smalloc.c revision 6548f47f241013c7f6e1bb4b8a341f7d7a78764f 
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	4		/* 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	char file[PATH_MAX];			/* filename for fd */
41	unsigned int mmap_size;
42};
43
44struct block_hdr {
45	unsigned int size;
46#ifdef SMALLOC_REDZONE
47	unsigned int prered;
48#endif
49};
50
51static struct pool mp[MAX_POOLS];
52static unsigned int nr_pools;
53static unsigned int last_pool;
54static struct fio_mutex *lock;
55
56static inline void pool_lock(struct pool *pool)
57{
58	if (pool->lock)
59		fio_mutex_down(pool->lock);
60}
61
62static inline void pool_unlock(struct pool *pool)
63{
64	if (pool->lock)
65		fio_mutex_up(pool->lock);
66}
67
68static inline void global_read_lock(void)
69{
70	if (lock)
71		fio_mutex_down_read(lock);
72}
73
74static inline void global_read_unlock(void)
75{
76	if (lock)
77		fio_mutex_up_read(lock);
78}
79
80static inline void global_write_lock(void)
81{
82	if (lock)
83		fio_mutex_down_write(lock);
84}
85
86static inline void global_write_unlock(void)
87{
88	if (lock)
89		fio_mutex_up_write(lock);
90}
91
92static inline int ptr_valid(struct pool *pool, void *ptr)
93{
94	unsigned int pool_size = pool->nr_blocks * SMALLOC_BPL;
95
96	return (ptr >= pool->map) && (ptr < pool->map + pool_size);
97}
98
99static inline unsigned int size_to_blocks(unsigned int size)
100{
101	return (size + SMALLOC_BPB - 1) / SMALLOC_BPB;
102}
103
104static int blocks_iter(struct pool *pool, unsigned int pool_idx,
105		       unsigned int idx, unsigned int nr_blocks,
106		       int (*func)(unsigned int *map, unsigned int mask))
107{
108
109	while (nr_blocks) {
110		unsigned int this_blocks, mask;
111		unsigned int *map;
112
113		if (pool_idx >= pool->nr_blocks)
114			return 0;
115
116		map = &pool->bitmap[pool_idx];
117
118		this_blocks = nr_blocks;
119		if (this_blocks + idx > SMALLOC_BPI) {
120			this_blocks = SMALLOC_BPI - idx;
121			idx = SMALLOC_BPI - this_blocks;
122		}
123
124		if (this_blocks == SMALLOC_BPI)
125			mask = -1U;
126		else
127			mask = ((1U << this_blocks) - 1) << idx;
128
129		if (!func(map, mask))
130			return 0;
131
132		nr_blocks -= this_blocks;
133		idx = 0;
134		pool_idx++;
135	}
136
137	return 1;
138}
139
140static int mask_cmp(unsigned int *map, unsigned int mask)
141{
142	return !(*map & mask);
143}
144
145static int mask_clear(unsigned int *map, unsigned int mask)
146{
147	assert((*map & mask) == mask);
148	*map &= ~mask;
149	return 1;
150}
151
152static int mask_set(unsigned int *map, unsigned int mask)
153{
154	assert(!(*map & mask));
155	*map |= mask;
156	return 1;
157}
158
159static int blocks_free(struct pool *pool, unsigned int pool_idx,
160		       unsigned int idx, unsigned int nr_blocks)
161{
162	return blocks_iter(pool, pool_idx, idx, nr_blocks, mask_cmp);
163}
164
165static void set_blocks(struct pool *pool, unsigned int pool_idx,
166		       unsigned int idx, unsigned int nr_blocks)
167{
168	blocks_iter(pool, pool_idx, idx, nr_blocks, mask_set);
169}
170
171static void clear_blocks(struct pool *pool, unsigned int pool_idx,
172			 unsigned int idx, unsigned int nr_blocks)
173{
174	blocks_iter(pool, pool_idx, idx, nr_blocks, mask_clear);
175}
176
177static int find_next_zero(int word, int start)
178{
179	assert(word != -1U);
