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. */
32 #ifdef HAVE_MMAP_ANYWHERE
40 #if !defined (MAP_ANONYMOUS) && defined (MAP_ANON)
41 #define MAP_ANONYMOUS MAP_ANON
46 This garbage-collecting allocator allocates objects on one of a set
47 of pages. Each page can allocate objects of a single size only;
48 available sizes are powers of two starting at four bytes. The size
49 of an allocation request is rounded up to the next power of two
50 (`order'), and satisfied from the appropriate page.
52 Each page is recorded in a page-entry, which also maintains an
53 in-use bitmap of object positions on the page. This allows the
54 allocation state of a particular object to be flipped without
55 touching the page itself.
57 Each page-entry also has a context depth, which is used to track
58 pushing and popping of allocation contexts. Only objects allocated
59 in the current (highest-numbered) context may be collected.
61 Page entries are arranged in an array of singly-linked lists. The
62 array is indexed by the allocation size, in bits, of the pages on
63 it; i.e. all pages on a list allocate objects of the same size.
64 Pages are ordered on the list such that all non-full pages precede
65 all full pages, with non-full pages arranged in order of decreasing
68 Empty pages (of all orders) are kept on a single page cache list,
69 and are considered first when new pages are required; they are
70 deallocated at the start of the next collection if they haven't
71 been recycled by then. */
74 /* Define GGC_POISON to poison memory marked unused by the collector. */
77 /* Define GGC_ALWAYS_COLLECT to perform collection every time
78 ggc_collect is invoked. Otherwise, collection is performed only
79 when a significant amount of memory has been allocated since the
81 #undef GGC_ALWAYS_COLLECT
83 #ifdef ENABLE_GC_CHECKING
86 #ifdef ENABLE_GC_ALWAYS_COLLECT
87 #define GGC_ALWAYS_COLLECT
90 /* Define GGC_DEBUG_LEVEL to print debugging information.
91 0: No debugging output.
92 1: GC statistics only.
93 2: Page-entry allocations/deallocations as well.
94 3: Object allocations as well.
95 4: Object marks as well. */
96 #define GGC_DEBUG_LEVEL (0)
98 #ifndef HOST_BITS_PER_PTR
99 #define HOST_BITS_PER_PTR HOST_BITS_PER_LONG
102 /* The "" allocated string. */
105 /* A two-level tree is used to look up the page-entry for a given
106 pointer. Two chunks of the pointer's bits are extracted to index
107 the first and second levels of the tree, as follows:
111 msb +----------------+----+------+------+ lsb
117 The bottommost HOST_PAGE_SIZE_BITS are ignored, since page-entry
118 pages are aligned on system page boundaries. The next most
119 significant PAGE_L2_BITS and PAGE_L1_BITS are the second and first
120 index values in the lookup table, respectively.
122 For 32-bit architectures and the settings below, there are no
123 leftover bits. For architectures with wider pointers, the lookup
124 tree points to a list of pages, which must be scanned to find the
127 #define PAGE_L1_BITS (8)
128 #define PAGE_L2_BITS (32 - PAGE_L1_BITS - G.lg_pagesize)
129 #define PAGE_L1_SIZE ((size_t) 1 << PAGE_L1_BITS)
130 #define PAGE_L2_SIZE ((size_t) 1 << PAGE_L2_BITS)
132 #define LOOKUP_L1(p) \
133 (((size_t) (p) >> (32 - PAGE_L1_BITS)) & ((1 << PAGE_L1_BITS) - 1))
135 #define LOOKUP_L2(p) \
136 (((size_t) (p) >> G.lg_pagesize) & ((1 << PAGE_L2_BITS) - 1))
139 /* A page_entry records the status of an allocation page. This
140 structure is dynamically sized to fit the bitmap in_use_p. */
141 typedef struct page_entry
143 /* The next page-entry with objects of the same size, or NULL if
