2 * Stress userfaultfd syscall.
4 * Copyright (C) 2015 Red Hat, Inc.
6 * This work is licensed under the terms of the GNU GPL, version 2. See
7 * the COPYING file in the top-level directory.
9 * This test allocates two virtual areas and bounces the physical
10 * memory across the two virtual areas (from area_src to area_dst)
13 * There are three threads running per CPU:
15 * 1) one per-CPU thread takes a per-page pthread_mutex in a random
16 * page of the area_dst (while the physical page may still be in
17 * area_src), and increments a per-page counter in the same page,
18 * and checks its value against a verification region.
20 * 2) another per-CPU thread handles the userfaults generated by
21 * thread 1 above. userfaultfd blocking reads or poll() modes are
22 * exercised interleaved.
24 * 3) one last per-CPU thread transfers the memory in the background
25 * at maximum bandwidth (if not already transferred by thread
26 * 2). Each cpu thread takes cares of transferring a portion of the
29 * When all threads of type 3 completed the transfer, one bounce is
30 * complete. area_src and area_dst are then swapped. All threads are
31 * respawned and so the bounce is immediately restarted in the
34 * per-CPU threads 1 by triggering userfaults inside
35 * pthread_mutex_lock will also verify the atomicity of the memory
36 * transfer (UFFDIO_COPY).
38 * The program takes two parameters: the amounts of physical memory in
39 * megabytes (MiB) of the area and the number of bounces to execute.
41 * # 100MiB 99999 bounces
42 * ./userfaultfd 100 99999
45 * ./userfaultfd 1000 99
47 * # 10MiB-~6GiB 999 bounces, continue forever unless an error triggers
48 * while ./userfaultfd $[RANDOM % 6000 + 10] 999; do true; done
56 #include <sys/types.h>
64 #include <sys/syscall.h>
65 #include <sys/ioctl.h>
67 #include "../../../../include/uapi/linux/userfaultfd.h"
70 #define __NR_userfaultfd 323
71 #elif defined(__i386__)
72 #define __NR_userfaultfd 374
73 #elif defined(__powewrpc__)
74 #define __NR_userfaultfd 364
76 #error "missing __NR_userfaultfd definition"
79 static unsigned long nr_cpus, nr_pages, nr_pages_per_cpu, page_size;
81 #define BOUNCE_RANDOM (1<<0)
82 #define BOUNCE_RACINGFAULTS (1<<1)
83 #define BOUNCE_VERIFY (1<<2)
84 #define BOUNCE_POLL (1<<3)
87 static unsigned long long *count_verify;
88 static int uffd, finished, *pipefd;
89 static char *area_src, *area_dst;
90 static char *zeropage;
93 /* pthread_mutex_t starts at page offset 0 */
94 #define area_mutex(___area, ___nr) \
95 ((pthread_mutex_t *) ((___area) + (___nr)*page_size))
97 * count is placed in the page after pthread_mutex_t naturally aligned
98 * to avoid non alignment faults on non-x86 archs.
100 #define area_count(___area, ___nr) \
101 ((volatile unsigned long long *) ((unsigned long) \
102 ((___area) + (___nr)*page_size + \
103 sizeof(pthread_mutex_t) + \
104 sizeof(unsigned long long) - 1) & \
105 ~(unsigned long)(sizeof(unsigned long long) \
108 static int my_bcmp(char *str1, char *str2, size_t n)
111 for (i = 0; i < n; i++)
112 if (str1[i] != str2[i])
117 static void *locking_thread(void *arg)
119 unsigned long cpu = (unsigned long) arg;
120 struct random_data rand;
121 unsigned long page_nr = *(&(page_nr)); /* uninitialized warning */
123 unsigned long long count;
128 if (bounces & BOUNCE_RANDOM) {
129 seed = (unsigned int) time(NULL) - bounces;
130 if (!(bounces & BOUNCE_RACINGFAULTS))
132 bzero(&rand, sizeof(rand));
133 bzero(&randstate, sizeof(randstate));
134 if (initstate_r(seed, randstate, sizeof(randstate), &rand))
135 fprintf(stderr, "srandom_r error\n"), exit(1);
138 if (!(bounces & BOUNCE_RACINGFAULTS))
139 page_nr += cpu * nr_pages_per_cpu;
