1 /* "Bag-of-pages" garbage collector for the GNU compiler.
2 Copyright (C) 1999, 2000 Free Software Foundation, Inc.
4 This file is part of GNU CC.
6 GNU CC is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
11 GNU CC is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with GNU CC; see the file COPYING. If not, write to
18 the Free Software Foundation, 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
31 #ifdef HAVE_MMAP_ANYWHERE
39 #if !defined (MAP_ANONYMOUS) && defined (MAP_ANON)
40 #define MAP_ANONYMOUS MAP_ANON
45 This garbage-collecting allocator allocates objects on one of a set
46 of pages. Each page can allocate objects of a single size only;
47 available sizes are powers of two starting at four bytes. The size
48 of an allocation request is rounded up to the next power of two
49 (`order'), and satisfied from the appropriate page.
51 Each page is recorded in a page-entry, which also maintains an
52 in-use bitmap of object positions on the page. This allows the
53 allocation state of a particular object to be flipped without
54 touching the page itself.
56 Each page-entry also has a context depth, which is used to track
57 pushing and popping of allocation contexts. Only objects allocated
58 in the current (highest-numbered) context may be collected.
60 Page entries are arranged in an array of singly-linked lists. The
61 array is indexed by the allocation size, in bits, of the pages on
62 it; i.e. all pages on a list allocate objects of the same size.
63 Pages are ordered on the list such that all non-full pages precede
64 all full pages, with non-full pages arranged in order of decreasing
67 Empty pages (of all orders) are kept on a single page cache list,
68 and are considered first when new pages are required; they are
69 deallocated at the start of the next collection if they haven't
70 been recycled by then. */
73 /* Define GGC_POISON to poison memory marked unused by the collector. */
76 /* Define GGC_ALWAYS_COLLECT to perform collection every time
77 ggc_collect is invoked. Otherwise, collection is performed only
78 when a significant amount of memory has been allocated since the
80 #undef GGC_ALWAYS_COLLECT
82 #ifdef ENABLE_GC_CHECKING
85 #ifdef ENABLE_GC_ALWAYS_COLLECT
86 #define GGC_ALWAYS_COLLECT
89 /* Define GGC_DEBUG_LEVEL to print debugging information.
90 0: No debugging output.
91 1: GC statistics only.
92 2: Page-entry allocations/deallocations as well.
93 3: Object allocations as well.
94 4: Object marks as well. */
95 #define GGC_DEBUG_LEVEL (0)
97 #ifndef HOST_BITS_PER_PTR
98 #define HOST_BITS_PER_PTR HOST_BITS_PER_LONG
101 /* The "" allocated string. */
104 /* A two-level tree is used to look up the page-entry for a given
105 pointer. Two chunks of the pointer's bits are extracted to index
106 the first and second levels of the tree, as follows:
110 msb +----------------+----+------+------+ lsb
116 The bottommost HOST_PAGE_SIZE_BITS are ignored, since page-entry
117 pages are aligned on system page boundaries. The next most
118 significant PAGE_L2_BITS and PAGE_L1_BITS are the second and first
119 index values in the lookup table, respectively.
