tools/perf/bench/futex-wake-parallel.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2015 Davidlohr Bueso.
   4  *
   5  * Block a bunch of threads and let parallel waker threads wakeup an
   6  * equal amount of them. The program output reflects the avg latency
   7  * for each individual thread to service its share of work. Ultimately
   8  * it can be used to measure futex_wake() changes.
   9  */
  10 #include "bench.h"
  11 #include <linux/compiler.h>
  12 #include "../util/debug.h"
  13 #include "../util/mutex.h"
  14
  15 #ifndef HAVE_PTHREAD_BARRIER
  16 int bench_futex_wake_parallel(int argc __maybe_unused, const char **argv __maybe_unused)
  17 {
  18         pr_err("%s: pthread_barrier_t unavailable, disabling this test...\n", __func__);
  19         return 0;
  20 }
  21 #else /* HAVE_PTHREAD_BARRIER */
  22 /* For the CLR_() macros */
  23 #include <string.h>
  24 #include <pthread.h>
  25
  26 #include <signal.h>
  27 #include "../util/stat.h"
  28 #include <subcmd/parse-options.h>
  29 #include <linux/kernel.h>
  30 #include <linux/time64.h>
  31 #include <errno.h>
  32 #include "futex.h"
  33 #include <perf/cpumap.h>
  34
  35 #include <err.h>
  36 #include <stdlib.h>
  37 #include <sys/time.h>
  38 #include <sys/mman.h>
  39
  40 struct thread_data {
  41         pthread_t worker;
  42         unsigned int nwoken;
  43         struct timeval runtime;
  44 };
  45
  46 static unsigned int nwakes = 1;
  47
  48 /* all threads will block on the same futex -- hash bucket chaos ;) */
  49 static u_int32_t futex = 0;
  50
  51 static pthread_t *blocked_worker;
  52 static bool done = false;
  53 static struct mutex thread_lock;
  54 static struct cond thread_parent, thread_worker;
  55 static pthread_barrier_t barrier;
  56 static struct stats waketime_stats, wakeup_stats;
  57 static unsigned int threads_starting;
  58 static int futex_flag = 0;
  59
  60 static struct bench_futex_parameters params;
  61
  62 static const struct option options[] = {
  63         OPT_UINTEGER('t', "threads", &params.nthreads, "Specify amount of threads"),
  64         OPT_UINTEGER('w', "nwakers", &params.nwakes, "Specify amount of waking threads"),
  65         OPT_BOOLEAN( 's', "silent",  &params.silent, "Silent mode: do not display data/details"),
  66         OPT_BOOLEAN( 'S', "shared",  &params.fshared, "Use shared futexes instead of private ones"),
  67         OPT_BOOLEAN( 'm', "mlockall", &params.mlockall, "Lock all current and future memory"),
  68
  69         OPT_END()
  70 };
  71
  72 static const char * const bench_futex_wake_parallel_usage[] = {
  73         "perf bench futex wake-parallel <options>",
  74         NULL
  75 };
  76
  77 static void *waking_workerfn(void *arg)
  78 {
  79         struct thread_data *waker = (struct thread_data *) arg;
  80         struct timeval start, end;
  81
  82         pthread_barrier_wait(&barrier);
  83
  84         gettimeofday(&start, NULL);
  85
  86         waker->nwoken = futex_wake(&futex, nwakes, futex_flag);
  87         if (waker->nwoken != nwakes)
  88                 warnx("couldn't wakeup all tasks (%d/%d)",
  89                       waker->nwoken, nwakes);
  90
  91         gettimeofday(&end, NULL);
  92         timersub(&end, &start, &waker->runtime);
  93
  94         pthread_exit(NULL);
  95         return NULL;
  96 }
  97
  98 static void wakeup_threads(struct thread_data *td, pthread_attr_t thread_attr)
  99 {
 100         unsigned int i;
 101
 102         pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE);
 103
 104         pthread_barrier_init(&barrier, NULL, params.nwakes + 1);
 105
 106         /* create and block all threads */
 107         for (i = 0; i < params.nwakes; i++) {
 108                 /*
 109                  * Thread creation order will impact per-thread latency
 110                  * as it will affect the order to acquire the hb spinlock.
 111                  * For now let the scheduler decide.
