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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Context switch microbenchmark.
4 *
5 * Copyright (C) 2015 Anton Blanchard <[email protected]>, IBM
6 */
7
8#define _GNU_SOURCE
9#include <errno.h>
10#include <sched.h>
11#include <string.h>
12#include <stdio.h>
13#include <unistd.h>
14#include <stdlib.h>
15#include <getopt.h>
16#include <signal.h>
17#include <assert.h>
18#include <pthread.h>
19#include <limits.h>
20#include <sys/time.h>
21#include <sys/syscall.h>
22#include <sys/sysinfo.h>
23#include <sys/types.h>
24#include <sys/shm.h>
25#include <linux/futex.h>
26#ifdef __powerpc__
27#include <altivec.h>
28#endif
29#include "utils.h"
30
31static unsigned int timeout = 30;
32
33static int touch_vdso;
34struct timeval tv;
35
36static int touch_fp = 1;
37double fp;
38
39static int touch_vector = 1;
40vector int a, b, c;
41
42#ifdef __powerpc__
43static int touch_altivec = 1;
44
45/*
46 * Note: LTO (Link Time Optimisation) doesn't play well with this function
47 * attribute. Be very careful enabling LTO for this test.
48 */
49static void __attribute__((__target__("no-vsx"))) altivec_touch_fn(void)
50{
51 c = a + b;
52}
53#endif
54
55static void touch(void)
56{
57 if (touch_vdso)
58 gettimeofday(&tv, NULL);
59
60 if (touch_fp)
61 fp += 0.1;
62
63#ifdef __powerpc__
64 if (touch_altivec)
65 altivec_touch_fn();
66#endif
67
68 if (touch_vector)
69 c = a + b;
70
71 asm volatile("# %0 %1 %2": : "r"(&tv), "r"(&fp), "r"(&c));
72}
73
74static void start_thread_on(void *(*fn)(void *), void *arg, unsigned long cpu)
75{
76 int rc;
77 pthread_t tid;
78 cpu_set_t cpuset;
79 pthread_attr_t attr;
80
81 CPU_ZERO(&cpuset);
82 CPU_SET(cpu, &cpuset);
83
84 rc = pthread_attr_init(&attr);
85 if (rc) {
86 errno = rc;
87 perror("pthread_attr_init");
88 exit(1);
89 }
90
91 rc = pthread_attr_setaffinity_np(&attr, sizeof(cpu_set_t), &cpuset);
92 if (rc) {
93 errno = rc;
94 perror("pthread_attr_setaffinity_np");
95 exit(1);
96 }
97
98 rc = pthread_create(&tid, &attr, fn, arg);
99 if (rc) {
100 errno = rc;
101 perror("pthread_create");
102 exit(1);
103 }
104}
105
106static void start_process_on(void *(*fn)(void *), void *arg, unsigned long cpu)
107{
108 int pid, ncpus;
109 cpu_set_t *cpuset;
110 size_t size;
111
112 pid = fork();
113 if (pid == -1) {
114 perror("fork");
115 exit(1);
116 }
117
118 if (pid)
119 return;
120
121 ncpus = get_nprocs();
122 size = CPU_ALLOC_SIZE(ncpus);
123 cpuset = CPU_ALLOC(ncpus);
124 if (!cpuset) {
125 perror("malloc");
126 exit(1);
127 }
128 CPU_ZERO_S(size, cpuset);
129 CPU_SET_S(cpu, size, cpuset);
130
131 if (sched_setaffinity(0, size, cpuset)) {
132 perror("sched_setaffinity");
133 CPU_FREE(cpuset);
134 exit(1);
135 }
136
137 CPU_FREE(cpuset);
138 fn(arg);
139
140 exit(0);
141}
142
143static unsigned long iterations;
144static unsigned long iterations_prev;
145
146static void sigalrm_handler(int junk)
147{
148 unsigned long i = iterations;
149
150 printf("%ld\n", i - iterations_prev);
151 iterations_prev = i;
152
153 if (--timeout == 0)
154 kill(0, SIGUSR1);
155
156 alarm(1);
157}
158
159static void sigusr1_handler(int junk)
160{
161 exit(0);
162}
163
