// SPDX-License-Identifier: GPL-2.0
/*
* A test of splitting PMD THPs and PTE-mapped THPs from a specified virtual
* address range in a process via <debugfs>/split_huge_pages interface.
*/
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <unistd.h>
#include <inttypes.h>
#include <string.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <malloc.h>
#include <stdbool.h>
#include <time.h>
#include "vm_util.h"
#include "../kselftest.h"
uint64_t pagesize;
unsigned int pageshift;
uint64_t pmd_pagesize;
#define SPLIT_DEBUGFS "/sys/kernel/debug/split_huge_pages"
#define SMAP_PATH "/proc/self/smaps"
#define INPUT_MAX 80
#define PID_FMT "%d,0x%lx,0x%lx,%d"
#define PATH_FMT "%s,0x%lx,0x%lx,%d"
#define PFN_MASK ((1UL<<55)-1)
#define KPF_THP (1UL<<22)
int is_backed_by_thp(char *vaddr, int pagemap_file, int kpageflags_file)
{
uint64_t paddr;
uint64_t page_flags;
if (pagemap_file) {
pread(pagemap_file, &paddr, sizeof(paddr),
((long)vaddr >> pageshift) * sizeof(paddr));
if (kpageflags_file) {
pread(kpageflags_file, &page_flags, sizeof(page_flags),
(paddr & PFN_MASK) * sizeof(page_flags));
return !!(page_flags & KPF_THP);
}
}
return 0;
}
static void write_file(const char *path, const char *buf, size_t buflen)
{
int fd;
ssize_t numwritten;
fd = open(path, O_WRONLY);
if (fd == -1)
ksft_exit_fail_msg("%s open failed: %s\n", path, strerror(errno));
numwritten = write(fd, buf, buflen - 1);
close(fd);
if (numwritten < 1)
ksft_exit_fail_msg("Write failed\n");
}
static void write_debugfs(const char *fmt, ...)
{
char input[INPUT_MAX];
int ret;
va_list argp;
va_start(argp, fmt);
ret = vsnprintf(input, INPUT_MAX, fmt, argp);
va_end(argp);
if (ret >= INPUT_MAX)
ksft_exit_fail_msg("%s: Debugfs input is too long\n", __func__);
write_file(SPLIT_DEBUGFS, input, ret + 1);
}
void split_pmd_thp(void)
{
char *one_page;
size_t len = 4 * pmd_pagesize;
size_t i;
one_page = memalign(pmd_pagesize, len);
if (!one_page)
ksft_exit_fail_msg("Fail to allocate memory: %s\n", strerror(errno));
madvise(one_page, len, MADV_HUGEPAGE);
for (i = 0; i < len; i++)
one_page[i] = (char)i;
if (!check_huge_anon(one_page, 4, pmd_pagesize))
ksft_exit_fail_msg("No THP is allocated\n");
/* split all THPs */
write_debugfs(PID_FMT, getpid(), (uint64_t)one_page,
(uint64_t)one_page + len, 0);
for (i = 0; i < len; i++)
if (one_page[i] != (char)i)
ksft_exit_fail_msg("%ld byte corrupted\n", i);
if (!check_huge_anon(one_page, 0, pmd_pagesize))
ksft_exit_fail_msg("Still AnonHugePages not split\n");
ksft_test_result_pass("Split huge pages successful\n");
free(one_page);
}
void split_pte_mapped_thp(void)
{
char *one_page, *pte_mapped, *pte_mapped2;
size_t len = 4 * pmd_pagesize;
uint64_t thp_size;
size_t i;
const char *pagemap_template = "/proc/%d/pagemap";
const char *kpageflags_proc = "/proc/kpageflags";
char pagemap_proc[255];
int pagemap_fd;
int kpageflags_fd;
if (snprintf(pagemap_proc, 255, pagemap_template, getpid()) < 0)
ksft_exit_fail_msg("get pagemap proc error: %s\n", strerror(errno));
pagemap_fd = open(pagemap_proc, O_RDONLY);
if (pagemap_fd == -1)
ksft_exit_fail_msg("read pagemap: %s\n", strerror(errno));
kpageflags_fd = open(kpageflags_proc, O_RDONLY);
if (kpageflags_fd == -1)
ksft_exit_fail_msg("read kpageflags: %s\n", strerror(errno));
one_page = mmap((void *)(1UL << 30), len, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
if (one_page == MAP_FAILED)
ksft_exit_fail_msg("Fail to allocate memory: %s\n", strerror(errno));
