1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2013 Davidlohr Bueso <davidlohr@hp.com>
4 *
5 * futex-hash: Stress the hell out of the Linux kernel futex uaddr hashing.
6 *
7 * This program is particularly useful for measuring the kernel's futex hash
8 * table/function implementation. In order for it to make sense, use with as
9 * many threads and futexes as possible.
10 */
11
12 /* For the CLR_() macros */
13 #include <string.h>
14 #include <pthread.h>
15
16 #include <errno.h>
17 #include <signal.h>
18 #include <stdlib.h>
19 #include <linux/compiler.h>
20 #include <linux/kernel.h>
21 #include <linux/zalloc.h>
22 #include <sys/time.h>
23 #include <sys/mman.h>
24 #include <sys/prctl.h>
25 #include <perf/cpumap.h>
26
27 #include "../util/mutex.h"
28 #include "../util/stat.h"
29 #include <subcmd/parse-options.h>
30 #include "bench.h"
31 #include "futex.h"
32
33 #include <err.h>
34
35 static bool done = false;
36 static int futex_flag = 0;
37
38 struct timeval bench__start, bench__end, bench__runtime;
39 static struct mutex thread_lock;
40 static unsigned int threads_starting;
41 static struct stats throughput_stats;
42 static struct cond thread_parent, thread_worker;
43
44 struct worker {
45 int tid;
46 u_int32_t *futex;
47 pthread_t thread;
48 unsigned long ops;
49 };
50
51 static struct bench_futex_parameters params = {
52 .nfutexes = 1024,
53 .runtime = 10,
54 .nbuckets = -1,
55 };
56
57 static const struct option options[] = {
58 OPT_INTEGER( 'b', "buckets", ¶ms.nbuckets, "Specify amount of hash buckets"),
59 OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"),
60 OPT_UINTEGER('r', "runtime", ¶ms.runtime, "Specify runtime (in seconds)"),
61 OPT_UINTEGER('f', "futexes", ¶ms.nfutexes, "Specify amount of futexes per threads"),
62 OPT_BOOLEAN( 's', "silent", ¶ms.silent, "Silent mode: do not display data/details"),
63 OPT_BOOLEAN( 'S', "shared", ¶ms.fshared, "Use shared futexes instead of private ones"),
64 OPT_BOOLEAN( 'm', "mlockall", ¶ms.mlockall, "Lock all current and future memory"),
65 OPT_END()
66 };
67
68 static const char * const bench_futex_hash_usage[] = {
69 "perf bench futex hash <options>",
70 NULL
71 };
72
workerfn(void * arg)73 static void *workerfn(void *arg)
74 {
75 int ret;
76 struct worker *w = (struct worker *) arg;
77 unsigned int i;
78 unsigned long ops = w->ops; /* avoid cacheline bouncing */
79
80 mutex_lock(&thread_lock);
81 threads_starting--;
82 if (!threads_starting)
83 cond_signal(&thread_parent);
84 cond_wait(&thread_worker, &thread_lock);
85 mutex_unlock(&thread_lock);
86
87 do {
88 for (i = 0; i < params.nfutexes; i++, ops++) {
89 /*
90 * We want the futex calls to fail in order to stress
91 * the hashing of uaddr and not measure other steps,
92 * such as internal waitqueue handling, thus enlarging
93 * the critical region protected by hb->lock.
