tools/perf/bench/futex-hash.c

   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
  24 #include "../util/stat.h"
  25 #include <subcmd/parse-options.h>
  26 #include "bench.h"
  27 #include "futex.h"
  28 #include "cpumap.h"
  29
  30 #include <err.h>
  31
  32 static unsigned int nthreads = 0;
  33 static unsigned int nsecs    = 10;
  34 /* amount of futexes per thread */
  35 static unsigned int nfutexes = 1024;
  36 static bool fshared = false, done = false, silent = false;
  37 static int futex_flag = 0;
  38
  39 struct timeval start, end, runtime;
  40 static pthread_mutex_t thread_lock;
  41 static unsigned int threads_starting;
  42 static struct stats throughput_stats;
  43 static pthread_cond_t thread_parent, thread_worker;
  44
  45 struct worker {
  46         int tid;
  47         u_int32_t *futex;
  48         pthread_t thread;
  49         unsigned long ops;
  50 };
  51
  52 static const struct option options[] = {
  53         OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"),
  54         OPT_UINTEGER('r', "runtime", &nsecs,    "Specify runtime (in seconds)"),
  55         OPT_UINTEGER('f', "futexes", &nfutexes, "Specify amount of futexes per threads"),
  56         OPT_BOOLEAN( 's', "silent",  &silent,   "Silent mode: do not display data/details"),
  57         OPT_BOOLEAN( 'S', "shared",  &fshared,  "Use shared futexes instead of private ones"),
  58         OPT_END()
  59 };
  60
  61 static const char * const bench_futex_hash_usage[] = {
  62         "perf bench futex hash <options>",
  63         NULL
  64 };
  65
  66 static void *workerfn(void *arg)
  67 {
  68         int ret;
  69         struct worker *w = (struct worker *) arg;
  70         unsigned int i;
  71         unsigned long ops = w->ops; /* avoid cacheline bouncing */
  72
  73         pthread_mutex_lock(&thread_lock);
  74         threads_starting--;
  75         if (!threads_starting)
  76                 pthread_cond_signal(&thread_parent);
  77         pthread_cond_wait(&thread_worker, &thread_lock);
  78         pthread_mutex_unlock(&thread_lock);
  79
  80         do {
  81                 for (i = 0; i < nfutexes; i++, ops++) {
  82                         /*
  83                          * We want the futex calls to fail in order to stress
  84                          * the hashing of uaddr and not measure other steps,
  85                          * such as internal waitqueue handling, thus enlarging
  86                          * the critical region protected by hb->lock.
  87                          */
  88                         ret = futex_wait(&w->futex[i], 1234, NULL, futex_flag);
  89                         if (!silent &&
  90                             (!ret || errno != EAGAIN || errno != EWOULDBLOCK))
  91                                 warn("Non-expected futex return call");
  92                 }
  93         }  while (!done);
  94
  95         w->ops = ops;
  96         return NULL;
  97 }
  98
  99 static void toggle_done(int sig __maybe_unused,
 100                         siginfo_t *info __maybe_unused,
 101                         void *uc __maybe_unused)
 102 {
 103         /* inform all threads that we're done for the day */
 104         done = true;
 105         gettimeofday(&end, NULL);
 106         timersub(&end, &start, &runtime);
 107 }
 108
 109 static void print_summary(void)
 110 {
 111         unsigned long avg = avg_stats(&throughput_stats);
 112         double stddev = stddev_stats(&throughput_stats);
 113
 114         printf("%sAveraged %ld operations/sec (+- %.2f%%), total secs = %d\n",
 115                !silent ? "\n" : "", avg, rel_stddev_stats(stddev, avg),
 116                (int) runtime.tv_sec);
 117 }
 118
 119 int bench_futex_hash(int argc, const char **argv)
 120 {
 121         int ret = 0;
 122         cpu_set_t cpuset;
 123         struct sigaction act;
 124         unsigned int i;
 125         pthread_attr_t thread_attr;
 126         struct worker *worker = NULL;
