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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. */
30 #ifdef HAVE_MMAP_ANYWHERE
38 #if !defined (MAP_ANONYMOUS) && defined (MAP_ANON)
39 #define MAP_ANONYMOUS MAP_ANON
44 This garbage-collecting allocator allocates objects on one of a set
45 of pages. Each page can allocate objects of a single size only;
46 available sizes are powers of two starting at four bytes. The size
47 of an allocation request is rounded up to the next power of two
48 (`order'), and satisfied from the appropriate page.
50 Each page is recorded in a page-entry, which also maintains an
51 in-use bitmap of object positions on the page. This allows the
52 allocation state of a particular object to be flipped without
53 touching the page itself.
55 Each page-entry also has a context depth, which is used to track
56 pushing and popping of allocation contexts. Only objects allocated
57 in the current (highest-numbered) context may be collected.
59 Page entries are arranged in an array of singly-linked lists. The
60 array is indexed by the allocation size, in bits, of the pages on
61 it; i.e. all pages on a list allocate objects of the same size.
62 Pages are ordered on the list such that all non-full pages precede
63 all full pages, with non-full pages arranged in order of decreasing
66 Empty pages (of all orders) are kept on a single page cache list,
67 and are considered first when new pages are required; they are
68 deallocated at the start of the next collection if they haven't
69 been recycled by then. */
72 /* Define GGC_POISON to poison memory marked unused by the collector. */
75 /* Define GGC_ALWAYS_COLLECT to perform collection every time
76 ggc_collect is invoked. Otherwise, collection is performed only
77 when a significant amount of memory has been allocated since the
79 #undef GGC_ALWAYS_COLLECT
81 #ifdef ENABLE_GC_CHECKING
84 #ifdef ENABLE_GC_ALWAYS_COLLECT
85 #define GGC_ALWAYS_COLLECT
88 /* Define GGC_DEBUG_LEVEL to print debugging information.
89 0: No debugging output.
90 1: GC statistics only.
91 2: Page-entry allocations/deallocations as well.
92 3: Object allocations as well.
93 4: Object marks as well. */
94 #define GGC_DEBUG_LEVEL (0)
96 #ifndef HOST_BITS_PER_PTR
97 #define HOST_BITS_PER_PTR HOST_BITS_PER_LONG
100 /* Timing information for collect execution goes into here. */
103 /* The "" allocated string. */
106 /* A two-level tree is used to look up the page-entry for a given
107 pointer. Two chunks of the pointer's bits are extracted to index
108 the first and second levels of the tree, as follows:
112 msb +----------------+----+------+------+ lsb
118 The bottommost HOST_PAGE_SIZE_BITS are ignored, since page-entry
119 pages are aligned on system page boundaries. The next most
120 significant PAGE_L2_BITS and PAGE_L1_BITS are the second and first
121 index values in the lookup table, respectively.