94 */
95 ret = futex_wait(&w->futex[i], 1234, NULL, futex_flag);
96 if (!params.silent &&
97 (!ret || errno != EAGAIN || errno != EWOULDBLOCK))
98 warn("Non-expected futex return call");
99 }
100 } while (!done);
101
102 w->ops = ops;
103 return NULL;
104 }
105
toggle_done(int sig __maybe_unused,siginfo_t * info __maybe_unused,void * uc __maybe_unused)106 static void toggle_done(int sig __maybe_unused,
107 siginfo_t *info __maybe_unused,
108 void *uc __maybe_unused)
109 {
110 /* inform all threads that we're done for the day */
111 done = true;
112 gettimeofday(&bench__end, NULL);
113 timersub(&bench__end, &bench__start, &bench__runtime);
114 }
115
print_summary(void)116 static void print_summary(void)
117 {
118 unsigned long avg = avg_stats(&throughput_stats);
119 double stddev = stddev_stats(&throughput_stats);
120
121 printf("%sAveraged %ld operations/sec (+- %.2f%%), total secs = %d\n",
122 !params.silent ? "\n" : "", avg, rel_stddev_stats(stddev, avg),
123 (int)bench__runtime.tv_sec);
124 futex_print_nbuckets(¶ms);
125 }
126
bench_futex_hash(int argc,const char ** argv)127 int bench_futex_hash(int argc, const char **argv)
128 {
129 int ret = 0;
130 cpu_set_t *cpuset;
131 struct sigaction act;
132 unsigned int i;
133 pthread_attr_t thread_attr;
134 struct worker *worker = NULL;
135 struct perf_cpu_map *cpu;
136 int nrcpus;
137 size_t size;
138
139 argc = parse_options(argc, argv, options, bench_futex_hash_usage, 0);
140 if (argc) {
141 usage_with_options(bench_futex_hash_usage, options);
142 exit(EXIT_FAILURE);
143 }
144
145 cpu = perf_cpu_map__new_online_cpus();
146 if (!cpu)
147 goto errmem;
148
149 memset(&act, 0, sizeof(act));
150 sigfillset(&act.sa_mask);
151 act.sa_sigaction = toggle_done;
152 sigaction(SIGINT, &act, NULL);
153
154 if (params.mlockall) {
155 if (mlockall(MCL_CURRENT | MCL_FUTURE))
156 err(EXIT_FAILURE, "mlockall");
157 }
158
159 if (!params.nthreads) /* default to the number of CPUs */
160 params.nthreads = perf_cpu_map__nr(cpu);
161
162 worker = calloc(params.nthreads, sizeof(*worker));
163 if (!worker)
164 goto errmem;
165
166 if (!params.fshared)
167 futex_flag = FUTEX_PRIVATE_FLAG;
168 futex_set_nbuckets_param(¶ms);
169
170 printf("Run summary [PID %d]: %d threads, each operating on %d [%s] futexes for %d secs.\n\n",
171 getpid(), params.nthreads, params.nfutexes, params.fshared ? "shared":"private", params.runtime);
172
173 init_stats(&throughput_stats);
174 mutex_init(&thread_lock);
175 cond_init(&thread_parent);
176 cond_init(&thread_worker);
177
178 threads_starting = params.nthreads;
179 pthread_attr_init(&thread_attr);
180 gettimeofday(&bench__start, NULL);
181
182 nrcpus = cpu__max_cpu().cpu;
183 cpuset = CPU_ALLOC(nrcpus);
184 BUG_ON(!cpuset);
185 size = CPU_ALLOC_SIZE(nrcpus);
186
187 for (i = 0; i < params.nthreads; i++) {
188 worker[i].tid = i;
189 worker[i].futex = calloc(params.nfutexes, sizeof(*worker[i].futex));
190 if (!worker[i].futex)
191 goto errmem;
192
193 CPU_ZERO_S(size, cpuset);
194
195 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);
196 ret = pthread_attr_setaffinity_np(&thread_attr, size, cpuset);
197 if (ret) {
198 CPU_FREE(cpuset);
199 err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
200 }
201 ret = pthread_create(&worker[i].thread, &thread_attr, workerfn,
202 (void *)(struct worker *) &worker[i]);
203 if (ret) {
204 CPU_FREE(cpuset);
205 err(EXIT_FAILURE, "pthread_create");
206 }
207
208 }
209 CPU_FREE(cpuset);
210 pthread_attr_destroy(&thread_attr);
211
212 mutex_lock(&thread_lock);
213 while (threads_starting)
214 cond_wait(&thread_parent, &thread_lock);
215 cond_broadcast(&thread_worker);
216 mutex_unlock(&thread_lock);
217
218 sleep(params.runtime);
219 toggle_done(0, NULL, NULL);
220
221 for (i = 0; i < params.nthreads; i++) {
222 ret = pthread_join(worker[i].thread, NULL);
223 if (ret)
224 err(EXIT_FAILURE, "pthread_join");
225 }
226
227 /* cleanup & report results */
228 cond_destroy(&thread_parent);
229 cond_destroy(&thread_worker);
230 mutex_destroy(&thread_lock);
231
232 for (i = 0; i < params.nthreads; i++) {
233 unsigned long t = bench__runtime.tv_sec > 0 ?
234 worker[i].ops / bench__runtime.tv_sec : 0;
235 update_stats(&throughput_stats, t);
236 if (!params.silent) {
237 if (params.nfutexes == 1)
238 printf("[thread %2d] futex: %p [ %ld ops/sec ]\n",
239 worker[i].tid, &worker[i].futex[0], t);
240 else
241 printf("[thread %2d] futexes: %p ... %p [ %ld ops/sec ]\n",
242 worker[i].tid, &worker[i].futex[0],
243 &worker[i].futex[params.nfutexes-1], t);
244 }
245
246 zfree(&worker[i].futex);
247 }
248
249 print_summary();
250
251 free(worker);
252 free(cpu);
253 return ret;
254 errmem:
255 err(EXIT_FAILURE, "calloc");
256 }
257