tjh.dev
Linux kernel mirror (for testing)
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kernel
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linux
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 <stdio.h>
8#include "bench.h"
9#include "util/debug.h"
10#include "util/pmu.h"
11#include "util/pmus.h"
12#include "util/stat.h"
13#include <linux/atomic.h>
14#include <linux/err.h>
15#include <linux/time64.h>
16#include <subcmd/parse-options.h>
17
18static unsigned int iterations = 100;
19
20struct pmu_scan_result {
21 char *name;
22 int nr_aliases;
23 int nr_formats;
24 int nr_caps;
25};
26
27static const struct option options[] = {
28 OPT_UINTEGER('i', "iterations", &iterations,
29 "Number of iterations used to compute average"),
30 OPT_END()
31};
32
33static const char *const bench_usage[] = {
34 "perf bench internals pmu-scan <options>",
35 NULL
36};
37
38static int nr_pmus;
39static struct pmu_scan_result *results;
40
41static int save_result(void)
42{
43 struct perf_pmu *pmu;
44 struct list_head *list;
45 struct pmu_scan_result *r;
46
47 perf_pmu__scan(NULL);
48
49 perf_pmus__for_each_pmu(pmu) {
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->nr_caps = pmu->nr_caps;
59
60 r->nr_aliases = 0;
61 list_for_each(list, &pmu->aliases)
62 r->nr_aliases++;
63
64 r->nr_formats = 0;
65 list_for_each(list, &pmu->format)
66 r->nr_formats++;
67
68 pr_debug("pmu[%d] name=%s, nr_caps=%d, nr_aliases=%d, nr_formats=%d\n",
69 nr_pmus, r->name, r->nr_caps, r->nr_aliases, r->nr_formats);
70 nr_pmus++;
71 }
72
73 perf_pmu__destroy();
74 return 0;
75}
76
77static int check_result(void)
78{
79 struct pmu_scan_result *r;
80 struct perf_pmu *pmu;
81 struct list_head *list;
82 int nr;
83
84 for (int i = 0; i < nr_pmus; i++) {
85 r = &results[i];
86 pmu = perf_pmu__find(r->name);
87 if (pmu == NULL) {
88 pr_err("Cannot find PMU %s\n", r->name);
89 return -1;
90 }
91
92 if (pmu->nr_caps != (u32)r->nr_caps) {
93 pr_err("Unmatched number of event caps in %s: expect %d vs got %d\n",
94 pmu->name, r->nr_caps, pmu->nr_caps);
95 return -1;
96 }
97
98 nr = 0;
99 list_for_each(list, &pmu->aliases)
100 nr++;
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 unsigned int i;
136 int ret;
137
138 init_stats(&stats);
139 pr_info("Computing performance of sysfs PMU event scan for %u times\n",
140 iterations);
141
142 if (save_result() < 0) {
143 pr_err("Failed to initialize PMU scan result\n");
144 return -1;
145 }
146
147 for (i = 0; i < iterations; i++) {
148 gettimeofday(&start, NULL);
149 perf_pmu__scan(NULL);
150 gettimeofday(&end, NULL);
151
152 timersub(&end, &start, &diff);
153 runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
154 update_stats(&stats, runtime_us);
155
156 ret = check_result();
157 perf_pmu__destroy();
158 if (ret < 0)
159 break;
160 }
161
162 time_average = avg_stats(&stats);
163 time_stddev = stddev_stats(&stats);
164 pr_info(" Average PMU scanning took: %.3f usec (+- %.3f usec)\n",
165 time_average, time_stddev);
166
167 delete_result();
168 return 0;
169}
170
171int bench_pmu_scan(int argc, const char **argv)
172{
173 int err = 0;
174
175 argc = parse_options(argc, argv, options, bench_usage, 0);
176 if (argc) {
177 usage_with_options(bench_usage, options);
178 exit(EXIT_FAILURE);
179 }
180
181 err = run_pmu_scan();
182
183 return err;
184}