1 /* "Bag-of-pages" garbage collector for the GNU compiler.
2 Copyright (C) 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 2, or (at your option) any later
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING. If not, write to the Free
18 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
32 /* Prefer MAP_ANON(YMOUS) to /dev/zero, since we don't need to keep a
33 file open. Prefer either to valloc. */
35 # undef HAVE_MMAP_DEV_ZERO
37 # include <sys/mman.h>
39 # define MAP_FAILED -1
41 # if !defined (MAP_ANONYMOUS) && defined (MAP_ANON)
42 # define MAP_ANONYMOUS MAP_ANON
48 #ifdef HAVE_MMAP_DEV_ZERO
50 # include <sys/mman.h>
52 # define MAP_FAILED -1
59 #define USING_MALLOC_PAGE_GROUPS
64 This garbage-collecting allocator allocates objects on one of a set
65 of pages. Each page can allocate objects of a single size only;
66 available sizes are powers of two starting at four bytes. The size
67 of an allocation request is rounded up to the next power of two
68 (`order'), and satisfied from the appropriate page.
70 Each page is recorded in a page-entry, which also maintains an
71 in-use bitmap of object positions on the page. This allows the
72 allocation state of a particular object to be flipped without
73 touching the page itself.
75 Each page-entry also has a context depth, which is used to track
76 pushing and popping of allocation contexts. Only objects allocated
77 in the current (highest-numbered) context may be collected.
79 Page entries are arranged in an array of singly-linked lists. The
80 array is indexed by the allocation size, in bits, of the pages on
81 it; i.e. all pages on a list allocate objects of the same size.
82 Pages are ordered on the list such that all non-full pages precede
83 all full pages, with non-full pages arranged in order of decreasing
86 Empty pages (of all orders) are kept on a single page cache list,
87 and are considered first when new pages are required; they are
88 deallocated at the start of the next collection if they haven't
89 been recycled by then. */
92 /* Define GGC_POISON to poison memory marked unused by the collector. */
95 /* Define GGC_ALWAYS_COLLECT to perform collection every time
96 ggc_collect is invoked. Otherwise, collection is performed only
97 when a significant amount of memory has been allocated since the
99 #undef GGC_ALWAYS_COLLECT
101 #ifdef ENABLE_GC_CHECKING
104 #ifdef ENABLE_GC_ALWAYS_COLLECT
105 #define GGC_ALWAYS_COLLECT
108 /* Define GGC_DEBUG_LEVEL to print debugging information.
109 0: No debugging output.
110 1: GC statistics only.
111 2: Page-entry allocations/deallocations as well.
112 3: Object allocations as well.
113 4: Object marks as well. */
114 #define GGC_DEBUG_LEVEL (0)
116 #ifndef HOST_BITS_PER_PTR
117 #define HOST_BITS_PER_PTR HOST_BITS_PER_LONG
121 /* A two-level tree is used to look up the page-entry for a given
122 pointer. Two chunks of the pointer's bits are extracted to index
123 the first and second levels of the tree, as follows:
127 msb +----------------+----+------+------+ lsb
133 The bottommost HOST_PAGE_SIZE_BITS are ignored, since page-entry
134 pages are aligned on system page boundaries. The next most
135 significant PAGE_L2_BITS and PAGE_L1_BITS are the second and first
136 index values in the lookup table, respectively.
