r->nr_formats = 0;
64 list_for_each(list, &pmu->format)
65 r->nr_formats++;
66
67 pr_debug("pmu[%d] name=%s, nr_caps=%d, nr_aliases=%d, nr_formats=%d\n",
68 nr_pmus, r->name, r->nr_caps, r->nr_aliases, r->nr_formats);
69 nr_pmus++;
70 }
71
72 perf_pmus__destroy();
73 return 0;
74}
75
76static int check_result(bool core_only)
77{
78 struct pmu_scan_result *r;
79 struct perf_pmu *pmu;
80 struct list_head *list;
81 int nr;
82
83 for (int i = 0; i < nr_pmus; i++) {
84 r = &results[i];
85 if (core_only && !r->is_core)
86 continue;
87
88 pmu = perf_pmus__find(r->name);
89 if (pmu == NULL) {
90 pr_err("Cannot find PMU %s\n", r->name);
91 return -1;
92 }
93
94 if (pmu->nr_caps != (u32)r->nr_caps) {
95 pr_err("Unmatched number of event caps in %s: expect %d vs got %d\n",
96 pmu->name, r->nr_caps, pmu->nr_caps);
97 return -1;
98 }
99
100 nr = perf_pmu__num_events(pmu);
101 if (nr != r->nr_aliases) {
102 pr_err("Unmatched number of event aliases in %s: expect %d vs got %d\n",
103 pmu->name, r->nr_aliases, nr);
104 return -1;
105 }
106
107 nr = 0;
108 list_for_each(list, &pmu->format)
109 nr++;
110 if (nr != r->nr_formats) {
111 pr_err("Unmatched number of event formats in %s: expect %d vs got %d\n",
112 pmu->name, r->nr_formats, nr);
113 return -1;
114 }
115 }
116 return 0;
117}
118
119static void delete_result(void)
120{
121 for (int i = 0; i < nr_pmus; i++)
122 free(results[i].name);
123 free(results);
124
125 results = NULL;
126 nr_pmus = 0;
127}
128
129static int run_pmu_scan(void)
130{
131 struct stats stats;
132 struct timeval start, end, diff;
133 double time_average, time_stddev;
134 u64 runtime_us;
135 int ret;
136
137 init_stats(&stats);
138 pr_info("Computing performance of sysfs PMU event scan for %u times\n",
139 iterations);
140
141 if (save_result() < 0) {
142 pr_err("Failed to initialize PMU scan result\n");
143 return -1;
144 }
145
146 for (int j = 0; j < 2; j++) {
147 bool core_only = (j == 0);
148
149 for (unsigned int i = 0; i < iterations; i++) {
150 gettimeofday(&start, NULL);
151 if (core_only)
152 perf_pmus__scan_core(NULL);
153 else
154 perf_pmus__scan(NULL);
155 gettimeofday(&end, NULL);
156 timersub(&end, &start, &diff);
157 runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
158 update_stats(&stats, runtime_us);
159
160 ret = check_result(core_only);
161 perf_pmus__destroy();
162 if (ret < 0)
163 break;
164 }
165 time_average = avg_stats(&stats);
166 time_stddev = stddev_stats(&stats);
167 pr_info(" Average%s PMU scanning took: %.3f usec (+- %.3f usec)\n",
168 core_only ? " core" : "", time_average, time_stddev);
169 }
170 delete_result();
171 return 0;
172}
173
174int bench_pmu_scan(int argc, const char **argv)
175{
176 int err = 0;
177
178 argc = parse_options(argc, argv, options, bench_usage, 0);
179 if (argc) {
180 usage_with_options(bench_usage, options);
181 exit(EXIT_FAILURE);
182 }
183
184 err = run_pmu_scan();
185
186 return err;
187}
188

source code of linux/tools/perf/bench/pmu-scan.c