tools/perf/bench/futex-requeue.c

   1 /*
   2  * Copyright (C) 2013  Davidlohr Bueso <davidlohr@hp.com>
   3  *
   4  * futex-requeue: Block a bunch of threads on futex1 and requeue them
   5  *                on futex2, N at a time.
   6  *
   7  * This program is particularly useful to measure the latency of nthread
   8  * requeues without waking up any tasks -- thus mimicking a regular futex_wait.
   9  */
  10
  11 #include "../perf.h"
  12 #include "../util/util.h"
  13 #include "../util/stat.h"
  14 #include "../util/parse-options.h"
  15 #include "../util/header.h"
  16 #include "bench.h"
  17 #include "futex.h"
  18
  19 #include <err.h>
  20 #include <stdlib.h>
  21 #include <sys/time.h>
  22 #include <pthread.h>
  23
  24 static u_int32_t futex1 = 0, futex2 = 0;
  25
  26 /*
  27  * How many tasks to requeue at a time.
  28  * Default to 1 in order to make the kernel work more.
  29  */
  30 static unsigned int nrequeue = 1;
  31
  32 static pthread_t *worker;
  33 static bool done = 0, silent = 0;
  34 static pthread_mutex_t thread_lock;
  35 static pthread_cond_t thread_parent, thread_worker;
  36 static struct stats requeuetime_stats, requeued_stats;
  37 static unsigned int ncpus, threads_starting, nthreads = 0;
  38
  39 static const struct option options[] = {
  40         OPT_UINTEGER('t', "threads",  &nthreads, "Specify amount of threads"),
  41         OPT_UINTEGER('q', "nrequeue", &nrequeue, "Specify amount of threads to requeue at once"),
  42         OPT_BOOLEAN( 's', "silent",   &silent,   "Silent mode: do not display data/details"),
  43         OPT_END()
  44 };
  45
  46 static const char * const bench_futex_requeue_usage[] = {
  47         "perf bench futex requeue <options>",
  48         NULL
  49 };
  50
  51 static void print_summary(void)
  52 {
  53         double requeuetime_avg = avg_stats(&requeuetime_stats);
  54         double requeuetime_stddev = stddev_stats(&requeuetime_stats);
  55         unsigned int requeued_avg = avg_stats(&requeued_stats);
  56
  57         printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n",
  58                requeued_avg,
  59                nthreads,
  60                requeuetime_avg/1e3,
  61                rel_stddev_stats(requeuetime_stddev, requeuetime_avg));
  62 }
  63
  64 static void *workerfn(void *arg __maybe_unused)
  65 {
  66         pthread_mutex_lock(&thread_lock);
  67         threads_starting--;
  68         if (!threads_starting)
  69                 pthread_cond_signal(&thread_parent);
  70         pthread_cond_wait(&thread_worker, &thread_lock);
  71         pthread_mutex_unlock(&thread_lock);
  72
  73         futex_wait(&futex1, 0, NULL, FUTEX_PRIVATE_FLAG);
  74         return NULL;
  75 }
  76
  77 static void block_threads(pthread_t *w,
  78                           pthread_attr_t thread_attr)
  79 {
  80         cpu_set_t cpu;
  81         unsigned int i;
  82
  83         threads_starting = nthreads;
  84
  85         /* create and block all threads */
  86         for (i = 0; i < nthreads; i++) {
  87                 CPU_ZERO(&cpu);
  88                 CPU_SET(i % ncpus, &cpu);
  89
  90                 if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu))
  91                         err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
  92
  93                 if (pthread_create(&w[i], &thread_attr, workerfn, NULL))
  94                         err(EXIT_FAILURE, "pthread_create");
  95         }
  96 }
  97
  98 static void toggle_done(int sig __maybe_unused,
  99                         siginfo_t *info __maybe_unused,
 100                         void *uc __maybe_unused)
 101 {
 102         done = true;
 103 }
 104
 105 int bench_futex_requeue(int argc, const char **argv,
 106                         const char *prefix __maybe_unused)
 107 {
 108         int ret = 0;
 109         unsigned int i, j;
 110         struct sigaction act;