138 For 32-bit architectures and the settings below, there are no
139 leftover bits. For architectures with wider pointers, the lookup
140 tree points to a list of pages, which must be scanned to find the
143 #define PAGE_L1_BITS (8)
144 #define PAGE_L2_BITS (32 - PAGE_L1_BITS - G.lg_pagesize)
145 #define PAGE_L1_SIZE ((size_t) 1 << PAGE_L1_BITS)
146 #define PAGE_L2_SIZE ((size_t) 1 << PAGE_L2_BITS)
148 #define LOOKUP_L1(p) \
149 (((size_t) (p) >> (32 - PAGE_L1_BITS)) & ((1 << PAGE_L1_BITS) - 1))
151 #define LOOKUP_L2(p) \
152 (((size_t) (p) >> G.lg_pagesize) & ((1 << PAGE_L2_BITS) - 1))
154 /* The number of objects per allocation page, for objects on a page of
155 the indicated ORDER. */
156 #define OBJECTS_PER_PAGE(ORDER) objects_per_page_table[ORDER]
158 /* The size of an object on a page of the indicated ORDER. */
159 #define OBJECT_SIZE(ORDER) object_size_table[ORDER]
161 /* The number of extra orders, not corresponding to power-of-two sized
164 #define NUM_EXTRA_ORDERS ARRAY_SIZE (extra_order_size_table)
166 #define RTL_SIZE(NSLOTS) \
167 (sizeof (struct rtx_def) + ((NSLOTS) - 1) * sizeof (rtunion))
169 /* The Ith entry is the maximum size of an object to be stored in the
170 Ith extra order. Adding a new entry to this array is the *only*
171 thing you need to do to add a new special allocation size. */
173 static const size_t extra_order_size_table
[] = {
174 sizeof (struct tree_decl
),
175 sizeof (struct tree_list
),
176 RTL_SIZE (2), /* REG, MEM, PLUS, etc. */
177 RTL_SIZE (10), /* INSN, CALL_INSN, JUMP_INSN */
180 /* The total number of orders. */
182 #define NUM_ORDERS (HOST_BITS_PER_PTR + NUM_EXTRA_ORDERS)
184 /* We use this structure to determine the alignment required for
185 allocations. For power-of-two sized allocations, that's not a
186 problem, but it does matter for odd-sized allocations. */
188 struct max_alignment
{
192 #ifdef HAVE_LONG_DOUBLE
200 /* The biggest alignment required. */
202 #define MAX_ALIGNMENT (offsetof (struct max_alignment, u))
204 /* The Ith entry is the number of objects on a page or order I. */
206 static unsigned objects_per_page_table
[NUM_ORDERS
];
208 /* The Ith entry is the size of an object on a page of order I. */
210 static size_t object_size_table
[NUM_ORDERS
];
212 /* A page_entry records the status of an allocation page. This
213 structure is dynamically sized to fit the bitmap in_use_p. */
214 typedef struct page_entry
216 /* The next page-entry with objects of the same size, or NULL if
217 this is the last page-entry. */
218 struct page_entry
*next
;
220 /* The number of bytes allocated. (This will always be a multiple
221 of the host system page size.) */
224 /* The address at which the memory is allocated. */
227 #ifdef USING_MALLOC_PAGE_GROUPS
228 /* Back pointer to the page group this page came from. */
229 struct page_group
*group
;
232 /* Saved in-use bit vector for pages that aren't in the topmost
233 context during collection. */
234 unsigned long *save_in_use_p
;
236 /* Context depth of this page. */
237 unsigned short context_depth
;
239 /* The number of free objects remaining on this page. */
240 unsigned short num_free_objects
;
242 /* A likely candidate for the bit position of a free object for the
243 next allocation from this page. */
244 unsigned short next_bit_hint
;
246 /* The lg of size of objects allocated from this page. */
249 /* A bit vector indicating whether or not objects are in use. The
250 Nth bit is one if the Nth object on this page is allocated. This
251 array is dynamically sized. */
252 unsigned long in_use_p
[1];
255 #ifdef USING_MALLOC_PAGE_GROUPS
256 /* A page_group describes a large allocation from malloc, from which
257 we parcel out aligned pages. */
258 typedef struct page_group
260 /* A linked list of all extant page groups. */
261 struct page_group
*next
;
263 /* The address we received from malloc. */
266 /* The size of the block. */
269 /* A bitmask of pages in use. */
274 #if HOST_BITS_PER_PTR <= 32
276 /* On 32-bit hosts, we use a two level page table, as pictured above. */
277 typedef page_entry
**page_table
[PAGE_L1_SIZE
];
281 /* On 64-bit hosts, we use the same two level page tables plus a linked
282 list that disambiguates the top 32-bits. There will almost always be
283 exactly one entry in the list. */
284 typedef struct page_table_chain
286 struct page_table_chain
*next
;
288 page_entry
**table
[PAGE_L1_SIZE
];
293 /* The rest of the global variables. */
294 static struct globals
296 /* The Nth element in this array is a page with objects of size 2^N.
