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