tools/perf/bench/futex-requeue.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2013  Davidlohr Bueso <davidlohr@hp.com>
   4  *
   5  * futex-requeue: Block a bunch of threads on futex1 and requeue them
   6  *                on futex2, N at a time.
   7  *
   8  * This program is particularly useful to measure the latency of nthread
   9  * requeues without waking up any tasks (in the non-pi case) -- thus
  10  * mimicking a regular futex_wait.
  11  */
  12
  13 /* For the CLR_() macros */
  14 #include <string.h>
  15 #include <pthread.h>
  16
  17 #include <signal.h>
  18 #include "../util/stat.h"
  19 #include <subcmd/parse-options.h>
  20 #include <linux/compiler.h>
  21 #include <linux/kernel.h>
  22 #include <linux/time64.h>
  23 #include <errno.h>
  24 #include <perf/cpumap.h>
  25 #include "bench.h"
  26 #include "futex.h"
  27
  28 #include <err.h>
  29 #include <stdlib.h>
  30 #include <sys/time.h>
  31 #include <sys/mman.h>
  32
  33 static u_int32_t futex1 = 0, futex2 = 0;
  34
  35 static pthread_t *worker;
  36 static bool done = false;
  37 static pthread_mutex_t thread_lock;
  38 static pthread_cond_t thread_parent, thread_worker;
  39 static struct stats requeuetime_stats, requeued_stats;
  40 static unsigned int threads_starting;
  41 static int futex_flag = 0;
  42
  43 static struct bench_futex_parameters params = {
  44         /*
  45          * How many tasks to requeue at a time.
  46          * Default to 1 in order to make the kernel work more.
  47          */
  48         .nrequeue = 1,
  49 };
  50
  51 static const struct option options[] = {
  52         OPT_UINTEGER('t', "threads",  &params.nthreads, "Specify amount of threads"),
  53         OPT_UINTEGER('q', "nrequeue", &params.nrequeue, "Specify amount of threads to requeue at once"),
  54         OPT_BOOLEAN( 's', "silent",   &params.silent, "Silent mode: do not display data/details"),
  55         OPT_BOOLEAN( 'S', "shared",   &params.fshared, "Use shared futexes instead of private ones"),
  56         OPT_BOOLEAN( 'm', "mlockall", &params.mlockall, "Lock all current and future memory"),
  57         OPT_BOOLEAN( 'B', "broadcast", &params.broadcast, "Requeue all threads at once"),
  58         OPT_BOOLEAN( 'p', "pi", &params.pi, "Use PI-aware variants of FUTEX_CMP_REQUEUE"),
  59
  60         OPT_END()
  61 };
  62
  63 static const char * const bench_futex_requeue_usage[] = {
  64         "perf bench futex requeue <options>",
  65         NULL
  66 };
  67
  68 static void print_summary(void)
  69 {
  70         double requeuetime_avg = avg_stats(&requeuetime_stats);
  71         double requeuetime_stddev = stddev_stats(&requeuetime_stats);
  72         unsigned int requeued_avg = avg_stats(&requeued_stats);
  73
  74         printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n",
  75                requeued_avg,
  76                params.nthreads,
  77                requeuetime_avg / USEC_PER_MSEC,
  78                rel_stddev_stats(requeuetime_stddev, requeuetime_avg));
  79 }
  80
  81 static void *workerfn(void *arg __maybe_unused)
  82 {
  83         int ret;
  84
  85         pthread_mutex_lock(&thread_lock);
  86         threads_starting--;
  87         if (!threads_starting)
  88                 pthread_cond_signal(&thread_parent);
  89         pthread_cond_wait(&thread_worker, &thread_lock);
  90         pthread_mutex_unlock(&thread_lock);
  91
  92         while (1) {
  93                 if (!params.pi) {
  94                         ret = futex_wait(&futex1, 0, NULL, futex_flag);
  95                         if (!ret)
  96                                 break;
  97
  98                         if (ret && errno != EAGAIN) {
  99                                 if (!params.silent)
 100                                         warnx("futex_wait");
 101                                 break;
 102                         }
 103                 } else {
 104                         ret = futex_wait_requeue_pi(&futex1, 0, &futex2,
 105                                                     NULL, futex_flag);
 106                         if (!ret) {
 107                                 /* got the lock at futex2 */
 108                                 futex_unlock_pi(&futex2, futex_flag);
 109                                 break;
 110                         }
 111
 112                         if (ret && errno != EAGAIN) {
 113                                 if (!params.silent)
 114                                         warnx("futex_wait_requeue_pi");
 115                                 break;
 116                         }
 117                 }
 118         }
 119
 120         return NULL;
 121 }