144 this is the last page-entry. */
145 struct page_entry
*next
;
147 /* The number of bytes allocated. (This will always be a multiple
148 of the host system page size.) */
151 /* The address at which the memory is allocated. */
154 /* Saved in-use bit vector for pages that aren't in the topmost
155 context during collection. */
156 unsigned long *save_in_use_p
;
158 /* Context depth of this page. */
159 unsigned short context_depth
;
161 /* The number of free objects remaining on this page. */
162 unsigned short num_free_objects
;
164 /* A likely candidate for the bit position of a free object for the
165 next allocation from this page. */
166 unsigned short next_bit_hint
;
168 /* The lg of size of objects allocated from this page. */
171 /* A bit vector indicating whether or not objects are in use. The
172 Nth bit is one if the Nth object on this page is allocated. This
173 array is dynamically sized. */
174 unsigned long in_use_p
[1];
178 #if HOST_BITS_PER_PTR <= 32
180 /* On 32-bit hosts, we use a two level page table, as pictured above. */
181 typedef page_entry
**page_table
[PAGE_L1_SIZE
];
185 /* On 64-bit hosts, we use the same two level page tables plus a linked
186 list that disambiguates the top 32-bits. There will almost always be
187 exactly one entry in the list. */
188 typedef struct page_table_chain
190 struct page_table_chain
*next
;
192 page_entry
**table
[PAGE_L1_SIZE
];
197 /* The rest of the global variables. */
198 static struct globals
200 /* The Nth element in this array is a page with objects of size 2^N.
201 If there are any pages with free objects, they will be at the
202 head of the list. NULL if there are no page-entries for this
204 page_entry
*pages
[HOST_BITS_PER_PTR
];
206 /* The Nth element in this array is the last page with objects of
207 size 2^N. NULL if there are no page-entries for this object
209 page_entry
*page_tails
[HOST_BITS_PER_PTR
];
211 /* Lookup table for associating allocation pages with object addresses. */
214 /* The system's page size. */
218 /* Bytes currently allocated. */
221 /* Bytes currently allocated at the end of the last collection. */
222 size_t allocated_last_gc
;
224 /* Total amount of memory mapped. */
227 /* The current depth in the context stack. */
228 unsigned short context_depth
;
230 /* A file descriptor open to /dev/zero for reading. */
231 #if defined (HAVE_MMAP_ANYWHERE) && !defined(MAP_ANONYMOUS)
235 /* A cache of free system pages. */
236 page_entry
*free_pages
;
238 /* The file descriptor for debugging output. */
243 /* Compute DIVIDEND / DIVISOR, rounded up. */
244 #define DIV_ROUND_UP(Dividend, Divisor) \
245 (((Dividend) + (Divisor) - 1) / (Divisor))
247 /* The number of objects per allocation page, for objects of size
249 #define OBJECTS_PER_PAGE(Order) \
250 ((Order) >= G.lg_pagesize ? 1 : G.pagesize / ((size_t)1 << (Order)))
252 /* The size in bytes required to maintain a bitmap for the objects
254 #define BITMAP_SIZE(Num_objects) \
255 (DIV_ROUND_UP ((Num_objects), HOST_BITS_PER_LONG) * sizeof(long))
257 /* Skip garbage collection if the current allocation is not at least
258 this factor times the allocation at the end of the last collection.
259 In other words, total allocation must expand by (this factor minus
260 one) before collection is performed. */
261 #define GGC_MIN_EXPAND_FOR_GC (1.3)
263 /* Bound `allocated_last_gc' to 4MB, to prevent the memory expansion
264 test from triggering too often when the heap is small. */
265 #define GGC_MIN_LAST_ALLOCATED (4 * 1024 * 1024)
267 /* Allocate pages in chunks of this size, to throttle calls to mmap.