madvise(one_page, len, MADV_HUGEPAGE);
for (i = 0; i < len; i++)
one_page[i] = (char)i;
if (!check_huge_anon(one_page, 4, pmd_pagesize))
ksft_exit_fail_msg("No THP is allocated\n");
/* remap the first pagesize of first THP */
pte_mapped = mremap(one_page, pagesize, pagesize, MREMAP_MAYMOVE);
/* remap the Nth pagesize of Nth THP */
for (i = 1; i < 4; i++) {
pte_mapped2 = mremap(one_page + pmd_pagesize * i + pagesize * i,
pagesize, pagesize,
MREMAP_MAYMOVE|MREMAP_FIXED,
pte_mapped + pagesize * i);
if (pte_mapped2 == MAP_FAILED)
ksft_exit_fail_msg("mremap failed: %s\n", strerror(errno));
}
/* smap does not show THPs after mremap, use kpageflags instead */
thp_size = 0;
for (i = 0; i < pagesize * 4; i++)
if (i % pagesize == 0 &&
is_backed_by_thp(&pte_mapped[i], pagemap_fd, kpageflags_fd))
thp_size++;
if (thp_size != 4)
ksft_exit_fail_msg("Some THPs are missing during mremap\n");
/* split all remapped THPs */
write_debugfs(PID_FMT, getpid(), (uint64_t)pte_mapped,
(uint64_t)pte_mapped + pagesize * 4, 0);
/* smap does not show THPs after mremap, use kpageflags instead */
thp_size = 0;
for (i = 0; i < pagesize * 4; i++) {
if (pte_mapped[i] != (char)i)
ksft_exit_fail_msg("%ld byte corrupted\n", i);
if (i % pagesize == 0 &&
is_backed_by_thp(&pte_mapped[i], pagemap_fd, kpageflags_fd))
thp_size++;
}
if (thp_size)
ksft_exit_fail_msg("Still %ld THPs not split\n", thp_size);
ksft_test_result_pass("Split PTE-mapped huge pages successful\n");
munmap(one_page, len);
close(pagemap_fd);
close(kpageflags_fd);
}
void split_file_backed_thp(void)
{
int status;
int fd;
ssize_t num_written;
char tmpfs_template[] = "/tmp/thp_split_XXXXXX";
const char *tmpfs_loc = mkdtemp(tmpfs_template);
char testfile[INPUT_MAX];
uint64_t pgoff_start = 0, pgoff_end = 1024;
ksft_print_msg("Please enable pr_debug in split_huge_pages_in_file() for more info.\n");
status = mount("tmpfs", tmpfs_loc, "tmpfs", 0, "huge=always,size=4m");
if (status)
ksft_exit_fail_msg("Unable to create a tmpfs for testing\n");
status = snprintf(testfile, INPUT_MAX, "%s/thp_file", tmpfs_loc);
if (status >= INPUT_MAX) {
ksft_exit_fail_msg("Fail to create file-backed THP split testing file\n");
}
fd = open(testfile, O_CREAT|O_WRONLY, 0664);
if (fd == -1) {
ksft_perror("Cannot open testing file");
goto cleanup;
}
/* write something to the file, so a file-backed THP can be allocated */
num_written = write(fd, tmpfs_loc, strlen(tmpfs_loc) + 1);
close(fd);
if (num_written < 1) {
ksft_perror("Fail to write data to testing file");
goto cleanup;
}
/* split the file-backed THP */
write_debugfs(PATH_FMT, testfile, pgoff_start, pgoff_end, 0);
status = unlink(testfile);
if (status) {
ksft_perror("Cannot remove testing file");
goto cleanup;
}
status = umount(tmpfs_loc);
if (status) {
rmdir(tmpfs_loc);
ksft_exit_fail_msg("Unable to umount %s\n", tmpfs_loc);
}
status = rmdir(tmpfs_loc);
if (status)
ksft_exit_fail_msg("cannot remove tmp dir: %s\n", strerror(errno));
ksft_print_msg("Please check dmesg for more information\n");
ksft_test_result_pass("File-backed THP split test done\n");
return;
cleanup:
umount(tmpfs_loc);
rmdir(tmpfs_loc);
ksft_exit_fail_msg("Error occurred\n");
}
bool prepare_thp_fs(const char *xfs_path, char *thp_fs_template,
const char **thp_fs_loc)
{
if (xfs_path) {
*thp_fs_loc = xfs_path;
return false;
}
*thp_fs_loc = mkdtemp(thp_fs_template);
if (!*thp_fs_loc)
ksft_exit_fail_msg("cannot create temp folder\n");
return true;
}
void cleanup_thp_fs(const char *thp_fs_loc, bool created_tmp)