180	word >>= (start + 1);
181	return ffz(word) + start + 1;
182}
183
184static int add_pool(struct pool *pool, unsigned int alloc_size)
185{
186	void *ptr;
187	int fd, bitmap_blocks;
188
189	strcpy(pool->file, "/tmp/.fio_smalloc.XXXXXX");
190	fd = mkstemp(pool->file);
191	if (fd < 0)
192		goto out_close;
193
194#ifdef SMALLOC_REDZONE
195	alloc_size += sizeof(unsigned int);
196#endif
197	alloc_size += sizeof(struct block_hdr);
198	if (alloc_size < INITIAL_SIZE)
199		alloc_size = INITIAL_SIZE;
200
201	/* round up to nearest full number of blocks */
202	alloc_size = (alloc_size + SMALLOC_BPL - 1) & ~(SMALLOC_BPL - 1);
203	bitmap_blocks = alloc_size / SMALLOC_BPL;
204	alloc_size += bitmap_blocks * sizeof(unsigned int);
205	pool->mmap_size = alloc_size;
206
207	pool->nr_blocks = bitmap_blocks;
208	pool->free_blocks = bitmap_blocks * SMALLOC_BPB;
209
210	if (ftruncate(fd, alloc_size) < 0)
211		goto out_unlink;
212
213	ptr = mmap(NULL, alloc_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
214	if (ptr == MAP_FAILED)
215		goto out_unlink;
216
217	memset(ptr, 0, alloc_size);
218	pool->map = ptr;
219	pool->bitmap = (void *) ptr + (pool->nr_blocks * SMALLOC_BPL);
220
221#ifdef MP_SAFE
222	pool->lock = fio_mutex_init(1);
223	if (!pool->lock)
224		goto out_unlink;
225#endif
226
227	pool->fd = fd;
228
229	global_write_lock();
230	nr_pools++;
231	global_write_unlock();
232	return 0;
233out_unlink:
234	fprintf(stderr, "smalloc: failed adding pool\n");
235	if (pool->map)
236		munmap(pool->map, pool->mmap_size);
237	unlink(pool->file);
238out_close:
239	if (fd >= 0)
240		close(fd);
241	return 1;
242}
243
244void sinit(void)
245{
246	int ret;
247
248#ifdef MP_SAFE
249	lock = fio_mutex_rw_init();
250#endif
251	ret = add_pool(&mp[0], INITIAL_SIZE);
252	assert(!ret);
253}
254
255static void cleanup_pool(struct pool *pool)
256{
257	unlink(pool->file);
258	close(pool->fd);
259	munmap(pool->map, pool->mmap_size);
260
261	if (pool->lock)
262		fio_mutex_remove(pool->lock);
263}
264
265void scleanup(void)
266{
267	unsigned int i;
268
269	for (i = 0; i < nr_pools; i++)
270		cleanup_pool(&mp[i]);
271
272	if (lock)
273		fio_mutex_remove(lock);
274}
275
276#ifdef SMALLOC_REDZONE
277static void fill_redzone(struct block_hdr *hdr)
278{
279	unsigned int *postred = (void *) hdr + hdr->size - sizeof(unsigned int);
280
281	hdr->prered = SMALLOC_PRE_RED;
282	*postred = SMALLOC_POST_RED;
283}
284
285static void sfree_check_redzone(struct block_hdr *hdr)
286{
287	unsigned int *postred = (void *) hdr + hdr->size - sizeof(unsigned int);
288
289	if (hdr->prered != SMALLOC_PRE_RED) {
290		fprintf(stderr, "smalloc pre redzone destroyed!\n");
291		fprintf(stderr, "  ptr=%p, prered=%x, expected %x\n",
292				hdr, hdr->prered, SMALLOC_PRE_RED);
293		assert(0);
294	}
295	if (*postred != SMALLOC_POST_RED) {
296		fprintf(stderr, "smalloc post redzone destroyed!\n");
297		fprintf(stderr, "  ptr=%p, postred=%x, expected %x\n",
298				hdr, *postred, SMALLOC_POST_RED);
299		assert(0);
300	}
301}
302#else
303static void fill_redzone(struct block_hdr *hdr)
304{
305}
306
307static void sfree_check_redzone(struct block_hdr *hdr)
308{
309}
310#endif
311
312static void sfree_pool(struct pool *pool, void *ptr)
313{
314	struct block_hdr *hdr;
315	unsigned int i, idx;
316	unsigned long offset;
