aboutsummaryrefslogtreecommitdiffstats
path: root/tools/testing/selftests/vm/userfaultfd.c
blob: b619f672131ea787f8211c0706bfed4fec5d641f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
/*
 * Stress userfaultfd syscall.
 *
 *  Copyright (C) 2015  Red Hat, Inc.
 *
 *  This work is licensed under the terms of the GNU GPL, version 2. See
 *  the COPYING file in the top-level directory.
 *
 * This test allocates two virtual areas and bounces the physical
 * memory across the two virtual areas (from area_src to area_dst)
 * using userfaultfd.
 *
 * There are three threads running per CPU:
 *
 * 1) one per-CPU thread takes a per-page pthread_mutex in a random
 *    page of the area_dst (while the physical page may still be in
 *    area_src), and increments a per-page counter in the same page,
 *    and checks its value against a verification region.
 *
 * 2) another per-CPU thread handles the userfaults generated by
 *    thread 1 above. userfaultfd blocking reads or poll() modes are
 *    exercised interleaved.
 *
 * 3) one last per-CPU thread transfers the memory in the background
 *    at maximum bandwidth (if not already transferred by thread
 *    2). Each cpu thread takes cares of transferring a portion of the
 *    area.
 *
 * When all threads of type 3 completed the transfer, one bounce is
 * complete. area_src and area_dst are then swapped. All threads are
 * respawned and so the bounce is immediately restarted in the
 * opposite direction.
 *
 * per-CPU threads 1 by triggering userfaults inside
 * pthread_mutex_lock will also verify the atomicity of the memory
 * transfer (UFFDIO_COPY).
 *
 * The program takes two parameters: the amounts of physical memory in
 * megabytes (MiB) of the area and the number of bounces to execute.
 *
 * # 100MiB 99999 bounces
 * ./userfaultfd 100 99999
 *
 * # 1GiB 99 bounces
 * ./userfaultfd 1000 99
 *
 * # 10MiB-~6GiB 999 bounces, continue forever unless an error triggers
 * while ./userfaultfd $[RANDOM % 6000 + 10] 999; do true; done
 */

#define _GNU_SOURCE
#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <time.h>
#include <signal.h>
#include <poll.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/syscall.h>
#include <sys/ioctl.h>
#include <pthread.h>
#include "../../../../include/uapi/linux/userfaultfd.h"

#ifdef __x86_64__
#define __NR_userfaultfd 323
#elif defined(__i386__)
#define __NR_userfaultfd 359
#elif defined(__powewrpc__)
#define __NR_userfaultfd 364
#else
#error "missing __NR_userfaultfd definition"
#endif

static unsigned long nr_cpus, nr_pages, nr_pages_per_cpu, page_size;

#define BOUNCE_RANDOM		(1<<0)
#define BOUNCE_RACINGFAULTS	(1<<1)
#define BOUNCE_VERIFY		(1<<2)
#define BOUNCE_POLL		(1<<3)
static int bounces;

static unsigned long long *count_verify;
static int uffd, finished, *pipefd;
static char *area_src, *area_dst;
static char *zeropage;
pthread_attr_t attr;

/* pthread_mutex_t starts at page offset 0 */
#define area_mutex(___area, ___nr)					\
	((pthread_mutex_t *) ((___area) + (___nr)*page_size))
/*
 * count is placed in the page after pthread_mutex_t naturally aligned
 * to avoid non alignment faults on non-x86 archs.
 */
#define area_count(___area, ___nr)					\
	((volatile unsigned long long *) ((unsigned long)		\
				 ((___area) + (___nr)*page_size +	\
				  sizeof(pthread_mutex_t) +		\
				  sizeof(unsigned long long) - 1) &	\
				 ~(unsigned long)(sizeof(unsigned long long) \
						  -  1)))

static int my_bcmp(char *str1, char *str2, size_t n)
{
	unsigned long i;
	for (i = 0; i < n; i++)
		if (str1[i] != str2[i])
			return 1;
	return 0;
}

static void *locking_thread(void *arg)
{
	unsigned long cpu = (unsigned long) arg;
	struct random_data rand;
	unsigned long page_nr = *(&(page_nr)); /* uninitialized warning */
	int32_t rand_nr;
	unsigned long long count;
	char randstate[64];
	unsigned int seed;
	time_t start;