297 If there are any pages with free objects, they will be at the
298 head of the list. NULL if there are no page-entries for this
300 page_entry
*pages
[NUM_ORDERS
];
302 /* The Nth element in this array is the last page with objects of
303 size 2^N. NULL if there are no page-entries for this object
305 page_entry
*page_tails
[NUM_ORDERS
];
307 /* Lookup table for associating allocation pages with object addresses. */
310 /* The system's page size. */
314 /* Bytes currently allocated. */
317 /* Bytes currently allocated at the end of the last collection. */
318 size_t allocated_last_gc
;
320 /* Total amount of memory mapped. */
323 /* The current depth in the context stack. */
324 unsigned short context_depth
;
326 /* A file descriptor open to /dev/zero for reading. */
327 #if defined (HAVE_MMAP_DEV_ZERO)
331 /* A cache of free system pages. */
332 page_entry
*free_pages
;
334 #ifdef USING_MALLOC_PAGE_GROUPS
335 page_group
*page_groups
;
338 /* The file descriptor for debugging output. */
342 /* The size in bytes required to maintain a bitmap for the objects
344 #define BITMAP_SIZE(Num_objects) \
345 (CEIL ((Num_objects), HOST_BITS_PER_LONG) * sizeof(long))
347 /* Skip garbage collection if the current allocation is not at least
348 this factor times the allocation at the end of the last collection.
349 In other words, total allocation must expand by (this factor minus
350 one) before collection is performed. */
351 #define GGC_MIN_EXPAND_FOR_GC (1.3)
353 /* Bound `allocated_last_gc' to 4MB, to prevent the memory expansion
354 test from triggering too often when the heap is small. */
355 #define GGC_MIN_LAST_ALLOCATED (4 * 1024 * 1024)
357 /* Allocate pages in chunks of this size, to throttle calls to memory
358 allocation routines. The first page is used, the rest go onto the
359 free list. This cannot be larger than HOST_BITS_PER_INT for the
360 in_use bitmask for page_group. */
361 #define GGC_QUIRE_SIZE 16
363 static int ggc_allocated_p
PARAMS ((const void *));
364 static page_entry
*lookup_page_table_entry
PARAMS ((const void *));
365 static void set_page_table_entry
PARAMS ((void *, page_entry
*));
367 static char *alloc_anon
PARAMS ((char *, size_t));
369 #ifdef USING_MALLOC_PAGE_GROUPS
370 static size_t page_group_index
PARAMS ((char *, char *));
371 static void set_page_group_in_use
PARAMS ((page_group
*, char *));
372 static void clear_page_group_in_use
PARAMS ((page_group
*, char *));
374 static struct page_entry
* alloc_page
PARAMS ((unsigned));
375 static void free_page
PARAMS ((struct page_entry
*));
376 static void release_pages
PARAMS ((void));
377 static void clear_marks
PARAMS ((void));
378 static void sweep_pages
PARAMS ((void));
379 static void ggc_recalculate_in_use_p
PARAMS ((page_entry
*));
382 static void poison_pages
PARAMS ((void));
385 void debug_print_page_list
PARAMS ((int));
387 /* Returns non-zero if P was allocated in GC'able memory. */
396 #if HOST_BITS_PER_PTR <= 32
399 page_table table
= G
.lookup
;
400 size_t high_bits
= (size_t) p
& ~ (size_t) 0xffffffff;
405 if (table
->high_bits
== high_bits
)
409 base
= &table
->table
[0];
412 /* Extract the level 1 and 2 indices. */
416 return base
[L1
] && base
[L1
][L2
];
419 /* Traverse the page table and find the entry for a page.
420 Die (probably) if the object wasn't allocated via GC. */
422 static inline page_entry
*
423 lookup_page_table_entry(p
)
429 #if HOST_BITS_PER_PTR <= 32
432 page_table table
= G
.lookup
;
433 size_t high_bits
= (size_t) p
& ~ (size_t) 0xffffffff;
434 while (table
->high_bits
!= high_bits
)
436 base
= &table
->table
[0];
439 /* Extract the level 1 and 2 indices. */
446 /* Set the page table entry for a page. */
449 set_page_table_entry(p
, entry
)
456 #if HOST_BITS_PER_PTR <= 32
460 size_t high_bits
= (size_t) p
& ~ (size_t) 0xffffffff;
461 for (table
= G
.lookup
; table
; table
= table
->next
)
462 if (table
->high_bits
== high_bits
)
465 /* Not found -- allocate a new table. */
466 table
= (page_table
) xcalloc (1, sizeof(*table
));
467 table
->next
= G
.lookup
;
468 table
