1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * A test of splitting PMD THPs and PTE-mapped THPs from a specified virtual
4 * address range in a process via <debugfs>/split_huge_pages interface.
5 */
6
7 #define _GNU_SOURCE
8 #include <stdio.h>
9 #include <stdlib.h>
10 #include <stdarg.h>
11 #include <unistd.h>
12 #include <inttypes.h>
13 #include <string.h>
14 #include <fcntl.h>
15 #include <sys/mman.h>
16 #include <sys/mount.h>
17 #include <malloc.h>
18 #include <stdbool.h>
19 #include <time.h>
20 #include "vm_util.h"
21 #include "../kselftest.h"
22
23 uint64_t pagesize;
24 unsigned int pageshift;
25 uint64_t pmd_pagesize;
26
27 #define SPLIT_DEBUGFS "/sys/kernel/debug/split_huge_pages"
28 #define SMAP_PATH "/proc/self/smaps"
29 #define INPUT_MAX 80
30
31 #define PID_FMT "%d,0x%lx,0x%lx,%d"
32 #define PATH_FMT "%s,0x%lx,0x%lx,%d"
33
34 #define PFN_MASK ((1UL<<55)-1)
35 #define KPF_THP (1UL<<22)
36
37 int is_backed_by_thp(char *vaddr, int pagemap_file, int kpageflags_file)
38 {
39 uint64_t paddr;
40 uint64_t page_flags;
41
42 if (pagemap_file) {
43 pread(pagemap_file, &paddr, sizeof(paddr),
44 ((long)vaddr >> pageshift) * sizeof(paddr));
45
46 if (kpageflags_file) {
47 pread(kpageflags_file, &page_flags, sizeof(page_flags),
48 (paddr & PFN_MASK) * sizeof(page_flags));
49
50 return !!(page_flags & KPF_THP);
51 }
52 }
53 return 0;
54 }
55
56 static void write_file(const char *path, const char *buf, size_t buflen)
57 {
58 int fd;
59 ssize_t numwritten;
60
61 fd = open(path, O_WRONLY);
62 if (fd == -1)
63 ksft_exit_fail_msg("%s open failed: %s\n", path, strerror(errno));
64
65 numwritten = write(fd, buf, buflen - 1);
66 close(fd);
67 if (numwritten < 1)
68 ksft_exit_fail_msg("Write failed\n");
69 }
70
71 static void write_debugfs(const char *fmt, ...)
72 {
73 char input[INPUT_MAX];
74 int ret;
75 va_list argp;
76
77 va_start(argp, fmt);
78 ret = vsnprintf(input, INPUT_MAX, fmt, argp);
79 va_end(argp);
80
81 if (ret >= INPUT_MAX)
82 ksft_exit_fail_msg("%s: Debugfs input is too long\n", __func__);
83
84 write_file(SPLIT_DEBUGFS, input, ret + 1);
85 }
86
87 void split_pmd_thp(void)
88 {
89 char *one_page;
90 size_t len = 4 * pmd_pagesize;
91 size_t i;
92
93 one_page = memalign(pmd_pagesize, len);
94 if (!one_page)
95 ksft_exit_fail_msg("Fail to allocate memory: %s\n", strerror(errno));
96
97 madvise(one_page, len, MADV_HUGEPAGE);
98
99 for (i = 0; i < len; i++)
100 one_page[i] = (char)i;
101
102 if (!check_huge_anon(one_page, 4, pmd_pagesize))
103 ksft_exit_fail_msg("No THP is allocated\n");
104
105 /* split all THPs */
106 write_debugfs(PID_FMT, getpid(), (uint64_t)one_page,
107 (uint64_t)one_page + len, 0);
108
109 for (i = 0; i < len; i++)
110 if (one_page[i] != (char)i)
111 ksft_exit_fail_msg("%ld byte corrupted\n", i);
112
113
114 if (!check_huge_anon(one_page, 0, pmd_pagesize))
115 ksft_exit_fail_msg("Still AnonHugePages not split\n");
116
117 ksft_test_result_pass("Split huge pages successful\n");
118 free(one_page);
119 }
120
121 void split_pte_mapped_thp(void)
122 {