268 The first page is used, the rest go onto the free list. */
269 #define GGC_QUIRE_SIZE 16
272 static int ggc_allocated_p
PARAMS ((const void *));
273 static page_entry
*lookup_page_table_entry
PARAMS ((const void *));
274 static void set_page_table_entry
PARAMS ((void *, page_entry
*));
275 static char *alloc_anon
PARAMS ((char *, size_t));
276 static struct page_entry
* alloc_page
PARAMS ((unsigned));
277 static void free_page
PARAMS ((struct page_entry
*));
278 static void release_pages
PARAMS ((void));
279 static void clear_marks
PARAMS ((void));
280 static void sweep_pages
PARAMS ((void));
281 static void ggc_recalculate_in_use_p
PARAMS ((page_entry
*));
284 static void poison_pages
PARAMS ((void));
287 void debug_print_page_list
PARAMS ((int));
289 /* Returns non-zero if P was allocated in GC'able memory. */
298 #if HOST_BITS_PER_PTR <= 32
301 page_table table
= G
.lookup
;
302 size_t high_bits
= (size_t) p
& ~ (size_t) 0xffffffff;
307 if (table
->high_bits
== high_bits
)
311 base
= &table
->table
[0];
314 /* Extract the level 1 and 2 indicies. */
318 return base
[L1
] && base
[L1
][L2
];
321 /* Traverse the page table and find the entry for a page.
322 Die (probably) if the object wasn't allocated via GC. */
324 static inline page_entry
*
325 lookup_page_table_entry(p
)
331 #if HOST_BITS_PER_PTR <= 32
334 page_table table
= G
.lookup
;
335 size_t high_bits
= (size_t) p
& ~ (size_t) 0xffffffff;
336 while (table
->high_bits
!= high_bits
)
338 base
= &table
->table
[0];
341 /* Extract the level 1 and 2 indicies. */
348 /* Set the page table entry for a page. */
351 set_page_table_entry(p
, entry
)
358 #if HOST_BITS_PER_PTR <= 32
362 size_t high_bits
= (size_t) p
& ~ (size_t) 0xffffffff;
363 for (table
= G
.lookup
; table
; table
= table
->next
)
364 if (table
->high_bits
== high_bits
)
367 /* Not found -- allocate a new table. */
368 table
= (page_table
) xcalloc (1, sizeof(*table
));
369 table
->next
= G
.lookup
;
370 table
->high_bits
= high_bits
;
373 base
= &table
->table
[0];
376 /* Extract the level 1 and 2 indicies. */
380 if (base
[L1
] == NULL
)
381 base
[L1
] = (page_entry
**) xcalloc (PAGE_L2_SIZE
, sizeof (page_entry
*));
383 base
[L1
][L2
] = entry
;
386 /* Prints the page-entry for object size ORDER, for debugging. */
389 debug_print_page_list (order
)
393 printf ("Head=%p, Tail=%p:\n", (PTR
) G
.pages
[order
],
394 (PTR
) G
.page_tails
[order
]);
398 printf ("%p(%1d|%3d) -> ", (PTR
) p
, p
->context_depth
,
399 p
->num_free_objects
);
406 /* Allocate SIZE bytes of anonymous memory, preferably near PREF,
410 alloc_anon (pref
, size
)
411 char *pref ATTRIBUTE_UNUSED
;
416 #ifdef HAVE_MMAP_ANYWHERE
418 page
= (char *) mmap (pref
, size
, PROT_READ
| PROT_WRITE
,
419 MAP_PRIVATE
| MAP_ANONYMOUS
, -1, 0);
421 page
= (char *) mmap (pref
, size
, PROT_READ
| PROT_WRITE
,
422 MAP_PRIVATE
, G
.dev_zero_fd
, 0);
424 if (page
== (char *) MAP_FAILED
)
426 fputs ("Virtual memory exhausted!\n", stderr
);
431 page
= (char *) valloc (size
);
434 fputs ("Virtual memory exhausted!\n", stderr
);
437 #endif /* HAVE_VALLOC */
438 #endif /* HAVE_MMAP_ANYWHERE */
440 /* Remember that we allocated this memory. */
441 G
.bytes_mapped
+= size
;
446 /* Allocate a new page for allocating objects of size 2^ORDER,
447 and return an entry for it. The entry is not added to the
448 appropriate page_table list. */
450 static inline struct page_entry
*
454 struct page_entry
*entry
, *p
, **pp
;
458 size_t page_entry_size
;
461 num_objects
= OBJECTS_PER_PAGE (order
);
462 bitmap_size
