1 /* Memory allocator `malloc'. */
3 /* Copyright (c) 2010-2021. The SimGrid Team. All rights reserved. */
5 /* This program is free software; you can redistribute it and/or modify it
6 * under the terms of the license (GNU LGPL) which comes with this package. */
8 /* Copyright 1990, 1991, 1992 Free Software Foundation
10 Written May 1989 by Mike Haertel.
11 Heavily modified Mar 1992 by Fred Fish for mmap'd version. */
13 #include <string.h> /* Prototypes for memcpy, memmove, memset, etc */
15 #include "mmprivate.h"
17 /* Prototypes for local functions */
19 static void initialize(xbt_mheap_t mdp);
20 static void *register_morecore(xbt_mheap_t mdp, size_t size);
21 static void *align(xbt_mheap_t mdp, size_t size);
23 /* Allocation aligned on block boundary.
25 * It never returns NULL, but dies verbosely on error.
27 static void *align(struct mdesc *mdp, size_t size)
30 unsigned long int adj;
32 result = mmorecore(mdp, size);
34 /* if this reservation does not fill up the last block of our resa,
35 * complete the reservation by also asking for the full latest block.
37 * Also, the returned block is aligned to the end of block (but I've
38 * no fucking idea of why, actually -- http://abstrusegoose.com/432 --
39 * but not doing so seems to lead to issues).
41 adj = RESIDUAL(result, BLOCKSIZE);
43 adj = BLOCKSIZE - adj;
45 result = (char *) result + adj;
50 /** Initialize heapinfo about the heapinfo pages :)
53 static void initialize_heapinfo_heapinfo(const s_xbt_mheap_t* mdp)
55 // Update heapinfo about the heapinfo pages (!):
56 xbt_assert((uintptr_t) mdp->heapinfo % BLOCKSIZE == 0);
57 size_t block = BLOCK(mdp->heapinfo);
58 size_t nblocks = mdp->heapsize * sizeof(malloc_info) / BLOCKSIZE;
60 for (size_t j=0; j!=nblocks; ++j) {
61 mdp->heapinfo[block+j].type = MMALLOC_TYPE_FREE;
62 mdp->heapinfo[block+j].free_block.size = 0;
63 mdp->heapinfo[block+j].free_block.next = 0;
64 mdp->heapinfo[block+j].free_block.prev = 0;
66 mdp->heapinfo[block].free_block.size = nblocks;
69 /* Finish the initialization of the mheap. If we want to inline it
70 * properly, we need to make the align function publicly visible, too */
71 static void initialize(xbt_mheap_t mdp)
73 // Update mdp meta-data:
74 mdp->heapsize = HEAP / BLOCKSIZE;
75 mdp->heapinfo = (malloc_info *)
76 align(mdp, mdp->heapsize * sizeof(malloc_info));
77 mdp->heapbase = (void *) mdp->heapinfo;
78 mdp->flags |= MMALLOC_INITIALIZED;
80 // Update root heapinfo:
81 memset((void *) mdp->heapinfo, 0, mdp->heapsize * sizeof(malloc_info));
82 mdp->heapinfo[0].type = MMALLOC_TYPE_FREE;
83 mdp->heapinfo[0].free_block.size = 0;
84 mdp->heapinfo[0].free_block.next = mdp->heapinfo[0].free_block.prev = 0;
87 initialize_heapinfo_heapinfo(mdp);
89 for (int i = 0; i < BLOCKLOG; i++) {
90 malloc_info mi; /* to compute the offset of the swag hook */
91 xbt_swag_init(&(mdp->fraghead[i]), xbt_swag_offset(mi, freehook));
95 static inline void update_hook(void **a, size_t offset)
98 *a = (char*)*a + offset;
101 /* Get neatly aligned memory from the low level layers, and register it
102 * into the heap info table as necessary. */
103 static void *register_morecore(struct mdesc *mdp, size_t size)
105 void* result = align(mdp, size); // Never returns NULL
107 /* Check if we need to grow the info table (in a multiplicative manner) */
108 if ((size_t) BLOCK((char *) result + size) > mdp->heapsize) {
109 size_t newsize = mdp->heapsize;
110 while ((size_t) BLOCK((char *) result + size) > newsize)
113 /* Copy old info into new location */
114 malloc_info* oldinfo = mdp->heapinfo;