->high_bits
= high_bits
;
471 base
= &table
->table
[0];
474 /* Extract the level 1 and 2 indices. */
478 if (base
[L1
] == NULL
)
479 base
[L1
] = (page_entry
**) xcalloc (PAGE_L2_SIZE
, sizeof (page_entry
*));
481 base
[L1
][L2
] = entry
;
484 /* Prints the page-entry for object size ORDER, for debugging. */
487 debug_print_page_list (order
)
491 printf ("Head=%p, Tail=%p:\n", (PTR
) G
.pages
[order
],
492 (PTR
) G
.page_tails
[order
]);
496 printf ("%p(%1d|%3d) -> ", (PTR
) p
, p
->context_depth
,
497 p
->num_free_objects
);
505 /* Allocate SIZE bytes of anonymous memory, preferably near PREF,
506 (if non-null). The ifdef structure here is intended to cause a
507 compile error unless exactly one of the HAVE_* is defined. */
510 alloc_anon (pref
, size
)
511 char *pref ATTRIBUTE_UNUSED
;
514 #ifdef HAVE_MMAP_ANON
515 char *page
= (char *) mmap (pref
, size
, PROT_READ
| PROT_WRITE
,
516 MAP_PRIVATE
| MAP_ANONYMOUS
, -1, 0);
518 #ifdef HAVE_MMAP_DEV_ZERO
519 char *page
= (char *) mmap (pref
, size
, PROT_READ
| PROT_WRITE
,
520 MAP_PRIVATE
, G
.dev_zero_fd
, 0);
523 if (page
== (char *) MAP_FAILED
)
525 perror ("virtual memory exhausted");
526 exit (FATAL_EXIT_CODE
);
529 /* Remember that we allocated this memory. */
530 G
.bytes_mapped
+= size
;
535 #ifdef USING_MALLOC_PAGE_GROUPS
536 /* Compute the index for this page into the page group. */
539 page_group_index (allocation
, page
)
540 char *allocation
, *page
;
542 return (size_t) (page
- allocation
) >> G
.lg_pagesize
;
545 /* Set and clear the in_use bit for this page in the page group. */
548 set_page_group_in_use (group
, page
)
552 group
->in_use
|= 1 << page_group_index (group
->allocation
, page
);
556 clear_page_group_in_use (group
, page
)
560 group
->in_use
&= ~(1 << page_group_index (group
->allocation
, page
));
564 /* Allocate a new page for allocating objects of size 2^ORDER,
565 and return an entry for it. The entry is not added to the
566 appropriate page_table list. */
568 static inline struct page_entry
*
572 struct page_entry
*entry
, *p
, **pp
;
576 size_t page_entry_size
;
578 #ifdef USING_MALLOC_PAGE_GROUPS
582 num_objects
= OBJECTS_PER_PAGE (order
);
583 bitmap_size
= BITMAP_SIZE (num_objects
+ 1);
584 page_entry_size
= sizeof (page_entry
) - sizeof (long) + bitmap_size
;
585 entry_size
= num_objects
* OBJECT_SIZE (order
);
586 if (entry_size
< G
.pagesize
)
587 entry_size
= G
.pagesize
;
592 /* Check the list of free pages for one we can use. */
593 for (pp
= &G
.free_pages
, p
= *pp
; p
; pp
= &p
->next
, p
= *pp
)
594 if (p
->bytes
== entry_size
)
599 /* Recycle the allocated memory from this page ... */
603 #ifdef USING_MALLOC_PAGE_GROUPS
607 /* ... and, if possible, the page entry itself. */
608 if (p
->order
== order
)
611 memset (entry
, 0, page_entry_size
);
617 else if (entry_size
== G
.pagesize
)
619 /* We want just one page. Allocate a bunch of them and put the
620 extras on the freelist. (Can only do this optimization with
621 mmap for backing store.) */
622 struct page_entry
*e
, *f
= G
.free_pages
;
625 page
= alloc_anon (NULL
, G
.pagesize
* GGC_QUIRE_SIZE
);
627 /* This loop counts down so that the chain will be in ascending
629 for (i
= GGC_QUIRE_SIZE
- 1; i
>= 1; i
--)
631 e
= (struct page_entry
*) xcalloc (1, page_entry_size
);
633 e
->bytes
= G
.pagesize
;
634 e
->page
= page
+ (i
<< G
.lg_pagesize
);
642 page
= alloc_anon (NULL
, entry_size
);
644 #ifdef USING_MALLOC_PAGE_GROUPS
647 /* Allocate a large block of memory and serve out the aligned
648 pages therein. This results in much less memory wastage
649 than the traditional implementation of valloc. */
651 char *allocation
, *a
, *enda
;
652 size_t alloc_size
, head_slop
, tail_slop
;
653 int multiple_pages
= (entry_size
== G
.pagesize
);
656 alloc_size
= GGC_QUIRE_SIZE
* G
.pagesize
;
658 alloc_size
= entry_size
+ G
.pagesize
- 1;
659 allocation
= xmalloc (alloc_size
);
661 page
= (char *) (((size_t) allocation
+ G
.pagesize
- 1) & -G
.pagesize
);
662 head_slop
= page
- allocation
;
664 tail_slop
= ((size_t) allocation
+ alloc_size