164struct actions {
165 void (*setup)(int, int);
166 void *(*thread1)(void *);
167 void *(*thread2)(void *);
168};
169
170#define READ 0
171#define WRITE 1
172
173static int pipe_fd1[2];
174static int pipe_fd2[2];
175
176static void pipe_setup(int cpu1, int cpu2)
177{
178 if (pipe(pipe_fd1) || pipe(pipe_fd2))
179 exit(1);
180}
181
182static void *pipe_thread1(void *arg)
183{
184 signal(SIGALRM, sigalrm_handler);
185 alarm(1);
186
187 while (1) {
188 assert(read(pipe_fd1[READ], &c, 1) == 1);
189 touch();
190
191 assert(write(pipe_fd2[WRITE], &c, 1) == 1);
192 touch();
193
194 iterations += 2;
195 }
196
197 return NULL;
198}
199
200static void *pipe_thread2(void *arg)
201{
202 while (1) {
203 assert(write(pipe_fd1[WRITE], &c, 1) == 1);
204 touch();
205
206 assert(read(pipe_fd2[READ], &c, 1) == 1);
207 touch();
208 }
209
210 return NULL;
211}
212
213static struct actions pipe_actions = {
214 .setup = pipe_setup,
215 .thread1 = pipe_thread1,
216 .thread2 = pipe_thread2,
217};
218
219static void yield_setup(int cpu1, int cpu2)
220{
221 if (cpu1 != cpu2) {
222 fprintf(stderr, "Both threads must be on the same CPU for yield test\n");
223 exit(1);
224 }
225}
226
227static void *yield_thread1(void *arg)
228{
229 signal(SIGALRM, sigalrm_handler);
230 alarm(1);
231
232 while (1) {
233 sched_yield();
234 touch();
235
236 iterations += 2;
237 }
238
239 return NULL;
240}
241
242static void *yield_thread2(void *arg)
243{
244 while (1) {
245 sched_yield();
246 touch();
247 }
248
249 return NULL;
250}
251
252static struct actions yield_actions = {
253 .setup = yield_setup,
254 .thread1 = yield_thread1,
255 .thread2 = yield_thread2,
256};
257
258static long sys_futex(void *addr1, int op, int val1, struct timespec *timeout,
259 void *addr2, int val3)
260{
261 return syscall(SYS_futex, addr1, op, val1, timeout, addr2, val3);
262}
263
264static unsigned long cmpxchg(unsigned long *p, unsigned long expected,
265 unsigned long desired)
266{
267 unsigned long exp = expected;
268
269 __atomic_compare_exchange_n(p, &exp, desired, 0,
270 __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
271 return exp;
272}
273
274static unsigned long xchg(unsigned long *p, unsigned long val)
275{
276 return __atomic_exchange_n(p, val, __ATOMIC_SEQ_CST);
277}
278
279static int processes;
280
281static int mutex_lock(unsigned long *m)
282{
283 int c;
284 int flags = FUTEX_WAIT;
285 if (!processes)
286 flags |= FUTEX_PRIVATE_FLAG;
287
288 c = cmpxchg(m, 0, 1);
289 if (!c)
290 return 0;
291
292 if (c == 1)
293 c = xchg(m, 2);
294
295 while (c) {
296 sys_futex(m, flags, 2, NULL, NULL, 0);
297 c = xchg(m, 2);
298 }
299
300 return 0;
301}
302
303static int mutex_unlock(unsigned long *m)
304{
305 int flags = FUTEX_WAKE;
306 if (!processes)
307 flags |= FUTEX_PRIVATE_FLAG;
308
309 if (*m == 2)
310 *m = 0;
311 else if (xchg(m, 0) == 1)
312 return 0;
313
314 sys_futex(m, flags, 1, NULL, NULL, 0);
315
316 return 0;
317}
318
319static unsigned long *m1, *m2;
320
321static void futex_setup(int cpu1, int cpu2)
322{
323 if (!processes) {
324 static unsigned long _m1, _m2;
325 m1 = &_m1;
326 m2 = &_m2;
327 } else {
328 int shmid;
329 void *shmaddr;
330