123 For 32-bit architectures and the settings below, there are no
124 leftover bits. For architectures with wider pointers, the lookup
125 tree points to a list of pages, which must be scanned to find the
128 #define PAGE_L1_BITS (8)
129 #define PAGE_L2_BITS (32 - PAGE_L1_BITS - G.lg_pagesize)
130 #define PAGE_L1_SIZE ((size_t) 1 << PAGE_L1_BITS)
131 #define PAGE_L2_SIZE ((size_t) 1 << PAGE_L2_BITS)
133 #define LOOKUP_L1(p) \
134 (((size_t) (p) >> (32 - PAGE_L1_BITS)) & ((1 << PAGE_L1_BITS) - 1))
136 #define LOOKUP_L2(p) \
137 (((size_t) (p) >> G.lg_pagesize) & ((1 << PAGE_L2_BITS) - 1))
140 /* A page_entry records the status of an allocation page. This
141 structure is dynamically sized to fit the bitmap in_use_p. */
142 typedef struct page_entry
144 /* The next page-entry with objects of the same size, or NULL if
145 this is the last page-entry. */
146 struct page_entry
*next
;
148 /* The number of bytes allocated. (This will always be a multiple
149 of the host system page size.) */
152 /* The address at which the memory is allocated. */
155 /* Saved in-use bit vector for pages that aren't in the topmost
156 context during collection. */
157 unsigned long *save_in_use_p
;
159 /* Context depth of this page. */
160 unsigned char context_depth
;
162 /* The lg of size of objects allocated from this page. */
165 /* The number of free objects remaining on this page. */
166 unsigned short num_free_objects
;
168 /* A likely candidate for the bit position of a free object for the
169 next allocation from this page. */
170 unsigned short next_bit_hint
;
172 /* A bit vector indicating whether or not objects are in use. The
173 Nth bit is one if the Nth object on this page is allocated. This
174 array is dynamically sized. */
175 unsigned long in_use_p
[1];
179 #if HOST_BITS_PER_PTR <= 32
181 /* On 32-bit hosts, we use a two level page table, as pictured above. */
182 typedef page_entry
**page_table
[PAGE_L1_SIZE
];
186 /* On 64-bit hosts, we use the same two level page tables plus a linked
187 list that disambiguates the top 32-bits. There will almost always be
188 exactly one entry in the list. */
189 typedef struct page_table_chain
191 struct page_table_chain
*next
;
193 page_entry
**table
[PAGE_L1_SIZE
];
198 /* The rest of the global variables. */
199 static struct globals
201 /* The Nth element in this array is a page with objects of size 2^N.
202 If there are any pages with free objects, they will be at the
203 head of the list. NULL if there are no page-entries for this
205 page_entry
*pages
[HOST_BITS_PER_PTR
];
207 /* The Nth element in this array is the last page with objects of
208 size 2^N. NULL if there are no page-entries for this object
210 page_entry
*page_tails
[HOST_BITS_PER_PTR
];
212 /* Lookup table for associating allocation pages with object addresses. */
215 /* The system's page size. */
219 /* Bytes currently allocated. */
222 /* Bytes currently allocated at the end of the last collection. */
223 size_t allocated_last_gc
;
225 /* Total amount of memory mapped. */
228 /* The current depth in the context stack. */
229 unsigned char context_depth
;
231 /* A file descriptor open to /dev/zero for reading. */
232 #if defined (HAVE_MMAP_ANYWHERE) && !defined(MAP_ANONYMOUS)
236 /* A cache of free system pages. */
237 page_entry
*free_pages
;
239 /* The file descriptor for debugging output. */
244 /* Compute DIVIDEND / DIVISOR, rounded up. */
245 #define DIV_ROUND_UP(Dividend, Divisor) \
246 (((Dividend) + (Divisor) - 1) / (Divisor))
248 /* The number of objects per allocation page, for objects of size
250 #define OBJECTS_PER_PAGE(Order) \
251 ((Order) >= G.lg_pagesize ? 1 : G.pagesize / ((size_t)1 << (Order)))
253 /* The size in bytes required to maintain a bitmap for the objects
255 #define BITMAP_SIZE(Num_objects) \
256 (DIV_ROUND_UP ((Num_objects), HOST_BITS_PER_LONG) * sizeof(long))
258 /* Skip garbage collection if the current allocation is not at least
259 this factor times the allocation at the end of the last collection.