121 For 32-bit architectures and the settings below, there are no
122 leftover bits. For architectures with wider pointers, the lookup
123 tree points to a list of pages, which must be scanned to find the
126 #define PAGE_L1_BITS (8)
127 #define PAGE_L2_BITS (32 - PAGE_L1_BITS - G.lg_pagesize)
128 #define PAGE_L1_SIZE ((size_t) 1 << PAGE_L1_BITS)
129 #define PAGE_L2_SIZE ((size_t) 1 << PAGE_L2_BITS)
131 #define LOOKUP_L1(p) \
132 (((size_t) (p) >> (32 - PAGE_L1_BITS)) & ((1 << PAGE_L1_BITS) - 1))
134 #define LOOKUP_L2(p) \
135 (((size_t) (p) >> G.lg_pagesize) & ((1 << PAGE_L2_BITS) - 1))
138 /* A page_entry records the status of an allocation page. This
139 structure is dynamically sized to fit the bitmap in_use_p. */
140 typedef struct page_entry
142 /* The next page-entry with objects of the same size, or NULL if
143 this is the last page-entry. */
144 struct page_entry *next;
146 /* The number of bytes allocated. (This will always be a multiple
147 of the host system page size.) */
150 /* The address at which the memory is allocated. */
153 /* Saved in-use bit vector for pages that aren't in the topmost
154 context during collection. */
155 unsigned long *save_in_use_p;
157 /* Context depth of this page. */
158 unsigned short context_depth;
160 /* The number of free objects remaining on this page. */
161 unsigned short num_free_objects;
163 /* A likely candidate for the bit position of a free object for the
164 next allocation from this page. */
165 unsigned short next_bit_hint;
167 /* The lg of size of objects allocated from this page. */
170 /* A bit vector indicating whether or not objects are in use. The
171 Nth bit is one if the Nth object on this page is allocated. This
172 array is dynamically sized. */
173 unsigned long in_use_p[1];
177 #if HOST_BITS_PER_PTR <= 32
179 /* On 32-bit hosts, we use a two level page table, as pictured above. */
180 typedef page_entry **page_table[PAGE_L1_SIZE];
184 /* On 64-bit hosts, we use the same two level page tables plus a linked
185 list that disambiguates the top 32-bits. There will almost always be
186 exactly one entry in the list. */
187 typedef struct page_table_chain
189 struct page_table_chain *next;
191 page_entry **table[PAGE_L1_SIZE];
196 /* The rest of the global variables. */
197 static struct globals
199 /* The Nth element in this array is a page with objects of size 2^N.
200 If there are any pages with free objects, they will be at the
201 head of the list. NULL if there are no page-entries for this
203 page_entry *pages[HOST_BITS_PER_PTR];
205 /* The Nth element in this array is the last page with objects of
206 size 2^N. NULL if there are no page-entries for this object
208 page_entry *page_tails[HOST_BITS_PER_PTR];
210 /* Lookup table for associating allocation pages with object addresses. */
213 /* The system's page size. */
217 /* Bytes currently allocated. */
220 /* Bytes currently allocated at the end of the last collection. */
221 size_t allocated_last_gc;
223 /* Total amount of memory mapped. */
226 /* The current depth in the context stack. */
227 unsigned short context_depth;
229 /* A file descriptor open to /dev/zero for reading. */
230 #if defined (HAVE_MMAP_ANYWHERE) && !defined(MAP_ANONYMOUS)
234 /* A cache of free system pages. */
235 page_entry *free_pages;
237 /* The file descriptor for debugging output. */
242 /* Compute DIVIDEND / DIVISOR, rounded up. */
243 #define DIV_ROUND_UP(Dividend, Divisor) \
244 (((Dividend) + (Divisor) - 1) / (Divisor))
246 /* The number of objects per allocation page, for objects of size
248 #define OBJECTS_PER_PAGE(Order) \
249 ((Order) >= G.lg_pagesize ? 1 : G.pagesize / ((size_t)1 << (Order)))
251 /* The size in bytes required to maintain a bitmap for the objects
253 #define BITMAP_SIZE(Num_objects) \
254 (DIV_ROUND_UP ((Num_objects), HOST_BITS_PER_LONG) * sizeof(long))
256 /* Skip garbage collection if the current allocation is not at least
257 this factor times the allocation at the end of the last collection.
258 In other words, total allocation must expand by (this factor minus
259 one) before collection is performed. */
260 #define GGC_MIN_EXPAND_FOR_GC (1.3)
262 /* Bound `allocated_last_gc' to 4MB, to prevent the memory expansion
263 test from triggering too often when the heap is small. */
264 #define GGC_MIN_LAST_ALLOCATED (4 * 1024 * 1024)
267 static int ggc_allocated_p PARAMS ((const void *));
268 static page_entry *lookup_page_table_entry PARAMS ((const void *));
269 static void set_page_table_entry PARAMS ((void *, page_entry *));
270 static char *alloc_anon PARAMS ((char *, size_t));
271 static struct page_entry * alloc_page PARAMS ((unsigned));
272 static void free_page PARAMS ((struct page_entry *));
273 static void release_pages PARAMS ((void));
274 static void clear_marks PARAMS ((void));
275 static void sweep_pages PARAMS ((void));
276 static void ggc_recalculate_in_use_p PARAMS ((page_entry *));
279 static void poison_pages PARAMS ((void));
282 void debug_print_page_list PARAMS ((int));
284 /* Returns non-zero if P was allocated in GC'able memory. */
293 #if HOST_BITS_PER_PTR <= 32
296 page_table table = G.lookup;
297 size_t high_bits = (size_t) p & ~ (size_t) 0xffffffff;
302 if (table->high_bits == high_bits)
306 base = &table->table[0];
309 /* Extract the level 1 and 2 indicies. */
313 return base[L1] && base[L1][L2];
316 /* Traverse the page table and find the entry for a page.