 111         pthread_attr_t thread_attr;
 112
 113         argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0);
 114         if (argc)
 115                 goto err;
 116
 117         ncpus = sysconf(_SC_NPROCESSORS_ONLN);
 118
 119         sigfillset(&act.sa_mask);
 120         act.sa_sigaction = toggle_done;
 121         sigaction(SIGINT, &act, NULL);
 122
 123         if (!nthreads)
 124                 nthreads = ncpus;
 125
 126         worker = calloc(nthreads, sizeof(*worker));
 127         if (!worker)
 128                 err(EXIT_FAILURE, "calloc");
 129
 130         printf("Run summary [PID %d]: Requeuing %d threads (from %p to %p), "
 131                "%d at a time.\n\n",
 132                getpid(), nthreads, &futex1, &futex2, nrequeue);
 133
 134         init_stats(&requeued_stats);
 135         init_stats(&requeuetime_stats);
 136         pthread_attr_init(&thread_attr);
 137         pthread_mutex_init(&thread_lock, NULL);
 138         pthread_cond_init(&thread_parent, NULL);
 139         pthread_cond_init(&thread_worker, NULL);
 140
 141         for (j = 0; j < bench_repeat && !done; j++) {
 142                 unsigned int nrequeued = 0;
 143                 struct timeval start, end, runtime;
 144
 145                 /* create, launch & block all threads */
 146                 block_threads(worker, thread_attr);
 147
 148                 /* make sure all threads are already blocked */
 149                 pthread_mutex_lock(&thread_lock);
 150                 while (threads_starting)
 151                         pthread_cond_wait(&thread_parent, &thread_lock);
 152                 pthread_cond_broadcast(&thread_worker);
 153                 pthread_mutex_unlock(&thread_lock);
 154
 155                 usleep(100000);
 156
 157                 /* Ok, all threads are patiently blocked, start requeueing */
 158                 gettimeofday(&start, NULL);
 159                 for (nrequeued = 0; nrequeued < nthreads; nrequeued += nrequeue)
 160                         /*
 161                          * Do not wakeup any tasks blocked on futex1, allowing
 162                          * us to really measure futex_wait functionality.
 163                          */
 164                         futex_cmp_requeue(&futex1, 0, &futex2, 0, nrequeue,
 165                                           FUTEX_PRIVATE_FLAG);
 166                 gettimeofday(&end, NULL);
 167                 timersub(&end, &start, &runtime);
 168
 169                 update_stats(&requeued_stats, nrequeued);
 170                 update_stats(&requeuetime_stats, runtime.tv_usec);
 171
 172                 if (!silent) {
 173                         printf("[Run %d]: Requeued %d of %d threads in %.4f ms\n",
 174                                j + 1, nrequeued, nthreads, runtime.tv_usec/1e3);
 175                 }
 176
 177                 /* everybody should be blocked on futex2, wake'em up */
 178                 nrequeued = futex_wake(&futex2, nthreads, FUTEX_PRIVATE_FLAG);
 179                 if (nthreads != nrequeued)
 180                         warnx("couldn't wakeup all tasks (%d/%d)", nrequeued, nthreads);
 181
 182                 for (i = 0; i < nthreads; i++) {
 183                         ret = pthread_join(worker[i], NULL);
 184                         if (ret)
 185                                 err(EXIT_FAILURE, "pthread_join");
 186                 }
 187
 188         }
 189
 190         /* cleanup & report results */
 191         pthread_cond_destroy(&thread_parent);
 192         pthread_cond_destroy(&thread_worker);
 193         pthread_mutex_destroy(&thread_lock);
 194         pthread_attr_destroy(&thread_attr);
 195
 196         print_summary();
 197
 198         free(worker);
 199         return ret;
 200 err:
 201         usage_with_options(bench_futex_requeue_usage, options);
 202         exit(EXIT_FAILURE);
 203 }