Commit | Line | Data |
---|---|---|
3f21a6b7 URS |
1 | // SPDX-License-Identifier: GPL-2.0 |
2 | ||
3 | /* | |
4 | * Test module for stress and analyze performance of vmalloc allocator. | |
5 | * (C) 2018 Uladzislau Rezki (Sony) <urezki@gmail.com> | |
6 | */ | |
7 | #include <linux/init.h> | |
8 | #include <linux/kernel.h> | |
9 | #include <linux/module.h> | |
10 | #include <linux/vmalloc.h> | |
11 | #include <linux/random.h> | |
12 | #include <linux/kthread.h> | |
13 | #include <linux/moduleparam.h> | |
14 | #include <linux/completion.h> | |
15 | #include <linux/delay.h> | |
16 | #include <linux/rwsem.h> | |
17 | #include <linux/mm.h> | |
da4fc00a URS |
18 | #include <linux/rcupdate.h> |
19 | #include <linux/slab.h> | |
3f21a6b7 URS |
20 | |
21 | #define __param(type, name, init, msg) \ | |
22 | static type name = init; \ | |
23 | module_param(name, type, 0444); \ | |
24 | MODULE_PARM_DESC(name, msg) \ | |
25 | ||
80f47599 URS |
26 | __param(int, nr_threads, 0, |
27 | "Number of workers to perform tests(min: 1 max: USHRT_MAX)"); | |
3f21a6b7 URS |
28 | |
29 | __param(bool, sequential_test_order, false, | |
30 | "Use sequential stress tests order"); | |
31 | ||
32 | __param(int, test_repeat_count, 1, | |
33 | "Set test repeat counter"); | |
34 | ||
35 | __param(int, test_loop_count, 1000000, | |
36 | "Set test loop counter"); | |
37 | ||
f8bcbecf URS |
38 | __param(int, nr_pages, 0, |
39 | "Set number of pages for fix_size_alloc_test(default: 1)"); | |
40 | ||
6b1ead59 QP |
41 | __param(bool, use_huge, false, |
42 | "Use vmalloc_huge in fix_size_alloc_test"); | |
43 | ||
3f21a6b7 URS |
44 | __param(int, run_test_mask, INT_MAX, |
45 | "Set tests specified in the mask.\n\n" | |
da4fc00a URS |
46 | "\t\tid: 1, name: fix_size_alloc_test\n" |
47 | "\t\tid: 2, name: full_fit_alloc_test\n" | |
48 | "\t\tid: 4, name: long_busy_list_alloc_test\n" | |
49 | "\t\tid: 8, name: random_size_alloc_test\n" | |
50 | "\t\tid: 16, name: fix_align_alloc_test\n" | |
51 | "\t\tid: 32, name: random_size_align_alloc_test\n" | |
52 | "\t\tid: 64, name: align_shift_alloc_test\n" | |
53 | "\t\tid: 128, name: pcpu_alloc_test\n" | |
54 | "\t\tid: 256, name: kvfree_rcu_1_arg_vmalloc_test\n" | |
55 | "\t\tid: 512, name: kvfree_rcu_2_arg_vmalloc_test\n" | |
869cb29a | 56 | "\t\tid: 1024, name: vm_map_ram_test\n" |
3f21a6b7 URS |
57 | /* Add a new test case description here. */ |
58 | ); | |
59 | ||
3f21a6b7 URS |
60 | /* |
61 | * Read write semaphore for synchronization of setup | |
62 | * phase that is done in main thread and workers. | |
63 | */ | |
64 | static DECLARE_RWSEM(prepare_for_test_rwsem); | |
65 | ||
66 | /* | |
67 | * Completion tracking for worker threads. | |
68 | */ | |
69 | static DECLARE_COMPLETION(test_all_done_comp); | |
70 | static atomic_t test_n_undone = ATOMIC_INIT(0); | |
71 | ||
72 | static inline void | |
73 | test_report_one_done(void) | |
74 | { | |
75 | if (atomic_dec_and_test(&test_n_undone)) | |
76 | complete(&test_all_done_comp); | |
77 | } | |
78 | ||
79 | static int random_size_align_alloc_test(void) | |