{
int status;
if (!created_tmp)
return;
status = rmdir(thp_fs_loc);
if (status)
ksft_exit_fail_msg("cannot remove tmp dir: %s\n",
strerror(errno));
}
int create_pagecache_thp_and_fd(const char *testfile, size_t fd_size, int *fd,
char **addr)
{
size_t i;
int dummy = 0;
srand(time(NULL));
*fd = open(testfile, O_CREAT | O_RDWR, 0664);
if (*fd == -1)
ksft_exit_fail_msg("Failed to create a file at %s\n", testfile);
for (i = 0; i < fd_size; i++) {
unsigned char byte = (unsigned char)i;
write(*fd, &byte, sizeof(byte));
}
close(*fd);
sync();
*fd = open("/proc/sys/vm/drop_caches", O_WRONLY);
if (*fd == -1) {
ksft_perror("open drop_caches");
goto err_out_unlink;
}
if (write(*fd, "3", 1) != 1) {
ksft_perror("write to drop_caches");
goto err_out_unlink;
}
close(*fd);
*fd = open(testfile, O_RDWR);
if (*fd == -1) {
ksft_perror("Failed to open testfile\n");
goto err_out_unlink;
}
*addr = mmap(NULL, fd_size, PROT_READ|PROT_WRITE, MAP_SHARED, *fd, 0);
if (*addr == (char *)-1) {
ksft_perror("cannot mmap");
goto err_out_close;
}
madvise(*addr, fd_size, MADV_HUGEPAGE);
for (size_t i = 0; i < fd_size; i++)
dummy += *(*addr + i);
asm volatile("" : "+r" (dummy));
if (!check_huge_file(*addr, fd_size / pmd_pagesize, pmd_pagesize)) {
ksft_print_msg("No large pagecache folio generated, please provide a filesystem supporting large folio\n");
munmap(*addr, fd_size);
close(*fd);
unlink(testfile);
ksft_test_result_skip("Pagecache folio split skipped\n");
return -2;
}
return 0;
err_out_close:
close(*fd);
err_out_unlink:
unlink(testfile);
ksft_exit_fail_msg("Failed to create large pagecache folios\n");
return -1;
}
void split_thp_in_pagecache_to_order(size_t fd_size, int order, const char *fs_loc)
{
int fd;
char *addr;
size_t i;
char testfile[INPUT_MAX];
int err = 0;
err = snprintf(testfile, INPUT_MAX, "%s/test", fs_loc);
if (err < 0)
ksft_exit_fail_msg("cannot generate right test file name\n");
err = create_pagecache_thp_and_fd(testfile, fd_size, &fd, &addr);
if (err)
return;
err = 0;
write_debugfs(PID_FMT, getpid(), (uint64_t)addr, (uint64_t)addr + fd_size, order);
for (i = 0; i < fd_size; i++)
if (*(addr + i) != (char)i) {
ksft_print_msg("%lu byte corrupted in the file\n", i);
err = EXIT_FAILURE;
goto out;
}
if (!check_huge_file(addr, 0, pmd_pagesize)) {
ksft_print_msg("Still FilePmdMapped not split\n");
err = EXIT_FAILURE;
goto out;
}
out:
munmap(addr, fd_size);
close(fd);
unlink(testfile);
if (err)
ksft_exit_fail_msg("Split PMD-mapped pagecache folio to order %d failed\n", order);
ksft_test_result_pass("Split PMD-mapped pagecache folio to order %d passed\n", order);
}
int main(int argc, char **argv)
{
int i;
size_t fd_size;
char *optional_xfs_path = NULL;
char fs_loc_template[] = "/tmp/thp_fs_XXXXXX";
const char *fs_loc;
bool created_tmp;
ksft_print_header();
if (geteuid() != 0) {
ksft_print_msg("Please run the benchmark as root\n");
ksft_finished();
}
if (argc > 1)
optional_xfs_path = argv[1];
ksft_set_plan(3+9);
pagesize = getpagesize();
pageshift = ffs(pagesize) - 1;
pmd_pagesize = read_pmd_pagesize();
if (!pmd_pagesize)
ksft_exit_fail_msg("Reading PMD pagesize failed\n");
fd_size = 2 * pmd_pagesize;
split_pmd_thp();
split_pte_mapped_thp();
split_file_backed_thp();
created_tmp = prepare_thp_fs(optional_xfs_path, fs_loc_template,
&fs_loc);
for (i = 8; i >= 0; i--)
split_thp_in_pagecache_to_order(fd_size, i, fs_loc);
cleanup_thp_fs(fs_loc, created_tmp);
ksft_finished();
return 0;
}