317 Die (probably) if the object wasn't allocated via GC. */
319 static inline page_entry *
320 lookup_page_table_entry(p)
326 #if HOST_BITS_PER_PTR <= 32
329 page_table table = G.lookup;
330 size_t high_bits = (size_t) p & ~ (size_t) 0xffffffff;
331 while (table->high_bits != high_bits)
333 base = &table->table[0];
336 /* Extract the level 1 and 2 indicies. */
343 /* Set the page table entry for a page. */
346 set_page_table_entry(p, entry)
353 #if HOST_BITS_PER_PTR <= 32
357 size_t high_bits = (size_t) p & ~ (size_t) 0xffffffff;
358 for (table = G.lookup; table; table = table->next)
359 if (table->high_bits == high_bits)
362 /* Not found -- allocate a new table. */
363 table = (page_table) xcalloc (1, sizeof(*table));
364 table->next = G.lookup;
365 table->high_bits = high_bits;
368 base = &table->table[0];
371 /* Extract the level 1 and 2 indicies. */
375 if (base[L1] == NULL)
376 base[L1] = (page_entry **) xcalloc (PAGE_L2_SIZE, sizeof (page_entry *));
378 base[L1][L2] = entry;
381 /* Prints the page-entry for object size ORDER, for debugging. */
384 debug_print_page_list (order)
388 printf ("Head=%p, Tail=%p:\n", G.pages[order], G.page_tails[order]);
392 printf ("%p(%1d|%3d) -> ", p, p->context_depth, p->num_free_objects);
399 /* Allocate SIZE bytes of anonymous memory, preferably near PREF,
403 alloc_anon (pref, size)
404 char *pref ATTRIBUTE_UNUSED;
409 #ifdef HAVE_MMAP_ANYWHERE
411 page = (char *) mmap (pref, size, PROT_READ | PROT_WRITE,
412 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
414 page = (char *) mmap (pref, size, PROT_READ | PROT_WRITE,
415 MAP_PRIVATE, G.dev_zero_fd, 0);
417 if (page == (char *) MAP_FAILED)
419 fputs ("Virtual memory exhausted!\n", stderr);
424 page = (char *) valloc (size);
427 fputs ("Virtual memory exhausted!\n", stderr);
430 #endif /* HAVE_VALLOC */
431 #endif /* HAVE_MMAP_ANYWHERE */
433 /* Remember that we allocated this memory. */
434 G.bytes_mapped += size;
439 /* Allocate a new page for allocating objects of size 2^ORDER,
440 and return an entry for it. The entry is not added to the
441 appropriate page_table list. */
443 static inline struct page_entry *
447 struct page_entry *entry, *p, **pp;
451 size_t page_entry_size;
454 num_objects = OBJECTS_PER_PAGE (order);
455 bitmap_size = BITMAP_SIZE (num_objects + 1);
456 page_entry_size = sizeof (page_entry) - sizeof (long) + bitmap_size;
457 entry_size = num_objects * (1 << order);
462 /* Check the list of free pages for one we can use. */
463 for (pp = &G.free_pages, p = *pp; p ; pp = &p->next, p = *pp)
464 if (p->bytes == entry_size)
469 /* Recycle the allocated memory from this page ... */
472 /* ... and, if possible, the page entry itself. */
473 if (p->order == order)
476 memset (entry, 0, page_entry_size);
483 /* Actually allocate the memory. */
484 page = alloc_anon (NULL, entry_size);
488 entry = (struct page_entry *) xcalloc (1, page_entry_size);
490 entry->bytes = entry_size;
492 entry->context_depth = G.context_depth;
493 entry->order = order;
494 entry->num_free_objects = num_objects;
495 entry->next_bit_hint = 1;
497 /* Set the one-past-the-end in-use bit. This acts as a sentry as we
498 increment the hint. */
499 entry->in_use_p[num_objects / HOST_BITS_PER_LONG]
500 = (unsigned long) 1 << (num_objects % HOST_BITS_PER_LONG);
502 set_page_table_entry (page, entry);
504 if (GGC_DEBUG_LEVEL >= 2)
505 fprintf (G.debug_file,
506 "Allocating page at %p, object size=%d, data %p-%p\n", entry,
507 1 << order, page, page + entry_size - 1);
512 /* For a page that is no longer needed, put it on the free page list. */
518 if (GGC_DEBUG_LEVEL >= 2)
519 fprintf (G.debug_file,
520 "Deallocating page at %p, data %p-%p\n", entry,
521 entry->page, entry->page + entry->bytes - 1);
523 set_page_table_entry (entry->page, NULL);
525 entry->next = G.free_pages;
526 G.free_pages = entry;
529 /* Release the free page cache to the system. */
534 #ifdef HAVE_MMAP_ANYWHERE
535 page_entry *p, *next;
552 /* Gather up adjacent pages so they are unmapped together. */
553 if (p->page == start + len)
558 G.bytes_mapped -= len;
567 G.bytes_mapped -= len;
570 page_entry *p, *next;
572 for (p = G.free_pages; p ; p = next)
576 G.bytes_mapped -= p->bytes;
579 #endif /* HAVE_VALLOC */
