2 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
3 * Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
5 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
6 * OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
8 * Permission is hereby granted to use or copy this program
9 * for any purpose, provided the above notices are retained on all copies.
10 * Permission to modify the code and to distribute modified code is granted,
11 * provided the above notices are retained, and a notice that the code was
12 * modified is included with the above copyright notice.
14 /* Boehm, August 9, 1995 6:09 pm PDT */
18 * We maintain several hash tables of hblks that have had false hits.
19 * Each contains one bit per hash bucket; If any page in the bucket
20 * has had a false hit, we assume that all of them have.
21 * See the definition of page_hash_table in gc_private.h.
22 * False hits from the stack(s) are much more dangerous than false hits
23 * from elsewhere, since the former can pin a large object that spans the
24 * block, eventhough it does not start on the dangerous block.
28 * Externally callable routines are:
30 * GC_add_to_black_list_normal
31 * GC_add_to_black_list_stack
32 * GC_promote_black_lists
35 * All require that the allocator lock is held.
38 /* Pointers to individual tables. We replace one table by another by */
39 /* switching these pointers. */
40 word * GC_old_normal_bl;
41 /* Nonstack false references seen at last full */
43 word * GC_incomplete_normal_bl;
44 /* Nonstack false references seen since last */
45 /* full collection. */
46 word * GC_old_stack_bl;
47 word * GC_incomplete_stack_bl;
49 word GC_total_stack_black_listed;
51 word GC_black_list_spacing = MINHINCR*HBLKSIZE; /* Initial rough guess */
55 void GC_default_print_heap_obj_proc(p)
58 ptr_t base = GC_base(p);
60 GC_err_printf2("start: 0x%lx, appr. length: %ld", base, GC_size(base));
63 void (*GC_print_heap_obj)(/* char * s, ptr_t p */) =
64 GC_default_print_heap_obj_proc;
66 void GC_print_source_ptr(p)
69 ptr_t base = GC_base(p);
72 GC_err_printf0("in register");
74 GC_err_printf0("in root set");
77 GC_err_printf0("in object at ");
78 (*GC_print_heap_obj)(base);
84 # ifndef ALL_INTERIOR_POINTERS
85 GC_old_normal_bl = (word *)
86 GC_scratch_alloc((word)(sizeof (page_hash_table)));
87 GC_incomplete_normal_bl = (word *)GC_scratch_alloc
88 ((word)(sizeof(page_hash_table)));
89 if (GC_old_normal_bl == 0 || GC_incomplete_normal_bl == 0) {
90 GC_err_printf0("Insufficient memory for black list\n");
93 GC_clear_bl(GC_old_normal_bl);
94 GC_clear_bl(GC_incomplete_normal_bl);
96 GC_old_stack_bl = (word *)GC_scratch_alloc((word)(sizeof(page_hash_table)));
97 GC_incomplete_stack_bl = (word *)GC_scratch_alloc
98 ((word)(sizeof(page_hash_table)));
99 if (GC_old_stack_bl == 0 || GC_incomplete_stack_bl == 0) {
100 GC_err_printf0("Insufficient memory for black list\n");
103 GC_clear_bl(GC_old_stack_bl);
104 GC_clear_bl(GC_incomplete_stack_bl);
107 void GC_clear_bl(doomed)
110 BZERO(doomed, sizeof(page_hash_table));
113 void GC_copy_bl(old, new)
116 BCOPY(old, new, sizeof(page_hash_table));
119 static word total_stack_black_listed();
121 /* Signal the completion of a collection. Turn the incomplete black */
122 /* lists into new black lists, etc. */
123 void GC_promote_black_lists()
125 word * very_old_normal_bl = GC_old_normal_bl;
126 word * very_old_stack_bl = GC_old_stack_bl;
128 GC_old_normal_bl = GC_incomplete_normal_bl;
129 GC_old_stack_bl = GC_incomplete_stack_bl;
130 # ifndef ALL_INTERIOR_POINTERS
131 GC_clear_bl(very_old_normal_bl);
133 GC_clear_bl(very_old_stack_bl);
134 GC_incomplete_normal_bl = very_old_normal_bl;
135 GC_incomplete_stack_bl = very_old_stack_bl;
136 GC_total_stack_black_listed = total_stack_black_listed();
138 GC_printf1("%ld bytes in heap blacklisted for interior pointers\n",