) & (G
.pagesize
- 1);
666 tail_slop
= alloc_size
- entry_size
- head_slop
;
667 enda
= allocation
+ alloc_size
- tail_slop
;
669 /* We allocated N pages, which are likely not aligned, leaving
670 us with N-1 usable pages. We plan to place the page_group
671 structure somewhere in the slop. */
672 if (head_slop
>= sizeof (page_group
))
673 group
= (page_group
*)page
- 1;
676 /* We magically got an aligned allocation. Too bad, we have
677 to waste a page anyway. */
681 tail_slop
+= G
.pagesize
;
683 if (tail_slop
< sizeof (page_group
))
685 group
= (page_group
*)enda
;
686 tail_slop
-= sizeof (page_group
);
689 /* Remember that we allocated this memory. */
690 group
->next
= G
.page_groups
;
691 group
->allocation
= allocation
;
692 group
->alloc_size
= alloc_size
;
694 G
.page_groups
= group
;
695 G
.bytes_mapped
+= alloc_size
;
697 /* If we allocated multiple pages, put the rest on the free list. */
700 struct page_entry
*e
, *f
= G
.free_pages
;
701 for (a
= enda
- G
.pagesize
; a
!= page
; a
-= G
.pagesize
)
703 e
= (struct page_entry
*) xcalloc (1, page_entry_size
);
705 e
->bytes
= G
.pagesize
;
717 entry
= (struct page_entry
*) xcalloc (1, page_entry_size
);
719 entry
->bytes
= entry_size
;
721 entry
->context_depth
= G
.context_depth
;
722 entry
->order
= order
;
723 entry
->num_free_objects
= num_objects
;
724 entry
->next_bit_hint
= 1;
726 #ifdef USING_MALLOC_PAGE_GROUPS
727 entry
->group
= group
;
728 set_page_group_in_use (group
, page
);
731 /* Set the one-past-the-end in-use bit. This acts as a sentry as we
732 increment the hint. */
733 entry
->in_use_p
[num_objects
/ HOST_BITS_PER_LONG
]
734 = (unsigned long) 1 << (num_objects
% HOST_BITS_PER_LONG
);
736 set_page_table_entry (page
, entry
);
738 if (GGC_DEBUG_LEVEL
>= 2)
739 fprintf (G
.debug_file
,
740 "Allocating page at %p, object size=%lu, data %p-%p\n",
741 (PTR
) entry
, (unsigned long) OBJECT_SIZE (order
), page
,
742 page
+ entry_size
- 1);
747 /* For a page that is no longer needed, put it on the free page list. */
753 if (GGC_DEBUG_LEVEL
>= 2)
754 fprintf (G
.debug_file
,
755 "Deallocating page at %p, data %p-%p\n", (PTR
) entry
,
756 entry
->page
, entry
->page
+ entry
->bytes
- 1);
758 set_page_table_entry (entry
->page
, NULL
);
760 #ifdef USING_MALLOC_PAGE_GROUPS
761 clear_page_group_in_use (entry
->group
, entry
->page
);
764 entry
->next
= G
.free_pages
;
765 G
.free_pages
= entry
;
768 /* Release the free page cache to the system. */
774 page_entry
*p
, *next
;
778 /* Gather up adjacent pages so they are unmapped together. */
789 while (p
&& p
->page
== start
+ len
)
798 G
.bytes_mapped
-= len
;
803 #ifdef USING_MALLOC_PAGE_GROUPS
807 /* Remove all pages from free page groups from the list. */
809 while ((p
= *pp
) != NULL
)
810 if (p
->group
->in_use
== 0)
818 /* Remove all free page groups, and release the storage. */
820 while ((g
= *gp
) != NULL
)
824 G
.bytes_mapped
-= g
->alloc_size
;
825 free (g
->allocation
);
832 /* This table provides a fast way to determine ceil(log_2(size)) for
833 allocation requests. The minimum allocation size is eight bytes. */
835 static unsigned char size_lookup
[257] =
837 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4,
838 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
839 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
840 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
841 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
842 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
843 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
844 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
845 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
846 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
847 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
848 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
849 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
850 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
851 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
852 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