580 #endif /* HAVE_MMAP_ANYWHERE */
585 /* This table provides a fast way to determine ceil(log_2(size)) for
586 allocation requests. The minimum allocation size is four bytes. */
588 static unsigned char const size_lookup[257] =
590 2, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4,
591 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
592 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
593 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
594 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
595 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
596 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
597 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
598 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
599 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
600 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
601 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
602 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
603 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
604 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
605 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
609 /* Allocate a chunk of memory of SIZE bytes. If ZERO is non-zero, the
610 memory is zeroed; otherwise, its contents are undefined. */
613 ggc_alloc_obj (size, zero)
617 unsigned order, word, bit, object_offset;
618 struct page_entry *entry;
622 order = size_lookup[size];
626 while (size > ((size_t) 1 << order))
630 /* If there are non-full pages for this size allocation, they are at
631 the head of the list. */
632 entry = G.pages[order];
634 /* If there is no page for this object size, or all pages in this
635 context are full, allocate a new page. */
636 if (entry == NULL || entry->num_free_objects == 0)
638 struct page_entry *new_entry;
639 new_entry = alloc_page (order);
641 /* If this is the only entry, it's also the tail. */
643 G.page_tails[order] = new_entry;
645 /* Put new pages at the head of the page list. */
646 new_entry->next = entry;
648 G.pages[order] = new_entry;
650 /* For a new page, we know the word and bit positions (in the
651 in_use bitmap) of the first available object -- they're zero. */
652 new_entry->next_bit_hint = 1;
659 /* First try to use the hint left from the previous allocation
660 to locate a clear bit in the in-use bitmap. We've made sure
661 that the one-past-the-end bit is always set, so if the hint
662 has run over, this test will fail. */
663 unsigned hint = entry->next_bit_hint;
664 word = hint / HOST_BITS_PER_LONG;
665 bit = hint % HOST_BITS_PER_LONG;
667 /* If the hint didn't work, scan the bitmap from the beginning. */
668 if ((entry->in_use_p[word] >> bit) & 1)
671 while (~entry->in_use_p[word] == 0)
673 while ((entry->in_use_p[word] >> bit) & 1)
675 hint = word * HOST_BITS_PER_LONG + bit;
678 /* Next time, try the next bit. */
679 entry->next_bit_hint = hint + 1;
681 object_offset = hint << order;
684 /* Set the in-use bit. */
685 entry->in_use_p[word] |= ((unsigned long) 1 << bit);
687 /* Keep a running total of the number of free objects. If this page
688 fills up, we may have to move it to the end of the list if the
689 next page isn't full. If the next page is full, all subsequent
690 pages are full, so there's no need to move it. */
691 if (--entry->num_free_objects == 0
692 && entry->next != NULL
693 && entry->next->num_free_objects > 0)
695 G.pages[order] = entry->next;
697 G.page_tails[order]->next = entry;
698 G.page_tails[order] = entry;
701 /* Calculate the object's address. */
702 result = entry->page + object_offset;
705 /* `Poison' the entire allocated object before zeroing the requested area,
706 so that bytes beyond the end, if any, will not necessarily be zero. */
707 memset (result, 0xaf, 1 << order);
711 memset (result, 0, size);
713 /* Keep track of how many bytes are being allocated. This
714 information is used in deciding when to collect. */
715 G.allocated += (size_t) 1 << order;
717 if (GGC_DEBUG_LEVEL >= 3)
718 fprintf (G.debug_file,
719 "Allocating object, requested size=%d, actual=%d at %p on %p\n",
720 (int) size, 1 << order, result, entry);
725 /* If P is not marked, marks it and return false. Otherwise return true.