317
318	if (!ptr)
319		return;
320
321	ptr -= sizeof(*hdr);
322	hdr = ptr;
323
324	assert(ptr_valid(pool, ptr));
325
326	sfree_check_redzone(hdr);
327
328	offset = ptr - pool->map;
329	i = offset / SMALLOC_BPL;
330	idx = (offset % SMALLOC_BPL) / SMALLOC_BPB;
331
332	pool_lock(pool);
333	clear_blocks(pool, i, idx, size_to_blocks(hdr->size));
334	if (i < pool->next_non_full)
335		pool->next_non_full = i;
336	pool->free_blocks += size_to_blocks(hdr->size);
337	pool_unlock(pool);
338}
339
340void sfree(void *ptr)
341{
342	struct pool *pool = NULL;
343	unsigned int i;
344
345	if (!ptr)
346		return;
347
348	global_read_lock();
349
350	for (i = 0; i < nr_pools; i++) {
351		if (ptr_valid(&mp[i], ptr)) {
352			pool = &mp[i];
353			break;
354		}
355	}
356
357	global_read_unlock();
358
359	assert(pool);
360	sfree_pool(pool, ptr);
361}
362
363static void *__smalloc_pool(struct pool *pool, unsigned int size)
364{
365	unsigned int nr_blocks;
366	unsigned int i;
367	unsigned int offset;
368	unsigned int last_idx;
369	void *ret = NULL;
370
371	pool_lock(pool);
372
373	nr_blocks = size_to_blocks(size);
374	if (nr_blocks > pool->free_blocks)
375		goto fail;
376
377	i = pool->next_non_full;
378	last_idx = 0;
379	offset = -1U;
380	while (i < pool->nr_blocks) {
381		unsigned int idx;
382
383		if (pool->bitmap[i] == -1U) {
384			i++;
385			pool->next_non_full = i;
386			last_idx = 0;
387			continue;
388		}
389
390		idx = find_next_zero(pool->bitmap[i], last_idx);
391		if (!blocks_free(pool, i, idx, nr_blocks)) {
392			idx += nr_blocks;
393			if (idx < SMALLOC_BPI)
394				last_idx = idx;
395			else {
396				last_idx = 0;
397				while (idx >= SMALLOC_BPI) {
398					i++;
399					idx -= SMALLOC_BPI;
400				}
401			}
402			continue;
403		}
404		set_blocks(pool, i, idx, nr_blocks);
405		offset = i * SMALLOC_BPL + idx * SMALLOC_BPB;
406		break;
407	}
408
409	if (i < pool->nr_blocks) {
410		pool->free_blocks -= nr_blocks;
411		ret = pool->map + offset;
412	}
413fail:
414	pool_unlock(pool);
415	return ret;
416}
417
418static void *smalloc_pool(struct pool *pool, unsigned int size)
419{
420	unsigned int alloc_size = size + sizeof(struct block_hdr);
421	void *ptr;
422
423#ifdef SMALLOC_REDZONE
424	alloc_size += sizeof(unsigned int);
425#endif
426
427	ptr = __smalloc_pool(pool, alloc_size);
428	if (ptr) {
429		struct block_hdr *hdr = ptr;
430
431		hdr->size = alloc_size;
432		fill_redzone(hdr);
433
434		ptr += sizeof(*hdr);
435		memset(ptr, 0, size);
436	}
437
438	return ptr;
439}
440
441void *smalloc(unsigned int size)
442{
443	unsigned int i;
444
445	global_read_lock();
446	i = last_pool;
447
448	do {
449		for (; i < nr_pools; i++) {
450			void *ptr = smalloc_pool(&mp[i], size);
451
452			if (ptr) {
453				last_pool = i;
454				global_read_unlock();
455				return ptr;
456			}
457		}
458		if (last_pool) {
459			last_pool = 0;
460			continue;
461		}
462
463		if (nr_pools + 1 > MAX_POOLS)
464			break;
465		else {
466			i = nr_pools;
467			global_read_unlock();
468			if (add_pool(&mp[nr_pools], size))
469				goto out;
470			global_read_lock();
471		}
472	} while (1);
473
474	global_read_unlock();
475out:
476	return NULL;
477}
478
479char *smalloc_strdup(const char *str)
480{
481	char *ptr;
482
483	ptr = smalloc(strlen(str) + 1);
484	strcpy(ptr, str);
485	return ptr;
486}
487