115 malloc_info* newinfo = (malloc_info*)align(mdp, newsize * sizeof(malloc_info));
116 memcpy(newinfo, oldinfo, mdp->heapsize * sizeof(malloc_info));
118 /* Initialize the new blockinfo : */
119 memset((char*) newinfo + mdp->heapsize * sizeof(malloc_info), 0,
120 (newsize - mdp->heapsize)* sizeof(malloc_info));
122 /* Update the swag of busy blocks containing free fragments by applying the offset to all swag_hooks. Yeah. My hand is right in the fan and I still type */
123 size_t offset=((char*)newinfo)-((char*)oldinfo);
125 for (int i = 1 /*first element of heapinfo describes the mdesc area*/; i < mdp->heaplimit; i++) {
126 update_hook(&newinfo[i].freehook.next, offset);
127 update_hook(&newinfo[i].freehook.prev, offset);
129 // also update the starting points of the swag
130 for (int i = 0; i < BLOCKLOG; i++) {
131 update_hook(&mdp->fraghead[i].head, offset);
132 update_hook(&mdp->fraghead[i].tail, offset);
134 mdp->heapinfo = newinfo;
136 /* mark the space previously occupied by the block info as free by first marking it
137 * as occupied in the regular way, and then freing it */
138 for (int it = 0; it < BLOCKIFY(mdp->heapsize * sizeof(malloc_info)); it++) {
139 newinfo[BLOCK(oldinfo)+it].type = MMALLOC_TYPE_UNFRAGMENTED;
140 newinfo[BLOCK(oldinfo)+it].busy_block.ignore = 0;
143 newinfo[BLOCK(oldinfo)].busy_block.size = BLOCKIFY(mdp->heapsize * sizeof(malloc_info));
144 newinfo[BLOCK(oldinfo)].busy_block.busy_size = size;
145 mfree(mdp, (void *) oldinfo);
146 mdp->heapsize = newsize;
148 initialize_heapinfo_heapinfo(mdp);
151 mdp->heaplimit = BLOCK((char *) result + size);
155 /* Allocate memory from the heap. */
156 void *mmalloc(xbt_mheap_t mdp, size_t size) {
157 void *res= mmalloc_no_memset(mdp,size);
158 if (mdp->options & XBT_MHEAP_OPTION_MEMSET) {
164 static void mmalloc_mark_used(xbt_mheap_t mdp, size_t block, size_t nblocks, size_t requested_size)
166 for (int it = 0; it < nblocks; it++) {
167 mdp->heapinfo[block + it].type = MMALLOC_TYPE_UNFRAGMENTED;
168 mdp->heapinfo[block + it].busy_block.busy_size = 0;
169 mdp->heapinfo[block + it].busy_block.ignore = 0;
170 mdp->heapinfo[block + it].busy_block.size = 0;
172 mdp->heapinfo[block].busy_block.size = nblocks;
173 mdp->heapinfo[block].busy_block.busy_size = requested_size;
174 mdp->heapstats.chunks_used++;
175 mdp->heapstats.bytes_used += nblocks * BLOCKSIZE;
178 /* Splitting mmalloc this way is mandated by a trick in mrealloc, that gives
179 back the memory of big blocks to the system before reallocating them: we don't
180 want to loose the beginning of the area when this happens */
181 void *mmalloc_no_memset(xbt_mheap_t mdp, size_t size)
186 size_t requested_size = size; // The amount of memory requested by user, for real
188 /* Work even if the user was stupid enough to ask a ridiculously small block (even 0-length),
189 * ie return a valid block that can be realloced and freed.
190 * glibc malloc does not use this trick but return a constant pointer, but we need to enlist the free fragments later on.
192 if (size < SMALLEST_POSSIBLE_MALLOC)
193 size = SMALLEST_POSSIBLE_MALLOC;
195 if (!(mdp->flags & MMALLOC_INITIALIZED))
198 /* Determine the allocation policy based on the request size. */
199 if (size <= BLOCKSIZE / 2) {
200 /* Small allocation to receive a fragment of a block.
201 Determine the logarithm to base two of the fragment size. */
204 while ((size /= 2) != 0) {
208 /* Look in the fragment lists for a free fragment of the desired size. */
209 if (xbt_swag_size(&mdp->fraghead[log])>0) {
210 /* There are free fragments of this size; Get one of them and prepare to return it.