123 char *one_page, *pte_mapped, *pte_mapped2;
124 size_t len = 4 * pmd_pagesize;
125 uint64_t thp_size;
126 size_t i;
127 const char *pagemap_template = "/proc/%d/pagemap";
128 const char *kpageflags_proc = "/proc/kpageflags";
129 char pagemap_proc[255];
130 int pagemap_fd;
131 int kpageflags_fd;
132
133 if (snprintf(pagemap_proc, 255, pagemap_template, getpid()) < 0)
134 ksft_exit_fail_msg("get pagemap proc error: %s\n", strerror(errno));
135
136 pagemap_fd = open(pagemap_proc, O_RDONLY);
137 if (pagemap_fd == -1)
138 ksft_exit_fail_msg("read pagemap: %s\n", strerror(errno));
139
140 kpageflags_fd = open(kpageflags_proc, O_RDONLY);
141 if (kpageflags_fd == -1)
142 ksft_exit_fail_msg("read kpageflags: %s\n", strerror(errno));
143
144 one_page = mmap((void *)(1UL << 30), len, PROT_READ | PROT_WRITE,
145 MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
146 if (one_page == MAP_FAILED)
147 ksft_exit_fail_msg("Fail to allocate memory: %s\n", strerror(errno));
148
149 madvise(one_page, len, MADV_HUGEPAGE);
150
151 for (i = 0; i < len; i++)
152 one_page[i] = (char)i;
153
154 if (!check_huge_anon(one_page, 4, pmd_pagesize))
155 ksft_exit_fail_msg("No THP is allocated\n");
156
157 /* remap the first pagesize of first THP */
158 pte_mapped = mremap(one_page, pagesize, pagesize, MREMAP_MAYMOVE);
159
160 /* remap the Nth pagesize of Nth THP */
161 for (i = 1; i < 4; i++) {
162 pte_mapped2 = mremap(one_page + pmd_pagesize * i + pagesize * i,
163 pagesize, pagesize,
164 MREMAP_MAYMOVE|MREMAP_FIXED,
165 pte_mapped + pagesize * i);
166 if (pte_mapped2 == MAP_FAILED)
167 ksft_exit_fail_msg("mremap failed: %s\n", strerror(errno));
168 }
169
170 /* smap does not show THPs after mremap, use kpageflags instead */
171 thp_size = 0;
172 for (i = 0; i < pagesize * 4; i++)
173 if (i % pagesize == 0 &&
174 is_backed_by_thp(&pte_mapped[i], pagemap_fd, kpageflags_fd))
175 thp_size++;
176
177 if (thp_size != 4)
178 ksft_exit_fail_msg("Some THPs are missing during mremap\n");
179
180 /* split all remapped THPs */
181 write_debugfs(PID_FMT, getpid(), (uint64_t)pte_mapped,
182 (uint64_t)pte_mapped + pagesize * 4, 0);
183
184 /* smap does not show THPs after mremap, use kpageflags instead */
185 thp_size = 0;
186 for (i = 0; i < pagesize * 4; i++) {
187 if (pte_mapped[i] != (char)i)
188 ksft_exit_fail_msg("%ld byte corrupted\n", i);
189
190 if (i % pagesize == 0 &&
191 is_backed_by_thp(&pte_mapped[i], pagemap_fd, kpageflags_fd))
192 thp_size++;
193 }
194
195 if (thp_size)
196 ksft_exit_fail_msg("Still %ld THPs not split\n", thp_size);
197
198 ksft_test_result_pass("Split PTE-mapped huge pages successful\n");
199 munmap(one_page, len);
200 close(pagemap_fd);
201 close(kpageflags_fd);
202 }
203
204 void split_file_backed_thp(void)
205 {
206 int status;
207 int fd;
208 ssize_t num_written;
209 char tmpfs_template[] = "/tmp/thp_split_XXXXXX";
210 const char *tmpfs_loc = mkdtemp(tmpfs_template);
211 char testfile[INPUT_MAX];
212 uint64_t pgoff_start = 0, pgoff_end = 1024;
213
214 ksft_print_msg("Please enable pr_debug in split_huge_pages_in_file() for more info.\n");