331 shmid = shmget(IPC_PRIVATE, getpagesize(), SHM_R | SHM_W);
332 if (shmid < 0) {
333 perror("shmget");
334 exit(1);
335 }
336
337 shmaddr = shmat(shmid, NULL, 0);
338 if (shmaddr == (char *)-1) {
339 perror("shmat");
340 shmctl(shmid, IPC_RMID, NULL);
341 exit(1);
342 }
343
344 shmctl(shmid, IPC_RMID, NULL);
345
346 m1 = shmaddr;
347 m2 = shmaddr + sizeof(*m1);
348 }
349
350 *m1 = 0;
351 *m2 = 0;
352
353 mutex_lock(m1);
354 mutex_lock(m2);
355}
356
357static void *futex_thread1(void *arg)
358{
359 signal(SIGALRM, sigalrm_handler);
360 alarm(1);
361
362 while (1) {
363 mutex_lock(m2);
364 mutex_unlock(m1);
365
366 iterations += 2;
367 }
368
369 return NULL;
370}
371
372static void *futex_thread2(void *arg)
373{
374 while (1) {
375 mutex_unlock(m2);
376 mutex_lock(m1);
377 }
378
379 return NULL;
380}
381
382static struct actions futex_actions = {
383 .setup = futex_setup,
384 .thread1 = futex_thread1,
385 .thread2 = futex_thread2,
386};
387
388static 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 },
394#ifdef __powerpc__
395 { "no-altivec", no_argument, &touch_altivec, 0 },
396#endif
397 { "no-vector", no_argument, &touch_vector, 0 },
398 { 0, },
399};
400
401static void usage(void)
402{
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");
409#ifdef __powerpc__
410 fprintf(stderr, "\t\t--no-altivec\tDon't touch altivec\n");
411#endif
412 fprintf(stderr, "\t\t--no-vector\tDon't touch vector\n");
413}
414
415int main(int argc, char *argv[])
416{
417 signed char c;
418 struct actions *actions = &yield_actions;
419 int cpu1;
420 int cpu2;
421 static void (*start_fn)(void *(*fn)(void *), void *arg, unsigned long cpu);
422
423 while (1) {
424 int option_index = 0;
425
426 c = getopt_long(argc, argv, "", options, &option_index);
427
428 if (c == -1)
429 break;
430
431 switch (c) {
432 case 0:
433 if (options[option_index].flag != 0)
434 break;
435
436 usage();
437 exit(1);
438 break;
439
440 case 't':
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;
447 } else {
448 usage();
449 exit(1);
450 }
451 break;
452
453 case 's':
454 timeout = atoi(optarg);
455 break;
456
457 default:
458 usage();
459 exit(1);
460 }
461 }
462
463 if (processes)
464 start_fn = start_process_on;
465 else
466 start_fn = start_thread_on;
467
468 if (((argc - optind) != 2)) {
469 cpu1 = cpu2 = pick_online_cpu();
470 } else {
471 cpu1 = atoi(argv[optind++]);
472 cpu2 = atoi(argv[optind++]);
473 }
474
475 printf("Using %s with ", processes ? "processes" : "threads");
476
477 if (actions == &pipe_actions)
478 printf("pipe");
479 else if (actions == &yield_actions)
480 printf("yield");
481 else
482 printf("futex");
483
484 if (!have_hwcap(PPC_FEATURE_HAS_ALTIVEC))
485 touch_altivec = 0;
486
487 if (!have_hwcap(PPC_FEATURE_HAS_VSX))
488 touch_vector = 0;
489
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");
493
494 /* Create a new process group so we can signal everyone for exit */
495 setpgid(getpid(), getpid());
496
497 signal(SIGUSR1, sigusr1_handler);
498
499 actions->setup(cpu1, cpu2);
500
501 start_fn(actions->thread1, NULL, cpu1);
502 start_fn(actions->thread2, NULL, cpu2);
503
504 while (1)
505 sleep(3600);
506
507 return 0;
508}