80 | { | |
5e21f2d5 URS |
81 | unsigned long size, align; |
82 | unsigned int rnd; | |
3f21a6b7 URS |
83 | void *ptr; |
84 | int i; | |
85 | ||
86 | for (i = 0; i < test_loop_count; i++) { | |
f743f16c | 87 | rnd = get_random_u8(); |
3f21a6b7 URS |
88 | |
89 | /* | |
90 | * Maximum 1024 pages, if PAGE_SIZE is 4096. | |
91 | */ | |
92 | align = 1 << (rnd % 23); | |
93 | ||
94 | /* | |
95 | * Maximum 10 pages. | |
96 | */ | |
97 | size = ((rnd % 10) + 1) * PAGE_SIZE; | |
98 | ||
c3f896dc CH |
99 | ptr = __vmalloc_node(size, align, GFP_KERNEL | __GFP_ZERO, 0, |
100 | __builtin_return_address(0)); | |
3f21a6b7 URS |
101 | if (!ptr) |
102 | return -1; | |
103 | ||
104 | vfree(ptr); | |
105 | } | |
106 | ||
107 | return 0; | |
108 | } | |
109 | ||
110 | /* | |
111 | * This test case is supposed to be failed. | |
112 | */ | |
113 | static int align_shift_alloc_test(void) | |
114 | { | |
115 | unsigned long align; | |
116 | void *ptr; | |
117 | int i; | |
118 | ||
119 | for (i = 0; i < BITS_PER_LONG; i++) { | |
120 | align = ((unsigned long) 1) << i; | |
121 | ||
c3f896dc CH |
122 | ptr = __vmalloc_node(PAGE_SIZE, align, GFP_KERNEL|__GFP_ZERO, 0, |
123 | __builtin_return_address(0)); | |
3f21a6b7 URS |
124 | if (!ptr) |
125 | return -1; | |
126 | ||
127 | vfree(ptr); | |
128 | } | |
129 | ||
130 | return 0; | |
131 | } | |
132 | ||
133 | static int fix_align_alloc_test(void) | |
134 | { | |
135 | void *ptr; | |
136 | int i; | |
137 | ||
138 | for (i = 0; i < test_loop_count; i++) { | |
c3f896dc CH |
139 | ptr = __vmalloc_node(5 * PAGE_SIZE, THREAD_ALIGN << 1, |
140 | GFP_KERNEL | __GFP_ZERO, 0, | |
141 | __builtin_return_address(0)); | |
3f21a6b7 URS |
142 | if (!ptr) |
143 | return -1; | |
144 | ||
145 | vfree(ptr); | |
146 | } | |
147 | ||
148 | return 0; | |
149 | } | |
150 | ||
151 | static int random_size_alloc_test(void) | |
152 | { | |
153 | unsigned int n; | |
154 | void *p; | |
155 | int i; | |
156 | ||
157 | for (i = 0; i < test_loop_count; i++) { | |
e8a533cb | 158 | n = get_random_u32_inclusive(1, 100); |
3f21a6b7 URS |
159 | p = vmalloc(n * PAGE_SIZE); |
160 | ||
161 | if (!p) | |
162 | return -1; | |
163 | ||
164 | *((__u8 *)p) = 1; | |
165 | vfree(p); | |
166 | } | |
167 | ||
168 | return 0; | |
169 | } | |
170 | ||
171 | static int long_busy_list_alloc_test(void) | |
172 | { | |
173 | void *ptr_1, *ptr_2; | |
174 | void **ptr; | |
175 | int rv = -1; | |
176 | int i; | |
177 | ||
178 | ptr = vmalloc(sizeof(void *) * 15000); | |
179 | if (!ptr) | |
180 | return rv; | |
181 | ||
182 | for (i = 0; i < 15000; i++) | |
183 | ptr[i] = vmalloc(1 * PAGE_SIZE); | |
184 | ||
185 | for (i = 0; i < test_loop_count; i++) { | |
186 | ptr_1 = vmalloc(100 * PAGE_SIZE); | |
187 | if (!ptr_1) | |
188 | goto leave; | |
189 | ||
190 | ptr_2 = vmalloc(1 * PAGE_SIZE); | |
191 | if (!ptr_2) { | |
192 | vfree(ptr_1); | |
193 | goto leave; | |
194 | } | |
195 | ||
196 | *((__u8 *)ptr_1) = 0; | |
197 | *((__u8 *)ptr_2) = 1; | |
198 | ||
199 | vfree(ptr_1); | |
200 | vfree(ptr_2); | |
201 | } | |
202 | ||
