1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Context switch microbenchmark.
21 #include <sys/syscall.h>
22 #include <sys/sysinfo.h>
23 #include <sys/types.h>
25 #include <linux/futex.h>
31 static unsigned int timeout = 30;
33 static int touch_vdso;
36 static int touch_fp = 1;
39 static int touch_vector = 1;
43 static int touch_altivec = 1;
46 * Note: LTO (Link Time Optimisation) doesn't play well with this function
47 * attribute. Be very careful enabling LTO for this test.
49 static void __attribute__((__target__("no-vsx"))) altivec_touch_fn(void)
55 static void touch(void)
58 gettimeofday(&tv, NULL);
71 asm volatile("# %0 %1 %2": : "r"(&tv), "r"(&fp), "r"(&c));
74 static void start_thread_on(void *(*fn)(void *), void *arg, unsigned long cpu)
82 CPU_SET(cpu, &cpuset);
84 rc = pthread_attr_init(&attr);
87 perror("pthread_attr_init");
91 rc = pthread_attr_setaffinity_np(&attr, sizeof(cpu_set_t), &cpuset);
94 perror("pthread_attr_setaffinity_np");
98 rc = pthread_create(&tid, &attr, fn, arg);
101 perror("pthread_create");
106 static void start_process_on(void *(*fn)(void *), void *arg, unsigned long cpu)
121 ncpus = get_nprocs();
122 size = CPU_ALLOC_SIZE(ncpus);
123 cpuset = CPU_ALLOC(ncpus);
128 CPU_ZERO_S(size, cpuset);
129 CPU_SET_S(cpu, size, cpuset);
131 if (sched_setaffinity(0, size, cpuset)) {
132 perror("sched_setaffinity");
143 static unsigned long iterations;
144 static unsigned long iterations_prev;
146 static void sigalrm_handler(int junk)
148 unsigned long i = iterations;
150 printf("%ld\n", i - iterations_prev);
159 static void sigusr1_handler(int junk)
165 void (*setup)(int, int);
166 void *(*thread1)(void *);
167 void *(*thread2)(void *);
173 static int pipe_fd1[2];
174 static int pipe_fd2[2];
176 static void pipe_setup(int cpu1, int cpu2)
178 if (pipe(pipe_fd1) || pipe(pipe_fd2))
182 static void *pipe_thread1(void *arg)
184 signal(SIGALRM, sigalrm_handler);
188 assert(read(pipe_fd1[READ], &c, 1) == 1);
191 assert(write(pipe_fd2[WRITE], &c, 1) == 1);
200 static void *pipe_thread2(void *arg)
203 assert(write(pipe_fd1[WRITE], &c, 1) == 1);
206 assert(read(pipe_fd2[READ], &c, 1) == 1);
213 static struct actions pipe_actions = {
215 .thread1 = pipe_thread1,
216 .thread2 = pipe_thread2,
219 static void yield_setup(int cpu1, int cpu2)
222 fprintf(stderr, "Both threads must be on the same CPU for yield test\n");
227 static void *yield_thread1(void *arg)
229 signal(SIGALRM, sigalrm_handler);
242 static void *yield_thread2(void *arg)
252 static struct actions yield_actions = {
253 .setup = yield_setup,
254 .thread1 = yield_thread1,
255 .thread2 = yield_thread2,
258 static long sys_futex(void *addr1, int op, int val1, struct timespec *timeout,
259 void *addr2, int val3)
261 return syscall(SYS_futex, addr1, op, val1, timeout, addr2, val3);
264 static unsigned long cmpxchg(unsigned long *p, unsigned long expected,
265 unsigned long desired)
267 unsigned long exp = expected;
269 __atomic_compare_exchange_n(p, &exp, desired, 0,
270 __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
274 static unsigned long xchg(unsigned long *p, unsigned long val)
276 return __atomic_exchange_n(p, val, __ATOMIC_SEQ_CST);
279 static int processes;
281 static int mutex_lock(unsigned long *m)