 127         struct cpu_map *cpu;
 128
 129         argc = parse_options(argc, argv, options, bench_futex_hash_usage, 0);
 130         if (argc) {
 131                 usage_with_options(bench_futex_hash_usage, options);
 132                 exit(EXIT_FAILURE);
 133         }
 134
 135         cpu = cpu_map__new(NULL);
 136         if (!cpu)
 137                 goto errmem;
 138
 139         sigfillset(&act.sa_mask);
 140         act.sa_sigaction = toggle_done;
 141         sigaction(SIGINT, &act, NULL);
 142
 143         if (!nthreads) /* default to the number of CPUs */
 144                 nthreads = cpu->nr;
 145
 146         worker = calloc(nthreads, sizeof(*worker));
 147         if (!worker)
 148                 goto errmem;
 149
 150         if (!fshared)
 151                 futex_flag = FUTEX_PRIVATE_FLAG;
 152
 153         printf("Run summary [PID %d]: %d threads, each operating on %d [%s] futexes for %d secs.\n\n",
 154                getpid(), nthreads, nfutexes, fshared ? "shared":"private", nsecs);
 155
 156         init_stats(&throughput_stats);
 157         pthread_mutex_init(&thread_lock, NULL);
 158         pthread_cond_init(&thread_parent, NULL);
 159         pthread_cond_init(&thread_worker, NULL);
 160
 161         threads_starting = nthreads;
 162         pthread_attr_init(&thread_attr);
 163         gettimeofday(&start, NULL);
 164         for (i = 0; i < nthreads; i++) {
 165                 worker[i].tid = i;
 166                 worker[i].futex = calloc(nfutexes, sizeof(*worker[i].futex));
 167                 if (!worker[i].futex)
 168                         goto errmem;
 169
 170                 CPU_ZERO(&cpuset);
 171                 CPU_SET(cpu->map[i % cpu->nr], &cpuset);
 172
 173                 ret = pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpuset);
 174                 if (ret)
 175                         err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
 176
 177                 ret = pthread_create(&worker[i].thread, &thread_attr, workerfn,
 178                                      (void *)(struct worker *) &worker[i]);
 179                 if (ret)
 180                         err(EXIT_FAILURE, "pthread_create");
 181
 182         }
 183         pthread_attr_destroy(&thread_attr);
 184
 185         pthread_mutex_lock(&thread_lock);
 186         while (threads_starting)
 187                 pthread_cond_wait(&thread_parent, &thread_lock);
 188         pthread_cond_broadcast(&thread_worker);
 189         pthread_mutex_unlock(&thread_lock);
 190
 191         sleep(nsecs);
 192         toggle_done(0, NULL, NULL);
 193
 194         for (i = 0; i < nthreads; i++) {
 195                 ret = pthread_join(worker[i].thread, NULL);
 196                 if (ret)
 197                         err(EXIT_FAILURE, "pthread_join");
 198         }
 199
 200         /* cleanup & report results */
 201         pthread_cond_destroy(&thread_parent);
 202         pthread_cond_destroy(&thread_worker);
 203         pthread_mutex_destroy(&thread_lock);
 204
 205         for (i = 0; i < nthreads; i++) {
 206                 unsigned long t = worker[i].ops/runtime.tv_sec;
 207                 update_stats(&throughput_stats, t);
 208                 if (!silent) {
 209                         if (nfutexes == 1)
 210                                 printf("[thread %2d] futex: %p [ %ld ops/sec ]\n",
 211                                        worker[i].tid, &worker[i].futex[0], t);
 212                         else
 213                                 printf("[thread %2d] futexes: %p ... %p [ %ld ops/sec ]\n",
 214                                        worker[i].tid, &worker[i].futex[0],
 215                                        &worker[i].futex[nfutexes-1], t);
 216                 }
 217
 218                 zfree(&worker[i].futex);
 219         }
 220
 221         print_summary();
 222
 223         free(worker);
 224         free(cpu);
 225         return ret;
 226 errmem:
 227         err(EXIT_FAILURE, "calloc");
 228 }