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 bool is_core;
26};
27
28static const struct option options[] = {
29 OPT_UINTEGER('i', "iterations", &iterations,
30 "Number of iterations used to compute average"),
31 OPT_END()
32};
33
34static const char *const bench_usage[] = {
35 "perf bench internals pmu-scan <options>",
36 NULL
37};
38
39static int nr_pmus;
40static struct pmu_scan_result *results;
41
42static int save_result(void)
43{
44 struct perf_pmu *pmu = NULL;
45 struct list_head *list;
46 struct pmu_scan_result *r;
47
48 while ((pmu = perf_pmus__scan(pmu)) != NULL) {
49 r = realloc(results, (nr_pmus + 1) * sizeof(*r));
50 if (r == NULL)
51 return -ENOMEM;
52
53 results = r;
54 r = results + nr_pmus;
55
56 r->name = strdup(pmu->name);
57 r->is_core = pmu->is_core;
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_pmus__destroy();
74 return 0;
75}
76
77static int check_result(bool core_only)
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 if (core_only && !r->is_core)
87 continue;
88
89 pmu = perf_pmus__find(r->name);
90 if (pmu == NULL) {
91 pr_err("Cannot find PMU %s\n", r->name);
92 return -1;
93 }
94
95 if (pmu->nr_caps != (u32)r->nr_caps) {
96 pr_err("Unmatched number of event caps in %s: expect %d vs got %d\n",
97 pmu->name, r->nr_caps, pmu->nr_caps);
98 return -1;
99 }
100
101 nr = 0;
102 list_for_each(list, &pmu->aliases)
103 nr++;
104 if (nr != r->nr_aliases) {
105 pr_err("Unmatched number of event aliases in %s: expect %d vs got %d\n",
106 pmu->name, r->nr_aliases, nr);
107 return -1;
108 }
109
110 nr = 0;
111 list_for_each(list, &pmu->format)
112 nr++;
113 if (nr != r->nr_formats) {
114 pr_err("Unmatched number of event formats in %s: expect %d vs got %d\n",
115 pmu->name, r->nr_formats, nr);
116 return -1;
117 }
118 }
119 return 0;
120}
121
122static void delete_result(void)
123{
124 for (int i = 0; i < nr_pmus; i++)
125 free(results[i].name);
126 free(results);
127
128 results = NULL;
129 nr_pmus = 0;
130}
131
132static int run_pmu_scan(void)
133{
134 struct stats stats;
135 struct timeval start, end, diff;
136 double time_average, time_stddev;
137 u64 runtime_us;
138 int ret;
139
140 init_stats(&stats);
141 pr_info("Computing performance of sysfs PMU event scan for %u times\n",
142 iterations);
143
144 if (save_result() < 0) {
145 pr_err("Failed to initialize PMU scan result\n");
146 return -1;
147 }
148
149 for (int j = 0; j < 2; j++) {
150 bool core_only = (j == 0);
151
152 for (unsigned int i = 0; i < iterations; i++) {
153 gettimeofday(&start, NULL);
154 if (core_only)
155 perf_pmus__scan_core(NULL);
156 else
157 perf_pmus__scan(NULL);
158 gettimeofday(&end, NULL);
159 timersub(&end, &start, &diff);
160 runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
161 update_stats(&stats, runtime_us);
162
163 ret = check_result(core_only);
164 perf_pmus__destroy();
165 if (ret < 0)
166 break;
167 }
168 time_average = avg_stats(&stats);
169 time_stddev = stddev_stats(&stats);
170 pr_info(" Average%s PMU scanning took: %.3f usec (+- %.3f usec)\n",
171 core_only ? " core" : "", time_average, time_stddev);
172 }
173 delete_result();
174 return 0;
175}
176
177int bench_pmu_scan(int argc, const char **argv)
178{
179 int err = 0;
180
181 argc = parse_options(argc, argv, options, bench_usage, 0);
182 if (argc) {
183 usage_with_options(bench_usage, options);
184 exit(EXIT_FAILURE);
185 }
186
187 err = run_pmu_scan();
188
189 return err;
190}