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Release 4.10 tools/perf/bench/futex-wake-parallel.c

Directory: tools/perf/bench
 * Copyright (C) 2015 Davidlohr Bueso.
 * Block a bunch of threads and let parallel waker threads wakeup an
 * equal amount of them. The program output reflects the avg latency
 * for each individual thread to service its share of work. Ultimately
 * it can be used to measure futex_wake() changes.

/* For the CLR_() macros */
#include <pthread.h>

#include <signal.h>
#include "../util/stat.h"
#include <subcmd/parse-options.h>
#include <linux/compiler.h>
#include <linux/kernel.h>
#include <linux/time64.h>
#include <errno.h>
#include "bench.h"
#include "futex.h"

#include <err.h>
#include <stdlib.h>
#include <sys/time.h>

struct thread_data {
pthread_t worker;
unsigned int nwoken;
struct timeval runtime;

static unsigned int nwakes = 1;

/* all threads will block on the same futex -- hash bucket chaos ;) */

static u_int32_t futex = 0;

static pthread_t *blocked_worker;

static bool done = false, silent = false, fshared = false;

static unsigned int nblocked_threads = 0, nwaking_threads = 0;

static pthread_mutex_t thread_lock;

static pthread_cond_t thread_parent, thread_worker;

static struct stats waketime_stats, wakeup_stats;

static unsigned int ncpus, threads_starting;

static int futex_flag = 0;

static const struct option options[] = {
	OPT_UINTEGER('t', "threads", &nblocked_threads, "Specify amount of threads"),
	OPT_UINTEGER('w', "nwakers", &nwaking_threads, "Specify amount of waking 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_wake_parallel_usage[] = {
	"perf bench futex wake-parallel <options>",

static void *waking_workerfn(void *arg) { struct thread_data *waker = (struct thread_data *) arg; struct timeval start, end; gettimeofday(&start, NULL); waker->nwoken = futex_wake(&futex, nwakes, futex_flag); if (waker->nwoken != nwakes) warnx("couldn't wakeup all tasks (%d/%d)", waker->nwoken, nwakes); gettimeofday(&end, NULL); timersub(&end, &start, &waker->runtime); pthread_exit(NULL); return NULL; }


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static void wakeup_threads(struct thread_data *td, pthread_attr_t thread_attr) { unsigned int i; pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE); /* create and block all threads */ for (i = 0; i < nwaking_threads; i++) { /* * Thread creation order will impact per-thread latency * as it will affect the order to acquire the hb spinlock. * For now let the scheduler decide. */ if (pthread_create(&td[i].worker, &thread_attr, waking_workerfn, (void *)&td[i])) err(EXIT_FAILURE, "pthread_create"); } for (i = 0; i < nwaking_threads; i++) if (pthread_join(td[i].worker, NULL)) err(EXIT_FAILURE, "pthread_join"); }


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static void *blocked_workerfn(void *arg __maybe_unused) { 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); while (1) { /* handle spurious wakeups */ if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR) break; } pthread_exit(NULL); return NULL; }


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static void block_threads(pthread_t *w, pthread_attr_t thread_attr) { cpu_set_t cpu; unsigned int i; threads_starting = nblocked_threads; /* create and block all threads */ for (i = 0; i < nblocked_threads; i++) { CPU_ZERO(&cpu); CPU_SET(i % ncpus, &cpu); if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu)) err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); if (pthread_create(&w[i], &thread_attr, blocked_workerfn, NULL)) err(EXIT_FAILURE, "pthread_create"); } }


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static void print_run(struct thread_data *waking_worker, unsigned int run_num) { unsigned int i, wakeup_avg; double waketime_avg, waketime_stddev; struct stats __waketime_stats, __wakeup_stats; init_stats(&__wakeup_stats); init_stats(&__waketime_stats); for (i = 0; i < nwaking_threads; i++) { update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec); update_stats(&__wakeup_stats, waking_worker[i].nwoken); } waketime_avg = avg_stats(&__waketime_stats); waketime_stddev = stddev_stats(&__waketime_stats); wakeup_avg = avg_stats(&__wakeup_stats); printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) " "in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg, nblocked_threads, waketime_avg / USEC_PER_MSEC, rel_stddev_stats(waketime_stddev, waketime_avg)); }


