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0fb298cf DB |
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 | ||
8a158589 ACM |
11 | /* For the CLR_() macros */ |
12 | #include <pthread.h> | |
13 | ||
9c304f6c | 14 | #include <signal.h> |
0fb298cf | 15 | #include "../util/stat.h" |
4b6ab94e | 16 | #include <subcmd/parse-options.h> |
86695f59 | 17 | #include <linux/compiler.h> |
9c304f6c ACM |
18 | #include <linux/kernel.h> |
19 | #include <errno.h> | |
0fb298cf DB |
20 | #include "bench.h" |
21 | #include "futex.h" | |
22 | ||
23 | #include <err.h> | |
24 | #include <stdlib.h> | |
25 | #include <sys/time.h> | |
0fb298cf DB |
26 | |
27 | static u_int32_t futex1 = 0, futex2 = 0; | |
28 | ||
29 | /* | |
30 | * How many tasks to requeue at a time. | |
31 | * Default to 1 in order to make the kernel work more. | |
32 | */ | |
33 | static unsigned int nrequeue = 1; | |
34 | ||
0fb298cf | 35 | static pthread_t *worker; |
86c87e13 | 36 | static bool done = false, silent = false, fshared = false; |
0fb298cf DB |
37 | static pthread_mutex_t thread_lock; |
38 | static pthread_cond_t thread_parent, thread_worker; | |
39 | static struct stats requeuetime_stats, requeued_stats; | |
40 | static unsigned int ncpus, threads_starting, nthreads = 0; | |
86c87e13 | 41 | static int futex_flag = 0; |
0fb298cf DB |
42 | |
43 | static const struct option options[] = { | |
44 | OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"), | |
45 | OPT_UINTEGER('q', "nrequeue", &nrequeue, "Specify amount of threads to requeue at once"), | |
0fb298cf | 46 | OPT_BOOLEAN( 's', "silent", &silent, "Silent mode: do not display data/details"), |
86c87e13 | 47 | OPT_BOOLEAN( 'S', "shared", &fshared, "Use shared futexes instead of private ones"), |
0fb298cf DB |
48 | OPT_END() |
49 | }; | |
50 | ||
51 | static const char * const bench_futex_requeue_usage[] = { | |
52 | "perf bench futex requeue <options>", | |
53 | NULL | |
54 | }; | |
55 | ||
56 | static void print_summary(void) | |
57 | { | |
58 | double requeuetime_avg = avg_stats(&requeuetime_stats); | |
59 | double requeuetime_stddev = stddev_stats(&requeuetime_stats); | |
60 | unsigned int requeued_avg = avg_stats(&requeued_stats); | |
61 | ||
62 | printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n", | |
63 | requeued_avg, | |
64 | nthreads, | |
65 | requeuetime_avg/1e3, | |
66 | rel_stddev_stats(requeuetime_stddev, requeuetime_avg)); | |
67 | } | |
68 | ||
69 | static void *workerfn(void *arg __maybe_unused) | |
70 | { | |
71 | pthread_mutex_lock(&thread_lock); | |
72 | threads_starting--; | |
73 | if (!threads_starting) | |
74 | pthread_cond_signal(&thread_parent); | |
75 | pthread_cond_wait(&thread_worker, &thread_lock); | |
76 | pthread_mutex_unlock(&thread_lock); | |
77 | ||
86c87e13 | 78 | futex_wait(&futex1, 0, NULL, futex_flag); |
0fb298cf DB |
79 | return NULL; |
80 | } | |
81 | ||
82 | static void block_threads(pthread_t *w, | |
83 | pthread_attr_t thread_attr) | |
84 | { | |
85 | cpu_set_t cpu; | |
86 | unsigned int i; | |
87 | ||
88 | threads_starting = nthreads; | |
89 | ||
90 | /* create and block all threads */ | |
91 | for (i = 0; i < nthreads; i++) { | |
92 | CPU_ZERO(&cpu); | |
93 | CPU_SET(i % ncpus, &cpu); | |
94 | ||
95 | if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu)) | |
96 | err(EXIT_FAILURE, "pthread_attr_setaffinity_np"); | |
97 | ||
98 | if (pthread_create(&w[i], &thread_attr, workerfn, NULL)) | |
99 | err(EXIT_FAILURE, "pthread_create"); | |
100 | } | |
101 | } | |
102 | ||
103 | static void toggle_done(int sig __maybe_unused, | |
104 | siginfo_t *info __maybe_unused, | |
105 | void *uc __maybe_unused) | |
106 | { | |
107 | done = true; | |
108 | } | |
109 | ||
110 | int bench_futex_requeue(int argc, const char **argv, | |