203 | /* Success */ | |
204 | rv = 0; | |
205 | ||
206 | leave: | |
207 | for (i = 0; i < 15000; i++) | |
208 | vfree(ptr[i]); | |
209 | ||
210 | vfree(ptr); | |
211 | return rv; | |
212 | } | |
213 | ||
214 | static int full_fit_alloc_test(void) | |
215 | { | |
216 | void **ptr, **junk_ptr, *tmp; | |
217 | int junk_length; | |
218 | int rv = -1; | |
219 | int i; | |
220 | ||
221 | junk_length = fls(num_online_cpus()); | |
222 | junk_length *= (32 * 1024 * 1024 / PAGE_SIZE); | |
223 | ||
224 | ptr = vmalloc(sizeof(void *) * junk_length); | |
225 | if (!ptr) | |
226 | return rv; | |
227 | ||
228 | junk_ptr = vmalloc(sizeof(void *) * junk_length); | |
229 | if (!junk_ptr) { | |
230 | vfree(ptr); | |
231 | return rv; | |
232 | } | |
233 | ||
234 | for (i = 0; i < junk_length; i++) { | |
235 | ptr[i] = vmalloc(1 * PAGE_SIZE); | |
236 | junk_ptr[i] = vmalloc(1 * PAGE_SIZE); | |
237 | } | |
238 | ||
239 | for (i = 0; i < junk_length; i++) | |
240 | vfree(junk_ptr[i]); | |
241 | ||
242 | for (i = 0; i < test_loop_count; i++) { | |
243 | tmp = vmalloc(1 * PAGE_SIZE); | |
244 | ||
245 | if (!tmp) | |
246 | goto error; | |
247 | ||
248 | *((__u8 *)tmp) = 1; | |
249 | vfree(tmp); | |
250 | } | |
251 | ||
252 | /* Success */ | |
253 | rv = 0; | |
254 | ||
255 | error: | |
256 | for (i = 0; i < junk_length; i++) | |
257 | vfree(ptr[i]); | |
258 | ||
259 | vfree(ptr); | |
260 | vfree(junk_ptr); | |
261 | ||
262 | return rv; | |
263 | } | |
264 | ||
265 | static int fix_size_alloc_test(void) | |
266 | { | |
267 | void *ptr; | |
268 | int i; | |
269 | ||
270 | for (i = 0; i < test_loop_count; i++) { | |
6b1ead59 QP |
271 | if (use_huge) |
272 | ptr = vmalloc_huge((nr_pages > 0 ? nr_pages:1) * PAGE_SIZE, GFP_KERNEL); | |
273 | else | |
274 | ptr = vmalloc((nr_pages > 0 ? nr_pages:1) * PAGE_SIZE); | |
3f21a6b7 URS |
275 | |
276 | if (!ptr) | |
277 | return -1; | |
278 | ||
279 | *((__u8 *)ptr) = 0; | |
280 | ||
281 | vfree(ptr); | |
282 | } | |
283 | ||
284 | return 0; | |
285 | } | |
286 | ||
287 | static int | |
288 | pcpu_alloc_test(void) | |
289 | { | |
290 | int rv = 0; | |
291 | #ifndef CONFIG_NEED_PER_CPU_KM | |
292 | void __percpu **pcpu; | |
293 | size_t size, align; | |
294 | int i; | |
295 | ||
296 | pcpu = vmalloc(sizeof(void __percpu *) * 35000); | |
297 | if (!pcpu) | |
298 | return -1; | |
299 | ||
300 | for (i = 0; i < 35000; i++) { | |
e8a533cb | 301 | size = get_random_u32_inclusive(1, PAGE_SIZE / 4); |
3f21a6b7 URS |
302 | |
303 | /* | |
304 | * Maximum PAGE_SIZE | |
305 | */ | |
e8a533cb | 306 | align = 1 << get_random_u32_inclusive(1, 11); |
3f21a6b7 URS |
307 | |
308 | pcpu[i] = __alloc_percpu(size, align); | |
309 | if (!pcpu[i]) | |
310 | rv = -1; | |
311 | } | |
312 | ||
313 | for (i = 0; i < 35000; i++) | |
314 | free_percpu(pcpu[i]); | |
315 | ||
316 | vfree(pcpu); | |
317 | #endif | |
318 | return rv; | |
319 | } | |
320 | ||
da4fc00a URS |
321 | struct test_kvfree_rcu { |
322 | struct rcu_head rcu; | |
323 | unsigned char array[20]; | |
324 | }; | |
325 | ||
326 | static int | |
327 | kvfree_rcu_1_arg_vmalloc_test(void) | |