215
216 status = mount("tmpfs", tmpfs_loc, "tmpfs", 0, "huge=always,size=4m");
217
218 if (status)
219 ksft_exit_fail_msg("Unable to create a tmpfs for testing\n");
220
221 status = snprintf(testfile, INPUT_MAX, "%s/thp_file", tmpfs_loc);
222 if (status >= INPUT_MAX) {
223 ksft_exit_fail_msg("Fail to create file-backed THP split testing file\n");
224 }
225
226 fd = open(testfile, O_CREAT|O_WRONLY, 0664);
227 if (fd == -1) {
228 ksft_perror("Cannot open testing file");
229 goto cleanup;
230 }
231
232 /* write something to the file, so a file-backed THP can be allocated */
233 num_written = write(fd, tmpfs_loc, strlen(tmpfs_loc) + 1);
234 close(fd);
235
236 if (num_written < 1) {
237 ksft_perror("Fail to write data to testing file");
238 goto cleanup;
239 }
240
241 /* split the file-backed THP */
242 write_debugfs(PATH_FMT, testfile, pgoff_start, pgoff_end, 0);
243
244 status = unlink(testfile);
245 if (status) {
246 ksft_perror("Cannot remove testing file");
247 goto cleanup;
248 }
249
250 status = umount(tmpfs_loc);
251 if (status) {
252 rmdir(tmpfs_loc);
253 ksft_exit_fail_msg("Unable to umount %s\n", tmpfs_loc);
254 }
255
256 status = rmdir(tmpfs_loc);
257 if (status)
258 ksft_exit_fail_msg("cannot remove tmp dir: %s\n", strerror(errno));
259
260 ksft_print_msg("Please check dmesg for more information\n");
261 ksft_test_result_pass("File-backed THP split test done\n");
262 return;
263
264 cleanup:
265 umount(tmpfs_loc);
266 rmdir(tmpfs_loc);
267 ksft_exit_fail_msg("Error occurred\n");
268 }
269
270 bool prepare_thp_fs(const char *xfs_path, char *thp_fs_template,
271 const char **thp_fs_loc)
272 {
273 if (xfs_path) {
274 *thp_fs_loc = xfs_path;
275 return false;
276 }
277
278 *thp_fs_loc = mkdtemp(thp_fs_template);
279
280 if (!*thp_fs_loc)
281 ksft_exit_fail_msg("cannot create temp folder\n");
282
283 return true;
284 }
285
286 void cleanup_thp_fs(const char *thp_fs_loc, bool created_tmp)
287 {
288 int status;
289
290 if (!created_tmp)
291 return;
292
293 status = rmdir(thp_fs_loc);
294 if (status)
295 ksft_exit_fail_msg("cannot remove tmp dir: %s\n",
296 strerror(errno));
297 }
298
299 int create_pagecache_thp_and_fd(const char *testfile, size_t fd_size, int *fd,
300 char **addr)
301 {
302 size_t i;
303 int dummy = 0;
304
305 srand(time(NULL));
306
307 *fd = open(testfile, O_CREAT | O_RDWR, 0664);
308 if (*fd == -1)
309 ksft_exit_fail_msg("Failed to create a file at %s\n", testfile);
310
311 for (i = 0; i < fd_size; i++) {
312 unsigned char byte = (unsigned char)i;
313
314 write(*fd, &byte, sizeof(byte));
315 }
316 close(*fd);
317 sync();
318 *fd = open("/proc/sys/vm/drop_caches", O_WRONLY);
319 if (*fd == -1) {
320 ksft_perror("open drop_caches");
321 goto err_out_unlink;
322 }
323 if (write(*fd, "3", 1) != 1) {
324 ksft_perror("write to drop_caches");
325 goto err_out_unlink;
326 }
327 close(*fd);
328
329 *fd = open(testfile, O_RDWR);
330 if (*fd == -1) {
331 ksft_perror("Failed to open testfile\n");
332 goto err_out_unlink;
333 }
334