211 Update the block's nfree and if no other free fragment, get out of the swag. */
213 /* search a fragment that I could return as a result */
214 malloc_info *candidate_info = xbt_swag_getFirst(&mdp->fraghead[log]);
215 size_t candidate_block = (candidate_info - &(mdp->heapinfo[0]));
216 size_t candidate_frag;
217 for (candidate_frag=0;candidate_frag<(size_t) (BLOCKSIZE >> log);candidate_frag++)
218 if (candidate_info->busy_frag.frag_size[candidate_frag] == -1)
220 xbt_assert(candidate_frag < (size_t) (BLOCKSIZE >> log),
221 "Block %zu was registered as containing free fragments of type %zu, but I can't find any",candidate_block,log);
223 result = (void*) (((char*)ADDRESS(candidate_block)) + (candidate_frag << log));
225 /* Remove this fragment from the list of free guys */
226 candidate_info->busy_frag.nfree--;
227 if (candidate_info->busy_frag.nfree == 0) {
228 xbt_swag_remove(candidate_info,&mdp->fraghead[log]);
231 /* Update our metadata about this fragment */
232 candidate_info->busy_frag.frag_size[candidate_frag] = requested_size;
233 candidate_info->busy_frag.ignore[candidate_frag] = 0;
235 /* Update the statistics. */
236 mdp -> heapstats.chunks_used++;
237 mdp -> heapstats.bytes_used += 1 << log;
238 mdp -> heapstats.chunks_free--;
239 mdp -> heapstats.bytes_free -= 1 << log;
242 /* No free fragments of the desired size, so get a new block
243 and break it into fragments, returning the first. */
245 result = mmalloc(mdp, BLOCKSIZE); // does not return NULL
246 block = BLOCK(result);
248 mdp->heapinfo[block].type = (int)log;
249 /* Link all fragments but the first as free, and add the block to the swag of blocks containing free frags */
251 for (i = 1; i < (size_t) (BLOCKSIZE >> log); ++i) {
252 mdp->heapinfo[block].busy_frag.frag_size[i] = -1;
253 mdp->heapinfo[block].busy_frag.ignore[i] = 0;
255 mdp->heapinfo[block].busy_frag.nfree = i - 1;
256 mdp->heapinfo[block].freehook.prev = NULL;
257 mdp->heapinfo[block].freehook.next = NULL;
259 xbt_swag_insert(&mdp->heapinfo[block], &(mdp->fraghead[log]));
261 /* mark the fragment returned as busy */
262 mdp->heapinfo[block].busy_frag.frag_size[0] = requested_size;
263 mdp->heapinfo[block].busy_frag.ignore[0] = 0;
266 mdp -> heapstats.chunks_free += (BLOCKSIZE >> log) - 1;
267 mdp -> heapstats.bytes_free += BLOCKSIZE - (1 << log);
268 mdp -> heapstats.bytes_used -= BLOCKSIZE - (1 << log);
271 /* Large allocation to receive one or more blocks.
272 Search the free list in a circle starting at the last place visited.
273 If we loop completely around without finding a large enough
274 space we will have to get more memory from the system. */
275 size_t blocks = BLOCKIFY(size);
276 size_t start = MALLOC_SEARCH_START;
277 block = MALLOC_SEARCH_START;
278 while (mdp->heapinfo[block].free_block.size < blocks) {
279 if (mdp->heapinfo[block].type >=0) { // Don't trust xbt_die and friends in malloc-level library, you fool!
281 "Internal error: found a free block not marked as such (block=%zu type=%d). Please report this bug.\n",
282 block, mdp->heapinfo[block].type);
286 block = mdp->heapinfo[block].free_block.next;
287 if (block == start) {
288 /* Need to get more from the system. Check to see if
289 the new core will be contiguous with the final free
290 block; if so we don't need to get as much. */
291 block = mdp->heapinfo[0].free_block.prev;
292 size_t lastblocks = mdp->heapinfo[block].free_block.size;
293 if (mdp->heaplimit != 0 &&
294 block + lastblocks == mdp->heaplimit &&
295 mmorecore(mdp, 0) == ADDRESS(block + lastblocks) &&
296 (register_morecore(mdp, (blocks - lastblocks) * BLOCKSIZE)) != NULL) {
297 /* Which block we are extending (the `final free
298 block' referred to above) might have changed, if
299 it got combined with a freed info table. */
300 block = mdp->heapinfo[0].free_block.prev;
302 mdp->heapinfo[block].free_block.size += (blocks - lastblocks);
305 result = register_morecore(mdp, blocks * BLOCKSIZE);
307 block = BLOCK(result);
308 mmalloc_mark_used(mdp, block, blocks, requested_size);
312 /* Need large block(s), but found some in the existing heap */
315 /* At this point we have found a suitable free list entry.
316 Figure out how to remove what we need from the list. */
317 result = ADDRESS(block);
318 if (mdp->heapinfo[block].free_block.size > blocks) {
319 /* The block we found has a bit left over,
320 so relink the tail end back into the free list. */
321 mdp->heapinfo[block + blocks].free_block.size
322 = mdp->heapinfo[block].free_block.size - blocks;
323 mdp->heapinfo[block + blocks].free_block.next
324 = mdp->heapinfo[block].free_block.next;
325 mdp->heapinfo[block + blocks].free_block.prev
326 = mdp->heapinfo[block].free_block.prev;
327 mdp->heapinfo[mdp->heapinfo[block].free_block.prev].free_block.next
328 = mdp->heapinfo[mdp->heapinfo[block].free_block.next].free_block.prev
329 = mdp->heapindex = block + blocks;
331 /* The block exactly matches our requirements,
332 so just remove it from the list. */
333 mdp->heapinfo[mdp->heapinfo[block].free_block.next].free_block.prev
334 = mdp->heapinfo[block].free_block.prev;
335 mdp->heapinfo[mdp->heapinfo[block].free_block.prev].free_block.next
336 = mdp->heapindex = mdp->heapinfo[block].free_block.next;
339 mmalloc_mark_used(mdp, block, blocks, requested_size);
340 mdp -> heapstats.bytes_free -= blocks * BLOCKSIZE;