260 In other words, total allocation must expand by (this factor minus
261 one) before collection is performed. */
262 #define GGC_MIN_EXPAND_FOR_GC (1.3)
264 /* Bound `allocated_last_gc' to 4MB, to prevent the memory expansion
265 test from triggering too often when the heap is small. */
266 #define GGC_MIN_LAST_ALLOCATED (4 * 1024 * 1024)
269 static int ggc_allocated_p
PROTO ((const void *));
270 static page_entry
*lookup_page_table_entry
PROTO ((const void *));
271 static void set_page_table_entry
PROTO ((void *, page_entry
*));
272 static char *alloc_anon
PROTO ((char *, size_t));
273 static struct page_entry
* alloc_page
PROTO ((unsigned));
274 static void free_page
PROTO ((struct page_entry
*));
275 static void release_pages
PROTO ((void));
276 static void clear_marks
PROTO ((void));
277 static void sweep_pages
PROTO ((void));
278 static void ggc_recalculate_in_use_p
PROTO ((page_entry
*));
281 static void poison_pages
PROTO ((void));
284 void debug_print_page_list
PROTO ((int));
286 /* Returns non-zero if P was allocated in GC'able memory. */
295 #if HOST_BITS_PER_PTR <= 32
298 page_table table
= G
.lookup
;
299 size_t high_bits
= (size_t) p
& ~ (size_t) 0xffffffff;
304 if (table
->high_bits
== high_bits
)
308 base
= &table
->table
[0];
311 /* Extract the level 1 and 2 indicies. */
315 return base
[L1
] && base
[L1
][L2
];
318 /* Traverse the page table and find the entry for a page.
319 Die (probably) if the object wasn't allocated via GC. */
321 static inline page_entry
*
322 lookup_page_table_entry(p
)
328 #if HOST_BITS_PER_PTR <= 32
331 page_table table
= G
.lookup
;
332 size_t high_bits
= (size_t) p
& ~ (size_t) 0xffffffff;
333 while (table
->high_bits
!= high_bits
)
335 base
= &table
->table
[0];
338 /* Extract the level 1 and 2 indicies. */
345 /* Set the page table entry for a page. */
348 set_page_table_entry(p
, entry
)
355 #if HOST_BITS_PER_PTR <= 32
359 size_t high_bits
= (size_t) p
& ~ (size_t) 0xffffffff;
360 for (table
= G
.lookup
; table
; table
= table
->next
)
361 if (table
->high_bits
== high_bits
)
364 /* Not found -- allocate a new table. */
365 table
= (page_table
) xcalloc (1, sizeof(*table
));
366 table
->next
= G
.lookup
;
367 table
->high_bits
= high_bits
;
370 base
= &table
->table
[0];
373 /* Extract the level 1 and 2 indicies. */
377 if (base
[L1
] == NULL
)
378 base
[L1
] = (page_entry
**) xcalloc (PAGE_L2_SIZE
, sizeof (page_entry
*));
380 base
[L1
][L2
] = entry
;
383 /* Prints the page-entry for object size ORDER, for debugging. */
386 debug_print_page_list (order
)
390 printf ("Head=%p, Tail=%p:\n", G
.pages
[order
], G
.page_tails
[order
]);
394 printf ("%p(%1d|%3d) -> ", p
, p
->context_depth
, p
->num_free_objects
);
401 /* Allocate SIZE bytes of anonymous memory, preferably near PREF,
405 alloc_anon (pref
, size
)
406 char *pref ATTRIBUTE_UNUSED
;
411 #ifdef HAVE_MMAP_ANYWHERE
413 page
= (char *) mmap (pref
, size
, PROT_READ
| PROT_WRITE
,
414 MAP_PRIVATE
| MAP_ANONYMOUS
, -1, 0);
416 page
= (char *) mmap (pref
, size
, PROT_READ
| PROT_WRITE
,
417 MAP_PRIVATE
, G
.dev_zero_fd
, 0);
419 if (page
== (char *) MAP_FAILED
)
421 fputs ("Virtual memory exhausted!\n", stderr
);
426 page
= (char *) valloc (size
);
429 fputs ("Virtual memory exhausted!\n", stderr
