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)
  99 {
 100         unsigned int i;
 101         pthread_attr_t thread_attr;
 102
 103         pthread_attr_init(&thread_attr);
 104         pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE);
 105
 106         pthread_barrier_init(&barrier, NULL, params.nwakes + 1);
 107
 108         /* create and block all threads */
 109         for (i = 0; i < params.nwakes; i++) {
 110                 /*
 111                  * Thread creation order will impact per-thread latency
 112                  * as it will affect the order to acquire the hb spinlock.
 113                  * For now let the scheduler decide.
 114                  */
 115                 if (pthread_create(&td[i].worker, &thread_attr,
 116                                    waking_workerfn, (void *)&td[i]))
 117                         err(EXIT_FAILURE, "pthread_create");
 118         }
 119
 120         pthread_barrier_wait(&barrier);
 121
 122         for (i = 0; i < params.nwakes; i++)
 123                 if (pthread_join(td[i].worker, NULL))
 124                         err(EXIT_FAILURE, "pthread_join");
 125
 126         pthread_barrier_destroy(&barrier);
 127         pthread_attr_destroy(&thread_attr);
 128 }
 129
 130 static void *blocked_workerfn(void *arg __maybe_unused)
 131 {
 132         mutex_lock(&thread_lock);
 133         threads_starting--;
 134         if (!threads_starting)
 135                 cond_signal(&thread_parent);
 136         cond_wait(&thread_worker, &thread_lock);
 137         mutex_unlock(&thread_lock);
 138
 139         while (1) { /* handle spurious wakeups */
 140                 if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR)
 141                         break;
 142         }
 143
 144         pthread_exit(NULL);
 145         return NULL;
 146 }
 147
 148 static void block_threads(pthread_t *w, struct perf_cpu_map *cpu)
 149 {
 150         cpu_set_t *cpuset;
 151         unsigned int i;
 152         int nrcpus = cpu__max_cpu().cpu;
 153         size_t size;
 154
 155         threads_starting = params.nthreads;
 156
 157         cpuset = CPU_ALLOC(nrcpus);
 158         BUG_ON(!cpuset);
 159         size = CPU_ALLOC_SIZE(nrcpus);
 160
 161         /* create and block all threads */
 162         for (i = 0; i < params.nthreads; i++) {
 163                 pthread_attr_t thread_attr;
 164
 165                 pthread_attr_init(&thread_attr);
 166                 CPU_ZERO_S(size, cpuset);
 167                 CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);
 168
 169                 if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {
 170                         CPU_FREE(cpuset);
 171                         err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
 172                 }
 173
 174                 if (pthread_create(&w[i], &thread_attr, blocked_workerfn, NULL)) {
 175                         CPU_FREE(cpuset);
 176                         err(EXIT_FAILURE, "pthread_create");
 177                 }
 178                 pthread_attr_destroy(&thread_attr);
 179         }
 180         CPU_FREE(cpuset);
 181 }
 182
 183 static void print_run(struct thread_data *waking_worker, unsigned int run_num)
 184 {
 185         unsigned int i, wakeup_avg;
 186         double waketime_avg, waketime_stddev;
 187         struct stats __waketime_stats, __wakeup_stats;
 188
 189         init_stats(&__wakeup_stats);
 190         init_stats(&__waketime_stats);
 191
 192         for (i = 0; i < params.nwakes; i++) {
 193                 update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec);
 194                 update_stats(&__wakeup_stats, waking_worker[i].nwoken);
 195         }
 196
 197         waketime_avg = avg_stats(&__waketime_stats);
 198         waketime_stddev = stddev_stats(&__waketime_stats);
 199         wakeup_avg = avg_stats(&__wakeup_stats);
 200
 201         printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) "
 202                "in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg,
 203                params.nthreads, waketime_avg / USEC_PER_MSEC,
 204                rel_stddev_stats(waketime_stddev, waketime_avg));
 205 }
 206
 207 static void print_summary(void)
 208 {
 209         unsigned int wakeup_avg;
 210         double waketime_avg, waketime_stddev;
 211
 212         waketime_avg = avg_stats(&waketime_stats);
 213         waketime_stddev = stddev_stats(&waketime_stats);
 214         wakeup_avg = avg_stats(&wakeup_stats);
 215
 216         printf("Avg per-thread latency (waking %d/%d threads) in %.4f ms (+-%.2f%%)\n",
 217                wakeup_avg,
 218                params.nthreads,
 219                waketime_avg / USEC_PER_MSEC,
