text: // SPDX-License-Identifier: GPL-2.0
  /*
   * Copyright (C) 2013  Davidlohr Bueso <davidlohr@hp.com>
   *
   * futex-hash: Stress the hell out of the Linux kernel futex uaddr hashing.
   *
   * This program is particularly useful for measuring the kernel's futex hash
   * table/function implementation. In order for it to make sense, use with as
   * many threads and futexes as possible.
   */
  
  /* For the CLR_() macros */
  #include <string.h>
  #include <pthread.h>
  
  #include <errno.h>
  #include <signal.h>
  #include <stdlib.h>
  #include <linux/compiler.h>
  #include <linux/kernel.h>
  #include <linux/zalloc.h>
  #include <sys/time.h>
  
  #include "../util/stat.h"
  #include <subcmd/parse-options.h>
  #include "bench.h"
  #include "futex.h"
  #include "cpumap.h"
  
  #include <err.h>
  
  static unsigned int nthreads = 0;
  static unsigned int nsecs    = 10;
  /* amount of futexes per thread */
  static unsigned int nfutexes = 1024;
  static bool fshared = false, done = false, silent = false;
  static int futex_flag = 0;
  
  struct timeval start, end, runtime;
  static pthread_mutex_t thread_lock;
  static unsigned int threads_starting;
  static struct stats throughput_stats;
  static pthread_cond_t thread_parent, thread_worker;
  
  struct worker {
  	int tid;
  	u_int32_t *futex;
  	pthread_t thread;
  	unsigned long ops;
  };
  
  static const struct option options[] = {
  	OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"),
  	OPT_UINTEGER('r', "runtime", &nsecs,    "Specify runtime (in seconds)"),
  	OPT_UINTEGER('f', "futexes", &nfutexes, "Specify amount of futexes per threads"),
  	OPT_BOOLEAN( 's', "silent",  &silent,   "Silent mode: do not display data/details"),
  	OPT_BOOLEAN( 'S', "shared",  &fshared,  "Use shared futexes instead of private ones"),
  	OPT_END()
  };
  
  static const char * const bench_futex_hash_usage[] = {
  	"perf bench futex hash <options>",
  	NULL
  };
  
  static void *workerfn(void *arg)
  {
  	int ret;
  	struct worker *w = (struct worker *) arg;
  	unsigned int i;
  	unsigned long ops = w->ops; /* avoid cacheline bouncing */
  
  	pthread_mutex_lock(&thread_lock);
  	threads_starting--;
  	if (!threads_starting)
  		pthread_cond_signal(&thread_parent);
  	pthread_cond_wait(&thread_worker, &thread_lock);
  	pthread_mutex_unlock(&thread_lock);
  
  	do {
  		for (i = 0; i < nfutexes; i++, ops++) {
  			/*
  			 * We want the futex calls to fail in order to stress
  			 * the hashing of uaddr and not measure other steps,
  			 * such as internal waitqueue handling, thus enlarging
  			 * the critical region protected by hb->lock.
  			 */
  			ret = futex_wait(&w->futex[i], 1234, NULL, futex_flag);
  			if (!silent &&
  			    (!ret || errno != EAGAIN || errno != EWOULDBLOCK))
  				warn("Non-expected futex return call");
  		}
  	}  while (!done);
  
  	w->ops = ops;
  	return NULL;
  }
  
  static void toggle_done(int sig __maybe_unused,
  			siginfo_t *info __maybe_unused,
  			void *uc __maybe_unused)
  {
  	/* inform all threads that we're done for the day */
  	done = true;
  	gettimeofday(&end, NULL);
  	timersub(&end, &start, &runtime);
  }
  
  static void print_summary(void)
  {
  	unsigned long avg = avg_stats(&throughput_stats);
  	double stddev = stddev_stats(&throughput_stats);
  
  	printf("%sAveraged %ld operations/sec (+- %.2f%%), total secs = %d\n",
  	       !silent ? "\n" : "", avg, rel_stddev_stats(stddev, avg),
  	       (int) runtime.tv_sec);
  }
  