);
432 #endif /* HAVE_VALLOC */
433 #endif /* HAVE_MMAP_ANYWHERE */
435 /* Remember that we allocated this memory. */
436 G
.bytes_mapped
+= size
;
441 /* Allocate a new page for allocating objects of size 2^ORDER,
442 and return an entry for it. The entry is not added to the
443 appropriate page_table list. */
445 static inline struct page_entry
*
449 struct page_entry
*entry
, *p
, **pp
;
453 size_t page_entry_size
;
456 num_objects
= OBJECTS_PER_PAGE (order
);
457 bitmap_size
= BITMAP_SIZE (num_objects
+ 1);
458 page_entry_size
= sizeof (page_entry
) - sizeof (long) + bitmap_size
;
459 entry_size
= num_objects
* (1 << order
);
464 /* Check the list of free pages for one we can use. */
465 for (pp
= &G
.free_pages
, p
= *pp
; p
; pp
= &p
->next
, p
= *pp
)
466 if (p
->bytes
== entry_size
)
471 /* Recycle the allocated memory from this page ... */
474 /* ... and, if possible, the page entry itself. */
475 if (p
->order
== order
)
478 memset (entry
, 0, page_entry_size
);
485 /* Actually allocate the memory. */
486 page
= alloc_anon (NULL
, entry_size
);
490 entry
= (struct page_entry
*) xcalloc (1, page_entry_size
);
492 entry
->bytes
= entry_size
;
494 entry
->context_depth
= G
.context_depth
;
495 entry
->order
= order
;
496 entry
->num_free_objects
= num_objects
;
497 entry
->next_bit_hint
= 1;
499 /* Set the one-past-the-end in-use bit. This acts as a sentry as we
500 increment the hint. */
501 entry
->in_use_p
[num_objects
/ HOST_BITS_PER_LONG
]
502 = (unsigned long) 1 << (num_objects
% HOST_BITS_PER_LONG
);
504 set_page_table_entry (page
, entry
);
506 if (GGC_DEBUG_LEVEL
>= 2)
507 fprintf (G
.debug_file
,
508 "Allocating page at %p, object size=%d, data %p-%p\n", entry
,
509 1 << order
, page
, page
+ entry_size
- 1);
514 /* For a page that is no longer needed, put it on the free page list. */
520 if (GGC_DEBUG_LEVEL
>= 2)
521 fprintf (G
.debug_file
,
522 "Deallocating page at %p, data %p-%p\n", entry
,
523 entry
->page
, entry
->page
+ entry
->bytes
- 1);
525 set_page_table_entry (entry
->page
, NULL
);
527 entry
->next
= G
.free_pages
;
528 G
.free_pages
= entry
;
531 /* Release the free page cache to the system. */
536 #ifdef HAVE_MMAP_ANYWHERE
537 page_entry
*p
, *next
;
554 /* Gather up adjacent pages so they are unmapped together. */
555 if (p
->page
== start
+ len
)
560 G
.bytes_mapped
-= len
;
569 G
.bytes_mapped
-= len
;
572 page_entry
*p
, *next
;
574 for (p
= G
.free_pages
; p
; p
= next
)
578 G
.bytes_mapped
-= p
->bytes
;
581 #endif /* HAVE_VALLOC */
582 #endif /* HAVE_MMAP_ANYWHERE */
587 /* This table provides a fast way to determine ceil(log_2(size)) for
588 allocation requests. The minimum allocation size is four bytes. */
590 static unsigned char const size_lookup
[257] =
592 2, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4,
593 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
594 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
595 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
596 6, 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, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
599 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
600 7, 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,