726 P must have been allocated by the GC allocator; it mustn't point to
727 static objects, stack variables, or memory allocated with malloc. */
737 /* Look up the page on which the object is alloced. If the object
738 wasn't allocated by the collector, we'll probably die. */
739 entry = lookup_page_table_entry (p);
740 #ifdef ENABLE_CHECKING
745 /* Calculate the index of the object on the page; this is its bit
746 position in the in_use_p bitmap. */
747 bit = (((const char *) p) - entry->page) >> entry->order;
748 word = bit / HOST_BITS_PER_LONG;
749 mask = (unsigned long) 1 << (bit % HOST_BITS_PER_LONG);
751 /* If the bit was previously set, skip it. */
752 if (entry->in_use_p[word] & mask)
755 /* Otherwise set it, and decrement the free object count. */
756 entry->in_use_p[word] |= mask;
757 entry->num_free_objects -= 1;
759 G.allocated += (size_t) 1 << entry->order;
761 if (GGC_DEBUG_LEVEL >= 4)
762 fprintf (G.debug_file, "Marking %p\n", p);
767 /* Mark P, but check first that it was allocated by the collector. */
770 ggc_mark_if_gcable (p)
773 if (p && ggc_allocated_p (p))
777 /* Return the size of the gc-able object P. */
783 page_entry *pe = lookup_page_table_entry (p);
784 return 1 << pe->order;
787 /* Initialize the ggc-mmap allocator. */
792 G.pagesize = getpagesize();
793 G.lg_pagesize = exact_log2 (G.pagesize);
795 #if defined (HAVE_MMAP_ANYWHERE) && !defined(MAP_ANONYMOUS)
796 G.dev_zero_fd = open ("/dev/zero", O_RDONLY);
797 if (G.dev_zero_fd == -1)
802 G.debug_file = fopen ("ggc-mmap.debug", "w");
804 G.debug_file = stdout;
807 G.allocated_last_gc = GGC_MIN_LAST_ALLOCATED;
809 #ifdef HAVE_MMAP_ANYWHERE
810 /* StunOS has an amazing off-by-one error for the first mmap allocation
811 after fiddling with RLIMIT_STACK. The result, as hard as it is to
812 believe, is an unaligned page allocation, which would cause us to
813 hork badly if we tried to use it. */
815 char *p = alloc_anon (NULL, G.pagesize);
816 if ((size_t)p & (G.pagesize - 1))
818 /* How losing. Discard this one and try another. If we still
819 can't get something useful, give up. */
821 p = alloc_anon (NULL, G.pagesize);
822 if ((size_t)p & (G.pagesize - 1))
825 munmap (p, G.pagesize);
829 empty_string = ggc_alloc_string ("", 0);
830 ggc_add_string_root (&empty_string, 1);
833 /* Increment the `GC context'. Objects allocated in an outer context
834 are never freed, eliminating the need to register their roots. */
842 if (G.context_depth == 0)
846 /* Merge the SAVE_IN_USE_P and IN_USE_P arrays in P so that IN_USE_P
847 reflects reality. Recalculate NUM_FREE_OBJECTS as well. */
850 ggc_recalculate_in_use_p (p)
856 /* Because the past-the-end bit in in_use_p is always set, we
857 pretend there is one additional object. */
858 num_objects = OBJECTS_PER_PAGE (p->order) + 1;
860 /* Reset the free object count. */
861 p->num_free_objects = num_objects;
863 /* Combine the IN_USE_P and SAVE_IN_USE_P arrays. */
865 i < DIV_ROUND_UP (BITMAP_SIZE (num_objects),
866 sizeof (*p->in_use_p));
871 /* Something is in use if it is marked, or if it was in use in a
872 context further down the context stack. */
873 p->in_use_p[i] |= p->save_in_use_p[i];
875 /* Decrement the free object count for every object allocated. */
876 for (j = p->in_use_p[i]; j; j >>= 1)
877 p->num_free_objects -= (j & 1);
880 if (p->num_free_objects >= num_objects)
