Add :collapse mod to userfaultfd selftest. Currently this mod is
only valid for "shmem" test type, but could be used for other test
types.
When provided, memory allocated by ->allocate_area() will be
hugepage-aligned enforced to be hugepage-sized. userfaultf_minor_test,
after the UFFD-registered mapping has been populated by UUFD minor
fault handler, attempt to MADV_COLLAPSE the UFFD-registered mapping to
collapse the memory into a pmd-mapped THP.
This test is meant to be a functional test of what occurs during
UFFD-driven live migration of VMs backed by huge tmpfs where, after
a hugepage-sized region has been successfully migrated (in native
page-sized chunks, to avoid latency of fetched a hugepage over the
network), we want to reclaim previous VM performance by remapping it
at the PMD level.
Signed-off-by: Zach O'Keefe <zokeefe@xxxxxxxxxx>
---
tools/testing/selftests/vm/Makefile | 1 +
tools/testing/selftests/vm/userfaultfd.c | 171 ++++++++++++++++++-----
2 files changed, 134 insertions(+), 38 deletions(-)
diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index df4fa77febca..c22b5b613296 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -101,6 +101,7 @@ $(OUTPUT)/khugepaged: vm_util.c
$(OUTPUT)/madv_populate: vm_util.c
$(OUTPUT)/soft-dirty: vm_util.c
$(OUTPUT)/split_huge_page_test: vm_util.c
+$(OUTPUT)/userfaultfd: vm_util.c
ifeq ($(MACHINE),x86_64)
BINARIES_32 := $(patsubst %,$(OUTPUT)/%,$(BINARIES_32))
diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index 7be709d9eed0..74babdbc02e5 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -61,10 +61,11 @@
#include <sys/random.h>
#include "../kselftest.h"
+#include "vm_util.h"
#ifdef __NR_userfaultfd
-static unsigned long nr_cpus, nr_pages, nr_pages_per_cpu, page_size;
+static unsigned long nr_cpus, nr_pages, nr_pages_per_cpu, page_size, hpage_size;
#define BOUNCE_RANDOM (1<<0)
#define BOUNCE_RACINGFAULTS (1<<1)
@@ -79,6 +80,8 @@ static int test_type;
#define UFFD_FLAGS (O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY)
+#define BASE_PMD_ADDR ((void *)(1UL << 30))
+
/* test using /dev/userfaultfd, instead of userfaultfd(2) */
static bool test_dev_userfaultfd;
@@ -97,9 +100,10 @@ static int huge_fd;
static unsigned long long *count_verify;
static int uffd = -1;
static int uffd_flags, finished, *pipefd;
-static char *area_src, *area_src_alias, *area_dst, *area_dst_alias;
+static char *area_src, *area_src_alias, *area_dst, *area_dst_alias, *area_remap;
static char *zeropage;
pthread_attr_t attr;
+static bool test_collapse;
/* Userfaultfd test statistics */
struct uffd_stats {
@@ -127,6 +131,8 @@ struct uffd_stats {
#define swap(a, b) \
do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)
+#define factor_of_2(x) ((x) ^ ((x) & ((x) - 1)))
+
const char *examples =
"# Run anonymous memory test on 100MiB region with 99999 bounces:\n"
"./userfaultfd anon 100 99999\n\n"
@@ -152,6 +158,8 @@ static void usage(void)
"Supported mods:\n");
fprintf(stderr, "\tsyscall - Use userfaultfd(2) (default)\n");
fprintf(stderr, "\tdev - Use /dev/userfaultfd instead of userfaultfd(2)\n");
+ fprintf(stderr, "\tcollapse - Test MADV_COLLAPSE of UFFDIO_REGISTER_MODE_MINOR\n"
+ "memory\n");
fprintf(stderr, "\nExample test mod usage:\n");