 220                rel_stddev_stats(waketime_stddev, waketime_avg));
 221 }
 222
 223
 224 static void do_run_stats(struct thread_data *waking_worker)
 225 {
 226         unsigned int i;
 227
 228         for (i = 0; i < params.nwakes; i++) {
 229                 update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec);
 230                 update_stats(&wakeup_stats, waking_worker[i].nwoken);
 231         }
 232
 233 }
 234
 235 static void toggle_done(int sig __maybe_unused,
 236                         siginfo_t *info __maybe_unused,
 237                         void *uc __maybe_unused)
 238 {
 239         done = true;
 240 }
 241
 242 int bench_futex_wake_parallel(int argc, const char **argv)
 243 {
 244         int ret = 0;
 245         unsigned int i, j;
 246         struct sigaction act;
 247         struct thread_data *waking_worker;
 248         struct perf_cpu_map *cpu;
 249
 250         argc = parse_options(argc, argv, options,
 251                              bench_futex_wake_parallel_usage, 0);
 252         if (argc) {
 253                 usage_with_options(bench_futex_wake_parallel_usage, options);
 254                 exit(EXIT_FAILURE);
 255         }
 256
 257         memset(&act, 0, sizeof(act));
 258         sigfillset(&act.sa_mask);
 259         act.sa_sigaction = toggle_done;
 260         sigaction(SIGINT, &act, NULL);
 261
 262         if (params.mlockall) {
 263                 if (mlockall(MCL_CURRENT | MCL_FUTURE))
 264                         err(EXIT_FAILURE, "mlockall");
 265         }
 266
 267         cpu = perf_cpu_map__new_online_cpus();
 268         if (!cpu)
 269                 err(EXIT_FAILURE, "calloc");
 270
 271         if (!params.nthreads)
 272                 params.nthreads = perf_cpu_map__nr(cpu);
 273
 274         /* some sanity checks */
 275         if (params.nwakes > params.nthreads ||
 276             !params.nwakes)
 277                 params.nwakes = params.nthreads;
 278
 279         if (params.nthreads % params.nwakes)
 280                 errx(EXIT_FAILURE, "Must be perfectly divisible");
 281         /*
 282          * Each thread will wakeup nwakes tasks in
 283          * a single futex_wait call.
 284          */
 285         nwakes = params.nthreads/params.nwakes;
 286
 287         blocked_worker = calloc(params.nthreads, sizeof(*blocked_worker));
 288         if (!blocked_worker)
 289                 err(EXIT_FAILURE, "calloc");
 290
 291         if (!params.fshared)
 292                 futex_flag = FUTEX_PRIVATE_FLAG;
 293
 294         printf("Run summary [PID %d]: blocking on %d threads (at [%s] "
 295                "futex %p), %d threads waking up %d at a time.\n\n",
 296                getpid(), params.nthreads, params.fshared ? "shared":"private",
 297                &futex, params.nwakes, nwakes);
 298
 299         init_stats(&wakeup_stats);
 300         init_stats(&waketime_stats);
 301
 302         mutex_init(&thread_lock);
 303         cond_init(&thread_parent);
 304         cond_init(&thread_worker);
 305
 306         for (j = 0; j < bench_repeat && !done; j++) {
 307                 waking_worker = calloc(params.nwakes, sizeof(*waking_worker));
 308                 if (!waking_worker)
 309                         err(EXIT_FAILURE, "calloc");
 310
 311                 /* create, launch & block all threads */
 312                 block_threads(blocked_worker, cpu);
 313
 314                 /* make sure all threads are already blocked */
 315                 mutex_lock(&thread_lock);
 316                 while (threads_starting)
 317                         cond_wait(&thread_parent, &thread_lock);
 318                 cond_broadcast(&thread_worker);
 319                 mutex_unlock(&thread_lock);
 320
 321                 usleep(200000);
 322
 323                 /* Ok, all threads are patiently blocked, start waking folks up */
 324                 wakeup_threads(waking_worker);
 325
 326                 for (i = 0; i < params.nthreads; i++) {
 327                         ret = pthread_join(blocked_worker[i], NULL);
 328                         if (ret)
 329                                 err(EXIT_FAILURE, "pthread_join");
 330                 }
 331
 332                 do_run_stats(waking_worker);
 333                 if (!params.silent)
 334                         print_run(waking_worker, j);
 335
 336                 free(waking_worker);
 337         }
 338
 339         /* cleanup & report results */
 340         cond_destroy(&thread_parent);
 341         cond_destroy(&thread_worker);
 342         mutex_destroy(&thread_lock);
 343
 344         print_summary();
 345
 346         free(blocked_worker);
 347         perf_cpu_map__put(cpu);
 348         return ret;
 349 }
 350 #endif /* HAVE_PTHREAD_BARRIER */