 112                  */
 113                 if (pthread_create(&td[i].worker, &thread_attr,
 114                                    waking_workerfn, (void *)&td[i]))
 115                         err(EXIT_FAILURE, "pthread_create");
 116         }
 117
 118         pthread_barrier_wait(&barrier);
 119
 120         for (i = 0; i < params.nwakes; i++)
 121                 if (pthread_join(td[i].worker, NULL))
 122                         err(EXIT_FAILURE, "pthread_join");
 123
 124         pthread_barrier_destroy(&barrier);
 125 }
 126
 127 static void *blocked_workerfn(void *arg __maybe_unused)
 128 {
 129         mutex_lock(&thread_lock);
 130         threads_starting--;
 131         if (!threads_starting)
 132                 cond_signal(&thread_parent);
 133         cond_wait(&thread_worker, &thread_lock);
 134         mutex_unlock(&thread_lock);
 135
 136         while (1) { /* handle spurious wakeups */
 137                 if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR)
 138                         break;
 139         }
 140
 141         pthread_exit(NULL);
 142         return NULL;
 143 }
 144
 145 static void block_threads(pthread_t *w, pthread_attr_t thread_attr,
 146                           struct perf_cpu_map *cpu)
 147 {
 148         cpu_set_t *cpuset;
 149         unsigned int i;
 150         int nrcpus = perf_cpu_map__nr(cpu);
 151         size_t size;
 152
 153         threads_starting = params.nthreads;
 154
 155         cpuset = CPU_ALLOC(nrcpus);
 156         BUG_ON(!cpuset);
 157         size = CPU_ALLOC_SIZE(nrcpus);
 158
 159         /* create and block all threads */
 160         for (i = 0; i < params.nthreads; i++) {
 161                 CPU_ZERO_S(size, cpuset);
 162                 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);
 163
 164                 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {
 165                         CPU_FREE(cpuset);
 166                         err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
 167                 }
 168
 169                 if (pthread_create(&w[i], &thread_attr, blocked_workerfn, NULL)) {
 170                         CPU_FREE(cpuset);
 171                         err(EXIT_FAILURE, "pthread_create");
 172                 }
 173         }
 174         CPU_FREE(cpuset);
 175 }
 176
 177 static void print_run(struct thread_data *waking_worker, unsigned int run_num)
 178 {
 179         unsigned int i, wakeup_avg;
 180         double waketime_avg, waketime_stddev;
 181         struct stats __waketime_stats, __wakeup_stats;
 182
 183         init_stats(&__wakeup_stats);
 184         init_stats(&__waketime_stats);
 185
 186         for (i = 0; i < params.nwakes; i++) {
 187                 update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec);
 188                 update_stats(&__wakeup_stats, waking_worker[i].nwoken);
 189         }
 190
 191         waketime_avg = avg_stats(&__waketime_stats);
 192         waketime_stddev = stddev_stats(&__waketime_stats);
 193         wakeup_avg = avg_stats(&__wakeup_stats);
 194
 195         printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) "
 196                "in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg,
 197                params.nthreads, waketime_avg / USEC_PER_MSEC,
 198                rel_stddev_stats(waketime_stddev, waketime_avg));
 199 }
 200
 201 static void print_summary(void)
 202 {
 203         unsigned int wakeup_avg;
 204         double waketime_avg, waketime_stddev;
 205
 206         waketime_avg = avg_stats(&waketime_stats);
 207         waketime_stddev = stddev_stats(&waketime_stats);
 208         wakeup_avg = avg_stats(&wakeup_stats);
 209
 210         printf("Avg per-thread latency (waking %d/%d threads) in %.4f ms (+-%.2f%%)\n",
 211                wakeup_avg,
 212                params.nthreads,
 213                waketime_avg / USEC_PER_MSEC,
 214                rel_stddev_stats(waketime_stddev, waketime_avg));
 215 }
 216
 217
 218 static void do_run_stats(struct thread_data *waking_worker)
 219 {
 220         unsigned int i;
 221
 222         for (i = 0; i < params.nwakes; i++) {
 223                 update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec);
 224                 update_stats(&wakeup_stats, waking_worker[i].nwoken);
 225         }
 226
 227 }
 228
 229 static void toggle_done(int sig __maybe_unused,
