smalloc.c revision b8a6582e89999f88c574b905b89743762d8080df 
1/*
2 * simple memory allocator, backed by mmap() so that it hands out memory
3 * that can be shared across processes and threads
4 */
5#include <sys/mman.h>
6#include <stdio.h>
7#include <stdlib.h>
8#include <assert.h>
9#include <string.h>
10#include <unistd.h>
11#include <sys/types.h>
12#include <limits.h>
13
14#include "mutex.h"
15#include "arch/arch.h"
16
17#define MP_SAFE			/* define to make thread safe */
18#define SMALLOC_REDZONE		/* define to detect memory corruption */
19
20#define SMALLOC_BPB	32	/* block size, bytes-per-bit in bitmap */
21#define SMALLOC_BPI	(sizeof(unsigned int) * 8)
22#define SMALLOC_BPL	(SMALLOC_BPB * SMALLOC_BPI)
23
24#define INITIAL_SIZE	1024*1024	/* new pool size */
25#define MAX_POOLS	128		/* maximum number of pools to setup */
26
27#define SMALLOC_PRE_RED		0xdeadbeefU
28#define SMALLOC_POST_RED	0x5aa55aa5U
29
30unsigned int smalloc_pool_size = INITIAL_SIZE;
31
32struct pool {
33	struct fio_mutex *lock;			/* protects this pool */
34	void *map;				/* map of blocks */
35	unsigned int *bitmap;			/* blocks free/busy map */
36	unsigned int free_blocks;		/* free blocks */
37	unsigned int nr_blocks;			/* total blocks */
38	unsigned int next_non_full;
39	int fd;					/* memory backing fd */
40	unsigned int mmap_size;
41};
42
43struct block_hdr {
44	unsigned int size;
45#ifdef SMALLOC_REDZONE
46	unsigned int prered;
47#endif
48};
49
50static struct pool mp[MAX_POOLS];
51static unsigned int nr_pools;
52static unsigned int last_pool;
53static struct fio_mutex *lock;
54
55static inline void pool_lock(struct pool *pool)
56{
57	if (pool->lock)
58		fio_mutex_down(pool->lock);
59}
60
61static inline void pool_unlock(struct pool *pool)
62{
63	if (pool->lock)
64		fio_mutex_up(pool->lock);
65}
66
67static inline void global_read_lock(void)
68{
69	if (lock)
70		fio_mutex_down_read(lock);
71}
72
73static inline void global_read_unlock(void)
74{
75	if (lock)
76		fio_mutex_up_read(lock);
77}
78
79static inline void global_write_lock(void)
80{
81	if (lock)
82		fio_mutex_down_write(lock);
83}
84
85static inline void global_write_unlock(void)
86{
87	if (lock)
88		fio_mutex_up_write(lock);
89}
90
91static inline int ptr_valid(struct pool *pool, void *ptr)
92{
93	unsigned int pool_size = pool->nr_blocks * SMALLOC_BPL;
94
95	return (ptr >= pool->map) && (ptr < pool->map + pool_size);
96}
97
98static inline unsigned int size_to_blocks(unsigned int size)
99{
100	return (size + SMALLOC_BPB - 1) / SMALLOC_BPB;
101}
102
103static int blocks_iter(struct pool *pool, unsigned int pool_idx,
104		       unsigned int idx, unsigned int nr_blocks,
105		       int (*func)(unsigned int *map, unsigned int mask))
106{
107
108	while (nr_blocks) {
109		unsigned int this_blocks, mask;
110		unsigned int *map;
111
112		if (pool_idx >= pool->nr_blocks)
113			return 0;
114
115		map = &pool->bitmap[pool_idx];
116
117		this_blocks = nr_blocks;
118		if (this_blocks + idx > SMALLOC_BPI) {
119			this_blocks = SMALLOC_BPI - idx;
120			idx = SMALLOC_BPI - this_blocks;
121		}
122
123		if (this_blocks == SMALLOC_BPI)
124			mask = -1U;
125		else
126			mask = ((1U << this_blocks) - 1) << idx;
127
128		if (!func(map, mask))
129			return 0;
130
131		nr_blocks -= this_blocks;
132		idx = 0;
133		pool_idx++;
134	}
135
136	return 1;
137}
138
139static int mask_cmp(unsigned int *map, unsigned int mask)
140{
141	return !(*map & mask);
142}
143
144static int mask_clear(unsigned int *map, unsigned int mask)
145{
146	assert((*map & mask) == mask);
147	*map &= ~mask;
148	return 1;
149}
150
151static int mask_set(unsigned int *map, unsigned int mask)
152{
153	assert(!(*map & mask));
154	*map |= mask;
155	return 1;
156}
157