fprintf(stderr, "# Run anonymous memory test with /dev/userfaultfd:\n");
fprintf(stderr, "./userfaultfd anon:dev 100 99999\n\n");
@@ -229,12 +237,10 @@ static void anon_release_pages(char *rel_area)
err("madvise(MADV_DONTNEED) failed");
}
-static void anon_allocate_area(void **alloc_area)
+static void anon_allocate_area(void **alloc_area, bool is_src)
{
*alloc_area = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
- if (*alloc_area == MAP_FAILED)
- err("mmap of anonymous memory failed");
}
static void noop_alias_mapping(__u64 *start, size_t len, unsigned long offset)
@@ -252,7 +258,7 @@ static void hugetlb_release_pages(char *rel_area)
}
}
-static void hugetlb_allocate_area(void **alloc_area)
+static void hugetlb_allocate_area(void **alloc_area, bool is_src)
{
void *area_alias = NULL;
char **alloc_area_alias;
@@ -262,7 +268,7 @@ static void hugetlb_allocate_area(void **alloc_area)
nr_pages * page_size,
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB |
- (*alloc_area == area_src ? 0 : MAP_NORESERVE),
+ (is_src ? 0 : MAP_NORESERVE),
-1,
0);
else
@@ -270,9 +276,9 @@ static void hugetlb_allocate_area(void **alloc_area)
nr_pages * page_size,
PROT_READ | PROT_WRITE,
MAP_SHARED |
- (*alloc_area == area_src ? 0 : MAP_NORESERVE),
+ (is_src ? 0 : MAP_NORESERVE),
huge_fd,
- *alloc_area == area_src ? 0 : nr_pages * page_size);
+ is_src ? 0 : nr_pages * page_size);
if (*alloc_area == MAP_FAILED)
err("mmap of hugetlbfs file failed");
@@ -282,12 +288,12 @@ static void hugetlb_allocate_area(void **alloc_area)
PROT_READ | PROT_WRITE,
MAP_SHARED,
huge_fd,
- *alloc_area == area_src ? 0 : nr_pages * page_size);
+ is_src ? 0 : nr_pages * page_size);
if (area_alias == MAP_FAILED)
err("mmap of hugetlb file alias failed");
}
- if (*alloc_area == area_src) {
+ if (is_src) {
alloc_area_alias = &area_src_alias;
} else {
alloc_area_alias = &area_dst_alias;
@@ -310,21 +316,36 @@ static void shmem_release_pages(char *rel_area)
err("madvise(MADV_REMOVE) failed");
}
-static void shmem_allocate_area(void **alloc_area)
+static void shmem_allocate_area(void **alloc_area, bool is_src)
{
void *area_alias = NULL;
- bool is_src = alloc_area == (void **)&area_src;
- unsigned long offset = is_src ? 0 : nr_pages * page_size;
+ size_t bytes = nr_pages * page_size;
+ unsigned long offset = is_src ? 0 : bytes;
+ char *p = NULL, *p_alias = NULL;
+
+ if (test_collapse) {
+ p = BASE_PMD_ADDR;
+ if (!is_src)
+ /* src map + alias + interleaved hpages */
+ p += 2 * (bytes + hpage_size);
+ p_alias = p;
+ p_alias += bytes;
+ p_alias += hpage_size; /* Prevent src/dst VMA merge */
+ }
- *alloc_area = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
- MAP_SHARED, shm_fd, offset);
+ *alloc_area = mmap(p, bytes, PROT_READ | PROT_WRITE, MAP_SHARED,
+ shm_fd, offset);
if (*alloc_area == MAP_FAILED)
err("mmap of memfd failed");
+ if (test_collapse && *alloc_area != p)
+ err("mmap of memfd failed at %p", p);
- area_alias = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
- MAP_SHARED, shm_fd, offset);
+ area_alias = mmap(p_alias, bytes, PROT_READ | PROT_WRITE, MAP_SHARED,
+ shm_fd, offset);
if (area_alias == MAP_FAILED)
err("mmap of memfd alias failed");
+ if (test_collapse && area_alias != p_alias)
