userfaultfd: selftest
This test allocates two virtual areas and bounces the physical memory
across the two virtual areas using only userfaultfd.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index 231b9a0..0d68547 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -8,10 +8,13 @@
BINARIES += map_hugetlb
BINARIES += thuge-gen
BINARIES += transhuge-stress
+BINARIES += userfaultfd
all: $(BINARIES)
%: %.c
$(CC) $(CFLAGS) -o $@ $^ -lrt
+userfaultfd: userfaultfd.c
+ $(CC) $(CFLAGS) -O2 -o $@ $^ -lpthread
TEST_PROGS := run_vmtests
TEST_FILES := $(BINARIES)
diff --git a/tools/testing/selftests/vm/run_vmtests b/tools/testing/selftests/vm/run_vmtests
index 49ece11..831adeb 100755
--- a/tools/testing/selftests/vm/run_vmtests
+++ b/tools/testing/selftests/vm/run_vmtests
@@ -86,6 +86,17 @@
echo "[PASS]"
fi
+echo "--------------------"
+echo "running userfaultfd"
+echo "--------------------"
+./userfaultfd 128 32
+if [ $? -ne 0 ]; then
+ echo "[FAIL]"
+ exitcode=1
+else
+ echo "[PASS]"
+fi
+
#cleanup
umount $mnt
rm -rf $mnt
diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
new file mode 100644
index 0000000..0c0b839
--- /dev/null
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -0,0 +1,636 @@
+/*
+ * 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) << 32;
+ }
+ } 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 *)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 *)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();
+}