 122
 123 static void block_threads(pthread_t *w,
 124                           pthread_attr_t thread_attr, struct perf_cpu_map *cpu)
 125 {
 126         cpu_set_t *cpuset;
 127         unsigned int i;
 128         int nrcpus = perf_cpu_map__nr(cpu);
 129         size_t size;
 130
 131         threads_starting = params.nthreads;
 132
 133         cpuset = CPU_ALLOC(nrcpus);
 134         BUG_ON(!cpuset);
 135         size = CPU_ALLOC_SIZE(nrcpus);
 136
 137         /* create and block all threads */
 138         for (i = 0; i < params.nthreads; i++) {
 139                 CPU_ZERO_S(size, cpuset);
 140                 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);
 141
 142                 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {
 143                         CPU_FREE(cpuset);
 144                         err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
 145                 }
 146
 147                 if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) {
 148                         CPU_FREE(cpuset);
 149                         err(EXIT_FAILURE, "pthread_create");
 150                 }
 151         }
 152         CPU_FREE(cpuset);
 153 }
 154
 155 static void toggle_done(int sig __maybe_unused,
 156                         siginfo_t *info __maybe_unused,
 157                         void *uc __maybe_unused)
 158 {
 159         done = true;
 160 }
 161
 162 int bench_futex_requeue(int argc, const char **argv)
 163 {
 164         int ret = 0;
 165         unsigned int i, j;
 166         struct sigaction act;
 167         pthread_attr_t thread_attr;
 168         struct perf_cpu_map *cpu;
 169
 170         argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0);
 171         if (argc)
 172                 goto err;
 173
 174         cpu = perf_cpu_map__new(NULL);
 175         if (!cpu)
 176                 err(EXIT_FAILURE, "cpu_map__new");
 177
 178         memset(&act, 0, sizeof(act));
 179         sigfillset(&act.sa_mask);
 180         act.sa_sigaction = toggle_done;
 181         sigaction(SIGINT, &act, NULL);
 182
 183         if (params.mlockall) {
 184                 if (mlockall(MCL_CURRENT | MCL_FUTURE))
 185                         err(EXIT_FAILURE, "mlockall");
 186         }
 187
 188         if (!params.nthreads)
 189                 params.nthreads = perf_cpu_map__nr(cpu);
 190
 191         worker = calloc(params.nthreads, sizeof(*worker));
 192         if (!worker)
 193                 err(EXIT_FAILURE, "calloc");
 194
 195         if (!params.fshared)
 196                 futex_flag = FUTEX_PRIVATE_FLAG;
 197
 198         if (params.nrequeue > params.nthreads)
 199                 params.nrequeue = params.nthreads;
 200
 201         if (params.broadcast)
 202                 params.nrequeue = params.nthreads;
 203
 204         printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %s%p), "
 205                "%d at a time.\n\n",  getpid(), params.nthreads,
 206                params.fshared ? "shared":"private", &futex1,
 207                params.pi ? "PI ": "", &futex2, params.nrequeue);
 208
 209         init_stats(&requeued_stats);
 210         init_stats(&requeuetime_stats);
 211         pthread_attr_init(&thread_attr);
 212         pthread_mutex_init(&thread_lock, NULL);
 213         pthread_cond_init(&thread_parent, NULL);
 214         pthread_cond_init(&thread_worker, NULL);
 215
 216         for (j = 0; j < bench_repeat && !done; j++) {
 217                 unsigned int nrequeued = 0, wakeups = 0;
 218                 struct timeval start, end, runtime;
 219
 220                 /* create, launch & block all threads */
 221                 block_threads(worker, thread_attr, cpu);
 222
 223                 /* make sure all threads are already blocked */
 224                 pthread_mutex_lock(&thread_lock);
 225                 while (threads_starting)
 226                         pthread_cond_wait(&thread_parent, &thread_lock);
 227                 pthread_cond_broadcast(&thread_worker);
 228                 pthread_mutex_unlock(&thread_lock);
 229
 230                 usleep(100000);
 231
 232                 /* Ok, all threads are patiently blocked, start requeueing */
 233                 gettimeofday(&start, NULL);
 234                 while (nrequeued < params.nthreads) {
 235                         int r;
 236
 237                         /*
 238                          * For the regular non-pi case, do not wakeup any tasks
 239                          * blocked on futex1, allowing us to really measure
 240                          * futex_wait functionality. For the PI case the first
 241                          * waiter is always awoken.
