2 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
3 * Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
4 * Copyright (c) 1996 by Silicon Graphics. All rights reserved.
6 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
7 * OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
9 * Permission is hereby granted to use or copy this program
10 * for any purpose, provided the above notices are retained on all copies.
11 * Permission to modify the code and to distribute modified code is granted,
12 * provided the above notices are retained, and a notice that the code was
13 * modified is included with the above copyright notice.
18 * 1. allocation of heap block headers
19 * 2. A map from addresses to heap block addresses to heap block headers
21 * Access speed is crucial. We implement an index structure based on a 2
25 # include "private/gc_priv.h"
27 STATIC bottom_index * GC_all_bottom_indices = 0;
28 /* Pointer to first (lowest addr) */
31 STATIC bottom_index * GC_all_bottom_indices_end = 0;
32 /* Pointer to last (highest addr) */
35 /* Non-macro version of header location routine */
36 hdr * GC_find_header(ptr_t h)
47 /* Handle a header cache miss. Returns a pointer to the */
48 /* header corresponding to p, if p can possibly be a valid */
49 /* object pointer, and 0 otherwise. */
50 /* GUARANTEED to return 0 for a pointer past the first page */
51 /* of an object unless both GC_all_interior_pointers is set */
52 /* and p is in fact a valid object pointer. */
53 /* Never returns a pointer to a free hblk. */
54 #ifdef PRINT_BLACK_LIST
55 hdr * GC_header_cache_miss(ptr_t p, hdr_cache_entry *hce, ptr_t source)
57 hdr * GC_header_cache_miss(ptr_t p, hdr_cache_entry *hce)
63 if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
64 if (GC_all_interior_pointers) {
68 current = (ptr_t)HBLKPTR(current);
70 current = current - HBLKSIZE*(word)hhdr;
72 } while(IS_FORWARDING_ADDR_OR_NIL(hhdr));
73 /* current points to near the start of the large object */
74 if (hhdr -> hb_flags & IGNORE_OFF_PAGE)
76 if (HBLK_IS_FREE(hhdr)
77 || p - current >= (ptrdiff_t)(hhdr->hb_sz)) {
78 GC_ADD_TO_BLACK_LIST_NORMAL(p, source);
79 /* Pointer past the end of the block */
83 GC_ADD_TO_BLACK_LIST_NORMAL(p, source);
84 /* And return zero: */
86 GC_ASSERT(hhdr == 0 || !HBLK_IS_FREE(hhdr));
88 /* Pointers past the first page are probably too rare */
89 /* to add them to the cache. We don't. */
90 /* And correctness relies on the fact that we don't. */
93 GC_ADD_TO_BLACK_LIST_NORMAL(p, source);
98 if (HBLK_IS_FREE(hhdr)) {
99 GC_ADD_TO_BLACK_LIST_NORMAL(p, source);
102 hce -> block_addr = (word)(p) >> LOG_HBLKSIZE;
103 hce -> hce_hdr = hhdr;
109 /* Routines to dynamically allocate collector data structures that will */
110 /* never be freed. */
112 static ptr_t scratch_free_ptr = 0;
114 /* GC_scratch_last_end_ptr is end point of last obtained scratch area. */
115 /* GC_scratch_end_ptr is end point of current scratch area. */
117 ptr_t GC_scratch_alloc(size_t bytes)
119 register ptr_t result = scratch_free_ptr;
121 bytes += GRANULE_BYTES-1;
122 bytes &= ~(GRANULE_BYTES-1);
123 scratch_free_ptr += bytes;
124 if (scratch_free_ptr <= GC_scratch_end_ptr) {
128 word bytes_to_get = MINHINCR * HBLKSIZE;
130 if (bytes_to_get <= bytes) {
131 /* Undo the damage, and get memory directly */
132 bytes_to_get = bytes;
134 bytes_to_get += GC_page_size - 1;
135 bytes_to_get &= ~(GC_page_size - 1);
137 result = (ptr_t)GET_MEM(bytes_to_get);
138 GC_add_to_our_memory(result, bytes_to_get);
139 scratch_free_ptr -= bytes;
140 GC_scratch_last_end_ptr = result + bytes;
143 result = (ptr_t)GET_MEM(bytes_to_get);
144 GC_add_to_our_memory(result, bytes_to_get);
147 GC_printf("Out of memory - trying to allocate less\n");
148 scratch_free_ptr -= bytes;
149 bytes_to_get = bytes;
151 bytes_to_get += GC_page_size - 1;
152 bytes_to_get &= ~(GC_page_size - 1);
154 result = (ptr_t)GET_MEM(bytes_to_get);
155 GC_add_to_our_memory(result, bytes_to_get);
158 scratch_free_ptr = result;
159 GC_scratch_end_ptr = scratch_free_ptr + bytes_to_get;
160 GC_scratch_last_end_ptr = GC_scratch_end_ptr;
161 return(GC_scratch_alloc(bytes));
165 static hdr * hdr_free_list = 0;
167 /* Return an uninitialized header */
168 static hdr * alloc_hdr(void)
170 register hdr * result;
172 if (hdr_free_list == 0) {
173 result = (hdr *) GC_scratch_alloc((word)(sizeof(hdr)));
175 result = hdr_free_list;
176 hdr_free_list = (hdr *) (result -> hb_next);
181 static void free_hdr(hdr * hhdr)