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static void print_summary(void) { unsigned int wakeup_avg; double waketime_avg, waketime_stddev; waketime_avg = avg_stats(&waketime_stats); waketime_stddev = stddev_stats(&waketime_stats); wakeup_avg = avg_stats(&wakeup_stats); printf("Avg per-thread latency (waking %d/%d threads) in %.4f ms (+-%.2f%%)\n", wakeup_avg, nblocked_threads, waketime_avg / USEC_PER_MSEC, rel_stddev_stats(waketime_stddev, waketime_avg)); }


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static void do_run_stats(struct thread_data *waking_worker) { unsigned int i; for (i = 0; i < nwaking_threads; i++) { update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec); update_stats(&wakeup_stats, waking_worker[i].nwoken); } }


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static void toggle_done(int sig __maybe_unused, siginfo_t *info __maybe_unused, void *uc __maybe_unused) { done = true; }


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int bench_futex_wake_parallel(int argc, const char **argv, const char *prefix __maybe_unused) { int ret = 0; unsigned int i, j; struct sigaction act; pthread_attr_t thread_attr; struct thread_data *waking_worker; argc = parse_options(argc, argv, options, bench_futex_wake_parallel_usage, 0); if (argc) { usage_with_options(bench_futex_wake_parallel_usage, options); exit(EXIT_FAILURE); } sigfillset(&act.sa_mask); act.sa_sigaction = toggle_done; sigaction(SIGINT, &act, NULL); ncpus = sysconf(_SC_NPROCESSORS_ONLN); nwaking_threads = futexbench_sanitize_numeric(nwaking_threads); if (!nblocked_threads) nblocked_threads = ncpus; else nblocked_threads = futexbench_sanitize_numeric(nblocked_threads); /* some sanity checks */ if (nwaking_threads > nblocked_threads || !nwaking_threads) nwaking_threads = nblocked_threads; if (nblocked_threads % nwaking_threads) errx(EXIT_FAILURE, "Must be perfectly divisible"); /* * Each thread will wakeup nwakes tasks in * a single futex_wait call. */ nwakes = nblocked_threads/nwaking_threads; blocked_worker = calloc(nblocked_threads, sizeof(*blocked_worker)); if (!blocked_worker) err(EXIT_FAILURE, "calloc"); if (!fshared) futex_flag = FUTEX_PRIVATE_FLAG; printf("Run summary [PID %d]: blocking on %d threads (at [%s] " "futex %p), %d threads waking up %d at a time.\n\n", getpid(), nblocked_threads, fshared ? "shared":"private", &futex, nwaking_threads, nwakes); init_stats(&wakeup_stats); init_stats(&waketime_stats); pthread_attr_init(&thread_attr); pthread_mutex_init(&thread_lock, NULL); pthread_cond_init(&thread_parent, NULL); pthread_cond_init(&thread_worker, NULL); for (j = 0; j < bench_repeat && !done; j++) { waking_worker = calloc(nwaking_threads, sizeof(*waking_worker)); if (!waking_worker) err(EXIT_FAILURE, "calloc"); /* create, launch & block all threads */ block_threads(blocked_worker, thread_attr); /* make sure all threads are already blocked */ 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); usleep(100000); /* Ok, all threads are patiently blocked, start waking folks up */ wakeup_threads(waking_worker, thread_attr); for (i = 0; i < nblocked_threads; i++) { ret = pthread_join(blocked_worker[i], NULL); if (ret) err(EXIT_FAILURE, "pthread_join"); } do_run_stats(waking_worker); if (!silent) print_run(waking_worker, j); free(waking_worker); } /* cleanup & report results */ pthread_cond_destroy(&thread_parent); pthread_cond_destroy(&thread_worker); pthread_mutex_destroy(&thread_lock); pthread_attr_destroy(&thread_attr); print_summary(); free(blocked_worker); return ret; }


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Directory: tools/perf/bench
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