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 */
15 # include "private/gc_priv.h"
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 STATIC word * GC_old_normal_bl;
41 /* Nonstack false references seen at last full */
43 STATIC word * GC_incomplete_normal_bl;
44 /* Nonstack false references seen since last */
45 /* full collection. */
46 STATIC word * GC_old_stack_bl;
47 STATIC word * GC_incomplete_stack_bl;
49 word GC_total_stack_black_listed;
51 word GC_black_list_spacing = MINHINCR*HBLKSIZE; /* Initial rough guess */
53 void GC_clear_bl(word *);
55 void GC_default_print_heap_obj_proc(ptr_t p)
57 ptr_t base = GC_base(p);
59 GC_err_printf("start: %p, appr. length: %ld", base,
60 (unsigned long)GC_size(base));
63 void (*GC_print_heap_obj) (ptr_t p) = GC_default_print_heap_obj_proc;
65 #ifdef PRINT_BLACK_LIST
66 STATIC void GC_print_source_ptr(ptr_t p)
68 ptr_t base = GC_base(p);
71 GC_err_printf("in register");
73 GC_err_printf("in root set");
76 GC_err_printf("in object at ");
77 /* FIXME: We can't call the debug version of GC_print_heap_obj */
78 /* (with PRINT_CALL_CHAIN) here because the lock is held and */
79 /* the world is stopped. */
80 GC_default_print_heap_obj_proc(base);
87 if (!GC_all_interior_pointers) {
88 GC_old_normal_bl = (word *)
89 GC_scratch_alloc((word)(sizeof (page_hash_table)));
90 GC_incomplete_normal_bl = (word *)GC_scratch_alloc
91 ((word)(sizeof(page_hash_table)));
92 if (GC_old_normal_bl == 0 || GC_incomplete_normal_bl == 0) {
93 GC_err_printf("Insufficient memory for black list\n");
96 GC_clear_bl(GC_old_normal_bl);
97 GC_clear_bl(GC_incomplete_normal_bl);
99 GC_old_stack_bl = (word *)GC_scratch_alloc((word)(sizeof(page_hash_table)));
100 GC_incomplete_stack_bl = (word *)GC_scratch_alloc
101 ((word)(sizeof(page_hash_table)));
102 if (GC_old_stack_bl == 0 || GC_incomplete_stack_bl == 0) {
103 GC_err_printf("Insufficient memory for black list\n");
106 GC_clear_bl(GC_old_stack_bl);
107 GC_clear_bl(GC_incomplete_stack_bl);
110 void GC_clear_bl(word *doomed)
112 BZERO(doomed, sizeof(page_hash_table));
115 void GC_copy_bl(word *old, word *new)
117 BCOPY(old, new, sizeof(page_hash_table));
120 static word total_stack_black_listed(void);
122 /* Signal the completion of a collection. Turn the incomplete black */
123 /* lists into new black lists, etc. */
124 void GC_promote_black_lists(void)
126 word * very_old_normal_bl = GC_old_normal_bl;
127 word * very_old_stack_bl = GC_old_stack_bl;
129 GC_old_normal_bl = GC_incomplete_normal_bl;
130 GC_old_stack_bl = GC_incomplete_stack_bl;
131 if (!GC_all_interior_pointers) {
132 GC_clear_bl(very_old_normal_bl);
134 GC_clear_bl(very_old_stack_bl);
135 GC_incomplete_normal_bl = very_old_normal_bl;
136 GC_incomplete_stack_bl = very_old_stack_bl;
137 GC_total_stack_black_listed = total_stack_black_listed();
138 if (GC_print_stats == VERBOSE)
139 GC_log_printf("%ld bytes in heap blacklisted for interior pointers\n",
140 (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;
148 if (GC_black_list_spacing > MAXHINCR * HBLKSIZE) {
149 GC_black_list_spacing = MAXHINCR * HBLKSIZE;
150 /* Makes it easier to allocate really huge blocks, which otherwise */
151 /* may have problems with nonuniform blacklist distributions. */
152 /* This way we should always succeed immediately after growing the */
157 void GC_unpromote_black_lists(void)
159 if (!GC_all_interior_pointers) {