 242                          */
 243                         if (!params.pi) {
 244                                 r = futex_cmp_requeue(&futex1, 0, &futex2, 0,
 245                                                       params.nrequeue,
 246                                                       futex_flag);
 247                         } else {
 248                                 r = futex_cmp_requeue_pi(&futex1, 0, &futex2,
 249                                                          params.nrequeue,
 250                                                          futex_flag);
 251                                 wakeups++; /* assume no error */
 252                         }
 253
 254                         if (r < 0)
 255                                 err(EXIT_FAILURE, "couldn't requeue from %p to %p",
 256                                     &futex1, &futex2);
 257
 258                         nrequeued += r;
 259                 }
 260
 261                 gettimeofday(&end, NULL);
 262                 timersub(&end, &start, &runtime);
 263
 264                 update_stats(&requeued_stats, nrequeued);
 265                 update_stats(&requeuetime_stats, runtime.tv_usec);
 266
 267                 if (!params.silent) {
 268                         if (!params.pi)
 269                                 printf("[Run %d]: Requeued %d of %d threads in "
 270                                        "%.4f ms\n", j + 1, nrequeued,
 271                                        params.nthreads,
 272                                        runtime.tv_usec / (double)USEC_PER_MSEC);
 273                         else {
 274                                 nrequeued -= wakeups;
 275                                 printf("[Run %d]: Awoke and Requeued (%d+%d) of "
 276                                        "%d threads in %.4f ms\n",
 277                                        j + 1, wakeups, nrequeued,
 278                                        params.nthreads,
 279                                        runtime.tv_usec / (double)USEC_PER_MSEC);
 280                         }
 281
 282                 }
 283
 284                 if (!params.pi) {
 285                         /* everybody should be blocked on futex2, wake'em up */
 286                         nrequeued = futex_wake(&futex2, nrequeued, futex_flag);
 287                         if (params.nthreads != nrequeued)
 288                                 warnx("couldn't wakeup all tasks (%d/%d)",
 289                                       nrequeued, params.nthreads);
 290                 }
 291
 292                 for (i = 0; i < params.nthreads; i++) {
 293                         ret = pthread_join(worker[i], NULL);
 294                         if (ret)
 295                                 err(EXIT_FAILURE, "pthread_join");
 296                 }
 297         }
 298
 299         /* cleanup & report results */
 300         pthread_cond_destroy(&thread_parent);
 301         pthread_cond_destroy(&thread_worker);
 302         pthread_mutex_destroy(&thread_lock);
 303         pthread_attr_destroy(&thread_attr);
 304
 305         print_summary();
 306
 307         free(worker);
 308         perf_cpu_map__put(cpu);
 309         return ret;
 310 err:
 311         usage_with_options(bench_futex_requeue_usage, options);
 312         exit(EXIT_FAILURE);
 313 }