= BITMAP_SIZE (num_objects
+ 1);
463 page_entry_size
= sizeof (page_entry
) - sizeof (long) + bitmap_size
;
464 entry_size
= num_objects
* (1 << order
);
469 /* Check the list of free pages for one we can use. */
470 for (pp
= &G
.free_pages
, p
= *pp
; p
; pp
= &p
->next
, p
= *pp
)
471 if (p
->bytes
== entry_size
)
476 /* Recycle the allocated memory from this page ... */
479 /* ... and, if possible, the page entry itself. */
480 if (p
->order
== order
)
483 memset (entry
, 0, page_entry_size
);
488 #ifdef HAVE_MMAP_ANYWHERE
489 else if (entry_size
== G
.pagesize
)
491 /* We want just one page. Allocate a bunch of them and put the
492 extras on the freelist. (Can only do this optimization with
493 mmap for backing store.) */
494 struct page_entry
*e
, *f
= G
.free_pages
;
497 page
= alloc_anon (NULL
, entry_size
* GGC_QUIRE_SIZE
);
498 /* This loop counts down so that the chain will be in ascending
500 for (i
= GGC_QUIRE_SIZE
- 1; i
>= 1; i
--)
502 e
= (struct page_entry
*) xcalloc (1, sizeof (struct page_entry
));
503 e
->bytes
= entry_size
;
504 e
->page
= page
+ i
*entry_size
;
512 page
= alloc_anon (NULL
, entry_size
);
515 entry
= (struct page_entry
*) xcalloc (1, page_entry_size
);
517 entry
->bytes
= entry_size
;
519 entry
->context_depth
= G
.context_depth
;
520 entry
->order
= order
;
521 entry
->num_free_objects
= num_objects
;
522 entry
->next_bit_hint
= 1;
524 /* Set the one-past-the-end in-use bit. This acts as a sentry as we
525 increment the hint. */
526 entry
->in_use_p
[num_objects
/ HOST_BITS_PER_LONG
]
527 = (unsigned long) 1 << (num_objects
% HOST_BITS_PER_LONG
);
529 set_page_table_entry (page
, entry
);
531 if (GGC_DEBUG_LEVEL
>= 2)
532 fprintf (G
.debug_file
,
533 "Allocating page at %p, object size=%d, data %p-%p\n",
534 (PTR
) entry
, 1 << order
, page
, page
+ entry_size
- 1);
539 /* For a page that is no longer needed, put it on the free page list. */
545 if (GGC_DEBUG_LEVEL
>= 2)
546 fprintf (G
.debug_file
,
547 "Deallocating page at %p, data %p-%p\n", (PTR
) entry
,
548 entry
->page
, entry
->page
+ entry
->bytes
- 1);
550 set_page_table_entry (entry
->page
, NULL
);
552 entry
->next
= G
.free_pages
;
553 G
.free_pages
= entry
;
556 /* Release the free page cache to the system. */
561 page_entry
*p
, *next
;
563 #ifdef HAVE_MMAP_ANYWHERE
567 /* Gather up adjacent pages so they are unmapped together. */
578 while (p
&& p
->page
== start
+ len
)
587 G
.bytes_mapped
-= len
;
592 for (p
= G
.free_pages
; p
; p
= next
)
596 G
.bytes_mapped
-= p
->bytes
;
599 #endif /* HAVE_VALLOC */
600 #endif /* HAVE_MMAP_ANYWHERE */
605 /* This table provides a fast way to determine ceil(log_2(size)) for
606 allocation requests. The minimum allocation size is four bytes. */
608 static unsigned char const size_lookup
[257] =
610 2, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4,
611 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
612 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
613 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
614 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
615 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
616 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
617 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
618 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
619 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
620 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
621 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
622 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