 230                         siginfo_t *info __maybe_unused,
 231                         void *uc __maybe_unused)
 232 {
 233         done = true;
 234 }
 235
 236 int bench_futex_wake_parallel(int argc, const char **argv)
 237 {
 238         int ret = 0;
 239         unsigned int i, j;
 240         struct sigaction act;
 241         pthread_attr_t thread_attr;
 242         struct thread_data *waking_worker;
 243         struct perf_cpu_map *cpu;
 244
 245         argc = parse_options(argc, argv, options,
 246                              bench_futex_wake_parallel_usage, 0);
 247         if (argc) {
 248                 usage_with_options(bench_futex_wake_parallel_usage, options);
 249                 exit(EXIT_FAILURE);
 250         }
 251
 252         memset(&act, 0, sizeof(act));
 253         sigfillset(&act.sa_mask);
 254         act.sa_sigaction = toggle_done;
 255         sigaction(SIGINT, &act, NULL);
 256
 257         if (params.mlockall) {
 258                 if (mlockall(MCL_CURRENT | MCL_FUTURE))
 259                         err(EXIT_FAILURE, "mlockall");
 260         }
 261
 262         cpu = perf_cpu_map__new(NULL);
 263         if (!cpu)
 264                 err(EXIT_FAILURE, "calloc");
 265
 266         if (!params.nthreads)
 267                 params.nthreads = perf_cpu_map__nr(cpu);
 268
 269         /* some sanity checks */
 270         if (params.nwakes > params.nthreads ||
 271             !params.nwakes)
 272                 params.nwakes = params.nthreads;
 273
 274         if (params.nthreads % params.nwakes)
 275                 errx(EXIT_FAILURE, "Must be perfectly divisible");
 276         /*
 277          * Each thread will wakeup nwakes tasks in
 278          * a single futex_wait call.
 279          */
 280         nwakes = params.nthreads/params.nwakes;
 281
 282         blocked_worker = calloc(params.nthreads, sizeof(*blocked_worker));
 283         if (!blocked_worker)
 284                 err(EXIT_FAILURE, "calloc");
 285
 286         if (!params.fshared)
 287                 futex_flag = FUTEX_PRIVATE_FLAG;
 288
 289         printf("Run summary [PID %d]: blocking on %d threads (at [%s] "
 290                "futex %p), %d threads waking up %d at a time.\n\n",
 291                getpid(), params.nthreads, params.fshared ? "shared":"private",
 292                &futex, params.nwakes, nwakes);
 293
 294         init_stats(&wakeup_stats);
 295         init_stats(&waketime_stats);
 296
 297         pthread_attr_init(&thread_attr);
 298         mutex_init(&thread_lock);
 299         cond_init(&thread_parent);
 300         cond_init(&thread_worker);
 301
 302         for (j = 0; j < bench_repeat && !done; j++) {
 303                 waking_worker = calloc(params.nwakes, sizeof(*waking_worker));
 304                 if (!waking_worker)
 305                         err(EXIT_FAILURE, "calloc");
 306
 307                 /* create, launch & block all threads */
 308                 block_threads(blocked_worker, thread_attr, cpu);
 309
 310                 /* make sure all threads are already blocked */
 311                 mutex_lock(&thread_lock);
 312                 while (threads_starting)
 313                         cond_wait(&thread_parent, &thread_lock);
 314                 cond_broadcast(&thread_worker);
 315                 mutex_unlock(&thread_lock);
 316
 317                 usleep(100000);
 318
 319                 /* Ok, all threads are patiently blocked, start waking folks up */
 320                 wakeup_threads(waking_worker, thread_attr);
 321
 322                 for (i = 0; i < params.nthreads; i++) {
 323                         ret = pthread_join(blocked_worker[i], NULL);
 324                         if (ret)
 325                                 err(EXIT_FAILURE, "pthread_join");
 326                 }
 327
 328                 do_run_stats(waking_worker);
 329                 if (!params.silent)
 330                         print_run(waking_worker, j);
 331
 332                 free(waking_worker);
 333         }
 334
 335         /* cleanup & report results */
 336         cond_destroy(&thread_parent);
 337         cond_destroy(&thread_worker);
 338         mutex_destroy(&thread_lock);
 339         pthread_attr_destroy(&thread_attr);
 340
 341         print_summary();
 342
 343         free(blocked_worker);
 344         perf_cpu_map__put(cpu);
 345         return ret;
 346 }
 347 #endif /* HAVE_PTHREAD_BARRIER */