	if (bounces & BOUNCE_RANDOM) {
		seed = (unsigned int) time(NULL) - bounces;
		if (!(bounces & BOUNCE_RACINGFAULTS))
			seed += cpu;
		bzero(&rand, sizeof(rand));
		bzero(&randstate, sizeof(randstate));
		if (initstate_r(seed, randstate, sizeof(randstate), &rand))
			fprintf(stderr, "srandom_r error\n"), exit(1);
	} else {
		page_nr = -bounces;
		if (!(bounces & BOUNCE_RACINGFAULTS))
			page_nr += cpu * nr_pages_per_cpu;
	}

	while (!finished) {
		if (bounces & BOUNCE_RANDOM) {
			if (random_r(&rand, &rand_nr))
				fprintf(stderr, "random_r 1 error\n"), exit(1);
			page_nr = rand_nr;
			if (sizeof(page_nr) > sizeof(rand_nr)) {
				if (random_r(&rand, &rand_nr))
					fprintf(stderr, "random_r 2 error\n"), exit(1);
				page_nr |= (((unsigned long) rand_nr) << 16) <<
					   16;
			}
		} else
			page_nr += 1;
		page_nr %= nr_pages;

		start = time(NULL);
		if (bounces & BOUNCE_VERIFY) {
			count = *area_count(area_dst, page_nr);
			if (!count)
				fprintf(stderr,
					"page_nr %lu wrong count %Lu %Lu\n",
					page_nr, count,
					count_verify[page_nr]), exit(1);


			/*
			 * We can't use bcmp (or memcmp) because that
			 * returns 0 erroneously if the memory is
			 * changing under it (even if the end of the
			 * page is never changing and always
			 * different).
			 */
#if 1
			if (!my_bcmp(area_dst + page_nr * page_size, zeropage,
				     page_size))
				fprintf(stderr,
					"my_bcmp page_nr %lu wrong count %Lu %Lu\n",
					page_nr, count,
					count_verify[page_nr]), exit(1);
#else
			unsigned long loops;

			loops = 0;
			/* uncomment the below line to test with mutex */
			/* pthread_mutex_lock(area_mutex(area_dst, page_nr)); */
			while (!bcmp(area_dst + page_nr * page_size, zeropage,
				     page_size)) {
				loops += 1;
				if (loops > 10)
					break;
			}
			/* uncomment below line to test with mutex */
			/* pthread_mutex_unlock(area_mutex(area_dst, page_nr)); */
			if (loops) {
				fprintf(stderr,
					"page_nr %lu all zero thread %lu %p %lu\n",
					page_nr, cpu, area_dst + page_nr * page_size,
					loops);
				if (loops > 10)
					exit(1);
			}
#endif
		}

		pthread_mutex_lock(area_mutex(area_dst, page_nr));
		count = *area_count(area_dst, page_nr);
		if (count != count_verify[page_nr]) {
			fprintf(stderr,
				"page_nr %lu memory corruption %Lu %Lu\n",
				page_nr, count,
				count_verify[page_nr]), exit(1);
		}
		count++;
		*area_count(area_dst, page_nr) = count_verify[page_nr] = count;
		pthread_mutex_unlock(area_mutex(area_dst, page_nr));

		if (time(NULL) - start > 1)
			fprintf(stderr,
				"userfault too slow %ld "
				"possible false positive with overcommit\n",
				time(NULL) - start);
	}

	return NULL;
}

static int copy_page(unsigned long offset)
{
	struct uffdio_copy uffdio_copy;

	if (offset >= nr_pages * page_size)
		fprintf(stderr, "unexpected offset %lu\n",
			offset), exit(1);
	uffdio_copy.dst = (unsigned long) area_dst + offset;
	uffdio_copy.src = (unsigned long) area_src + offset;
	uffdio_copy.len = page_size;
	uffdio_copy.mode = 0;
	uffdio_copy.copy = 0;
	if (ioctl(uffd, UFFDIO_COPY, &uffdio_copy)) {
		/* real retval in ufdio_copy.copy */
		if (uffdio_copy.copy != -EEXIST)
			fprintf(stderr, "UFFDIO_COPY error %Ld\n",
				uffdio_copy.copy), exit(1);
	} else if (uffdio_copy.copy != page_size) {
		fprintf(stderr, "UFFDIO_COPY unexpected copy %Ld\n",
			uffdio_copy.copy), exit(1);
	} else
		return 1;
	return 0;
}