623 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
624 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
625 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
629 /* Allocate a chunk of memory of SIZE bytes. If ZERO is non-zero, the
630 memory is zeroed; otherwise, its contents are undefined. */
636 unsigned order
, word
, bit
, object_offset
;
637 struct page_entry
*entry
;
641 order
= size_lookup
[size
];
645 while (size
> ((size_t) 1 << order
))
649 /* If there are non-full pages for this size allocation, they are at
650 the head of the list. */
651 entry
= G
.pages
[order
];
653 /* If there is no page for this object size, or all pages in this
654 context are full, allocate a new page. */
655 if (entry
== NULL
|| entry
->num_free_objects
== 0)
657 struct page_entry
*new_entry
;
658 new_entry
= alloc_page (order
);
660 /* If this is the only entry, it's also the tail. */
662 G
.page_tails
[order
] = new_entry
;
664 /* Put new pages at the head of the page list. */
665 new_entry
->next
= entry
;
667 G
.pages
[order
] = new_entry
;
669 /* For a new page, we know the word and bit positions (in the
670 in_use bitmap) of the first available object -- they're zero. */
671 new_entry
->next_bit_hint
= 1;
678 /* First try to use the hint left from the previous allocation
679 to locate a clear bit in the in-use bitmap. We've made sure
680 that the one-past-the-end bit is always set, so if the hint
681 has run over, this test will fail. */
682 unsigned hint
= entry
->next_bit_hint
;
683 word
= hint
/ HOST_BITS_PER_LONG
;
684 bit
= hint
% HOST_BITS_PER_LONG
;
686 /* If the hint didn't work, scan the bitmap from the beginning. */
687 if ((entry
->in_use_p
[word
] >> bit
) & 1)
690 while (~entry
->in_use_p
[word
] == 0)
692 while ((entry
->in_use_p
[word
] >> bit
) & 1)
694 hint
= word
* HOST_BITS_PER_LONG
+ bit
;
697 /* Next time, try the next bit. */
698 entry
->next_bit_hint
= hint
+ 1;
700 object_offset
= hint
<< order
;
703 /* Set the in-use bit. */
704 entry
->in_use_p
[word
] |= ((unsigned long) 1 << bit
);
706 /* Keep a running total of the number of free objects. If this page
707 fills up, we may have to move it to the end of the list if the
708 next page isn't full. If the next page is full, all subsequent
709 pages are full, so there's no need to move it. */
710 if (--entry
->num_free_objects
== 0
711 && entry
->next
!= NULL
712 && entry
->next
->num_free_objects
> 0)
714 G
.pages
[order
] = entry
->next
;
716 G
.page_tails
[order
]->next
= entry
;
717 G
.page_tails
[order
] = entry
;
720 /* Calculate the object's address. */
721 result
= entry
->page
+ object_offset
;
724 /* `Poison' the entire allocated object, including any padding at
726 memset (result
, 0xaf, 1 << order
);
729 /* Keep track of how many bytes are being allocated. This
730 information is used in deciding when to collect. */
731 G
.allocated
+= (size_t) 1 << order
;
733 if (GGC_DEBUG_LEVEL
>= 3)
734 fprintf (G
.debug_file
,
735 "Allocating object, requested size=%d, actual=%d at %p on %p\n",
736 (int) size
, 1 << order
, result
, (PTR
) entry
);
741 /* If P is not marked, marks it and return false. Otherwise return true.
742 P must have been allocated by the GC allocator; it mustn't point to
743 static objects, stack variables, or memory allocated with malloc. */
753 /* Look up the page on which the object is alloced. If the object
754 wasn't allocated by the collector, we'll probably die. */
755 entry
= lookup_page_table_entry (p
);
756 #ifdef ENABLE_CHECKING