183 hhdr -> hb_next = (struct hblk *) hdr_free_list;
184 hdr_free_list = hhdr;
187 #ifdef COUNT_HDR_CACHE_HITS
188 word GC_hdr_cache_hits = 0;
189 word GC_hdr_cache_misses = 0;
192 void GC_init_headers(void)
196 GC_all_nils = (bottom_index *)GC_scratch_alloc((word)sizeof(bottom_index));
197 BZERO(GC_all_nils, sizeof(bottom_index));
198 for (i = 0; i < TOP_SZ; i++) {
199 GC_top_index[i] = GC_all_nils;
203 /* Make sure that there is a bottom level index block for address addr */
204 /* Return FALSE on failure. */
205 static GC_bool get_index(word addr)
207 word hi = (word)(addr) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE);
210 bottom_index ** prev;
214 word i = TL_HASH(hi);
217 old = p = GC_top_index[i];
218 while(p != GC_all_nils) {
219 if (p -> key == hi) return(TRUE);
222 r = (bottom_index*)GC_scratch_alloc((word)(sizeof (bottom_index)));
223 if (r == 0) return(FALSE);
224 BZERO(r, sizeof (bottom_index));
225 r -> hash_link = old;
228 if (GC_top_index[hi] != GC_all_nils) return(TRUE);
229 r = (bottom_index*)GC_scratch_alloc((word)(sizeof (bottom_index)));
230 if (r == 0) return(FALSE);
231 GC_top_index[hi] = r;
232 BZERO(r, sizeof (bottom_index));
235 /* Add it to the list of bottom indices */
236 prev = &GC_all_bottom_indices; /* pointer to p */
237 pi = 0; /* bottom_index preceding p */
238 while ((p = *prev) != 0 && p -> key < hi) {
240 prev = &(p -> asc_link);
244 GC_all_bottom_indices_end = r;
253 /* Install a header for block h. */
254 /* The header is uninitialized. */
255 /* Returns the header or 0 on failure. */
256 struct hblkhdr * GC_install_header(struct hblk *h)
260 if (!get_index((word) h)) return(0);
261 result = alloc_hdr();
264 result -> hb_last_reclaimed = (unsigned short)GC_gc_no;
269 /* Set up forwarding counts for block h of size sz */
270 GC_bool GC_install_counts(struct hblk *h, size_t sz/* bytes */)
275 for (hbp = h; (char *)hbp < (char *)h + sz; hbp += BOTTOM_SZ) {
276 if (!get_index((word) hbp)) return(FALSE);
278 if (!get_index((word)h + sz - 1)) return(FALSE);
279 for (hbp = h + 1; (char *)hbp < (char *)h + sz; hbp += 1) {
280 i = HBLK_PTR_DIFF(hbp, h);
281 SET_HDR(hbp, (hdr *)(i > MAX_JUMP? MAX_JUMP : i));
286 /* Remove the header for block h */
287 void GC_remove_header(struct hblk *h)
296 /* Remove forwarding counts for h */
297 void GC_remove_counts(struct hblk *h, size_t sz/* bytes */)
299 register struct hblk * hbp;
301 for (hbp = h+1; (char *)hbp < (char *)h + sz; hbp += 1) {
306 /* Apply fn to all allocated blocks */
308 void GC_apply_to_all_blocks(void (*fn)(struct hblk *h, word client_data),
312 bottom_index * index_p;
314 for (index_p = GC_all_bottom_indices; index_p != 0;
315 index_p = index_p -> asc_link) {
316 for (j = BOTTOM_SZ-1; j >= 0;) {
317 if (!IS_FORWARDING_ADDR_OR_NIL(index_p->index[j])) {
318 if (!HBLK_IS_FREE(index_p->index[j])) {
319 (*fn)(((struct hblk *)
320 (((index_p->key << LOG_BOTTOM_SZ) + (word)j)
325 } else if (index_p->index[j] == 0) {
328 j -= (signed_word)(index_p->index[j]);
334 /* Get the next valid block whose address is at least h */
335 /* Return 0 if there is none. */
336 struct hblk * GC_next_used_block(struct hblk *h)
338 register bottom_index * bi;
339 register word j = ((word)h >> LOG_HBLKSIZE) & (BOTTOM_SZ-1);
342 if (bi == GC_all_nils) {
343 register word hi = (word)h >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE);
344 bi = GC_all_bottom_indices;
345 while (bi != 0 && bi -> key < hi) bi = bi -> asc_link;
349 while (j < BOTTOM_SZ) {
350 hdr * hhdr = bi -> index[j];
351 if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
354 if (!HBLK_IS_FREE(hhdr)) {
355 return((struct hblk *)
356 (((bi -> key << LOG_BOTTOM_SZ) + j)
359 j += divHBLKSZ(hhdr -> hb_sz);
369 /* Get the last (highest address) block whose address is */
370 /* at most h. Return 0 if there is none. */
371 /* Unlike the above, this may return a free block. */
372 struct hblk * GC_prev_block(struct hblk *h)
374 register bottom_index * bi;
375 register signed_word j = ((word)h >> LOG_HBLKSIZE) & (BOTTOM_SZ-1);
378 if (bi == GC_all_nils) {
379 register word hi = (word)h >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE);
380 bi = GC_all_bottom_indices_end;
381 while (bi != 0 && bi -> key > hi) bi = bi -> desc_link;
386 hdr * hhdr = bi -> index[j];
389 } else if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
390 j -= (signed_word)hhdr;
392 return((struct hblk *)
393 (((bi -> key << LOG_BOTTOM_SZ) + j)
398 bi = bi -> desc_link;