static void *uffd_poll_thread(void *arg)
{
	unsigned long cpu = (unsigned long) arg;
	struct pollfd pollfd[2];
	struct uffd_msg msg;
	int ret;
	unsigned long offset;
	char tmp_chr;
	unsigned long userfaults = 0;

	pollfd[0].fd = uffd;
	pollfd[0].events = POLLIN;
	pollfd[1].fd = pipefd[cpu*2];
	pollfd[1].events = POLLIN;

	for (;;) {
		ret = poll(pollfd, 2, -1);
		if (!ret)
			fprintf(stderr, "poll error %d\n", ret), exit(1);
		if (ret < 0)
			perror("poll"), exit(1);
		if (pollfd[1].revents & POLLIN) {
			if (read(pollfd[1].fd, &tmp_chr, 1) != 1)
				fprintf(stderr, "read pipefd error\n"),
					exit(1);
			break;
		}
		if (!(pollfd[0].revents & POLLIN))
			fprintf(stderr, "pollfd[0].revents %d\n",
				pollfd[0].revents), exit(1);
		ret = read(uffd, &msg, sizeof(msg));
		if (ret < 0) {
			if (errno == EAGAIN)
				continue;
			perror("nonblocking read error"), exit(1);
		}
		if (msg.event != UFFD_EVENT_PAGEFAULT)
			fprintf(stderr, "unexpected msg event %u\n",
				msg.event), exit(1);
		if (msg.arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE)
			fprintf(stderr, "unexpected write fault\n"), exit(1);
		offset = (char *)(unsigned long)msg.arg.pagefault.address -
			 area_dst;
		offset &= ~(page_size-1);
		if (copy_page(offset))
			userfaults++;
	}
	return (void *)userfaults;
}

pthread_mutex_t uffd_read_mutex = PTHREAD_MUTEX_INITIALIZER;

static void *uffd_read_thread(void *arg)
{
	unsigned long *this_cpu_userfaults;
	struct uffd_msg msg;
	unsigned long offset;
	int ret;

	this_cpu_userfaults = (unsigned long *) arg;
	*this_cpu_userfaults = 0;

	pthread_mutex_unlock(&uffd_read_mutex);
	/* from here cancellation is ok */

	for (;;) {
		ret = read(uffd, &msg, sizeof(msg));
		if (ret != sizeof(msg)) {
			if (ret < 0)
				perror("blocking read error"), exit(1);
			else
				fprintf(stderr, "short read\n"), exit(1);
		}
		if (msg.event != UFFD_EVENT_PAGEFAULT)
			fprintf(stderr, "unexpected msg event %u\n",
				msg.event), exit(1);
		if (bounces & BOUNCE_VERIFY &&
		    msg.arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE)
			fprintf(stderr, "unexpected write fault\n"), exit(1);
		offset = (char *)(unsigned long)msg.arg.pagefault.address -
			 area_dst;
		offset &= ~(page_size-1);
		if (copy_page(offset))
			(*this_cpu_userfaults)++;
	}
	return (void *)NULL;
}

static void *background_thread(void *arg)
{
	unsigned long cpu = (unsigned long) arg;
	unsigned long page_nr;

	for (page_nr = cpu * nr_pages_per_cpu;
	     page_nr < (cpu+1) * nr_pages_per_cpu;
	     page_nr++)
		copy_page(page_nr * page_size);

	return NULL;
}

static int stress(unsigned long *userfaults)
{
	unsigned long cpu;
	pthread_t locking_threads[nr_cpus];
	pthread_t uffd_threads[nr_cpus];
	pthread_t background_threads[nr_cpus];
	void **_userfaults = (void **) userfaults;

	finished = 0;
	for (cpu = 0; cpu < nr_cpus; cpu++) {
		if (pthread_create(&locking_threads[cpu], &attr,
				   locking_thread, (void *)cpu))
			return 1;
		if (bounces & BOUNCE_POLL) {
			if (pthread_create(&uffd_threads[cpu], &attr,
					   uffd_poll_thread, (void *)cpu))
				return 1;
		} else {
			if (pthread_create(&uffd_threads[cpu], &attr,
					   uffd_read_thread,
					   &_userfaults[cpu]))
				return 1;
			pthread_mutex_lock(&uffd_read_mutex);
		}
		if (pthread_create(&background_threads[cpu], &attr,
				   background_thread, (void *)cpu))
			return 1;
	}
	for (cpu = 0; cpu < nr_cpus; cpu++)
		if (pthread_join(background_threads[cpu], NULL))
			return 1;