158static int blocks_free(struct pool *pool, unsigned int pool_idx,
159		       unsigned int idx, unsigned int nr_blocks)
160{
161	return blocks_iter(pool, pool_idx, idx, nr_blocks, mask_cmp);
162}
163
164static void set_blocks(struct pool *pool, unsigned int pool_idx,
165		       unsigned int idx, unsigned int nr_blocks)
166{
167	blocks_iter(pool, pool_idx, idx, nr_blocks, mask_set);
168}
169
170static void clear_blocks(struct pool *pool, unsigned int pool_idx,
171			 unsigned int idx, unsigned int nr_blocks)
172{
173	blocks_iter(pool, pool_idx, idx, nr_blocks, mask_clear);
174}
175
176static int find_next_zero(int word, int start)
177{
178	assert(word != -1U);
179	word >>= (start + 1);
180	return ffz(word) + start + 1;
181}
182
183static int add_pool(struct pool *pool, unsigned int alloc_size)
184{
185	int fd, bitmap_blocks;
186	char file[] = "/tmp/.fio_smalloc.XXXXXX";
187	void *ptr;
188
189	fd = mkstemp(file);
190	if (fd < 0)
191		goto out_close;
192
193#ifdef SMALLOC_REDZONE
194	alloc_size += sizeof(unsigned int);
195#endif
196	alloc_size += sizeof(struct block_hdr);
197	if (alloc_size < INITIAL_SIZE)
198		alloc_size = INITIAL_SIZE;
199
200	/* round up to nearest full number of blocks */
201	alloc_size = (alloc_size + SMALLOC_BPL - 1) & ~(SMALLOC_BPL - 1);
202	bitmap_blocks = alloc_size / SMALLOC_BPL;
203	alloc_size += bitmap_blocks * sizeof(unsigned int);
204	pool->mmap_size = alloc_size;
205
206	pool->nr_blocks = bitmap_blocks;
207	pool->free_blocks = bitmap_blocks * SMALLOC_BPB;
208
209	if (ftruncate(fd, alloc_size) < 0)
210		goto out_unlink;
211
212	ptr = mmap(NULL, alloc_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
213	if (ptr == MAP_FAILED)
214		goto out_unlink;
215
216	memset(ptr, 0, alloc_size);
217	pool->map = ptr;
218	pool->bitmap = (void *) ptr + (pool->nr_blocks * SMALLOC_BPL);
219
220#ifdef MP_SAFE
221	pool->lock = fio_mutex_init(1);
222	if (!pool->lock)
223		goto out_unlink;
224#endif
225
226	/*
227	 * Unlink pool file now. It wont get deleted until the fd is closed,
228	 * which happens both for cleanup or unexpected quit. This way we
229	 * don't leave temp files around in case of a crash.
230	 */
231	unlink(file);
232	pool->fd = fd;
233
234	nr_pools++;
235	return 0;
236out_unlink:
237	fprintf(stderr, "smalloc: failed adding pool\n");
238	if (pool->map)
239		munmap(pool->map, pool->mmap_size);
240	unlink(file);
241out_close:
242	close(fd);
243	return 1;
244}
245
246void sinit(void)
247{
248	int ret;
249
250#ifdef MP_SAFE
251	lock = fio_mutex_rw_init();
252#endif
253	ret = add_pool(&mp[0], INITIAL_SIZE);
254	assert(!ret);
255}
256
257static void cleanup_pool(struct pool *pool)
258{
259	/*
260	 * This will also remove the temporary file we used as a backing
261	 * store, it was already unlinked
262	 */
263	close(pool->fd);
264	munmap(pool->map, pool->mmap_size);
265
266	if (pool->lock)
267		fio_mutex_remove(pool->lock);
268}
269
270void scleanup(void)
271{
272	unsigned int i;
273
274	for (i = 0; i < nr_pools; i++)
275		cleanup_pool(&mp[i]);
276
277	if (lock)
278		fio_mutex_remove(lock);
279}
280
281#ifdef SMALLOC_REDZONE
282static void fill_redzone(struct block_hdr *hdr)
283{
284	unsigned int *postred = (void *) hdr + hdr->size - sizeof(unsigned int);
285
286	hdr->prered = SMALLOC_PRE_RED;
287	*postred = SMALLOC_POST_RED;
288}
289
290static void sfree_check_redzone(struct block_hdr *hdr)
291{
292	unsigned int *postred = (void *) hdr + hdr->size - sizeof(unsigned int);
293
294	if (hdr->prered != SMALLOC_PRE_RED) {
295		fprintf(stderr, "smalloc pre redzone destroyed!\n");
296		fprintf(stderr, "  ptr=%p, prered=%x, expected %x\n",
297				hdr, hdr->prered, SMALLOC_PRE_RED);
298		assert(0);
299	}
300	if (*postred != SMALLOC_POST_RED) {
