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Linux/tools/testing/selftests/powerpc/benchmarks/context_switch.c

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  1 /*
  2  * Context switch microbenchmark.
  3  *
  4  * Copyright (C) 2015 Anton Blanchard <anton@au.ibm.com>, IBM
  5  *
  6  * This program is free software; you can redistribute it and/or
  7  * modify it under the terms of the GNU General Public License
  8  * as published by the Free Software Foundation; either version
  9  * 2 of the License, or (at your option) any later version.
 10  */
 11 
 12 #define _GNU_SOURCE
 13 #include <sched.h>
 14 #include <string.h>
 15 #include <stdio.h>
 16 #include <unistd.h>
 17 #include <stdlib.h>
 18 #include <getopt.h>
 19 #include <signal.h>
 20 #include <assert.h>
 21 #include <pthread.h>
 22 #include <limits.h>
 23 #include <sys/time.h>
 24 #include <sys/syscall.h>
 25 #include <sys/types.h>
 26 #include <sys/shm.h>
 27 #include <linux/futex.h>
 28 #ifdef __powerpc__
 29 #include <altivec.h>
 30 #endif
 31 #include "utils.h"
 32 
 33 static unsigned int timeout = 30;
 34 
 35 static int touch_vdso;
 36 struct timeval tv;
 37 
 38 static int touch_fp = 1;
 39 double fp;
 40 
 41 static int touch_vector = 1;
 42 vector int a, b, c;
 43 
 44 #ifdef __powerpc__
 45 static int touch_altivec = 1;
 46 
 47 /*
 48  * Note: LTO (Link Time Optimisation) doesn't play well with this function
 49  * attribute. Be very careful enabling LTO for this test.
 50  */
 51 static void __attribute__((__target__("no-vsx"))) altivec_touch_fn(void)
 52 {
 53         c = a + b;
 54 }
 55 #endif
 56 
 57 static void touch(void)
 58 {
 59         if (touch_vdso)
 60                 gettimeofday(&tv, NULL);
 61 
 62         if (touch_fp)
 63                 fp += 0.1;
 64 
 65 #ifdef __powerpc__
 66         if (touch_altivec)
 67                 altivec_touch_fn();
 68 #endif
 69 
 70         if (touch_vector)
 71                 c = a + b;
 72 
 73         asm volatile("# %0 %1 %2": : "r"(&tv), "r"(&fp), "r"(&c));
 74 }
 75 
 76 static void start_thread_on(void *(*fn)(void *), void *arg, unsigned long cpu)
 77 {
 78         pthread_t tid;
 79         cpu_set_t cpuset;
 80         pthread_attr_t attr;
 81 
 82         CPU_ZERO(&cpuset);
 83         CPU_SET(cpu, &cpuset);
 84 
 85         pthread_attr_init(&attr);
 86 
 87         if (pthread_attr_setaffinity_np(&attr, sizeof(cpu_set_t), &cpuset)) {
 88                 perror("pthread_attr_setaffinity_np");
 89                 exit(1);
 90         }
 91 
 92         if (pthread_create(&tid, &attr, fn, arg)) {
 93                 perror("pthread_create");
 94                 exit(1);
 95         }
 96 }
 97 
 98 static void start_process_on(void *(*fn)(void *), void *arg, unsigned long cpu)
 99 {
100         int pid;
101         cpu_set_t cpuset;
102 
103         pid = fork();
104         if (pid == -1) {
105                 perror("fork");
106                 exit(1);
107         }
108 
109         if (pid)
110                 return;
111 
112         CPU_ZERO(&cpuset);
113         CPU_SET(cpu, &cpuset);
114 
115         if (sched_setaffinity(0, sizeof(cpuset), &cpuset)) {
116                 perror("sched_setaffinity");
117                 exit(1);
118         }
119 
120         fn(arg);
121 
122         exit(0);
123 }
124 
125 static unsigned long iterations;
126 static unsigned long iterations_prev;
127 
128 static void sigalrm_handler(int junk)
129 {
130         unsigned long i = iterations;
131 
132         printf("%ld\n", i - iterations_prev);
133         iterations_prev = i;
134 
135         if (--timeout == 0)
136                 kill(0, SIGUSR1);
137 
138         alarm(1);
139 }
140 
141 static void sigusr1_handler(int junk)
142 {
143         exit(0);
144 }
145 
146 struct actions {
147         void (*setup)(int, int);
148         void *(*thread1)(void *);
149         void *(*thread2)(void *);
150 };
151 
152 #define READ 0
153 #define WRITE 1
154 
155 static int pipe_fd1[2];
156 static int pipe_fd2[2];
157 
158 static void pipe_setup(int cpu1, int cpu2)
159 {
160         if (pipe(pipe_fd1) || pipe(pipe_fd2))
161                 exit(1);
162 }
163 
164 static void *pipe_thread1(void *arg)
165 {
166         signal(SIGALRM, sigalrm_handler);
167         alarm(1);
168 
169         while (1) {
170                 assert(read(pipe_fd1[READ], &c, 1) == 1);
171                 touch();
172 
173                 assert(write(pipe_fd2[WRITE], &c, 1) == 1);
174                 touch();
175 
176                 iterations += 2;