139 (unsigned long)GC_total_stack_black_listed);
141 if (GC_total_stack_black_listed != 0) {
142 GC_black_list_spacing =
143 HBLKSIZE*(GC_heapsize/GC_total_stack_black_listed);
145 if (GC_black_list_spacing < 3 * HBLKSIZE) {
146 GC_black_list_spacing = 3 * HBLKSIZE;
150 void GC_unpromote_black_lists()
152 # ifndef ALL_INTERIOR_POINTERS
153 GC_copy_bl(GC_old_normal_bl, GC_incomplete_normal_bl);
155 GC_copy_bl(GC_old_stack_bl, GC_incomplete_stack_bl);
158 # ifndef ALL_INTERIOR_POINTERS
159 /* P is not a valid pointer reference, but it falls inside */
160 /* the plausible heap bounds. */
161 /* Add it to the normal incomplete black list if appropriate. */
162 #ifdef PRINT_BLACK_LIST
163 void GC_add_to_black_list_normal(p, source)
166 void GC_add_to_black_list_normal(p)
170 if (!(GC_modws_valid_offsets[p & (sizeof(word)-1)])) return;
172 register int index = PHT_HASH(p);
174 if (HDR(p) == 0 || get_pht_entry_from_index(GC_old_normal_bl, index)) {
175 # ifdef PRINT_BLACK_LIST
176 if (!get_pht_entry_from_index(GC_incomplete_normal_bl, index)) {
178 "Black listing (normal) 0x%lx referenced from 0x%lx ",
179 (unsigned long) p, (unsigned long) source);
180 GC_print_source_ptr(source);
184 set_pht_entry_from_index(GC_incomplete_normal_bl, index);
185 } /* else this is probably just an interior pointer to an allocated */
186 /* object, and isn't worth black listing. */
191 /* And the same for false pointers from the stack. */
192 #ifdef PRINT_BLACK_LIST
193 void GC_add_to_black_list_stack(p, source)
196 void GC_add_to_black_list_stack(p)
200 register int index = PHT_HASH(p);
202 if (HDR(p) == 0 || get_pht_entry_from_index(GC_old_stack_bl, index)) {
203 # ifdef PRINT_BLACK_LIST
204 if (!get_pht_entry_from_index(GC_incomplete_stack_bl, index)) {
206 "Black listing (stack) 0x%lx referenced from 0x%lx ",
207 (unsigned long)p, (unsigned long)source);
208 GC_print_source_ptr(source);
212 set_pht_entry_from_index(GC_incomplete_stack_bl, index);
217 * Is the block starting at h of size len bytes black listed? If so,
218 * return the address of the next plausible r such that (r, len) might not
219 * be black listed. (R may not actually be in the heap. We guarantee only
220 * that every smaller value of r after h is also black listed.)
221 * If (h,len) is not black listed, return 0.
222 * Knows about the structure of the black list hash tables.
224 struct hblk * GC_is_black_listed(h, len)
228 register int index = PHT_HASH((word)h);
230 word nblocks = divHBLKSZ(len);
232 # ifndef ALL_INTERIOR_POINTERS
233 if (get_pht_entry_from_index(GC_old_normal_bl, index)
234 || get_pht_entry_from_index(GC_incomplete_normal_bl, index)) {
240 if (GC_old_stack_bl[divWORDSZ(index)] == 0
241 && GC_incomplete_stack_bl[divWORDSZ(index)] == 0) {
243 i += WORDSZ - modWORDSZ(index);
245 if (get_pht_entry_from_index(GC_old_stack_bl, index)
246 || get_pht_entry_from_index(GC_incomplete_stack_bl, index)) {
251 if (i >= nblocks) break;
252 index = PHT_HASH((word)(h+i));
258 /* Return the number of blacklisted blocks in a given range. */
259 /* Used only for statistical purposes. */
260 /* Looks only at the GC_incomplete_stack_bl. */
261 word GC_number_stack_black_listed(start, endp1)
262 struct hblk *start, *endp1;
264 register struct hblk * h;
267 for (h = start; h < endp1; h++) {
268 register int index = PHT_HASH((word)h);
270 if (get_pht_entry_from_index(GC_old_stack_bl, index)) result++;
276 /* Return the total number of (stack) black-listed bytes. */
277 static word total_stack_black_listed()
282 for (i = 0; i < GC_n_heap_sects; i++) {
283 struct hblk * start = (struct hblk *) GC_heap_sects[i].hs_start;
284 word len = (word) GC_heap_sects[i].hs_bytes;
285 struct hblk * endp1 = start + len/HBLKSIZE;
287 total += GC_number_stack_black_listed(start, endp1);
289 return(total * HBLKSIZE);