	/*
	 * Be strict and immediately zap area_src, the whole area has
	 * been transferred already by the background treads. The
	 * area_src could then be faulted in in a racy way by still
	 * running uffdio_threads reading zeropages after we zapped
	 * area_src (but they're guaranteed to get -EEXIST from
	 * UFFDIO_COPY without writing zero pages into area_dst
	 * because the background threads already completed).
	 */
	if (madvise(area_src, nr_pages * page_size, MADV_DONTNEED)) {
		perror("madvise");
		return 1;
	}

	for (cpu = 0; cpu < nr_cpus; cpu++) {
		char c;
		if (bounces & BOUNCE_POLL) {
			if (write(pipefd[cpu*2+1], &c, 1) != 1) {
				fprintf(stderr, "pipefd write error\n");
				return 1;
			}
			if (pthread_join(uffd_threads[cpu], &_userfaults[cpu]))
				return 1;
		} else {
			if (pthread_cancel(uffd_threads[cpu]))
				return 1;
			if (pthread_join(uffd_threads[cpu], NULL))
				return 1;
		}
	}

	finished = 1;
	for (cpu = 0; cpu < nr_cpus; cpu++)
		if (pthread_join(locking_threads[cpu], NULL))
			return 1;

	return 0;
}

static int userfaultfd_stress(void)
{
	void *area;
	char *tmp_area;
	unsigned long nr;
	struct uffdio_register uffdio_register;
	struct uffdio_api uffdio_api;
	unsigned long cpu;
	int uffd_flags;
	unsigned long userfaults[nr_cpus];

	if (posix_memalign(&area, page_size, nr_pages * page_size)) {
		fprintf(stderr, "out of memory\n");
		return 1;
	}
	area_src = area;
	if (posix_memalign(&area, page_size, nr_pages * page_size)) {
		fprintf(stderr, "out of memory\n");
		return 1;
	}
	area_dst = area;

	uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
	if (uffd < 0) {
		fprintf(stderr,
			"userfaultfd syscall not available in this kernel\n");
		return 1;
	}
	uffd_flags = fcntl(uffd, F_GETFD, NULL);

	uffdio_api.api = UFFD_API;
	uffdio_api.features = 0;
	if (ioctl(uffd, UFFDIO_API, &uffdio_api)) {
		fprintf(stderr, "UFFDIO_API\n");
		return 1;
	}
	if (uffdio_api.api != UFFD_API) {
		fprintf(stderr, "UFFDIO_API error %Lu\n", uffdio_api.api);
		return 1;
	}

	count_verify = malloc(nr_pages * sizeof(unsigned long long));
	if (!count_verify) {
		perror("count_verify");
		return 1;
	}

	for (nr = 0; nr < nr_pages; nr++) {
		*area_mutex(area_src, nr) = (pthread_mutex_t)
			PTHREAD_MUTEX_INITIALIZER;
		count_verify[nr] = *area_count(area_src, nr) = 1;
	}

	pipefd = malloc(sizeof(int) * nr_cpus * 2);
	if (!pipefd) {
		perror("pipefd");
		return 1;
	}
	for (cpu = 0; cpu < nr_cpus; cpu++) {
		if (pipe2(&pipefd[cpu*2], O_CLOEXEC | O_NONBLOCK)) {
			perror("pipe");
			return 1;
		}
	}

	if (posix_memalign(&area, page_size, page_size)) {
		fprintf(stderr, "out of memory\n");
		return 1;
	}
	zeropage = area;
	bzero(zeropage, page_size);

	pthread_mutex_lock(&uffd_read_mutex);

	pthread_attr_init(&attr);
	pthread_attr_setstacksize(&attr, 16*1024*1024);

	while (bounces--) {
		unsigned long expected_ioctls;

		printf("bounces: %d, mode:", bounces);
		if (bounces & BOUNCE_RANDOM)
			printf(" rnd");
		if (bounces & BOUNCE_RACINGFAULTS)
			printf(" racing");
		if (bounces & BOUNCE_VERIFY)
			printf(" ver");
		if (bounces & BOUNCE_POLL)
			printf(" poll");
		printf(", ");
		fflush(stdout);

		if (bounces & BOUNCE_POLL)
			fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);
		else
			fcntl(uffd, F_SETFL, uffd_flags & ~O_NONBLOCK);