606 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
607 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
611 /* Allocate a chunk of memory of SIZE bytes. If ZERO is non-zero, the
612 memory is zeroed; otherwise, its contents are undefined. */
615 ggc_alloc_obj (size
, zero
)
619 unsigned order
, word
, bit
, object_offset
;
620 struct page_entry
*entry
;
624 order
= size_lookup
[size
];
628 while (size
> ((size_t) 1 << order
))
632 /* If there are non-full pages for this size allocation, they are at
633 the head of the list. */
634 entry
= G
.pages
[order
];
636 /* If there is no page for this object size, or all pages in this
637 context are full, allocate a new page. */
638 if (entry
== NULL
|| entry
->num_free_objects
== 0)
640 struct page_entry
*new_entry
;
641 new_entry
= alloc_page (order
);
643 /* If this is the only entry, it's also the tail. */
645 G
.page_tails
[order
] = new_entry
;
647 /* Put new pages at the head of the page list. */
648 new_entry
->next
= entry
;
650 G
.pages
[order
] = new_entry
;
652 /* For a new page, we know the word and bit positions (in the
653 in_use bitmap) of the first available object -- they're zero. */
654 new_entry
->next_bit_hint
= 1;
661 /* First try to use the hint left from the previous allocation
662 to locate a clear bit in the in-use bitmap. We've made sure
663 that the one-past-the-end bit is always set, so if the hint
664 has run over, this test will fail. */
665 unsigned hint
= entry
->next_bit_hint
;
666 word
= hint
/ HOST_BITS_PER_LONG
;
667 bit
= hint
% HOST_BITS_PER_LONG
;
669 /* If the hint didn't work, scan the bitmap from the beginning. */
670 if ((entry
->in_use_p
[word
] >> bit
) & 1)
673 while (~entry
->in_use_p
[word
] == 0)
675 while ((entry
->in_use_p
[word
] >> bit
) & 1)
677 hint
= word
* HOST_BITS_PER_LONG
+ bit
;
680 /* Next time, try the next bit. */
681 entry
->next_bit_hint
= hint
+ 1;
683 object_offset
= hint
<< order
;
686 /* Set the in-use bit. */
687 entry
->in_use_p
[word
] |= ((unsigned long) 1 << bit
);
689 /* Keep a running total of the number of free objects. If this page
690 fills up, we may have to move it to the end of the list if the
691 next page isn't full. If the next page is full, all subsequent
692 pages are full, so there's no need to move it. */
693 if (--entry
->num_free_objects
== 0
694 && entry
->next
!= NULL
695 && entry
->next
->num_free_objects
> 0)
697 G
.pages
[order
] = entry
->next
;
699 G
.page_tails
[order
]->next
= entry
;
700 G
.page_tails
[order
] = entry
;
703 /* Calculate the object's address. */
704 result
= entry
->page
+ object_offset
;
707 /* `Poison' the entire allocated object before zeroing the requested area,
708 so that bytes beyond the end, if any, will not necessarily be zero. */
709 memset (result
, 0xaf, 1 << order
);
713 memset (result
, 0, size
);
715 /* Keep track of how many bytes are being allocated. This
716 information is used in deciding when to collect. */
717 G
.allocated
+= (size_t) 1 << order
;
719 if (GGC_DEBUG_LEVEL
>= 3)
720 fprintf (G
.debug_file
,
721 "Allocating object, requested size=%d, actual=%d at %p on %p\n",
722 (int) size
, 1 << order
, result
, entry
);
727 /* If P is not marked, marks it and return false. Otherwise return true.