284 int flags = FUTEX_WAIT;
286 flags |= FUTEX_PRIVATE_FLAG;
288 c = cmpxchg(m, 0, 1);
296 sys_futex(m, flags, 2, NULL, NULL, 0);
303 static int mutex_unlock(unsigned long *m)
305 int flags = FUTEX_WAKE;
307 flags |= FUTEX_PRIVATE_FLAG;
311 else if (xchg(m, 0) == 1)
314 sys_futex(m, flags, 1, NULL, NULL, 0);
319 static unsigned long *m1, *m2;
321 static void futex_setup(int cpu1, int cpu2)
324 static unsigned long _m1, _m2;
331 shmid = shmget(IPC_PRIVATE, getpagesize(), SHM_R | SHM_W);
337 shmaddr = shmat(shmid, NULL, 0);
338 if (shmaddr == (char *)-1) {
340 shmctl(shmid, IPC_RMID, NULL);
344 shmctl(shmid, IPC_RMID, NULL);
347 m2 = shmaddr + sizeof(*m1);
357 static void *futex_thread1(void *arg)
359 signal(SIGALRM, sigalrm_handler);
372 static void *futex_thread2(void *arg)
382 static struct actions futex_actions = {
383 .setup = futex_setup,
384 .thread1 = futex_thread1,
385 .thread2 = futex_thread2,
388 static struct option options[] = {
389 { "test", required_argument, 0, 't' },
390 { "process", no_argument, &processes, 1 },
391 { "timeout", required_argument, 0, 's' },
392 { "vdso", no_argument, &touch_vdso, 1 },
393 { "no-fp", no_argument, &touch_fp, 0 },
395 { "no-altivec", no_argument, &touch_altivec, 0 },
397 { "no-vector", no_argument, &touch_vector, 0 },
401 static void usage(void)
403 fprintf(stderr, "Usage: context_switch2 <options> CPU1 CPU2\n\n");
404 fprintf(stderr, "\t\t--test=X\tpipe, futex or yield (default)\n");
405 fprintf(stderr, "\t\t--process\tUse processes (default threads)\n");
406 fprintf(stderr, "\t\t--timeout=X\tDuration in seconds to run (default 30)\n");
407 fprintf(stderr, "\t\t--vdso\t\ttouch VDSO\n");
408 fprintf(stderr, "\t\t--no-fp\t\tDon't touch FP\n");
410 fprintf(stderr, "\t\t--no-altivec\tDon't touch altivec\n");
412 fprintf(stderr, "\t\t--no-vector\tDon't touch vector\n");
415 int main(int argc, char *argv[])
418 struct actions *actions = &yield_actions;
421 static void (*start_fn)(void *(*fn)(void *), void *arg, unsigned long cpu);
424 int option_index = 0;
426 c = getopt_long(argc, argv, "", options, &option_index);
433 if (options[option_index].flag != 0)
441 if (!strcmp(optarg, "pipe")) {
442 actions = &pipe_actions;
443 } else if (!strcmp(optarg, "yield")) {
444 actions = &yield_actions;
445 } else if (!strcmp(optarg, "futex")) {
446 actions = &futex_actions;
454 timeout = atoi(optarg);
464 start_fn = start_process_on;
466 start_fn = start_thread_on;
468 if (((argc - optind) != 2)) {
469 cpu1 = cpu2 = pick_online_cpu();
471 cpu1 = atoi(argv[optind++]);
472 cpu2 = atoi(argv[optind++]);
475 printf("Using %s with ", processes ? "processes" : "threads");
477 if (actions == &pipe_actions)
479 else if (actions == &yield_actions)
484 if (!have_hwcap(PPC_FEATURE_HAS_ALTIVEC))
487 if (!have_hwcap(PPC_FEATURE_HAS_VSX))
490 printf(" on cpus %d/%d touching FP:%s altivec:%s vector:%s vdso:%s\n",
491 cpu1, cpu2, touch_fp ? "yes" : "no", touch_altivec ? "yes" : "no",
492 touch_vector ? "yes" : "no", touch_vdso ? "yes" : "no");
494 /* Create a new process group so we can signal everyone for exit */
495 setpgid(getpid(), getpid());
497 signal(SIGUSR1, sigusr1_handler);
499 actions->setup(cpu1, cpu2);
501 start_fn(actions->thread1, NULL, cpu1);
502 start_fn(actions->thread2, NULL, cpu2);