		/* register */
		uffdio_register.range.start = (unsigned long) area_dst;
		uffdio_register.range.len = nr_pages * page_size;
		uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
		if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register)) {
			fprintf(stderr, "register failure\n");
			return 1;
		}
		expected_ioctls = (1 << _UFFDIO_WAKE) |
				  (1 << _UFFDIO_COPY) |
				  (1 << _UFFDIO_ZEROPAGE);
		if ((uffdio_register.ioctls & expected_ioctls) !=
		    expected_ioctls) {
			fprintf(stderr,
				"unexpected missing ioctl for anon memory\n");
			return 1;
		}

		/*
		 * The madvise done previously isn't enough: some
		 * uffd_thread could have read userfaults (one of
		 * those already resolved by the background thread)
		 * and it may be in the process of calling
		 * UFFDIO_COPY. UFFDIO_COPY will read the zapped
		 * area_src and it would map a zero page in it (of
		 * course such a UFFDIO_COPY is perfectly safe as it'd
		 * return -EEXIST). The problem comes at the next
		 * bounce though: that racing UFFDIO_COPY would
		 * generate zeropages in the area_src, so invalidating
		 * the previous MADV_DONTNEED. Without this additional
		 * MADV_DONTNEED those zeropages leftovers in the
		 * area_src would lead to -EEXIST failure during the
		 * next bounce, effectively leaving a zeropage in the
		 * area_dst.
		 *
		 * Try to comment this out madvise to see the memory
		 * corruption being caught pretty quick.
		 *
		 * khugepaged is also inhibited to collapse THP after
		 * MADV_DONTNEED only after the UFFDIO_REGISTER, so it's
		 * required to MADV_DONTNEED here.
		 */
		if (madvise(area_dst, nr_pages * page_size, MADV_DONTNEED)) {
			perror("madvise 2");
			return 1;
		}

		/* bounce pass */
		if (stress(userfaults))
			return 1;

		/* unregister */
		if (ioctl(uffd, UFFDIO_UNREGISTER, &uffdio_register.range)) {
			fprintf(stderr, "register failure\n");
			return 1;
		}

		/* verification */
		if (bounces & BOUNCE_VERIFY) {
			for (nr = 0; nr < nr_pages; nr++) {
				if (my_bcmp(area_dst,
					    area_dst + nr * page_size,
					    sizeof(pthread_mutex_t))) {
					fprintf(stderr,
						"error mutex 2 %lu\n",
						nr);
					bounces = 0;
				}
				if (*area_count(area_dst, nr) != count_verify[nr]) {
					fprintf(stderr,
						"error area_count %Lu %Lu %lu\n",
						*area_count(area_src, nr),
						count_verify[nr],
						nr);
					bounces = 0;
				}
			}
		}

		/* prepare next bounce */
		tmp_area = area_src;
		area_src = area_dst;
		area_dst = tmp_area;

		printf("userfaults:");
		for (cpu = 0; cpu < nr_cpus; cpu++)
			printf(" %lu", userfaults[cpu]);
		printf("\n");
	}

	return 0;
}

int main(int argc, char **argv)
{
	if (argc < 3)
		fprintf(stderr, "Usage: <MiB> <bounces>\n"), exit(1);
	nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
	page_size = sysconf(_SC_PAGE_SIZE);
	if ((unsigned long) area_count(NULL, 0) + sizeof(unsigned long long) >
	    page_size)
		fprintf(stderr, "Impossible to run this test\n"), exit(2);
	nr_pages_per_cpu = atol(argv[1]) * 1024*1024 / page_size /
		nr_cpus;
	if (!nr_pages_per_cpu) {
		fprintf(stderr, "invalid MiB\n");
		fprintf(stderr, "Usage: <MiB> <bounces>\n"), exit(1);
	}
	bounces = atoi(argv[2]);
	if (bounces <= 0) {
		fprintf(stderr, "invalid bounces\n");
		fprintf(stderr, "Usage: <MiB> <bounces>\n"), exit(1);
	}
	nr_pages = nr_pages_per_cpu * nr_cpus;
	printf("nr_pages: %lu, nr_pages_per_cpu: %lu\n",
	       nr_pages, nr_pages_per_cpu);
	return userfaultfd_stress();
}

Privacy Policy