728 P must have been allocated by the GC allocator; it mustn't point to
729 static objects, stack variables, or memory allocated with malloc. */
739 /* Look up the page on which the object is alloced. If the object
740 wasn't allocated by the collector, we'll probably die. */
741 entry
= lookup_page_table_entry (p
);
742 #ifdef ENABLE_CHECKING
747 /* Calculate the index of the object on the page; this is its bit
748 position in the in_use_p bitmap. */
749 bit
= (((char *) p
) - entry
->page
) >> entry
->order
;
750 word
= bit
/ HOST_BITS_PER_LONG
;
751 mask
= (unsigned long) 1 << (bit
% HOST_BITS_PER_LONG
);
753 /* If the bit was previously set, skip it. */
754 if (entry
->in_use_p
[word
] & mask
)
757 /* Otherwise set it, and decrement the free object count. */
758 entry
->in_use_p
[word
] |= mask
;
759 entry
->num_free_objects
-= 1;
761 G
.allocated
+= (size_t) 1 << entry
->order
;
763 if (GGC_DEBUG_LEVEL
>= 4)
764 fprintf (G
.debug_file
, "Marking %p\n", p
);
769 /* Mark P, but check first that it was allocated by the collector. */
772 ggc_mark_if_gcable (p
)
775 if (p
&& ggc_allocated_p (p
))
779 /* Return the size of the gc-able object P. */
785 page_entry
*pe
= lookup_page_table_entry (p
);
786 return 1 << pe
->order
;
789 /* Initialize the ggc-mmap allocator. */
794 G
.pagesize
= getpagesize();
795 G
.lg_pagesize
= exact_log2 (G
.pagesize
);
797 #if defined (HAVE_MMAP_ANYWHERE) && !defined(MAP_ANONYMOUS)
798 G
.dev_zero_fd
= open ("/dev/zero", O_RDONLY
);
799 if (G
.dev_zero_fd
== -1)
804 G
.debug_file
= fopen ("ggc-mmap.debug", "w");
806 G
.debug_file
= stdout
;
809 G
.allocated_last_gc
= GGC_MIN_LAST_ALLOCATED
;
811 #ifdef HAVE_MMAP_ANYWHERE
812 /* StunOS has an amazing off-by-one error for the first mmap allocation
813 after fiddling with RLIMIT_STACK. The result, as hard as it is to
814 believe, is an unaligned page allocation, which would cause us to
815 hork badly if we tried to use it. */
817 char *p
= alloc_anon (NULL
, G
.pagesize
);
818 if ((size_t)p
& (G
.pagesize
- 1))
820 /* How losing. Discard this one and try another. If we still
821 can't get something useful, give up. */
823 p
= alloc_anon (NULL
, G
.pagesize
);
824 if ((size_t)p
& (G
.pagesize
- 1))
827 munmap (p
, G
.pagesize
);
831 empty_string
= ggc_alloc_string ("", 0);
832 ggc_add_string_root (&empty_string
, 1);
835 /* Increment the `GC context'. Objects allocated in an outer context
836 are never freed, eliminating the need to register their roots. */
844 if (G
.context_depth
== 0)
848 /* Merge the SAVE_IN_USE_P and IN_USE_P arrays in P so that IN_USE_P
849 reflects reality. Recalculate NUM_FREE_OBJECTS as well. */
852 ggc_recalculate_in_use_p (p
)
858 /* Because the past-the-end bit in in_use_p is always set, we
859 pretend there is one additional object. */
860 num_objects
= OBJECTS_PER_PAGE (p
->order
) + 1;
862 /* Reset the free object count. */
863 p
->num_free_objects
= num_objects
;
865 /* Combine the IN_USE_P and SAVE_IN_USE_P arrays. */
867 i
< DIV_ROUND_UP (BITMAP_SIZE (num_objects
),
868 sizeof (*p
->in_use_p
));
873 /* Something is in use if it is marked, or if it was in use in a
874 context further down the context stack. */
875 p
->in_use_p
[i
] |= p
->save_in_use_p
[i
];
877 /* Decrement the free object count for every object allocated. */
878 for (j
= p
->in_use_p
[i
]; j
; j
>>= 1)
879 p
->num_free_objects
-= (j
& 1);
882 if (p
->num_free_objects
>= num_objects
)
