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.
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 = NULL;
41 /* Nonstack false references seen at last full */
43 STATIC word * GC_incomplete_normal_bl = NULL;
44 /* Nonstack false references seen since last */
45 /* full collection. */
46 STATIC word * GC_old_stack_bl = NULL;
47 STATIC word * GC_incomplete_stack_bl = NULL;
49 STATIC word GC_total_stack_black_listed = 0;
50 /* Number of bytes on stack blacklist. */
52 GC_INNER word GC_black_list_spacing = MINHINCR * HBLKSIZE;
53 /* Initial rough guess. */
55 STATIC void GC_clear_bl(word *);
57 GC_INNER void GC_default_print_heap_obj_proc(ptr_t p)
59 ptr_t base = GC_base(p);
60 GC_err_printf("start: %p, appr. length: %ld", base,
61 (unsigned long)GC_size(base));
64 GC_INNER void (*GC_print_heap_obj)(ptr_t p) = GC_default_print_heap_obj_proc;
66 #ifdef PRINT_BLACK_LIST
67 STATIC void GC_print_source_ptr(ptr_t p)
69 ptr_t base = GC_base(p);
72 GC_err_printf("in register");
74 GC_err_printf("in root set");
77 GC_err_printf("in object at ");
78 /* FIXME: We can't call the debug version of GC_print_heap_obj */
79 /* (with PRINT_CALL_CHAIN) here because the lock is held and */
80 /* the world is stopped. */
81 GC_default_print_heap_obj_proc(base);
86 GC_INNER void GC_bl_init(void)
88 if (!GC_all_interior_pointers) {
89 GC_old_normal_bl = (word *)
90 GC_scratch_alloc((word)(sizeof (page_hash_table)));
91 GC_incomplete_normal_bl = (word *)GC_scratch_alloc
92 ((word)(sizeof(page_hash_table)));
93 if (GC_old_normal_bl == 0 || GC_incomplete_normal_bl == 0) {
94 GC_err_printf("Insufficient memory for black list\n");
97 GC_clear_bl(GC_old_normal_bl);
98 GC_clear_bl(GC_incomplete_normal_bl);
100 GC_old_stack_bl = (word *)GC_scratch_alloc((word)(sizeof(page_hash_table)));
101 GC_incomplete_stack_bl = (word *)GC_scratch_alloc
102 ((word)(sizeof(page_hash_table)));
103 if (GC_old_stack_bl == 0 || GC_incomplete_stack_bl == 0) {
104 GC_err_printf("Insufficient memory for black list\n");
107 GC_clear_bl(GC_old_stack_bl);
108 GC_clear_bl(GC_incomplete_stack_bl);
111 STATIC void GC_clear_bl(word *doomed)
113 BZERO(doomed, sizeof(page_hash_table));
116 STATIC void GC_copy_bl(word *old, word *new)
118 BCOPY(old, new, sizeof(page_hash_table));
121 static word total_stack_black_listed(void);
123 /* Signal the completion of a collection. Turn the incomplete black */
124 /* lists into new black lists, etc. */
125 GC_INNER void GC_promote_black_lists(void)
127 word * very_old_normal_bl = GC_old_normal_bl;
128 word * very_old_stack_bl = GC_old_stack_bl;
130 GC_old_normal_bl = GC_incomplete_normal_bl;
131 GC_old_stack_bl = GC_incomplete_stack_bl;
132 if (!GC_all_interior_pointers) {
133 GC_clear_bl(very_old_normal_bl);
135 GC_clear_bl(very_old_stack_bl);
136 GC_incomplete_normal_bl = very_old_normal_bl;
137 GC_incomplete_stack_bl = very_old_stack_bl;
138 GC_total_stack_black_listed = total_stack_black_listed();
139 if (GC_print_stats == VERBOSE)
140 GC_log_printf("%ld bytes in heap blacklisted for interior pointers\n",
141 (unsigned long)GC_total_stack_black_listed);
142 if (GC_total_stack_black_listed != 0) {
143 GC_black_list_spacing =
144 HBLKSIZE*(GC_heapsize/GC_total_stack_black_listed);
146 if (GC_black_list_spacing < 3 * HBLKSIZE) {
147 GC_black_list_spacing = 3 * HBLKSIZE;
149 if (GC_black_list_spacing > MAXHINCR * HBLKSIZE) {
150 GC_black_list_spacing = MAXHINCR * HBLKSIZE;
151 /* Makes it easier to allocate really huge blocks, which otherwise */
152 /* may have problems with nonuniform blacklist distributions. */
153 /* This way we should always succeed immediately after growing the */
158 GC_INNER void GC_unpromote_black_lists(void)
160 if (!GC_all_interior_pointers) {
161 GC_copy_bl(GC_old_normal_bl, GC_incomplete_normal_bl);
163 GC_copy_bl(GC_old_stack_bl, GC_incomplete_stack_bl);
166 /* P is not a valid pointer reference, but it falls inside */
167 /* the plausible heap bounds. */
168 /* Add it to the normal incomplete black list if appropriate. */
169 #ifdef PRINT_BLACK_LIST
170 GC_INNER void GC_add_to_black_list_normal(word p, ptr_t source)
172 GC_INNER void GC_add_to_black_list_normal(word p)
175 if (!(GC_modws_valid_offsets[p & (sizeof(word)-1)])) return;
177 word index = PHT_HASH((word)p);
179 if (HDR(p) == 0 || get_pht_entry_from_index(GC_old_normal_bl, index)) {
180 # ifdef PRINT_BLACK_LIST
181 if (!get_pht_entry_from_index(GC_incomplete_normal_bl, index)) {
183 "Black listing (normal) %p referenced from %p ",
185 GC_print_source_ptr(source);
189 set_pht_entry_from_index(GC_incomplete_normal_bl, index);
190 } /* else this is probably just an interior pointer to an allocated */
191 /* object, and isn't worth black listing. */
195 /* And the same for false pointers from the stack. */
196 #ifdef PRINT_BLACK_LIST
197 GC_INNER void GC_add_to_black_list_stack(word p, ptr_t source)
199 GC_INNER void GC_add_to_black_list_stack(word p)
202 word index = PHT_HASH((word)p);
204 if (HDR(p) == 0 || get_pht_entry_from_index(GC_old_stack_bl, index)) {
205 # ifdef PRINT_BLACK_LIST
206 if (!get_pht_entry_from_index(GC_incomplete_stack_bl, index)) {
208 "Black listing (stack) %p referenced from %p ",
210 GC_print_source_ptr(source);
214 set_pht_entry_from_index(GC_incomplete_stack_bl, index);
219 * Is the block starting at h of size len bytes black listed? If so,
220 * return the address of the next plausible r such that (r, len) might not
221 * be black listed. (R may not actually be in the heap. We guarantee only
222 * that every smaller value of r after h is also black listed.)
223 * If (h,len) is not black listed, return 0.
224 * Knows about the structure of the black list hash tables.
226 GC_INNER struct hblk * GC_is_black_listed(struct hblk *h, word len)
228 word index = PHT_HASH((word)h);
230 word nblocks = divHBLKSZ(len);
232 if (!GC_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));
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 STATIC word GC_number_stack_black_listed(struct hblk *start,
263 register struct hblk * h;
266 for (h = start; h < endp1; h++) {
267 word index = PHT_HASH((word)h);
269 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);