+ err("mmap of anonymous memory failed at %p", p_alias);
if (is_src)
area_src_alias = area_alias;
@@ -337,28 +358,39 @@ static void shmem_alias_mapping(__u64 *start, size_t len, unsigned long offset)
*start = (unsigned long)area_dst_alias + offset;
}
+static void shmem_check_pmd_mapping(void *p, int expect_nr_hpages)
+{
+ if (!check_huge_shmem(area_dst_alias, expect_nr_hpages, hpage_size))
+ err("Did not find expected %d number of hugepages",
+ expect_nr_hpages);
+}
+
struct uffd_test_ops {
- void (*allocate_area)(void **alloc_area);
+ void (*allocate_area)(void **alloc_area, bool is_src);
void (*release_pages)(char *rel_area);
void (*alias_mapping)(__u64 *start, size_t len, unsigned long offset);
+ void (*check_pmd_mapping)(void *p, int expect_nr_hpages);
};
static struct uffd_test_ops anon_uffd_test_ops = {
.allocate_area = anon_allocate_area,
.release_pages = anon_release_pages,
.alias_mapping = noop_alias_mapping,
+ .check_pmd_mapping = NULL,
};
static struct uffd_test_ops shmem_uffd_test_ops = {
.allocate_area = shmem_allocate_area,
.release_pages = shmem_release_pages,
.alias_mapping = shmem_alias_mapping,
+ .check_pmd_mapping = shmem_check_pmd_mapping,
};
static struct uffd_test_ops hugetlb_uffd_test_ops = {
.allocate_area = hugetlb_allocate_area,
.release_pages = hugetlb_release_pages,
.alias_mapping = hugetlb_alias_mapping,
+ .check_pmd_mapping = NULL,
};
static struct uffd_test_ops *uffd_test_ops;
@@ -478,6 +510,7 @@ static void uffd_test_ctx_clear(void)
munmap_area((void **)&area_src_alias);
munmap_area((void **)&area_dst);
munmap_area((void **)&area_dst_alias);
+ munmap_area((void **)&area_remap);
}
static void uffd_test_ctx_init(uint64_t features)
@@ -486,8 +519,8 @@ static void uffd_test_ctx_init(uint64_t features)
uffd_test_ctx_clear();
- uffd_test_ops->allocate_area((void **)&area_src);
- uffd_test_ops->allocate_area((void **)&area_dst);
+ uffd_test_ops->allocate_area((void **)&area_src, true);
+ uffd_test_ops->allocate_area((void **)&area_dst, false);
userfaultfd_open(&features);
@@ -804,6 +837,7 @@ static void *uffd_poll_thread(void *arg)
err("remove failure");
break;
case UFFD_EVENT_REMAP:
+ area_remap = area_dst; /* save for later unmap */
area_dst = (char *)(unsigned long)msg.arg.remap.to;
break;
}
@@ -1256,13 +1290,30 @@ static int userfaultfd_sig_test(void)
return userfaults != 0;
}
+void check_memory_contents(char *p)
+{
+ unsigned long i;
+ uint8_t expected_byte;
+ void *expected_page;
+
+ if (posix_memalign(&expected_page, page_size, page_size))
+ err("out of memory");
+
+ for (i = 0; i < nr_pages; ++i) {
+ expected_byte = ~((uint8_t)(i % ((uint8_t)-1)));
+ memset(expected_page, expected_byte, page_size);
+ if (my_bcmp(expected_page, p + (i * page_size), page_size))
+ err("unexpected page contents after minor fault");
+ }
+
+ free(expected_page);
+}
+
static int userfaultfd_minor_test(void)
{
- struct uffdio_register uffdio_register;
unsigned long p;
+ struct uffdio_register uffdio_register;
pthread_t uffd_mon;
- uint8_t expected_byte;
- void *expected_page;
char c;
struct uffd_stats stats = { 0 };
@@ -1301,17 +1352,7 @@ static int userfaultfd_minor_test(void)
* fault. uffd_poll_thread will resolve the fault by bit-flipping the
* page's contents, and then issuing a CONTINUE ioctl.