761 /* Calculate the index of the object on the page; this is its bit
762 position in the in_use_p bitmap. */
763 bit
= (((const char *) p
) - entry
->page
) >> entry
->order
;
764 word
= bit
/ HOST_BITS_PER_LONG
;
765 mask
= (unsigned long) 1 << (bit
% HOST_BITS_PER_LONG
);
767 /* If the bit was previously set, skip it. */
768 if (entry
->in_use_p
[word
] & mask
)
771 /* Otherwise set it, and decrement the free object count. */
772 entry
->in_use_p
[word
] |= mask
;
773 entry
->num_free_objects
-= 1;
775 if (GGC_DEBUG_LEVEL
>= 4)
776 fprintf (G
.debug_file
, "Marking %p\n", p
);
781 /* Mark P, but check first that it was allocated by the collector. */
784 ggc_mark_if_gcable (p
)
787 if (p
&& ggc_allocated_p (p
))
791 /* Return the size of the gc-able object P. */
797 page_entry
*pe
= lookup_page_table_entry (p
);
798 return 1 << pe
->order
;
801 /* Initialize the ggc-mmap allocator. */
806 G
.pagesize
= getpagesize();
807 G
.lg_pagesize
= exact_log2 (G
.pagesize
);
809 #if defined (HAVE_MMAP_ANYWHERE) && !defined(MAP_ANONYMOUS)
810 G
.dev_zero_fd
= open ("/dev/zero", O_RDONLY
);
811 if (G
.dev_zero_fd
== -1)
816 G
.debug_file
= fopen ("ggc-mmap.debug", "w");
818 G
.debug_file
= stdout
;
821 G
.allocated_last_gc
= GGC_MIN_LAST_ALLOCATED
;
823 #ifdef HAVE_MMAP_ANYWHERE
824 /* StunOS has an amazing off-by-one error for the first mmap allocation
825 after fiddling with RLIMIT_STACK. The result, as hard as it is to
826 believe, is an unaligned page allocation, which would cause us to
827 hork badly if we tried to use it. */
829 char *p
= alloc_anon (NULL
, G
.pagesize
);
830 if ((size_t)p
& (G
.pagesize
- 1))
832 /* How losing. Discard this one and try another. If we still
833 can't get something useful, give up. */
835 p
= alloc_anon (NULL
, G
.pagesize
);
836 if ((size_t)p
& (G
.pagesize
- 1))
839 munmap (p
, G
.pagesize
);
843 empty_string
= ggc_alloc_string ("", 0);
844 ggc_add_string_root (&empty_string
, 1);
847 /* Increment the `GC context'. Objects allocated in an outer context
848 are never freed, eliminating the need to register their roots. */
856 if (G
.context_depth
== 0)
860 /* Merge the SAVE_IN_USE_P and IN_USE_P arrays in P so that IN_USE_P
861 reflects reality. Recalculate NUM_FREE_OBJECTS as well. */
864 ggc_recalculate_in_use_p (p
)
870 /* Because the past-the-end bit in in_use_p is always set, we
871 pretend there is one additional object. */
872 num_objects
= OBJECTS_PER_PAGE (p
->order
) + 1;
874 /* Reset the free object count. */
875 p
->num_free_objects
= num_objects
;
877 /* Combine the IN_USE_P and SAVE_IN_USE_P arrays. */
879 i
< DIV_ROUND_UP (BITMAP_SIZE (num_objects
),
880 sizeof (*p
->in_use_p
));
885 /* Something is in use if it is marked, or if it was in use in a
886 context further down the context stack. */
887 p
->in_use_p
[i
] |= p
->save_in_use_p
[i
];
889 /* Decrement the free object count for every object allocated. */
890 for (j
= p
->in_use_p
[i
]; j
; j
>>= 1)
891 p
->num_free_objects
-= (j
& 1);
894 if (p
->num_free_objects
>= num_objects
)
898 /* Decrement the `GC context'. All objects allocated since the
899 previous ggc_push_context are migrated to the outer context. */
904 unsigned order
, depth
;
906 depth
= --G
.context_depth
;
908 /* Any remaining pages in the popped context are lowered to the new
909 current context; i.e. objects allocated in the popped context and
910 left over are imported into the previous context. */
911 for (order
= 2; order
< HOST_BITS_PER_PTR
; order
++)
915 for (p
= G
.pages
[order
]; p
!= NULL
; p
= p
->next
)