335 *addr = mmap(NULL, fd_size, PROT_READ|PROT_WRITE, MAP_SHARED, *fd, 0);
336 if (*addr == (char *)-1) {
337 ksft_perror("cannot mmap");
338 goto err_out_close;
339 }
340 madvise(*addr, fd_size, MADV_HUGEPAGE);
341
342 for (size_t i = 0; i < fd_size; i++)
343 dummy += *(*addr + i);
344 asm volatile("" : "+r" (dummy));
345
346 if (!check_huge_file(*addr, fd_size / pmd_pagesize, pmd_pagesize)) {
347 ksft_print_msg("No large pagecache folio generated, please provide a filesystem supporting large folio\n");
348 munmap(*addr, fd_size);
349 close(*fd);
350 unlink(testfile);
351 ksft_test_result_skip("Pagecache folio split skipped\n");
352 return -2;
353 }
354 return 0;
355 err_out_close:
356 close(*fd);
357 err_out_unlink:
358 unlink(testfile);
359 ksft_exit_fail_msg("Failed to create large pagecache folios\n");
360 return -1;
361 }
362
363 void split_thp_in_pagecache_to_order(size_t fd_size, int order, const char *fs_loc)
364 {
365 int fd;
366 char *addr;
367 size_t i;
368 char testfile[INPUT_MAX];
369 int err = 0;
370
371 err = snprintf(testfile, INPUT_MAX, "%s/test", fs_loc);
372
373 if (err < 0)
374 ksft_exit_fail_msg("cannot generate right test file name\n");
375
376 err = create_pagecache_thp_and_fd(testfile, fd_size, &fd, &addr);
377 if (err)
378 return;
379 err = 0;
380
381 write_debugfs(PID_FMT, getpid(), (uint64_t)addr, (uint64_t)addr + fd_size, order);
382
383 for (i = 0; i < fd_size; i++)
384 if (*(addr + i) != (char)i) {
385 ksft_print_msg("%lu byte corrupted in the file\n", i);
386 err = EXIT_FAILURE;
387 goto out;
388 }
389
390 if (!check_huge_file(addr, 0, pmd_pagesize)) {
391 ksft_print_msg("Still FilePmdMapped not split\n");
392 err = EXIT_FAILURE;
393 goto out;
394 }
395
396 out:
397 munmap(addr, fd_size);
398 close(fd);
399 unlink(testfile);
400 if (err)
401 ksft_exit_fail_msg("Split PMD-mapped pagecache folio to order %d failed\n", order);
402 ksft_test_result_pass("Split PMD-mapped pagecache folio to order %d passed\n", order);
403 }
404
405 int main(int argc, char **argv)
406 {
407 int i;
408 size_t fd_size;
409 char *optional_xfs_path = NULL;
410 char fs_loc_template[] = "/tmp/thp_fs_XXXXXX";
411 const char *fs_loc;
412 bool created_tmp;
413
414 ksft_print_header();
415
416 if (geteuid() != 0) {
417 ksft_print_msg("Please run the benchmark as root\n");
418 ksft_finished();
419 }
420
421 if (argc > 1)
422 optional_xfs_path = argv[1];
423
424 ksft_set_plan(3+9);
425
426 pagesize = getpagesize();
427 pageshift = ffs(pagesize) - 1;
428 pmd_pagesize = read_pmd_pagesize();
429 if (!pmd_pagesize)
430 ksft_exit_fail_msg("Reading PMD pagesize failed\n");
431
432 fd_size = 2 * pmd_pagesize;
433
434 split_pmd_thp();
435 split_pte_mapped_thp();
436 split_file_backed_thp();
437
438 created_tmp = prepare_thp_fs(optional_xfs_path, fs_loc_template,
439 &fs_loc);
440 for (i = 8; i >= 0; i--)
441 split_thp_in_pagecache_to_order(fd_size, i, fs_loc);
442 cleanup_thp_fs(fs_loc, created_tmp);
443
444 ksft_finished();
445
446 return 0;
447 }
448
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