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324 lines
8.6 KiB
324 lines
8.6 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Copyright (C) 2015 Davidlohr Bueso. |
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* |
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* Block a bunch of threads and let parallel waker threads wakeup an |
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* equal amount of them. The program output reflects the avg latency |
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* for each individual thread to service its share of work. Ultimately |
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* it can be used to measure futex_wake() changes. |
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*/ |
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#include "bench.h" |
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#include <linux/compiler.h> |
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#include "../util/debug.h" |
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#ifndef HAVE_PTHREAD_BARRIER |
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int bench_futex_wake_parallel(int argc __maybe_unused, const char **argv __maybe_unused) |
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{ |
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pr_err("%s: pthread_barrier_t unavailable, disabling this test...\n", __func__); |
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return 0; |
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} |
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#else /* HAVE_PTHREAD_BARRIER */ |
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/* For the CLR_() macros */ |
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#include <string.h> |
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#include <pthread.h> |
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#include <signal.h> |
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#include "../util/stat.h" |
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#include <subcmd/parse-options.h> |
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#include <linux/kernel.h> |
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#include <linux/time64.h> |
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#include <errno.h> |
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#include "futex.h" |
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#include <perf/cpumap.h> |
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#include <err.h> |
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#include <stdlib.h> |
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#include <sys/time.h> |
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struct thread_data { |
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pthread_t worker; |
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unsigned int nwoken; |
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struct timeval runtime; |
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}; |
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static unsigned int nwakes = 1; |
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/* all threads will block on the same futex -- hash bucket chaos ;) */ |
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static u_int32_t futex = 0; |
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static pthread_t *blocked_worker; |
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static bool done = false, silent = false, fshared = false; |
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static unsigned int nblocked_threads = 0, nwaking_threads = 0; |
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static pthread_mutex_t thread_lock; |
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static pthread_cond_t thread_parent, thread_worker; |
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static pthread_barrier_t barrier; |
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static struct stats waketime_stats, wakeup_stats; |
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static unsigned int threads_starting; |
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static int futex_flag = 0; |
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static const struct option options[] = { |
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OPT_UINTEGER('t', "threads", &nblocked_threads, "Specify amount of threads"), |
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OPT_UINTEGER('w', "nwakers", &nwaking_threads, "Specify amount of waking threads"), |
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OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"), |
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OPT_BOOLEAN( 'S', "shared", &fshared, "Use shared futexes instead of private ones"), |
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OPT_END() |
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}; |
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static const char * const bench_futex_wake_parallel_usage[] = { |
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"perf bench futex wake-parallel <options>", |
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NULL |
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}; |
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static void *waking_workerfn(void *arg) |
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{ |
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struct thread_data *waker = (struct thread_data *) arg; |
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struct timeval start, end; |
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pthread_barrier_wait(&barrier); |
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gettimeofday(&start, NULL); |
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waker->nwoken = futex_wake(&futex, nwakes, futex_flag); |
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if (waker->nwoken != nwakes) |
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warnx("couldn't wakeup all tasks (%d/%d)", |
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waker->nwoken, nwakes); |
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gettimeofday(&end, NULL); |
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timersub(&end, &start, &waker->runtime); |
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pthread_exit(NULL); |
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return NULL; |
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} |
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static void wakeup_threads(struct thread_data *td, pthread_attr_t thread_attr) |
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{ |
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unsigned int i; |
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pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE); |
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pthread_barrier_init(&barrier, NULL, nwaking_threads + 1); |
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/* create and block all threads */ |
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for (i = 0; i < nwaking_threads; i++) { |
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/* |
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* Thread creation order will impact per-thread latency |
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* as it will affect the order to acquire the hb spinlock. |
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* For now let the scheduler decide. |
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*/ |
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if (pthread_create(&td[i].worker, &thread_attr, |
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waking_workerfn, (void *)&td[i])) |
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err(EXIT_FAILURE, "pthread_create"); |
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} |
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pthread_barrier_wait(&barrier); |
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for (i = 0; i < nwaking_threads; i++) |
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if (pthread_join(td[i].worker, NULL)) |
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err(EXIT_FAILURE, "pthread_join"); |
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pthread_barrier_destroy(&barrier); |
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} |
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static void *blocked_workerfn(void *arg __maybe_unused) |
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{ |
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pthread_mutex_lock(&thread_lock); |
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threads_starting--; |
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if (!threads_starting) |
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pthread_cond_signal(&thread_parent); |
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pthread_cond_wait(&thread_worker, &thread_lock); |
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pthread_mutex_unlock(&thread_lock); |
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while (1) { /* handle spurious wakeups */ |
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if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR) |
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break; |
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} |
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pthread_exit(NULL); |
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return NULL; |
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} |
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static void block_threads(pthread_t *w, pthread_attr_t thread_attr, |
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struct perf_cpu_map *cpu) |
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{ |
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cpu_set_t cpuset; |
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unsigned int i; |
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threads_starting = nblocked_threads; |
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/* create and block all threads */ |
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for (i = 0; i < nblocked_threads; i++) { |
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CPU_ZERO(&cpuset); |
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CPU_SET(cpu->map[i % cpu->nr], &cpuset); |
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if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpuset)) |
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err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); |
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if (pthread_create(&w[i], &thread_attr, blocked_workerfn, NULL)) |
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err(EXIT_FAILURE, "pthread_create"); |
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} |
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} |