917 if (p
->context_depth
> depth
)
918 p
->context_depth
= depth
;
920 /* If this page is now in the topmost context, and we'd
921 saved its allocation state, restore it. */
922 else if (p
->context_depth
== depth
&& p
->save_in_use_p
)
924 ggc_recalculate_in_use_p (p
);
925 free (p
->save_in_use_p
);
926 p
->save_in_use_p
= 0;
932 /* Unmark all objects. */
939 for (order
= 2; order
< HOST_BITS_PER_PTR
; order
++)
941 size_t num_objects
= OBJECTS_PER_PAGE (order
);
942 size_t bitmap_size
= BITMAP_SIZE (num_objects
+ 1);
945 for (p
= G
.pages
[order
]; p
!= NULL
; p
= p
->next
)
947 #ifdef ENABLE_CHECKING
948 /* The data should be page-aligned. */
949 if ((size_t) p
->page
& (G
.pagesize
- 1))
953 /* Pages that aren't in the topmost context are not collected;
954 nevertheless, we need their in-use bit vectors to store GC
955 marks. So, back them up first. */
956 if (p
->context_depth
< G
.context_depth
)
958 if (! p
->save_in_use_p
)
959 p
->save_in_use_p
= xmalloc (bitmap_size
);
960 memcpy (p
->save_in_use_p
, p
->in_use_p
, bitmap_size
);
963 /* Reset reset the number of free objects and clear the
964 in-use bits. These will be adjusted by mark_obj. */
965 p
->num_free_objects
= num_objects
;
966 memset (p
->in_use_p
, 0, bitmap_size
);
968 /* Make sure the one-past-the-end bit is always set. */
969 p
->in_use_p
[num_objects
/ HOST_BITS_PER_LONG
]
970 = ((unsigned long) 1 << (num_objects
% HOST_BITS_PER_LONG
));
975 /* Free all empty pages. Partially empty pages need no attention
976 because the `mark' bit doubles as an `unused' bit. */
983 for (order
= 2; order
< HOST_BITS_PER_PTR
; order
++)
985 /* The last page-entry to consider, regardless of entries
986 placed at the end of the list. */
987 page_entry
* const last
= G
.page_tails
[order
];
989 size_t num_objects
= OBJECTS_PER_PAGE (order
);
991 page_entry
*p
, *previous
;
1001 page_entry
*next
= p
->next
;
1003 /* Loop until all entries have been examined. */
1006 /* Add all live objects on this page to the count of
1007 allocated memory. */
1008 live_objects
= num_objects
- p
->num_free_objects
;
1010 G
.allocated
+= ((size_t) 1 << order
) * live_objects
;
1012 /* Only objects on pages in the topmost context should get
1014 if (p
->context_depth
< G
.context_depth
)
1017 /* Remove the page if it's empty. */
1018 else if (live_objects
== 0)
1021 G
.pages
[order
] = next
;
1023 previous
->next
= next
;
1025 /* Are we removing the last element? */
1026 if (p
== G
.page_tails
[order
])
1027 G
.page_tails
[order
] = previous
;
1032 /* If the page is full, move it to the end. */
1033 else if (p
->num_free_objects
== 0)
1035 /* Don't move it if it's already at the end. */
1036 if (p
!= G
.page_tails
[order
])
1038 /* Move p to the end of the list. */
1040 G
.page_tails
[order
]->next
= p
;
1042 /* Update the tail pointer... */
1043 G
.page_tails
[order
] = p
;
1045 /* ... and the head pointer, if necessary. */
1047 G
.pages
[order
] = next
;
1049 previous
->next
= next
;
1054 /* If we've fallen through to here, it's a page in the
1055 topmost context that is neither full nor empty. Such a
1056 page must precede pages at lesser context depth in the
1057 list, so move it to the head. */
1058 else if (p
!= G
.pages
[order
])
1060 previous
->next
= p
->next
;
1061 p
->next
= G
.pages
[order
];
1063 /* Are we moving the last element? */
1064 if (G
.page_tails
[order
] == p
)
1065 G
.page_tails
[order
] = previous
;
1074 /* Now, restore the in_use_p vectors for any pages from contexts
1075 other than the current one. */