177         }
178 
179         return NULL;
180 }
181 
182 static void *pipe_thread2(void *arg)
183 {
184         while (1) {
185                 assert(write(pipe_fd1[WRITE], &c, 1) == 1);
186                 touch();
187 
188                 assert(read(pipe_fd2[READ], &c, 1) == 1);
189                 touch();
190         }
191 
192         return NULL;
193 }
194 
195 static struct actions pipe_actions = {
196         .setup = pipe_setup,
197         .thread1 = pipe_thread1,
198         .thread2 = pipe_thread2,
199 };
200 
201 static void yield_setup(int cpu1, int cpu2)
202 {
203         if (cpu1 != cpu2) {
204                 fprintf(stderr, "Both threads must be on the same CPU for yield test\n");
205                 exit(1);
206         }
207 }
208 
209 static void *yield_thread1(void *arg)
210 {
211         signal(SIGALRM, sigalrm_handler);
212         alarm(1);
213 
214         while (1) {
215                 sched_yield();
216                 touch();
217 
218                 iterations += 2;
219         }
220 
221         return NULL;
222 }
223 
224 static void *yield_thread2(void *arg)
225 {
226         while (1) {
227                 sched_yield();
228                 touch();
229         }
230 
231         return NULL;
232 }
233 
234 static struct actions yield_actions = {
235         .setup = yield_setup,
236         .thread1 = yield_thread1,
237         .thread2 = yield_thread2,
238 };
239 
240 static long sys_futex(void *addr1, int op, int val1, struct timespec *timeout,
241                       void *addr2, int val3)
242 {
243         return syscall(SYS_futex, addr1, op, val1, timeout, addr2, val3);
244 }
245 
246 static unsigned long cmpxchg(unsigned long *p, unsigned long expected,
247                              unsigned long desired)
248 {
249         unsigned long exp = expected;
250 
251         __atomic_compare_exchange_n(p, &exp, desired, 0,
252                                     __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
253         return exp;
254 }
255 
256 static unsigned long xchg(unsigned long *p, unsigned long val)
257 {
258         return __atomic_exchange_n(p, val, __ATOMIC_SEQ_CST);
259 }
260 
261 static int processes;
262 
263 static int mutex_lock(unsigned long *m)
264 {
265         int c;
266         int flags = FUTEX_WAIT;
267         if (!processes)
268                 flags |= FUTEX_PRIVATE_FLAG;
269 
270         c = cmpxchg(m, 0, 1);
271         if (!c)
272                 return 0;
273 
274         if (c == 1)
275                 c = xchg(m, 2);
276 
277         while (c) {
278                 sys_futex(m, flags, 2, NULL, NULL, 0);
279                 c = xchg(m, 2);
280         }
281 
282         return 0;
283 }
284 
285 static int mutex_unlock(unsigned long *m)
286 {
287         int flags = FUTEX_WAKE;
288         if (!processes)
289                 flags |= FUTEX_PRIVATE_FLAG;
290 
291         if (*m == 2)
292                 *m = 0;
293         else if (xchg(m, 0) == 1)
294                 return 0;
295 
296         sys_futex(m, flags, 1, NULL, NULL, 0);
297 
298         return 0;
299 }
300 
301 static unsigned long *m1, *m2;
302 
303 static void futex_setup(int cpu1, int cpu2)
304 {
305         if (!processes) {
306                 static unsigned long _m1, _m2;
307                 m1 = &_m1;
308                 m2 = &_m2;
309         } else {
310                 int shmid;
311                 void *shmaddr;
312 
313                 shmid = shmget(IPC_PRIVATE, getpagesize(), SHM_R | SHM_W);
314                 if (shmid < 0) {
315                         perror("shmget");
316                         exit(1);
317                 }
318 
319                 shmaddr = shmat(shmid, NULL, 0);
320                 if (shmaddr == (char *)-1) {
321                         perror("shmat");
322                         shmctl(shmid, IPC_RMID, NULL);
323                         exit(1);
324                 }
325 
326                 shmctl(shmid, IPC_RMID, NULL);
327 
328                 m1 = shmaddr;
329                 m2 = shmaddr + sizeof(*m1);
330         }
331 
332         *m1 = 0;
333         *m2 = 0;
334 
335         mutex_lock(m1);
336         mutex_lock(m2);
337 }
338 
339 static void *futex_thread1(void *arg)
340 {
341         signal(SIGALRM, sigalrm_handler);
342         alarm(1);
343 
344         while (1) {
345                 mutex_lock(m2);
346                 mutex_unlock(m1);
347 
348                 iterations += 2;
349         }
350 
351         return NULL;
352 }
353 
354 static void *futex_thread2(void *arg)