856 /* Allocate a chunk of memory of SIZE bytes. If ZERO is non-zero, the
857 memory is zeroed; otherwise, its contents are undefined. */
863 unsigned order
, word
, bit
, object_offset
;
864 struct page_entry
*entry
;
868 order
= size_lookup
[size
];
872 while (size
> OBJECT_SIZE (order
))
876 /* If there are non-full pages for this size allocation, they are at
877 the head of the list. */
878 entry
= G
.pages
[order
];
880 /* If there is no page for this object size, or all pages in this
881 context are full, allocate a new page. */
882 if (entry
== NULL
|| entry
->num_free_objects
== 0)
884 struct page_entry
*new_entry
;
885 new_entry
= alloc_page (order
);
887 /* If this is the only entry, it's also the tail. */
889 G
.page_tails
[order
] = new_entry
;
891 /* Put new pages at the head of the page list. */
892 new_entry
->next
= entry
;
894 G
.pages
[order
] = new_entry
;
896 /* For a new page, we know the word and bit positions (in the
897 in_use bitmap) of the first available object -- they're zero. */
898 new_entry
->next_bit_hint
= 1;
905 /* First try to use the hint left from the previous allocation
906 to locate a clear bit in the in-use bitmap. We've made sure
907 that the one-past-the-end bit is always set, so if the hint
908 has run over, this test will fail. */
909 unsigned hint
= entry
->next_bit_hint
;
910 word
= hint
/ HOST_BITS_PER_LONG
;
911 bit
= hint
% HOST_BITS_PER_LONG
;
913 /* If the hint didn't work, scan the bitmap from the beginning. */
914 if ((entry
->in_use_p
[word
] >> bit
) & 1)
917 while (~entry
->in_use_p
[word
] == 0)
919 while ((entry
->in_use_p
[word
] >> bit
) & 1)
921 hint
= word
* HOST_BITS_PER_LONG
+ bit
;
924 /* Next time, try the next bit. */
925 entry
->next_bit_hint
= hint
+ 1;
927 object_offset
= hint
* OBJECT_SIZE (order
);
930 /* Set the in-use bit. */
931 entry
->in_use_p
[word
] |= ((unsigned long) 1 << bit
);
933 /* Keep a running total of the number of free objects. If this page
934 fills up, we may have to move it to the end of the list if the
935 next page isn't full. If the next page is full, all subsequent
936 pages are full, so there's no need to move it. */
937 if (--entry
->num_free_objects
== 0
938 && entry
->next
!= NULL
939 && entry
->next
->num_free_objects
> 0)
941 G
.pages
[order
] = entry
->next
;
943 G
.page_tails
[order
]->next
= entry
;
944 G
.page_tails
[order
] = entry
;
947 /* Calculate the object's address. */
948 result
= entry
->page
+ object_offset
;
951 /* `Poison' the entire allocated object, including any padding at
953 memset (result
, 0xaf, OBJECT_SIZE (order
));
956 /* Keep track of how many bytes are being allocated. This
957 information is used in deciding when to collect. */
958 G
.allocated
+= OBJECT_SIZE (order
);
960 if (GGC_DEBUG_LEVEL
>= 3)
961 fprintf (G
.debug_file
,
962 "Allocating object, requested size=%lu, actual=%lu at %p on %p\n",
963 (unsigned long) size
, (unsigned long) OBJECT_SIZE (order
), result
,
969 /* If P is not marked, marks it and return false. Otherwise return true.
970 P must have been allocated by the GC allocator; it mustn't point to
971 static objects, stack variables, or memory allocated with malloc. */
981 /* Look up the page on which the object is alloced. If the object
982 wasn't allocated by the collector, we'll probably die. */
983 entry
= lookup_page_table_entry (p
);
984 #ifdef ENABLE_CHECKING
989 /* Calculate the index of the object on the page; this is its bit
990 position in the in_use_p bitmap. */
991 bit
= (((const char *) p
) - entry
->page
) / OBJECT_SIZE (entry
->order
);
992 word
= bit
/ HOST_BITS_PER_LONG
;
993 mask
= (unsigned long) 1 << (bit
% HOST_BITS_PER_LONG
);
995 /* If the bit was previously set, skip it. */
996 if (entry
->in_use_p
[word
] & mask
)
999 /* Otherwise set it, and decrement the free object count. */
1000 entry
->in_use_p
[word
] |= mask
;
1001 entry
->num_free_objects
-= 1;
1003 if (GGC_DEBUG_LEVEL
>= 4)
1004 fprintf (G
.debug_file
, "Marking %p\n", p
);
1009 /* Return 1 if P has been marked, zero otherwise.