143 if (bounces & BOUNCE_RANDOM) {
144 if (random_r(&rand, &rand_nr))
145 fprintf(stderr, "random_r 1 error\n"), exit(1);
147 if (sizeof(page_nr) > sizeof(rand_nr)) {
148 if (random_r(&rand, &rand_nr))
149 fprintf(stderr, "random_r 2 error\n"), exit(1);
150 page_nr |= ((unsigned long) rand_nr) << 32;
157 if (bounces & BOUNCE_VERIFY) {
158 count = *area_count(area_dst, page_nr);
161 "page_nr %lu wrong count %Lu %Lu\n",
163 count_verify[page_nr]), exit(1);
167 * We can't use bcmp (or memcmp) because that
168 * returns 0 erroneously if the memory is
169 * changing under it (even if the end of the
170 * page is never changing and always
174 if (!my_bcmp(area_dst + page_nr * page_size, zeropage,
177 "my_bcmp page_nr %lu wrong count %Lu %Lu\n",
179 count_verify[page_nr]), exit(1);
184 /* uncomment the below line to test with mutex */
185 /* pthread_mutex_lock(area_mutex(area_dst, page_nr)); */
186 while (!bcmp(area_dst + page_nr * page_size, zeropage,
192 /* uncomment below line to test with mutex */
193 /* pthread_mutex_unlock(area_mutex(area_dst, page_nr)); */
196 "page_nr %lu all zero thread %lu %p %lu\n",
197 page_nr, cpu, area_dst + page_nr * page_size,
205 pthread_mutex_lock(area_mutex(area_dst, page_nr));
206 count = *area_count(area_dst, page_nr);
207 if (count != count_verify[page_nr]) {
209 "page_nr %lu memory corruption %Lu %Lu\n",
211 count_verify[page_nr]), exit(1);
214 *area_count(area_dst, page_nr) = count_verify[page_nr] = count;
215 pthread_mutex_unlock(area_mutex(area_dst, page_nr));
217 if (time(NULL) - start > 1)
219 "userfault too slow %ld "
220 "possible false positive with overcommit\n",
227 static int copy_page(unsigned long offset)
229 struct uffdio_copy uffdio_copy;
231 if (offset >= nr_pages * page_size)
232 fprintf(stderr, "unexpected offset %lu\n",
234 uffdio_copy.dst = (unsigned long) area_dst + offset;
235 uffdio_copy.src = (unsigned long) area_src + offset;
236 uffdio_copy.len = page_size;
237 uffdio_copy.mode = 0;
238 uffdio_copy.copy = 0;
239 if (ioctl(uffd, UFFDIO_COPY, &uffdio_copy)) {
240 /* real retval in ufdio_copy.copy */
241 if (uffdio_copy.copy != -EEXIST)
242 fprintf(stderr, "UFFDIO_COPY error %Ld\n",
243 uffdio_copy.copy), exit(1);
244 } else if (uffdio_copy.copy != page_size) {
245 fprintf(stderr, "UFFDIO_COPY unexpected copy %Ld\n",
246 uffdio_copy.copy), exit(1);
252 static void *uffd_poll_thread(void *arg)
254 unsigned long cpu = (unsigned long) arg;
255 struct pollfd pollfd[2];
258 unsigned long offset;
260 unsigned long userfaults = 0;
263 pollfd[0].events = POLLIN;
264 pollfd[1].fd = pipefd[cpu*2];
265 pollfd[1].events = POLLIN;
268 ret = poll(pollfd, 2, -1);
270 fprintf(stderr, "poll error %d\n", ret), exit(1);
272 perror("poll"), exit(1);
273 if (pollfd[1].revents & POLLIN) {
274 if (read(pollfd[1].fd, &tmp_chr, 1) != 1)
275 fprintf(stderr, "read pipefd error\n"),
279 if (!(pollfd[0].revents & POLLIN))
280 fprintf(stderr, "pollfd[0].revents %d\n",
281 pollfd[0].revents), exit(1);
282 ret = read(uffd, &msg, sizeof(msg));
286 perror("nonblocking read error"), exit(1);
288 if (msg.event != UFFD_EVENT_PAGEFAULT)
289 fprintf(stderr, "unexpected msg event %u\n",
291 if (msg.arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE)
292 fprintf(stderr, "unexpected write fault\n"), exit(1);
293 offset = (char *)msg.arg.pagefault.address - area_dst;
294 offset &= ~(page_size-1);
295 if (copy_page(offset))
298 return (void *)userfaults;
301 pthread_mutex_t uffd_read_mutex = PTHREAD_MUTEX_INITIALIZER;
303 static void *uffd_read_thread(void *arg)
305 unsigned long *this_cpu_userfaults;
307 unsigned long offset;
310 this_cpu_userfaults = (unsigned long *) arg;