328 | { | |
329 | struct test_kvfree_rcu *p; | |
330 | int i; | |
331 | ||
332 | for (i = 0; i < test_loop_count; i++) { | |
333 | p = vmalloc(1 * PAGE_SIZE); | |
334 | if (!p) | |
335 | return -1; | |
336 | ||
337 | p->array[0] = 'a'; | |
c779b972 | 338 | kvfree_rcu_mightsleep(p); |
da4fc00a URS |
339 | } |
340 | ||
341 | return 0; | |
342 | } | |
343 | ||
344 | static int | |
345 | kvfree_rcu_2_arg_vmalloc_test(void) | |
346 | { | |
347 | struct test_kvfree_rcu *p; | |
348 | int i; | |
349 | ||
350 | for (i = 0; i < test_loop_count; i++) { | |
351 | p = vmalloc(1 * PAGE_SIZE); | |
352 | if (!p) | |
353 | return -1; | |
354 | ||
355 | p->array[0] = 'a'; | |
356 | kvfree_rcu(p, rcu); | |
357 | } | |
358 | ||
359 | return 0; | |
360 | } | |
361 | ||
869cb29a URS |
362 | static int |
363 | vm_map_ram_test(void) | |
364 | { | |
365 | unsigned long nr_allocated; | |
366 | unsigned int map_nr_pages; | |
367 | unsigned char *v_ptr; | |
368 | struct page **pages; | |
369 | int i; | |
370 | ||
371 | map_nr_pages = nr_pages > 0 ? nr_pages:1; | |
9f6c6ad1 | 372 | pages = kcalloc(map_nr_pages, sizeof(struct page *), GFP_KERNEL); |
869cb29a URS |
373 | if (!pages) |
374 | return -1; | |
375 | ||
376 | nr_allocated = alloc_pages_bulk_array(GFP_KERNEL, map_nr_pages, pages); | |
377 | if (nr_allocated != map_nr_pages) | |
378 | goto cleanup; | |
379 | ||
380 | /* Run the test loop. */ | |
381 | for (i = 0; i < test_loop_count; i++) { | |
382 | v_ptr = vm_map_ram(pages, map_nr_pages, NUMA_NO_NODE); | |
383 | *v_ptr = 'a'; | |
384 | vm_unmap_ram(v_ptr, map_nr_pages); | |
385 | } | |
386 | ||
387 | cleanup: | |
388 | for (i = 0; i < nr_allocated; i++) | |
389 | __free_page(pages[i]); | |
390 | ||
391 | kfree(pages); | |
392 | ||
393 | /* 0 indicates success. */ | |
394 | return nr_allocated != map_nr_pages; | |
395 | } | |
396 | ||
3f21a6b7 URS |
397 | struct test_case_desc { |
398 | const char *test_name; | |
399 | int (*test_func)(void); | |
400 | }; | |
401 | ||
402 | static struct test_case_desc test_case_array[] = { | |
403 | { "fix_size_alloc_test", fix_size_alloc_test }, | |
404 | { "full_fit_alloc_test", full_fit_alloc_test }, | |
405 | { "long_busy_list_alloc_test", long_busy_list_alloc_test }, | |
406 | { "random_size_alloc_test", random_size_alloc_test }, | |
407 | { "fix_align_alloc_test", fix_align_alloc_test }, | |
408 | { "random_size_align_alloc_test", random_size_align_alloc_test }, | |
409 | { "align_shift_alloc_test", align_shift_alloc_test }, | |
410 | { "pcpu_alloc_test", pcpu_alloc_test }, | |
da4fc00a URS |
411 | { "kvfree_rcu_1_arg_vmalloc_test", kvfree_rcu_1_arg_vmalloc_test }, |
412 | { "kvfree_rcu_2_arg_vmalloc_test", kvfree_rcu_2_arg_vmalloc_test }, | |
869cb29a | 413 | { "vm_map_ram_test", vm_map_ram_test }, |
3f21a6b7 URS |
414 | /* Add a new test case here. */ |
415 | }; | |
416 | ||
417 | struct test_case_data { | |
418 | int test_failed; | |
419 | int test_passed; | |
420 | u64 time; | |
421 | }; | |
422 | ||
3f21a6b7 URS |
423 | static struct test_driver { |