1010 P must have been allocated by the GC allocator; it mustn't point to
1011 static objects, stack variables, or memory allocated with malloc. */
1021 /* Look up the page on which the object is alloced. If the object
1022 wasn't allocated by the collector, we'll probably die. */
1023 entry
= lookup_page_table_entry (p
);
1024 #ifdef ENABLE_CHECKING
1029 /* Calculate the index of the object on the page; this is its bit
1030 position in the in_use_p bitmap. */
1031 bit
= (((const char *) p
) - entry
->page
) / OBJECT_SIZE (entry
->order
);
1032 word
= bit
/ HOST_BITS_PER_LONG
;
1033 mask
= (unsigned long) 1 << (bit
% HOST_BITS_PER_LONG
);
1035 return (entry
->in_use_p
[word
] & mask
) != 0;
1038 /* Return the size of the gc-able object P. */
1044 page_entry
*pe
= lookup_page_table_entry (p
);
1045 return OBJECT_SIZE (pe
->order
);
1048 /* Initialize the ggc-mmap allocator. */
1055 G
.pagesize
= getpagesize();
1056 G
.lg_pagesize
= exact_log2 (G
.pagesize
);
1058 #ifdef HAVE_MMAP_DEV_ZERO
1059 G
.dev_zero_fd
= open ("/dev/zero", O_RDONLY
);
1060 if (G
.dev_zero_fd
== -1)
1065 G
.debug_file
= fopen ("ggc-mmap.debug", "w");
1067 G
.debug_file
= stdout
;
1070 G
.allocated_last_gc
= GGC_MIN_LAST_ALLOCATED
;
1073 /* StunOS has an amazing off-by-one error for the first mmap allocation
1074 after fiddling with RLIMIT_STACK. The result, as hard as it is to
1075 believe, is an unaligned page allocation, which would cause us to
1076 hork badly if we tried to use it. */
1078 char *p
= alloc_anon (NULL
, G
.pagesize
);
1079 struct page_entry
*e
;
1080 if ((size_t)p
& (G
.pagesize
- 1))
1082 /* How losing. Discard this one and try another. If we still
1083 can't get something useful, give up. */
1085 p
= alloc_anon (NULL
, G
.pagesize
);
1086 if ((size_t)p
& (G
.pagesize
- 1))
1090 /* We have a good page, might as well hold onto it... */
1091 e
= (struct page_entry
*) xcalloc (1, sizeof (struct page_entry
));
1092 e
->bytes
= G
.pagesize
;
1094 e
->next
= G
.free_pages
;
1099 /* Initialize the object size table. */
1100 for (order
= 0; order
< HOST_BITS_PER_PTR
; ++order
)
1101 object_size_table
[order
] = (size_t) 1 << order
;
1102 for (order
= HOST_BITS_PER_PTR
; order
< NUM_ORDERS
; ++order
)
1104 size_t s
= extra_order_size_table
[order
- HOST_BITS_PER_PTR
];
1106 /* If S is not a multiple of the MAX_ALIGNMENT, then round it up
1107 so that we're sure of getting aligned memory. */
1108 s
= CEIL (s
, MAX_ALIGNMENT
) * MAX_ALIGNMENT
;
1109 object_size_table
[order
] = s
;
1112 /* Initialize the objects-per-page table. */
1113 for (order
= 0; order
< NUM_ORDERS
; ++order
)
1115 objects_per_page_table
[order
] = G
.pagesize
/ OBJECT_SIZE (order
);
1116 if (objects_per_page_table
[order
] == 0)
1117 objects_per_page_table
[order
] = 1;
1120 /* Reset the size_lookup array to put appropriately sized objects in
1121 the special orders. All objects bigger than the previous power
1122 of two, but no greater than the special size, should go in the
1124 for (order
= HOST_BITS_PER_PTR
; order
< NUM_ORDERS
; ++order
)
1129 o
= size_lookup
[OBJECT_SIZE (order
)];
1130 for (i
= OBJECT_SIZE (order
); size_lookup
[i
] == o
; --i
)
1131 size_lookup
[i
] = order
;
1135 /* Increment the `GC context'. Objects allocated in an outer context
1136 are never freed, eliminating the need to register their roots. */
1144 if (G
.context_depth
== 0)
1148 /* Merge the SAVE_IN_USE_P and IN_USE_P arrays in P so that IN_USE_P
1149 reflects reality. Recalculate NUM_FREE_OBJECTS as well. */
1152 ggc_recalculate_in_use_p (p
)
1158 /* Because the past-the-end bit in in_use_p is always set, we
1159 pretend there is one additional object. */
1160 num_objects
= OBJECTS_PER_PAGE (p
->order
) + 1;
