cregit-Linux how code gets into the kernel

Release 4.10 tools/perf/bench/futex-hash.c

Directory: tools/perf/bench
 * Copyright (C) 2013  Davidlohr Bueso <>
 * 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 <pthread.h>

#include <errno.h>
#include <signal.h>
#include <stdlib.h>
#include <linux/compiler.h>
#include <linux/kernel.h>
#include <sys/time.h>

#include "../util/stat.h"
#include <subcmd/parse-options.h>
#include "bench.h"
#include "futex.h"

#include <err.h>
#include <sys/time.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"),

static const char * const bench_futex_hash_usage[] = {
	"perf bench futex hash <options>",

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; }


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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); }


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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); }


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int bench_futex_hash(int argc, const char **argv, const char *prefix __maybe_unused) { int ret = 0; cpu_set_t cpu; struct sigaction act; unsigned int i, ncpus; pthread_attr_t thread_attr; struct worker *worker = NULL; argc = parse_options(argc, argv, options, bench_futex_hash_usage, 0); if (argc) { usage_with_options(bench_futex_hash_usage, options); exit(EXIT_FAILURE); } ncpus = sysconf(_SC_NPROCESSORS_ONLN); nsecs = futexbench_sanitize_numeric(nsecs); nfutexes = futexbench_sanitize_numeric(nfutexes); sigfillset(&act.sa_mask); act.sa_sigaction = toggle_done; sigaction(SIGINT, &act, NULL); if (!nthreads) /* default to the number of CPUs */ nthreads = ncpus; else nthreads = futexbench_sanitize_numeric(nthreads); 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(&cpu); CPU_SET(i % ncpus, &cpu); ret = pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu); 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); } free(worker[i].futex); } print_summary(); free(worker); return ret; errmem: err(EXIT_FAILURE, "calloc"); }


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Directory: tools/perf/bench
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