111 | const char *prefix __maybe_unused) | |
112 | { | |
113 | int ret = 0; | |
114 | unsigned int i, j; | |
115 | struct sigaction act; | |
116 | pthread_attr_t thread_attr; | |
117 | ||
118 | argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0); | |
119 | if (argc) | |
120 | goto err; | |
121 | ||
122 | ncpus = sysconf(_SC_NPROCESSORS_ONLN); | |
123 | ||
124 | sigfillset(&act.sa_mask); | |
125 | act.sa_sigaction = toggle_done; | |
126 | sigaction(SIGINT, &act, NULL); | |
127 | ||
128 | if (!nthreads) | |
129 | nthreads = ncpus; | |
130 | ||
131 | worker = calloc(nthreads, sizeof(*worker)); | |
132 | if (!worker) | |
133 | err(EXIT_FAILURE, "calloc"); | |
134 | ||
86c87e13 DB |
135 | if (!fshared) |
136 | futex_flag = FUTEX_PRIVATE_FLAG; | |
137 | ||
052b0f6e DB |
138 | if (nrequeue > nthreads) |
139 | nrequeue = nthreads; | |
140 | ||
86c87e13 DB |
141 | printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %p), " |
142 | "%d at a time.\n\n", getpid(), nthreads, | |
143 | fshared ? "shared":"private", &futex1, &futex2, nrequeue); | |
0fb298cf DB |
144 | |
145 | init_stats(&requeued_stats); | |
146 | init_stats(&requeuetime_stats); | |
147 | pthread_attr_init(&thread_attr); | |
148 | pthread_mutex_init(&thread_lock, NULL); | |
149 | pthread_cond_init(&thread_parent, NULL); | |
150 | pthread_cond_init(&thread_worker, NULL); | |
151 | ||
d9de84af | 152 | for (j = 0; j < bench_repeat && !done; j++) { |
0fb298cf DB |
153 | unsigned int nrequeued = 0; |
154 | struct timeval start, end, runtime; | |
155 | ||
156 | /* create, launch & block all threads */ | |
157 | block_threads(worker, thread_attr); | |
158 | ||
159 | /* make sure all threads are already blocked */ | |
160 | pthread_mutex_lock(&thread_lock); | |
161 | while (threads_starting) | |
162 | pthread_cond_wait(&thread_parent, &thread_lock); | |
163 | pthread_cond_broadcast(&thread_worker); | |
164 | pthread_mutex_unlock(&thread_lock); | |
165 | ||
166 | usleep(100000); | |
167 | ||
168 | /* Ok, all threads are patiently blocked, start requeueing */ | |
169 | gettimeofday(&start, NULL); | |
052b0f6e | 170 | while (nrequeued < nthreads) { |
0fb298cf DB |
171 | /* |
172 | * Do not wakeup any tasks blocked on futex1, allowing | |
173 | * us to really measure futex_wait functionality. | |
174 | */ | |
052b0f6e DB |
175 | nrequeued += futex_cmp_requeue(&futex1, 0, &futex2, 0, |
176 | nrequeue, futex_flag); | |
86c87e13 | 177 | } |
052b0f6e | 178 | |
0fb298cf DB |
179 | gettimeofday(&end, NULL); |
180 | timersub(&end, &start, &runtime); | |
181 | ||
182 | update_stats(&requeued_stats, nrequeued); | |
183 | update_stats(&requeuetime_stats, runtime.tv_usec); | |
184 | ||
185 | if (!silent) { | |
186 | printf("[Run %d]: Requeued %d of %d threads in %.4f ms\n", | |
187 | j + 1, nrequeued, nthreads, runtime.tv_usec/1e3); | |
188 | } | |
189 | ||
190 | /* everybody should be blocked on futex2, wake'em up */ | |
052b0f6e | 191 | nrequeued = futex_wake(&futex2, nrequeued, futex_flag); |
0fb298cf DB |
192 | if (nthreads != nrequeued) |
193 | warnx("couldn't wakeup all tasks (%d/%d)", nrequeued, nthreads); | |
194 | ||
195 | for (i = 0; i < nthreads; i++) { | |
196 | ret = pthread_join(worker[i], NULL); | |
197 | if (ret) | |
198 | err(EXIT_FAILURE, "pthread_join"); | |
199 | } | |
0fb298cf DB |
200 | } |
201 | ||
202 | /* cleanup & report results */ | |
203 | pthread_cond_destroy(&thread_parent); | |
204 | pthread_cond_destroy(&thread_worker); | |
205 | pthread_mutex_destroy(&thread_lock); | |
206 | pthread_attr_destroy(&thread_attr); | |
207 | ||
208 | print_summary(); | |
209 | ||
210 | free(worker); | |
211 | return ret; | |
212 | err: | |
213 | usage_with_options(bench_futex_requeue_usage, options); | |
214 | exit(EXIT_FAILURE); | |
215 | } |