355 {
356         while (1) {
357                 mutex_unlock(m2);
358                 mutex_lock(m1);
359         }
360 
361         return NULL;
362 }
363 
364 static struct actions futex_actions = {
365         .setup = futex_setup,
366         .thread1 = futex_thread1,
367         .thread2 = futex_thread2,
368 };
369 
370 static struct option options[] = {
371         { "test", required_argument, 0, 't' },
372         { "process", no_argument, &processes, 1 },
373         { "timeout", required_argument, 0, 's' },
374         { "vdso", no_argument, &touch_vdso, 1 },
375         { "no-fp", no_argument, &touch_fp, 0 },
376 #ifdef __powerpc__
377         { "no-altivec", no_argument, &touch_altivec, 0 },
378 #endif
379         { "no-vector", no_argument, &touch_vector, 0 },
380         { 0, },
381 };
382 
383 static void usage(void)
384 {
385         fprintf(stderr, "Usage: context_switch2 <options> CPU1 CPU2\n\n");
386         fprintf(stderr, "\t\t--test=X\tpipe, futex or yield (default)\n");
387         fprintf(stderr, "\t\t--process\tUse processes (default threads)\n");
388         fprintf(stderr, "\t\t--timeout=X\tDuration in seconds to run (default 30)\n");
389         fprintf(stderr, "\t\t--vdso\t\ttouch VDSO\n");
390         fprintf(stderr, "\t\t--no-fp\t\tDon't touch FP\n");
391 #ifdef __powerpc__
392         fprintf(stderr, "\t\t--no-altivec\tDon't touch altivec\n");
393 #endif
394         fprintf(stderr, "\t\t--no-vector\tDon't touch vector\n");
395 }
396 
397 int main(int argc, char *argv[])
398 {
399         signed char c;
400         struct actions *actions = &yield_actions;
401         int cpu1;
402         int cpu2;
403         static void (*start_fn)(void *(*fn)(void *), void *arg, unsigned long cpu);
404 
405         while (1) {
406                 int option_index = 0;
407 
408                 c = getopt_long(argc, argv, "", options, &option_index);
409 
410                 if (c == -1)
411                         break;
412 
413                 switch (c) {
414                 case 0:
415                         if (options[option_index].flag != 0)
416                                 break;
417 
418                         usage();
419                         exit(1);
420                         break;
421 
422                 case 't':
423                         if (!strcmp(optarg, "pipe")) {
424                                 actions = &pipe_actions;
425                         } else if (!strcmp(optarg, "yield")) {
426                                 actions = &yield_actions;
427                         } else if (!strcmp(optarg, "futex")) {
428                                 actions = &futex_actions;
429                         } else {
430                                 usage();
431                                 exit(1);
432                         }
433                         break;
434 
435                 case 's':
436                         timeout = atoi(optarg);
437                         break;
438 
439                 default:
440                         usage();
441                         exit(1);
442                 }
443         }
444 
445         if (processes)
446                 start_fn = start_process_on;
447         else
448                 start_fn = start_thread_on;
449 
450         if (((argc - optind) != 2)) {
451                 cpu1 = cpu2 = pick_online_cpu();
452         } else {
453                 cpu1 = atoi(argv[optind++]);
454                 cpu2 = atoi(argv[optind++]);
455         }
456 
457         printf("Using %s with ", processes ? "processes" : "threads");
458 
459         if (actions == &pipe_actions)
460                 printf("pipe");
461         else if (actions == &yield_actions)
462                 printf("yield");
463         else
464                 printf("futex");
465 
466         printf(" on cpus %d/%d touching FP:%s altivec:%s vector:%s vdso:%s\n",
467                cpu1, cpu2, touch_fp ?  "yes" : "no", touch_altivec ? "yes" : "no",
468                touch_vector ? "yes" : "no", touch_vdso ? "yes" : "no");
469 
470         /* Create a new process group so we can signal everyone for exit */
471         setpgid(getpid(), getpid());
472 
473         signal(SIGUSR1, sigusr1_handler);
474 
475         actions->setup(cpu1, cpu2);
476 
477         start_fn(actions->thread1, NULL, cpu1);
478         start_fn(actions->thread2, NULL, cpu2);
479 
480         while (1)
481                 sleep(3600);
482 
483         return 0;
484 }
485 

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