424 | struct task_struct *task; | |
80f47599 URS |
425 | struct test_case_data data[ARRAY_SIZE(test_case_array)]; |
426 | ||
3f21a6b7 URS |
427 | unsigned long start; |
428 | unsigned long stop; | |
80f47599 | 429 | } *tdriver; |
3f21a6b7 URS |
430 | |
431 | static void shuffle_array(int *arr, int n) | |
432 | { | |
34b46efd | 433 | int i, j; |
3f21a6b7 URS |
434 | |
435 | for (i = n - 1; i > 0; i--) { | |
3f21a6b7 | 436 | /* Cut the range. */ |
8032bf12 | 437 | j = get_random_u32_below(i); |
3f21a6b7 URS |
438 | |
439 | /* Swap indexes. */ | |
34b46efd | 440 | swap(arr[i], arr[j]); |
3f21a6b7 URS |
441 | } |
442 | } | |
443 | ||
444 | static int test_func(void *private) | |
445 | { | |
446 | struct test_driver *t = private; | |
3f21a6b7 | 447 | int random_array[ARRAY_SIZE(test_case_array)]; |
7507c402 | 448 | int index, i, j; |
3f21a6b7 URS |
449 | ktime_t kt; |
450 | u64 delta; | |
451 | ||
3f21a6b7 URS |
452 | for (i = 0; i < ARRAY_SIZE(test_case_array); i++) |
453 | random_array[i] = i; | |
454 | ||
455 | if (!sequential_test_order) | |
456 | shuffle_array(random_array, ARRAY_SIZE(test_case_array)); | |
457 | ||
458 | /* | |
459 | * Block until initialization is done. | |
460 | */ | |
461 | down_read(&prepare_for_test_rwsem); | |
462 | ||
463 | t->start = get_cycles(); | |
464 | for (i = 0; i < ARRAY_SIZE(test_case_array); i++) { | |
465 | index = random_array[i]; | |
466 | ||
467 | /* | |
468 | * Skip tests if run_test_mask has been specified. | |
469 | */ | |
470 | if (!((run_test_mask & (1 << index)) >> index)) | |
471 | continue; | |
472 | ||
473 | kt = ktime_get(); | |
474 | for (j = 0; j < test_repeat_count; j++) { | |
7507c402 | 475 | if (!test_case_array[index].test_func()) |
80f47599 | 476 | t->data[index].test_passed++; |
3f21a6b7 | 477 | else |
80f47599 | 478 | t->data[index].test_failed++; |
3f21a6b7 URS |
479 | } |
480 | ||
481 | /* | |
482 | * Take an average time that test took. | |
483 | */ | |
484 | delta = (u64) ktime_us_delta(ktime_get(), kt); | |
485 | do_div(delta, (u32) test_repeat_count); | |
486 | ||
80f47599 | 487 | t->data[index].time = delta; |
3f21a6b7 URS |
488 | } |
489 | t->stop = get_cycles(); | |
490 | ||
491 | up_read(&prepare_for_test_rwsem); | |
492 | test_report_one_done(); | |
493 | ||
494 | /* | |
495 | * Wait for the kthread_stop() call. | |
496 | */ | |
497 | while (!kthread_should_stop()) | |
498 | msleep(10); | |
499 | ||
500 | return 0; | |
501 | } | |
502 | ||
80f47599 | 503 | static int |
3f21a6b7 URS |
504 | init_test_configurtion(void) |
505 | { | |
506 | /* | |
80f47599 URS |
507 | * A maximum number of workers is defined as hard-coded |
508 | * value and set to USHRT_MAX. We add such gap just in | |
509 | * case and for potential heavy stressing. | |
3f21a6b7 | 510 | */ |
80f47599 | 511 | nr_threads = clamp(nr_threads, 1, (int) USHRT_MAX); |
3f21a6b7 | 512 | |
80f47599 URS |
513 | /* Allocate the space for test instances. */ |
514 | tdriver = kvcalloc(nr_threads, sizeof(*tdriver), GFP_KERNEL); | |
515 | if (tdriver == NULL) | |
516 | return -1; | |