160 GC_copy_bl(GC_old_normal_bl, GC_incomplete_normal_bl);
162 GC_copy_bl(GC_old_stack_bl, GC_incomplete_stack_bl);
165 /* P is not a valid pointer reference, but it falls inside */
166 /* the plausible heap bounds. */
167 /* Add it to the normal incomplete black list if appropriate. */
168 #ifdef PRINT_BLACK_LIST
169 void GC_add_to_black_list_normal(word p, ptr_t source)
171 void GC_add_to_black_list_normal(word p)
174 if (!(GC_modws_valid_offsets[p & (sizeof(word)-1)])) return;
176 word index = PHT_HASH((word)p);
178 if (HDR(p) == 0 || get_pht_entry_from_index(GC_old_normal_bl, index)) {
179 # ifdef PRINT_BLACK_LIST
180 if (!get_pht_entry_from_index(GC_incomplete_normal_bl, index)) {
182 "Black listing (normal) %p referenced from %p ",
184 GC_print_source_ptr(source);
188 set_pht_entry_from_index(GC_incomplete_normal_bl, index);
189 } /* else this is probably just an interior pointer to an allocated */
190 /* object, and isn't worth black listing. */
194 /* And the same for false pointers from the stack. */
195 #ifdef PRINT_BLACK_LIST
196 void GC_add_to_black_list_stack(word p, ptr_t source)
198 void GC_add_to_black_list_stack(word p)
201 word index = PHT_HASH((word)p);
203 if (HDR(p) == 0 || get_pht_entry_from_index(GC_old_stack_bl, index)) {
204 # ifdef PRINT_BLACK_LIST
205 if (!get_pht_entry_from_index(GC_incomplete_stack_bl, index)) {
207 "Black listing (stack) %p referenced from %p ",
209 GC_print_source_ptr(source);
213 set_pht_entry_from_index(GC_incomplete_stack_bl, index);
218 * Is the block starting at h of size len bytes black listed? If so,
219 * return the address of the next plausible r such that (r, len) might not
220 * be black listed. (R may not actually be in the heap. We guarantee only
221 * that every smaller value of r after h is also black listed.)
222 * If (h,len) is not black listed, return 0.
223 * Knows about the structure of the black list hash tables.
225 struct hblk * GC_is_black_listed(struct hblk *h, word len)
227 word index = PHT_HASH((word)h);
229 word nblocks = divHBLKSZ(len);
231 if (!GC_all_interior_pointers) {
232 if (get_pht_entry_from_index(GC_old_normal_bl, index)
233 || get_pht_entry_from_index(GC_incomplete_normal_bl, index)) {
239 if (GC_old_stack_bl[divWORDSZ(index)] == 0
240 && GC_incomplete_stack_bl[divWORDSZ(index)] == 0) {
242 i += WORDSZ - modWORDSZ(index);
244 if (get_pht_entry_from_index(GC_old_stack_bl, index)
245 || get_pht_entry_from_index(GC_incomplete_stack_bl, index)) {
250 if (i >= nblocks) break;
251 index = PHT_HASH((word)(h+i));
257 /* Return the number of blacklisted blocks in a given range. */
258 /* Used only for statistical purposes. */
259 /* Looks only at the GC_incomplete_stack_bl. */
260 word GC_number_stack_black_listed(struct hblk *start, struct hblk *endp1)
262 register struct hblk * h;
265 for (h = start; h < endp1; h++) {
266 word index = PHT_HASH((word)h);
268 if (get_pht_entry_from_index(GC_old_stack_bl, index)) result++;
274 /* Return the total number of (stack) black-listed bytes. */
275 static word total_stack_black_listed(void)
280 for (i = 0; i < GC_n_heap_sects; i++) {
281 struct hblk * start = (struct hblk *) GC_heap_sects[i].hs_start;
282 size_t len = (word) GC_heap_sects[i].hs_bytes;
283 struct hblk * endp1 = start + len/HBLKSIZE;
285 total += GC_number_stack_black_listed(start, endp1);
287 return(total * HBLKSIZE);