301		fprintf(stderr, "smalloc post redzone destroyed!\n");
302		fprintf(stderr, "  ptr=%p, postred=%x, expected %x\n",
303				hdr, *postred, SMALLOC_POST_RED);
304		assert(0);
305	}
306}
307#else
308static void fill_redzone(struct block_hdr *hdr)
309{
310}
311
312static void sfree_check_redzone(struct block_hdr *hdr)
313{
314}
315#endif
316
317static void sfree_pool(struct pool *pool, void *ptr)
318{
319	struct block_hdr *hdr;
320	unsigned int i, idx;
321	unsigned long offset;
322
323	if (!ptr)
324		return;
325
326	ptr -= sizeof(*hdr);
327	hdr = ptr;
328
329	assert(ptr_valid(pool, ptr));
330
331	sfree_check_redzone(hdr);
332
333	offset = ptr - pool->map;
334	i = offset / SMALLOC_BPL;
335	idx = (offset % SMALLOC_BPL) / SMALLOC_BPB;
336
337	pool_lock(pool);
338	clear_blocks(pool, i, idx, size_to_blocks(hdr->size));
339	if (i < pool->next_non_full)
340		pool->next_non_full = i;
341	pool->free_blocks += size_to_blocks(hdr->size);
342	pool_unlock(pool);
343}
344
345void sfree(void *ptr)
346{
347	struct pool *pool = NULL;
348	unsigned int i;
349
350	if (!ptr)
351		return;
352
353	global_read_lock();
354
355	for (i = 0; i < nr_pools; i++) {
356		if (ptr_valid(&mp[i], ptr)) {
357			pool = &mp[i];
358			break;
359		}
360	}
361
362	global_read_unlock();
363
364	assert(pool);
365	sfree_pool(pool, ptr);
366}
367
368static void *__smalloc_pool(struct pool *pool, unsigned int size)
369{
370	unsigned int nr_blocks;
371	unsigned int i;
372	unsigned int offset;
373	unsigned int last_idx;
374	void *ret = NULL;
375
376	pool_lock(pool);
377
378	nr_blocks = size_to_blocks(size);
379	if (nr_blocks > pool->free_blocks)
380		goto fail;
381
382	i = pool->next_non_full;
383	last_idx = 0;
384	offset = -1U;
385	while (i < pool->nr_blocks) {
386		unsigned int idx;
387
388		if (pool->bitmap[i] == -1U) {
389			i++;
390			pool->next_non_full = i;
391			last_idx = 0;
392			continue;
393		}
394
395		idx = find_next_zero(pool->bitmap[i], last_idx);
396		if (!blocks_free(pool, i, idx, nr_blocks)) {
397			idx += nr_blocks;
398			if (idx < SMALLOC_BPI)
399				last_idx = idx;
400			else {
401				last_idx = 0;
402				while (idx >= SMALLOC_BPI) {
403					i++;
404					idx -= SMALLOC_BPI;
405				}
406			}
407			continue;
408		}
409		set_blocks(pool, i, idx, nr_blocks);
410		offset = i * SMALLOC_BPL + idx * SMALLOC_BPB;
411		break;
412	}
413
414	if (i < pool->nr_blocks) {
415		pool->free_blocks -= nr_blocks;
416		ret = pool->map + offset;
417	}
418fail:
419	pool_unlock(pool);
420	return ret;
421}
422
423static void *smalloc_pool(struct pool *pool, unsigned int size)
424{
425	unsigned int alloc_size = size + sizeof(struct block_hdr);
426	void *ptr;
427
428#ifdef SMALLOC_REDZONE
429	alloc_size += sizeof(unsigned int);
430#endif
431
432	ptr = __smalloc_pool(pool, alloc_size);
433	if (ptr) {
434		struct block_hdr *hdr = ptr;
435
436		hdr->size = alloc_size;
437		fill_redzone(hdr);
438
439		ptr += sizeof(*hdr);
440		memset(ptr, 0, size);
441	}
442
443	return ptr;
444}
445
446void *smalloc(unsigned int size)
447{
448	unsigned int i;
449
450	global_write_lock();
451	i = last_pool;
452
453	do {
454		for (; i < nr_pools; i++) {
455			void *ptr = smalloc_pool(&mp[i], size);
456
457			if (ptr) {
458				last_pool = i;
459				global_write_unlock();
460				return ptr;
461			}
462		}
463		if (last_pool) {
464			last_pool = 0;
465			continue;
466		}
467
468		if (nr_pools + 1 > MAX_POOLS)
469			break;
470		else {
471			i = nr_pools;
472			if (add_pool(&mp[nr_pools], size))
473				goto out;
474		}
475	} while (1);
476
477out:
478	global_write_unlock();
479	return NULL;
480}
481
482char *smalloc_strdup(const char *str)
483{
484	char *ptr;
485
486	ptr = smalloc(strlen(str) + 1);
487	strcpy(ptr, str);
488	return ptr;
489}
490