3f21a6b7 URS |
517 | |
518 | if (test_repeat_count <= 0) | |
519 | test_repeat_count = 1; | |
520 | ||
521 | if (test_loop_count <= 0) | |
522 | test_loop_count = 1; | |
80f47599 URS |
523 | |
524 | return 0; | |
3f21a6b7 URS |
525 | } |
526 | ||
527 | static void do_concurrent_test(void) | |
528 | { | |
80f47599 | 529 | int i, ret; |
3f21a6b7 URS |
530 | |
531 | /* | |
532 | * Set some basic configurations plus sanity check. | |
533 | */ | |
80f47599 URS |
534 | ret = init_test_configurtion(); |
535 | if (ret < 0) | |
536 | return; | |
3f21a6b7 URS |
537 | |
538 | /* | |
539 | * Put on hold all workers. | |
540 | */ | |
541 | down_write(&prepare_for_test_rwsem); | |
542 | ||
80f47599 URS |
543 | for (i = 0; i < nr_threads; i++) { |
544 | struct test_driver *t = &tdriver[i]; | |
3f21a6b7 | 545 | |
80f47599 | 546 | t->task = kthread_run(test_func, t, "vmalloc_test/%d", i); |
3f21a6b7 URS |
547 | |
548 | if (!IS_ERR(t->task)) | |
549 | /* Success. */ | |
550 | atomic_inc(&test_n_undone); | |
551 | else | |
80f47599 | 552 | pr_err("Failed to start %d kthread\n", i); |
3f21a6b7 URS |
553 | } |
554 | ||
555 | /* | |
556 | * Now let the workers do their job. | |
557 | */ | |
558 | up_write(&prepare_for_test_rwsem); | |
559 | ||
560 | /* | |
561 | * Sleep quiet until all workers are done with 1 second | |
562 | * interval. Since the test can take a lot of time we | |
563 | * can run into a stack trace of the hung task. That is | |
564 | * why we go with completion_timeout and HZ value. | |
565 | */ | |
566 | do { | |
567 | ret = wait_for_completion_timeout(&test_all_done_comp, HZ); | |
568 | } while (!ret); | |
569 | ||
80f47599 URS |
570 | for (i = 0; i < nr_threads; i++) { |
571 | struct test_driver *t = &tdriver[i]; | |
572 | int j; | |
3f21a6b7 URS |
573 | |
574 | if (!IS_ERR(t->task)) | |
575 | kthread_stop(t->task); | |
576 | ||
80f47599 URS |
577 | for (j = 0; j < ARRAY_SIZE(test_case_array); j++) { |
578 | if (!((run_test_mask & (1 << j)) >> j)) | |
3f21a6b7 URS |
579 | continue; |
580 | ||
581 | pr_info( | |
582 | "Summary: %s passed: %d failed: %d repeat: %d loops: %d avg: %llu usec\n", | |
80f47599 URS |
583 | test_case_array[j].test_name, |
584 | t->data[j].test_passed, | |
585 | t->data[j].test_failed, | |
3f21a6b7 | 586 | test_repeat_count, test_loop_count, |
80f47599 | 587 | t->data[j].time); |
3f21a6b7 URS |
588 | } |
589 | ||
80f47599 URS |
590 | pr_info("All test took worker%d=%lu cycles\n", |
591 | i, t->stop - t->start); | |
3f21a6b7 | 592 | } |
80f47599 URS |
593 | |
594 | kvfree(tdriver); | |
3f21a6b7 URS |
595 | } |
596 | ||
597 | static int vmalloc_test_init(void) | |
598 | { | |
599 | do_concurrent_test(); | |
600 | return -EAGAIN; /* Fail will directly unload the module */ | |
601 | } | |
602 | ||
603 | static void vmalloc_test_exit(void) | |
604 | { | |
605 | } | |
606 | ||
607 | module_init(vmalloc_test_init) | |
608 | module_exit(vmalloc_test_exit) | |
609 | ||
610 | MODULE_LICENSE("GPL"); | |
611 | MODULE_AUTHOR("Uladzislau Rezki"); | |
612 | MODULE_DESCRIPTION("vmalloc test module"); |