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static void print_run(struct thread_data *waking_worker, unsigned int run_num) |
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{ |
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unsigned int i, wakeup_avg; |
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double waketime_avg, waketime_stddev; |
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struct stats __waketime_stats, __wakeup_stats; |
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init_stats(&__wakeup_stats); |
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init_stats(&__waketime_stats); |
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for (i = 0; i < nwaking_threads; i++) { |
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update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec); |
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update_stats(&__wakeup_stats, waking_worker[i].nwoken); |
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} |
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waketime_avg = avg_stats(&__waketime_stats); |
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waketime_stddev = stddev_stats(&__waketime_stats); |
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wakeup_avg = avg_stats(&__wakeup_stats); |
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printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) " |
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"in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg, |
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nblocked_threads, waketime_avg / USEC_PER_MSEC, |
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rel_stddev_stats(waketime_stddev, waketime_avg)); |
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} |
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static void print_summary(void) |
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{ |
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unsigned int wakeup_avg; |
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double waketime_avg, waketime_stddev; |
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waketime_avg = avg_stats(&waketime_stats); |
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waketime_stddev = stddev_stats(&waketime_stats); |
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wakeup_avg = avg_stats(&wakeup_stats); |
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printf("Avg per-thread latency (waking %d/%d threads) in %.4f ms (+-%.2f%%)\n", |
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wakeup_avg, |
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nblocked_threads, |
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waketime_avg / USEC_PER_MSEC, |
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rel_stddev_stats(waketime_stddev, waketime_avg)); |
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} |
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static void do_run_stats(struct thread_data *waking_worker) |
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{ |
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unsigned int i; |
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for (i = 0; i < nwaking_threads; i++) { |
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update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec); |
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update_stats(&wakeup_stats, waking_worker[i].nwoken); |
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} |
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} |
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static void toggle_done(int sig __maybe_unused, |
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siginfo_t *info __maybe_unused, |
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void *uc __maybe_unused) |
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{ |
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done = true; |
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} |
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int bench_futex_wake_parallel(int argc, const char **argv) |
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{ |
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int ret = 0; |
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unsigned int i, j; |
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struct sigaction act; |
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pthread_attr_t thread_attr; |
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struct thread_data *waking_worker; |
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struct perf_cpu_map *cpu; |
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argc = parse_options(argc, argv, options, |
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bench_futex_wake_parallel_usage, 0); |
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if (argc) { |
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usage_with_options(bench_futex_wake_parallel_usage, options); |
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exit(EXIT_FAILURE); |
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} |
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memset(&act, 0, sizeof(act)); |
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sigfillset(&act.sa_mask); |
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act.sa_sigaction = toggle_done; |
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sigaction(SIGINT, &act, NULL); |
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cpu = perf_cpu_map__new(NULL); |
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if (!cpu) |
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err(EXIT_FAILURE, "calloc"); |
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if (!nblocked_threads) |
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nblocked_threads = cpu->nr; |
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/* some sanity checks */ |
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if (nwaking_threads > nblocked_threads || !nwaking_threads) |
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nwaking_threads = nblocked_threads; |
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if (nblocked_threads % nwaking_threads) |
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errx(EXIT_FAILURE, "Must be perfectly divisible"); |
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/* |
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* Each thread will wakeup nwakes tasks in |
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* a single futex_wait call. |
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*/ |
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nwakes = nblocked_threads/nwaking_threads; |
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blocked_worker = calloc(nblocked_threads, sizeof(*blocked_worker)); |
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if (!blocked_worker) |
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err(EXIT_FAILURE, "calloc"); |
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if (!fshared) |
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futex_flag = FUTEX_PRIVATE_FLAG; |
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printf("Run summary [PID %d]: blocking on %d threads (at [%s] " |
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"futex %p), %d threads waking up %d at a time.\n\n", |
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getpid(), nblocked_threads, fshared ? "shared":"private", |
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&futex, nwaking_threads, nwakes); |
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init_stats(&wakeup_stats); |
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init_stats(&waketime_stats); |
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pthread_attr_init(&thread_attr); |
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pthread_mutex_init(&thread_lock, NULL); |
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pthread_cond_init(&thread_parent, NULL); |
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pthread_cond_init(&thread_worker, NULL); |
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for (j = 0; j < bench_repeat && !done; j++) { |
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waking_worker = calloc(nwaking_threads, sizeof(*waking_worker)); |
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if (!waking_worker) |
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err(EXIT_FAILURE, "calloc"); |
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/* create, launch & block all threads */ |
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block_threads(blocked_worker, thread_attr, cpu); |
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/* make sure all threads are already blocked */ |
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pthread_mutex_lock(&thread_lock); |
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while (threads_starting) |
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pthread_cond_wait(&thread_parent, &thread_lock); |
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pthread_cond_broadcast(&thread_worker); |
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pthread_mutex_unlock(&thread_lock); |
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usleep(100000); |
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/* Ok, all threads are patiently blocked, start waking folks up */ |
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wakeup_threads(waking_worker, thread_attr); |
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for (i = 0; i < nblocked_threads; i++) { |
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ret = pthread_join(blocked_worker[i], NULL); |
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if (ret) |
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err(EXIT_FAILURE, "pthread_join"); |
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} |
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do_run_stats(waking_worker); |
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if (!silent) |
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print_run(waking_worker, j); |
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free(waking_worker); |
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} |
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/* cleanup & report results */ |
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pthread_cond_destroy(&thread_parent); |
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pthread_cond_destroy(&thread_worker); |
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pthread_mutex_destroy(&thread_lock); |
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pthread_attr_destroy(&thread_attr); |
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print_summary(); |
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free(blocked_worker); |
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return ret; |
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} |
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#endif /* HAVE_PTHREAD_BARRIER */
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