311 *this_cpu_userfaults = 0;
313 pthread_mutex_unlock(&uffd_read_mutex);
314 /* from here cancellation is ok */
317 ret = read(uffd, &msg, sizeof(msg));
318 if (ret != sizeof(msg)) {
320 perror("blocking read error"), exit(1);
322 fprintf(stderr, "short read\n"), exit(1);
324 if (msg.event != UFFD_EVENT_PAGEFAULT)
325 fprintf(stderr, "unexpected msg event %u\n",
327 if (bounces & BOUNCE_VERIFY &&
328 msg.arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE)
329 fprintf(stderr, "unexpected write fault\n"), exit(1);
330 offset = (char *)msg.arg.pagefault.address - area_dst;
331 offset &= ~(page_size-1);
332 if (copy_page(offset))
333 (*this_cpu_userfaults)++;
338 static void *background_thread(void *arg)
340 unsigned long cpu = (unsigned long) arg;
341 unsigned long page_nr;
343 for (page_nr = cpu * nr_pages_per_cpu;
344 page_nr < (cpu+1) * nr_pages_per_cpu;
346 copy_page(page_nr * page_size);
351 static int stress(unsigned long *userfaults)
354 pthread_t locking_threads[nr_cpus];
355 pthread_t uffd_threads[nr_cpus];
356 pthread_t background_threads[nr_cpus];
357 void **_userfaults = (void **) userfaults;
360 for (cpu = 0; cpu < nr_cpus; cpu++) {
361 if (pthread_create(&locking_threads[cpu], &attr,
362 locking_thread, (void *)cpu))
364 if (bounces & BOUNCE_POLL) {
365 if (pthread_create(&uffd_threads[cpu], &attr,
366 uffd_poll_thread, (void *)cpu))
369 if (pthread_create(&uffd_threads[cpu], &attr,
373 pthread_mutex_lock(&uffd_read_mutex);
375 if (pthread_create(&background_threads[cpu], &attr,
376 background_thread, (void *)cpu))
379 for (cpu = 0; cpu < nr_cpus; cpu++)
380 if (pthread_join(background_threads[cpu], NULL))
384 * Be strict and immediately zap area_src, the whole area has
385 * been transferred already by the background treads. The
386 * area_src could then be faulted in in a racy way by still
387 * running uffdio_threads reading zeropages after we zapped
388 * area_src (but they're guaranteed to get -EEXIST from
389 * UFFDIO_COPY without writing zero pages into area_dst
390 * because the background threads already completed).
392 if (madvise(area_src, nr_pages * page_size, MADV_DONTNEED)) {
397 for (cpu = 0; cpu < nr_cpus; cpu++) {
399 if (bounces & BOUNCE_POLL) {
400 if (write(pipefd[cpu*2+1], &c, 1) != 1) {
401 fprintf(stderr, "pipefd write error\n");
404 if (pthread_join(uffd_threads[cpu], &_userfaults[cpu]))
407 if (pthread_cancel(uffd_threads[cpu]))
409 if (pthread_join(uffd_threads[cpu], NULL))
415 for (cpu = 0; cpu < nr_cpus; cpu++)
416 if (pthread_join(locking_threads[cpu], NULL))
422 static int userfaultfd_stress(void)
427 struct uffdio_register uffdio_register;
428 struct uffdio_api uffdio_api;
431 unsigned long userfaults[nr_cpus];
433 if (posix_memalign(&area, page_size, nr_pages * page_size)) {
434 fprintf(stderr, "out of memory\n");
438 if (posix_memalign(&area, page_size, nr_pages * page_size)) {
439 fprintf(stderr, "out of memory\n");
444 uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
447 "userfaultfd syscall not available in this kernel\n");
450 uffd_flags = fcntl(uffd, F_GETFD, NULL);
452 uffdio_api.api = UFFD_API;
453 uffdio_api.features = 0;
454 if (ioctl(uffd, UFFDIO_API, &uffdio_api)) {
455 fprintf(stderr, "UFFDIO_API\n");
458 if (uffdio_api.api != UFFD_API) {
459 fprintf(stderr, "UFFDIO_API error %Lu\n", uffdio_api.api);
463 count_verify = malloc(nr_pages * sizeof(unsigned long long));
465 perror("count_verify");
469 for (nr = 0; nr < nr_pages; nr++) {
470 *area_mutex(area_src, nr) = (pthread_mutex_t)
471 PTHREAD_MUTEX_INITIALIZER;
472 count_verify[nr] = *area_count(area_src, nr) = 1;
475 pipefd = malloc(sizeof(int) * nr_cpus * 2);