884 /* Decrement the `GC context'. All objects allocated since the
885 previous ggc_push_context are migrated to the outer context. */
890 unsigned order, depth;
892 depth = --G.context_depth;
894 /* Any remaining pages in the popped context are lowered to the new
895 current context; i.e. objects allocated in the popped context and
896 left over are imported into the previous context. */
897 for (order = 2; order < HOST_BITS_PER_PTR; order++)
901 for (p = G.pages[order]; p != NULL; p = p->next)
903 if (p->context_depth > depth)
904 p->context_depth = depth;
906 /* If this page is now in the topmost context, and we'd
907 saved its allocation state, restore it. */
908 else if (p->context_depth == depth && p->save_in_use_p)
910 ggc_recalculate_in_use_p (p);
911 free (p->save_in_use_p);
912 p->save_in_use_p = 0;
918 /* Unmark all objects. */
925 for (order = 2; order < HOST_BITS_PER_PTR; order++)
927 size_t num_objects = OBJECTS_PER_PAGE (order);
928 size_t bitmap_size = BITMAP_SIZE (num_objects + 1);
931 for (p = G.pages[order]; p != NULL; p = p->next)
933 #ifdef ENABLE_CHECKING
934 /* The data should be page-aligned. */
935 if ((size_t) p->page & (G.pagesize - 1))
939 /* Pages that aren't in the topmost context are not collected;
940 nevertheless, we need their in-use bit vectors to store GC
941 marks. So, back them up first. */
942 if (p->context_depth < G.context_depth)
944 if (! p->save_in_use_p)
945 p->save_in_use_p = xmalloc (bitmap_size);
946 memcpy (p->save_in_use_p, p->in_use_p, bitmap_size);
949 /* Reset reset the number of free objects and clear the
950 in-use bits. These will be adjusted by mark_obj. */
951 p->num_free_objects = num_objects;
952 memset (p->in_use_p, 0, bitmap_size);
954 /* Make sure the one-past-the-end bit is always set. */
955 p->in_use_p[num_objects / HOST_BITS_PER_LONG]
956 = ((unsigned long) 1 << (num_objects % HOST_BITS_PER_LONG));
961 /* Free all empty pages. Partially empty pages need no attention
962 because the `mark' bit doubles as an `unused' bit. */
969 for (order = 2; order < HOST_BITS_PER_PTR; order++)
971 /* The last page-entry to consider, regardless of entries
972 placed at the end of the list. */
973 page_entry * const last = G.page_tails[order];
975 size_t num_objects = OBJECTS_PER_PAGE (order);
976 page_entry *p, *previous;
986 page_entry *next = p->next;
988 /* Loop until all entries have been examined. */
991 /* Only objects on pages in the topmost context should get
993 if (p->context_depth < G.context_depth)
996 /* Remove the page if it's empty. */
997 else if (p->num_free_objects == num_objects)
1000 G.pages[order] = next;
1002 previous->next = next;
1004 /* Are we removing the last element? */
1005 if (p == G.page_tails[order])
1006 G.page_tails[order] = previous;
1011 /* If the page is full, move it to the end. */
1012 else if (p->num_free_objects == 0)
1014 /* Don't move it if it's already at the end. */
1015 if (p != G.page_tails[order])
1017 /* Move p to the end of the list. */
1019 G.page_tails[order]->next = p;
1021 /* Update the tail pointer... */
1022 G.page_tails[order] = p;
1024 /* ... and the head pointer, if necessary. */
1026 G.pages[order] = next;
1028 previous->next = next;
1033 /* If we've fallen through to here, it's a page in the
1034 topmost context that is neither full nor empty. Such a