886 /* Decrement the `GC context'. All objects allocated since the
887 previous ggc_push_context are migrated to the outer context. */
892 unsigned order
, depth
;
894 depth
= --G
.context_depth
;
896 /* Any remaining pages in the popped context are lowered to the new
897 current context; i.e. objects allocated in the popped context and
898 left over are imported into the previous context. */
899 for (order
= 2; order
< HOST_BITS_PER_PTR
; order
++)
903 for (p
= G
.pages
[order
]; p
!= NULL
; p
= p
->next
)
905 if (p
->context_depth
> depth
)
906 p
->context_depth
= depth
;
908 /* If this page is now in the topmost context, and we'd
909 saved its allocation state, restore it. */
910 else if (p
->context_depth
== depth
&& p
->save_in_use_p
)
912 ggc_recalculate_in_use_p (p
);
913 free (p
->save_in_use_p
);
914 p
->save_in_use_p
= 0;
920 /* Unmark all objects. */
927 for (order
= 2; order
< HOST_BITS_PER_PTR
; order
++)
929 size_t num_objects
= OBJECTS_PER_PAGE (order
);
930 size_t bitmap_size
= BITMAP_SIZE (num_objects
+ 1);
933 for (p
= G
.pages
[order
]; p
!= NULL
; p
= p
->next
)
935 #ifdef ENABLE_CHECKING
936 /* The data should be page-aligned. */
937 if ((size_t) p
->page
& (G
.pagesize
- 1))
941 /* Pages that aren't in the topmost context are not collected;
942 nevertheless, we need their in-use bit vectors to store GC
943 marks. So, back them up first. */
944 if (p
->context_depth
< G
.context_depth
)
946 if (! p
->save_in_use_p
)
947 p
->save_in_use_p
= xmalloc (bitmap_size
);
948 memcpy (p
->save_in_use_p
, p
->in_use_p
, bitmap_size
);
951 /* Reset reset the number of free objects and clear the
952 in-use bits. These will be adjusted by mark_obj. */
953 p
->num_free_objects
= num_objects
;
954 memset (p
->in_use_p
, 0, bitmap_size
);
956 /* Make sure the one-past-the-end bit is always set. */
957 p
->in_use_p
[num_objects
/ HOST_BITS_PER_LONG
]
958 = ((unsigned long) 1 << (num_objects
% HOST_BITS_PER_LONG
));
963 /* Free all empty pages. Partially empty pages need no attention
964 because the `mark' bit doubles as an `unused' bit. */
971 for (order
= 2; order
< HOST_BITS_PER_PTR
; order
++)
973 /* The last page-entry to consider, regardless of entries
974 placed at the end of the list. */
975 page_entry
* const last
= G
.page_tails
[order
];
977 size_t num_objects
= OBJECTS_PER_PAGE (order
);
978 page_entry
*p
, *previous
;
988 page_entry
*next
= p
->next
;
990 /* Loop until all entries have been examined. */
993 /* Only objects on pages in the topmost context should get
995 if (p
->context_depth
< G
.context_depth
)
998 /* Remove the page if it's empty. */
999 else if (p
->num_free_objects
== num_objects
)
1002 G
.pages
[order
] = next
;
1004 previous
->next
= next
;
1006 /* Are we removing the last element? */
1007 if (p
== G
.page_tails
[order
])
1008 G
.page_tails
[order
] = previous
;
1013 /* If the page is full, move it to the end. */
1014 else if (p
->num_free_objects
== 0)
1016 /* Don't move it if it's already at the end. */
1017 if (p
!= G
.page_tails
[order
])
1019 /* Move p to the end of the list. */
1021 G
.page_tails
[order
]->next
= p
;
1023 /* Update the tail pointer... */
1024 G
.page_tails
[order
] = p
;
1026 /* ... and the head pointer, if necessary. */
1028 G
.pages
[order
] = next
;
1030 previous
->next
= next
;
1035 /* If we've fallen through to here, it's a page in the
1036 topmost context that is neither full nor empty. Such a
