1 /* -----------------------------------------------------------------------------
2 * $Id: BlockAlloc.c,v 1.9 2001/07/23 17:23:19 simonmar Exp $
4 * (c) The GHC Team 1998-2000
6 * The block allocator and free list manager.
8 * This is the architecture independent part of the block allocator.
9 * It requires only the following support from the operating system:
13 * returns the address of an MBLOCK_SIZE region of memory, aligned on
14 * an MBLOCK_SIZE boundary. There is no requirement for successive
15 * calls to getMBlock to return strictly increasing addresses.
17 * ---------------------------------------------------------------------------*/
22 #include "BlockAlloc.h"
25 static void initMBlock(void *mblock);
26 static bdescr *allocMegaGroup(nat mblocks);
27 static void freeMegaGroup(bdescr *bd);
29 static bdescr *free_list;
31 /* -----------------------------------------------------------------------------
33 -------------------------------------------------------------------------- */
35 void initBlockAllocator(void)
40 /* -----------------------------------------------------------------------------
42 -------------------------------------------------------------------------- */
45 initGroup(nat n, bdescr *head)
52 head->free = head->start;
53 for (i=1, bd = head+1; i < n; i++, bd++) {
68 if (n > BLOCKS_PER_MBLOCK) {
69 return allocMegaGroup(BLOCKS_TO_MBLOCKS(n));
73 for (bd = free_list; bd != NULL; bd = bd->link) {
74 if (bd->blocks == n) { /* exactly the right size! */
76 /* no initialisation necessary - this is already a
77 * self-contained block group. */
79 bd->free = bd->start; /* block isn't free now */
83 if (bd->blocks > n) { /* block too big... */
84 bd->blocks -= n; /* take a chunk off the *end* */
86 initGroup(n, bd); /* initialise it */
92 mblock = getMBlock(); /* get a new megablock */
93 initMBlock(mblock); /* initialise the start fields */
94 bd = FIRST_BDESCR(mblock);
95 initGroup(n,bd); /* we know the group will fit */
96 if (n < BLOCKS_PER_MBLOCK) {
97 initGroup(BLOCKS_PER_MBLOCK-n, bd+n);
98 freeGroup(bd+n); /* add the rest on to the free list */
106 return allocGroup(1);
109 /* -----------------------------------------------------------------------------
110 Any request larger than BLOCKS_PER_MBLOCK needs a megablock group.
111 First, search the free list for enough contiguous megablocks to
112 fulfill the request - if we don't have enough, we need to
113 allocate some new ones.
115 A megablock group looks just like a normal block group, except that
116 the blocks field in the head will be larger than BLOCKS_PER_MBLOCK.
118 Note that any objects placed in this group must start in the first
119 megablock, since the other blocks don't have block descriptors.
120 -------------------------------------------------------------------------- */
123 allocMegaGroup(nat n)
126 bdescr *bd, *last, *grp_start, *grp_prev;
132 for (bd = free_list; bd != NULL; bd = bd->link) {
134 if (bd->blocks == BLOCKS_PER_MBLOCK) { /* whole megablock found */
136 /* is it the first one we've found or a non-contiguous megablock? */
137 if (grp_start == NULL ||
138 bd->start != last->start + MBLOCK_SIZE/sizeof(W_)) {
146 if (mbs_found == n) { /* found enough contig megablocks? */
151 else { /* only a partial megablock, start again */
158 /* found all the megablocks we need on the free list
160 if (mbs_found == n) {
161 /* remove the megablocks from the free list */
162 if (grp_prev == NULL) { /* bd now points to the last mblock */
163 free_list = bd->link;
165 grp_prev->link = bd->link;
169 /* the free list wasn't sufficient, allocate all new mblocks.
172 void *mblock = getMBlocks(n);
173 initMBlock(mblock); /* only need to init the 1st one */
174 grp_start = FIRST_BDESCR(mblock);
177 /* set up the megablock group */
178 initGroup(BLOCKS_PER_MBLOCK, grp_start);
179 grp_start->blocks = MBLOCK_GROUP_BLOCKS(n);
183 /* -----------------------------------------------------------------------------
185 -------------------------------------------------------------------------- */
187 /* coalesce the group p with p->link if possible.
189 * Returns p->link if no coalescing was done, otherwise returns a
190 * pointer to the newly enlarged group p.
193 static inline bdescr *
200 if (q != NULL && p->start + p->blocks * BLOCK_SIZE_W == q->start) {
202 p->blocks += q->blocks;
204 for (i = 0, bd = q; i < q->blocks; bd++, i++) {
218 /* are we dealing with a megablock group? */
219 if (p->blocks > BLOCKS_PER_MBLOCK) {
225 p->free = (void *)-1; /* indicates that this block is free */
228 /* fill the block group with garbage if sanity checking is on */
229 IF_DEBUG(sanity,memset(p->start, 0xaa, p->blocks * BLOCK_SIZE));
232 /* find correct place in free list to place new group */
234 for (bd = free_list; bd != NULL && bd->start < p->start;
239 /* now, last = previous group (or NULL) */
244 /* coalesce with previous group if possible */
245 p->link = last->link;
250 /* coalesce with next group if possible */
252 IF_DEBUG(sanity, checkFreeListSanity());
256 freeMegaGroup(bdescr *p)
260 n = p->blocks * BLOCK_SIZE / MBLOCK_SIZE + 1;
261 for (; n > 0; (W_)p += MBLOCK_SIZE, n--) {
262 initMBlock((void *)((W_)p & ~MBLOCK_MASK));
263 initGroup(BLOCKS_PER_MBLOCK, p);
269 freeChain(bdescr *bd)
280 initMBlock(void *mblock)
285 /* the first few Bdescr's in a block are unused, so we don't want to
286 * put them all on the free list.
288 block = FIRST_BLOCK(mblock);
289 bd = FIRST_BDESCR(mblock);
291 /* Initialise the start field of each block descriptor
293 for (; block <= LAST_BLOCK(mblock); bd += 1, (lnat)block += BLOCK_SIZE) {
298 /* -----------------------------------------------------------------------------
300 -------------------------------------------------------------------------- */
304 checkFreeListSanity(void)
308 for (bd = free_list; bd != NULL; bd = bd->link) {
309 IF_DEBUG(block_alloc,
310 fprintf(stderr,"group at 0x%x, length %d blocks\n",
311 (nat)bd->start, bd->blocks));
312 ASSERT(bd->blocks > 0);
313 if (bd->link != NULL) {
314 /* make sure we're fully coalesced */
315 ASSERT(bd->start + bd->blocks * BLOCK_SIZE_W != bd->link->start);
316 ASSERT(bd->start < bd->link->start);
325 lnat total_blocks = 0;
327 for (bd = free_list; bd != NULL; bd = bd->link) {
328 total_blocks += bd->blocks;