*/
-
- if (posix_memalign(&expected_page, page_size, page_size))
- err("out of memory");
-
- for (p = 0; p < nr_pages; ++p) {
- expected_byte = ~((uint8_t)(p % ((uint8_t)-1)));
- memset(expected_page, expected_byte, page_size);
- if (my_bcmp(expected_page, area_dst_alias + (p * page_size),
- page_size))
- err("unexpected page contents after minor fault");
- }
+ check_memory_contents(area_dst_alias);
if (write(pipefd[1], &c, sizeof(c)) != sizeof(c))
err("pipe write");
@@ -1320,6 +1361,23 @@ static int userfaultfd_minor_test(void)
uffd_stats_report(&stats, 1);
+ if (test_collapse) {
+ printf("testing collapse of uffd memory into PMD-mapped THPs:");
+ if (madvise(area_dst_alias, nr_pages * page_size,
+ MADV_COLLAPSE))
+ err("madvise(MADV_COLLAPSE)");
+
+ uffd_test_ops->check_pmd_mapping(area_dst,
+ nr_pages * page_size /
+ hpage_size);
+ /*
+ * This won't cause uffd-fault - it purely just makes sure there
+ * was no corruption.
+ */
+ check_memory_contents(area_dst_alias);
+ printf(" done.\n");
+ }
+
return stats.missing_faults != 0 || stats.minor_faults != nr_pages;
}
@@ -1656,6 +1714,8 @@ static void parse_test_type_arg(const char *raw_type)
test_dev_userfaultfd = true;
else if (!strcmp(token, "syscall"))
test_dev_userfaultfd = false;
+ else if (!strcmp(token, "collapse"))
+ test_collapse = true;
else
err("unrecognized test mod '%s'", token);
}
@@ -1663,8 +1723,11 @@ static void parse_test_type_arg(const char *raw_type)
if (!test_type)
err("failed to parse test type argument: '%s'", raw_type);
+ if (test_collapse && test_type != TEST_SHMEM)
+ err("Unsupported test: %s", raw_type);
+
if (test_type == TEST_HUGETLB)
- page_size = default_huge_page_size();
+ page_size = hpage_size;
else
page_size = sysconf(_SC_PAGE_SIZE);
@@ -1702,6 +1765,8 @@ static void sigalrm(int sig)
int main(int argc, char **argv)
{
+ size_t bytes;
+
if (argc < 4)
usage();
@@ -1709,11 +1774,41 @@ int main(int argc, char **argv)
err("failed to arm SIGALRM");
alarm(ALARM_INTERVAL_SECS);
+ hpage_size = default_huge_page_size();
parse_test_type_arg(argv[1]);
+ bytes = atol(argv[2]) * 1024 * 1024;
+
+ if (test_collapse && bytes & (hpage_size - 1))
+ err("MiB must be multiple of %lu if :collapse mod set",
+ hpage_size >> 20);
nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
- nr_pages_per_cpu = atol(argv[2]) * 1024*1024 / page_size /
- nr_cpus;
+
+ if (test_collapse) {
+ /* nr_cpus must divide (bytes / page_size), otherwise,
+ * area allocations of (nr_pages * paze_size) won't be a
+ * multiple of hpage_size, even if bytes is a multiple of
+ * hpage_size.
+ *
+ * This means that nr_cpus must divide (N * (2 << (H-P))
+ * where:
+ * bytes = hpage_size * N
+ * hpage_size = 2 << H
+ * page_size = 2 << P
+ *
+ * And we want to chose nr_cpus to be the largest value
+ * satisfying this constraint, not larger than the number
+ * of online CPUs. Unfortunately, prime factorization of
+ * N and nr_cpus may be arbitrary, so have to search for it.
+ * Instead, just use the highest power of 2 dividing both
+ * nr_cpus and (bytes / page_size).
+ */
+ int x = factor_of_2(nr_cpus);
+ int y = factor_of_2(bytes / page_size);
+
+ nr_cpus = x < y ? x : y;
+ }
+ nr_pages_per_cpu = bytes / page_size / nr_cpus;
if (!nr_pages_per_cpu) {
_err("invalid MiB");
usage();
--
2.37.2.672.g94769d06f0-goog