1037 page must precede pages at lesser context depth in the
1038 list, so move it to the head. */
1039 else if (p
!= G
.pages
[order
])
1041 previous
->next
= p
->next
;
1042 p
->next
= G
.pages
[order
];
1044 /* Are we moving the last element? */
1045 if (G
.page_tails
[order
] == p
)
1046 G
.page_tails
[order
] = previous
;
1055 /* Now, restore the in_use_p vectors for any pages from contexts
1056 other than the current one. */
1057 for (p
= G
.pages
[order
]; p
; p
= p
->next
)
1058 if (p
->context_depth
!= G
.context_depth
)
1059 ggc_recalculate_in_use_p (p
);
1064 /* Clobber all free objects. */
1071 for (order
= 2; order
< HOST_BITS_PER_PTR
; order
++)
1073 size_t num_objects
= OBJECTS_PER_PAGE (order
);
1074 size_t size
= (size_t) 1 << order
;
1077 for (p
= G
.pages
[order
]; p
!= NULL
; p
= p
->next
)
1081 if (p
->context_depth
!= G
.context_depth
)
1082 /* Since we don't do any collection for pages in pushed
1083 contexts, there's no need to do any poisoning. And
1084 besides, the IN_USE_P array isn't valid until we pop
1088 for (i
= 0; i
< num_objects
; i
++)
1091 word
= i
/ HOST_BITS_PER_LONG
;
1092 bit
= i
% HOST_BITS_PER_LONG
;
1093 if (((p
->in_use_p
[word
] >> bit
) & 1) == 0)
1094 memset (p
->page
+ i
* size
, 0xa5, size
);
1101 /* Top level mark-and-sweep routine. */
1108 /* Avoid frequent unnecessary work by skipping collection if the
1109 total allocations haven't expanded much since the last
1111 #ifndef GGC_ALWAYS_COLLECT
1112 if (G
.allocated
< GGC_MIN_EXPAND_FOR_GC
* G
.allocated_last_gc
)
1116 time
= get_run_time ();
1118 fprintf (stderr
, " {GC %luk -> ", (unsigned long)G
.allocated
/ 1024);
1120 /* Zero the total allocated bytes. We'll reaccumulate this while
1124 /* Release the pages we freed the last time we collected, but didn't
1125 reuse in the interim. */
1137 G
.allocated_last_gc
= G
.allocated
;
1138 if (G
.allocated_last_gc
< GGC_MIN_LAST_ALLOCATED
)
1139 G
.allocated_last_gc
= GGC_MIN_LAST_ALLOCATED
;
1141 time
= get_run_time () - time
;
1146 fprintf (stderr
, "%luk in %.3f}",
1147 (unsigned long) G
.allocated
/ 1024, time
* 1e-6);
1151 /* Print allocation statistics. */
1154 ggc_page_print_statistics ()
1156 struct ggc_statistics stats
;
1159 /* Clear the statistics. */
1160 bzero (&stats
, sizeof (stats
));
1162 /* Make sure collection will really occur. */
1163 G
.allocated_last_gc
= 0;
1165 /* Collect and print the statistics common across collectors. */
1166 ggc_print_statistics (stderr
, &stats
);
1168 /* Release free pages so that we will not count the bytes allocated
1169 there as part of the total allocated memory. */
1172 /* Collect some information about the various sizes of
1174 fprintf (stderr
, "\n%-4s%-16s%-16s\n", "Log", "Allocated", "Used");
1175 for (i
= 0; i
< HOST_BITS_PER_PTR
; ++i
)
1181 /* Skip empty entries. */
1185 allocated
= in_use
= 0;
1187 /* Figure out the total number of bytes allocated for objects of
1188 this size, and how many of them are actually in use. */
1189 for (p
= G
.pages
[i
]; p
; p
= p
->next
)
1191 allocated
+= p
->bytes
;
1193 (OBJECTS_PER_PAGE (i
) - p
->num_free_objects
) * (1 << i
);
1195 fprintf (stderr
, "%-3d %-15lu %-15lu\n", i
,
1196 (unsigned long) allocated
, (unsigned long) in_use
);
1199 /* Print out some global information. */
1200 fprintf (stderr
, "\nTotal bytes marked: %lu\n",
1201 (unsigned long) G
.allocated
);
1202 fprintf (stderr
, "Total bytes mapped: %lu\n",
1203 (unsigned long) G
.bytes_mapped
);