1076 for (p
= G
.pages
[order
]; p
; p
= p
->next
)
1077 if (p
->context_depth
!= G
.context_depth
)
1078 ggc_recalculate_in_use_p (p
);
1083 /* Clobber all free objects. */
1090 for (order
= 2; order
< HOST_BITS_PER_PTR
; order
++)
1092 size_t num_objects
= OBJECTS_PER_PAGE (order
);
1093 size_t size
= (size_t) 1 << order
;
1096 for (p
= G
.pages
[order
]; p
!= NULL
; p
= p
->next
)
1100 if (p
->context_depth
!= G
.context_depth
)
1101 /* Since we don't do any collection for pages in pushed
1102 contexts, there's no need to do any poisoning. And
1103 besides, the IN_USE_P array isn't valid until we pop
1107 for (i
= 0; i
< num_objects
; i
++)
1110 word
= i
/ HOST_BITS_PER_LONG
;
1111 bit
= i
% HOST_BITS_PER_LONG
;
1112 if (((p
->in_use_p
[word
] >> bit
) & 1) == 0)
1113 memset (p
->page
+ i
* size
, 0xa5, size
);
1120 /* Top level mark-and-sweep routine. */
1125 /* Avoid frequent unnecessary work by skipping collection if the
1126 total allocations haven't expanded much since the last
1128 #ifndef GGC_ALWAYS_COLLECT
1129 if (G
.allocated
< GGC_MIN_EXPAND_FOR_GC
* G
.allocated_last_gc
)
1133 timevar_push (TV_GC
);
1135 fprintf (stderr
, " {GC %luk -> ", (unsigned long) G
.allocated
/ 1024);
1137 /* Zero the total allocated bytes. This will be recalculated in the
1141 /* Release the pages we freed the last time we collected, but didn't
1142 reuse in the interim. */
1154 G
.allocated_last_gc
= G
.allocated
;
1155 if (G
.allocated_last_gc
< GGC_MIN_LAST_ALLOCATED
)
1156 G
.allocated_last_gc
= GGC_MIN_LAST_ALLOCATED
;
1158 timevar_pop (TV_GC
);
1161 fprintf (stderr
, "%luk}", (unsigned long) G
.allocated
/ 1024);
1164 /* Print allocation statistics. */
1165 #define SCALE(x) ((unsigned long) ((x) < 1024*10 \
1167 : ((x) < 1024*1024*10 \
1169 : (x) / (1024*1024))))
1170 #define LABEL(x) ((x) < 1024*10 ? ' ' : ((x) < 1024*1024*10 ? 'k' : 'M'))
1173 ggc_print_statistics ()
1175 struct ggc_statistics stats
;
1177 size_t total_overhead
= 0;
1179 /* Clear the statistics. */
1180 memset (&stats
, 0, sizeof (stats
));
1182 /* Make sure collection will really occur. */
1183 G
.allocated_last_gc
= 0;
1185 /* Collect and print the statistics common across collectors. */
1186 ggc_print_common_statistics (stderr
, &stats
);
1188 /* Release free pages so that we will not count the bytes allocated
1189 there as part of the total allocated memory. */
1192 /* Collect some information about the various sizes of
1194 fprintf (stderr
, "\n%-5s %10s %10s %10s\n",
1195 "Log", "Allocated", "Used", "Overhead");
1196 for (i
= 0; i
< HOST_BITS_PER_PTR
; ++i
)
1203 /* Skip empty entries. */
1207 overhead
= allocated
= in_use
= 0;
1209 /* Figure out the total number of bytes allocated for objects of
1210 this size, and how many of them are actually in use. Also figure
1211 out how much memory the page table is using. */
1212 for (p
= G
.pages
[i
]; p
; p
= p
->next
)
1214 allocated
+= p
->bytes
;
1216 (OBJECTS_PER_PAGE (i
) - p
->num_free_objects
) * (1 << i
);
1218 overhead
+= (sizeof (page_entry
) - sizeof (long)
1219 + BITMAP_SIZE (OBJECTS_PER_PAGE (i
) + 1));
1221 fprintf (stderr
, "%-5d %10ld%c %10ld%c %10ld%c\n", i
,
1222 SCALE (allocated
), LABEL (allocated
),
1223 SCALE (in_use
), LABEL (in_use
),
1224 SCALE (overhead
), LABEL (overhead
));
1225 total_overhead
+= overhead
;
1227 fprintf (stderr
, "%-5s %10ld%c %10ld%c %10ld%c\n", "Total",
1228 SCALE (G
.bytes_mapped
), LABEL (G
.bytes_mapped
),
1229 SCALE (G
.allocated
), LABEL(G
.allocated
),
1230 SCALE (total_overhead
), LABEL (total_overhead
));