  int bench_futex_hash(int argc, const char **argv)
  {
  	int ret = 0;
  	cpu_set_t cpuset;
  	struct sigaction act;
  	unsigned int i;
  	pthread_attr_t thread_attr;
  	struct worker *worker = NULL;
  	struct cpu_map *cpu;
  
  	argc = parse_options(argc, argv, options, bench_futex_hash_usage, 0);
  	if (argc) {
  		usage_with_options(bench_futex_hash_usage, options);
  		exit(EXIT_FAILURE);
  	}
  
  	cpu = cpu_map__new(NULL);
  	if (!cpu)
  		goto errmem;
  
  	sigfillset(&act.sa_mask);
  	act.sa_sigaction = toggle_done;
  	sigaction(SIGINT, &act, NULL);
  
  	if (!nthreads) /* default to the number of CPUs */
  		nthreads = cpu->nr;
  
  	worker = calloc(nthreads, sizeof(*worker));
  	if (!worker)
  		goto errmem;
  
  	if (!fshared)
  		futex_flag = FUTEX_PRIVATE_FLAG;
  
  	printf("Run summary [PID %d]: %d threads, each operating on %d [%s] futexes for %d secs.\n\n",
  	       getpid(), nthreads, nfutexes, fshared ? "shared":"private", nsecs);
  
  	init_stats(&throughput_stats);
  	pthread_mutex_init(&thread_lock, NULL);
  	pthread_cond_init(&thread_parent, NULL);
  	pthread_cond_init(&thread_worker, NULL);
  
  	threads_starting = nthreads;
  	pthread_attr_init(&thread_attr);
  	gettimeofday(&start, NULL);
  	for (i = 0; i < nthreads; i++) {
  		worker[i].tid = i;
  		worker[i].futex = calloc(nfutexes, sizeof(*worker[i].futex));
  		if (!worker[i].futex)
  			goto errmem;
  
  		CPU_ZERO(&cpuset);
  		CPU_SET(cpu->map[i % cpu->nr], &cpuset);
  
  		ret = pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpuset);
  		if (ret)
  			err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
  
  		ret = pthread_create(&worker[i].thread, &thread_attr, workerfn,
  				     (void *)(struct worker *) &worker[i]);
  		if (ret)
  			err(EXIT_FAILURE, "pthread_create");
  
  	}
  	pthread_attr_destroy(&thread_attr);
  
  	pthread_mutex_lock(&thread_lock);
  	while (threads_starting)
  		pthread_cond_wait(&thread_parent, &thread_lock);
  	pthread_cond_broadcast(&thread_worker);
  	pthread_mutex_unlock(&thread_lock);
  
  	sleep(nsecs);
  	toggle_done(0, NULL, NULL);
  
  	for (i = 0; i < nthreads; i++) {
  		ret = pthread_join(worker[i].thread, NULL);
  		if (ret)
  			err(EXIT_FAILURE, "pthread_join");
  	}
  
  	/* cleanup & report results */
  	pthread_cond_destroy(&thread_parent);
  	pthread_cond_destroy(&thread_worker);
  	pthread_mutex_destroy(&thread_lock);
  
  	for (i = 0; i < nthreads; i++) {
  		unsigned long t = worker[i].ops/runtime.tv_sec;
  		update_stats(&throughput_stats, t);
  		if (!silent) {
  			if (nfutexes == 1)
  				printf("[thread %2d] futex: %p [ %ld ops/sec ]\n",
  				       worker[i].tid, &worker[i].futex[0], t);
  			else
  				printf("[thread %2d] futexes: %p ... %p [ %ld ops/sec ]\n",
  				       worker[i].tid, &worker[i].futex[0],
  				       &worker[i].futex[nfutexes-1], t);
  		}
  
  		zfree(&worker[i].futex);
  	}
  
  	print_summary();
  
  	free(worker);
  	free(cpu);
  	return ret;
  errmem:
  	err(EXIT_FAILURE, "calloc");
  }
  