480 for (cpu = 0; cpu < nr_cpus; cpu++) {
481 if (pipe2(&pipefd[cpu*2], O_CLOEXEC | O_NONBLOCK)) {
487 if (posix_memalign(&area, page_size, page_size)) {
488 fprintf(stderr, "out of memory\n");
492 bzero(zeropage, page_size);
494 pthread_mutex_lock(&uffd_read_mutex);
496 pthread_attr_init(&attr);
497 pthread_attr_setstacksize(&attr, 16*1024*1024);
500 unsigned long expected_ioctls;
502 printf("bounces: %d, mode:", bounces);
503 if (bounces & BOUNCE_RANDOM)
505 if (bounces & BOUNCE_RACINGFAULTS)
507 if (bounces & BOUNCE_VERIFY)
509 if (bounces & BOUNCE_POLL)
514 if (bounces & BOUNCE_POLL)
515 fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);
517 fcntl(uffd, F_SETFL, uffd_flags & ~O_NONBLOCK);
520 uffdio_register.range.start = (unsigned long) area_dst;
521 uffdio_register.range.len = nr_pages * page_size;
522 uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
523 if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register)) {
524 fprintf(stderr, "register failure\n");
527 expected_ioctls = (1 << _UFFDIO_WAKE) |
528 (1 << _UFFDIO_COPY) |
529 (1 << _UFFDIO_ZEROPAGE);
530 if ((uffdio_register.ioctls & expected_ioctls) !=
533 "unexpected missing ioctl for anon memory\n");
538 * The madvise done previously isn't enough: some
539 * uffd_thread could have read userfaults (one of
540 * those already resolved by the background thread)
541 * and it may be in the process of calling
542 * UFFDIO_COPY. UFFDIO_COPY will read the zapped
543 * area_src and it would map a zero page in it (of
544 * course such a UFFDIO_COPY is perfectly safe as it'd
545 * return -EEXIST). The problem comes at the next
546 * bounce though: that racing UFFDIO_COPY would
547 * generate zeropages in the area_src, so invalidating
548 * the previous MADV_DONTNEED. Without this additional
549 * MADV_DONTNEED those zeropages leftovers in the
550 * area_src would lead to -EEXIST failure during the
551 * next bounce, effectively leaving a zeropage in the
554 * Try to comment this out madvise to see the memory
555 * corruption being caught pretty quick.
557 * khugepaged is also inhibited to collapse THP after
558 * MADV_DONTNEED only after the UFFDIO_REGISTER, so it's
559 * required to MADV_DONTNEED here.
561 if (madvise(area_dst, nr_pages * page_size, MADV_DONTNEED)) {
567 if (stress(userfaults))
571 if (ioctl(uffd, UFFDIO_UNREGISTER, &uffdio_register.range)) {
572 fprintf(stderr, "register failure\n");
577 if (bounces & BOUNCE_VERIFY) {
578 for (nr = 0; nr < nr_pages; nr++) {
579 if (my_bcmp(area_dst,
580 area_dst + nr * page_size,
581 sizeof(pthread_mutex_t))) {
583 "error mutex 2 %lu\n",
587 if (*area_count(area_dst, nr) != count_verify[nr]) {
589 "error area_count %Lu %Lu %lu\n",
590 *area_count(area_src, nr),
598 /* prepare next bounce */
603 printf("userfaults:");
604 for (cpu = 0; cpu < nr_cpus; cpu++)
605 printf(" %lu", userfaults[cpu]);
612 int main(int argc, char **argv)
615 fprintf(stderr, "Usage: <MiB> <bounces>\n"), exit(1);
616 nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
617 page_size = sysconf(_SC_PAGE_SIZE);
618 if ((unsigned long) area_count(NULL, 0) + sizeof(unsigned long long) >
620 fprintf(stderr, "Impossible to run this test\n"), exit(2);
621 nr_pages_per_cpu = atol(argv[1]) * 1024*1024 / page_size /
623 if (!nr_pages_per_cpu) {
624 fprintf(stderr, "invalid MiB\n");
625 fprintf(stderr, "Usage: <MiB> <bounces>\n"), exit(1);
627 bounces = atoi(argv[2]);
629 fprintf(stderr, "invalid bounces\n");
630 fprintf(stderr, "Usage: <MiB> <bounces>\n"), exit(1);
632 nr_pages = nr_pages_per_cpu * nr_cpus;
633 printf("nr_pages: %lu, nr_pages_per_cpu: %lu\n",
634 nr_pages, nr_pages_per_cpu);
635 return userfaultfd_stress();