1035 page must precede pages at lesser context depth in the
1036 list, so move it to the head. */
1037 else if (p != G.pages[order])
1039 previous->next = p->next;
1040 p->next = G.pages[order];
1042 /* Are we moving the last element? */
1043 if (G.page_tails[order] == p)
1044 G.page_tails[order] = previous;
1053 /* Now, restore the in_use_p vectors for any pages from contexts
1054 other than the current one. */
1055 for (p = G.pages[order]; p; p = p->next)
1056 if (p->context_depth != G.context_depth)
1057 ggc_recalculate_in_use_p (p);
1062 /* Clobber all free objects. */
1069 for (order = 2; order < HOST_BITS_PER_PTR; order++)
1071 size_t num_objects = OBJECTS_PER_PAGE (order);
1072 size_t size = (size_t) 1 << order;
1075 for (p = G.pages[order]; p != NULL; p = p->next)
1079 if (p->context_depth != G.context_depth)
1080 /* Since we don't do any collection for pages in pushed
1081 contexts, there's no need to do any poisoning. And
1082 besides, the IN_USE_P array isn't valid until we pop
1086 for (i = 0; i < num_objects; i++)
1089 word = i / HOST_BITS_PER_LONG;
1090 bit = i % HOST_BITS_PER_LONG;
1091 if (((p->in_use_p[word] >> bit) & 1) == 0)
1092 memset (p->page + i * size, 0xa5, size);
1099 /* Top level mark-and-sweep routine. */
1106 /* Avoid frequent unnecessary work by skipping collection if the
1107 total allocations haven't expanded much since the last
1109 #ifndef GGC_ALWAYS_COLLECT
1110 if (G.allocated < GGC_MIN_EXPAND_FOR_GC * G.allocated_last_gc)
1114 time = get_run_time ();
1116 fprintf (stderr, " {GC %luk -> ", (unsigned long) G.allocated / 1024);
1118 /* Zero the total allocated bytes. We'll reaccumulate this while
1122 /* Release the pages we freed the last time we collected, but didn't
1123 reuse in the interim. */
1135 G.allocated_last_gc = G.allocated;
1136 if (G.allocated_last_gc < GGC_MIN_LAST_ALLOCATED)
1137 G.allocated_last_gc = GGC_MIN_LAST_ALLOCATED;
1139 time = get_run_time () - time;
1144 fprintf (stderr, "%luk in %.3f}",
1145 (unsigned long) G.allocated / 1024, time * 1e-6);
1149 /* Print allocation statistics. */
1152 ggc_page_print_statistics ()
1154 struct ggc_statistics stats;
1157 /* Clear the statistics. */
1158 memset (&stats, 0, sizeof (stats));
1160 /* Make sure collection will really occur. */
1161 G.allocated_last_gc = 0;
1163 /* Collect and print the statistics common across collectors. */
1164 ggc_print_statistics (stderr, &stats);
1166 /* Release free pages so that we will not count the bytes allocated
1167 there as part of the total allocated memory. */
1170 /* Collect some information about the various sizes of
1172 fprintf (stderr, "\n%-4s%-16s%-16s\n", "Log", "Allocated", "Used");
1173 for (i = 0; i < HOST_BITS_PER_PTR; ++i)
1179 /* Skip empty entries. */
1183 allocated = in_use = 0;
1185 /* Figure out the total number of bytes allocated for objects of
1186 this size, and how many of them are actually in use. */
1187 for (p = G.pages[i]; p; p = p->next)
1189 allocated += p->bytes;
1191 (OBJECTS_PER_PAGE (i) - p->num_free_objects) * (1 << i);
1193 fprintf (stderr, "%-3d %-15lu %-15lu\n", i,
1194 (unsigned long) allocated, (unsigned long) in_use);
1197 /* Print out some global information. */
1198 fprintf (stderr, "\nTotal bytes marked: %lu\n",
1199 (unsigned long) G.allocated);
1200 fprintf (stderr, "Total bytes mapped: %lu\n",
1201 (unsigned long) G.bytes_mapped);