1162 /* Reset the free object count. */
1163 p
->num_free_objects
= num_objects
;
1165 /* Combine the IN_USE_P and SAVE_IN_USE_P arrays. */
1167 i
< CEIL (BITMAP_SIZE (num_objects
),
1168 sizeof (*p
->in_use_p
));
1173 /* Something is in use if it is marked, or if it was in use in a
1174 context further down the context stack. */
1175 p
->in_use_p
[i
] |= p
->save_in_use_p
[i
];
1177 /* Decrement the free object count for every object allocated. */
1178 for (j
= p
->in_use_p
[i
]; j
; j
>>= 1)
1179 p
->num_free_objects
-= (j
& 1);
1182 if (p
->num_free_objects
>= num_objects
)
1186 /* Decrement the `GC context'. All objects allocated since the
1187 previous ggc_push_context are migrated to the outer context. */
1192 unsigned order
, depth
;
1194 depth
= --G
.context_depth
;
1196 /* Any remaining pages in the popped context are lowered to the new
1197 current context; i.e. objects allocated in the popped context and
1198 left over are imported into the previous context. */
1199 for (order
= 2; order
< NUM_ORDERS
; order
++)
1203 for (p
= G
.pages
[order
]; p
!= NULL
; p
= p
->next
)
1205 if (p
->context_depth
> depth
)
1206 p
->context_depth
= depth
;
1208 /* If this page is now in the topmost context, and we'd
1209 saved its allocation state, restore it. */
1210 else if (p
->context_depth
== depth
&& p
->save_in_use_p
)
1212 ggc_recalculate_in_use_p (p
);
1213 free (p
->save_in_use_p
);
1214 p
->save_in_use_p
= 0;
1220 /* Unmark all objects. */
1227 for (order
= 2; order
< NUM_ORDERS
; order
++)
1229 size_t num_objects
= OBJECTS_PER_PAGE (order
);
1230 size_t bitmap_size
= BITMAP_SIZE (num_objects
+ 1);
1233 for (p
= G
.pages
[order
]; p
!= NULL
; p
= p
->next
)
1235 #ifdef ENABLE_CHECKING
1236 /* The data should be page-aligned. */
1237 if ((size_t) p
->page
& (G
.pagesize
- 1))
1241 /* Pages that aren't in the topmost context are not collected;
1242 nevertheless, we need their in-use bit vectors to store GC
1243 marks. So, back them up first. */
1244 if (p
->context_depth
< G
.context_depth
)
1246 if (! p
->save_in_use_p
)
1247 p
->save_in_use_p
= xmalloc (bitmap_size
);
1248 memcpy (p
->save_in_use_p
, p
->in_use_p
, bitmap_size
);
1251 /* Reset reset the number of free objects and clear the
1252 in-use bits. These will be adjusted by mark_obj. */
1253 p
->num_free_objects
= num_objects
;
1254 memset (p
->in_use_p
, 0, bitmap_size
);
1256 /* Make sure the one-past-the-end bit is always set. */
1257 p
->in_use_p
[num_objects
/ HOST_BITS_PER_LONG
]
1258 = ((unsigned long) 1 << (num_objects
% HOST_BITS_PER_LONG
));
1263 /* Free all empty pages. Partially empty pages need no attention
1264 because the `mark' bit doubles as an `unused' bit. */
1271 for (order
= 2; order
< NUM_ORDERS
; order
++)
1273 /* The last page-entry to consider, regardless of entries
1274 placed at the end of the list. */
1275 page_entry
* const last
= G
.page_tails
[order
];
1277 size_t num_objects
= OBJECTS_PER_PAGE (order
);
1278 size_t live_objects
;
1279 page_entry
*p
, *previous
;
1289 page_entry
*next
= p
->next
;
1291 /* Loop until all entries have been examined. */
1294 /* Add all live objects on this page to the count of
1295 allocated memory. */
1296 live_objects
= num_objects
- p
->num_free_objects
;
1298 G
.allocated
+= OBJECT_SIZE (order
) * live_objects
;
1300 /* Only objects on pages in the topmost context should get
1302 if (p
->context_depth
< G
.context_depth
)
1305 /* Remove the page if it's empty. */
1306 else if (live_objects
== 0)
1309 G
.pages
[order
] = next
;
1311 previous
->next
= next
;
1313 /* Are we removing the last element? */
1314 if (p
== G
.page_tails
[order
])
1315 G
.page_tails
[order
] = previous
;
1320 /* If the page is full, move it to the end. */
1321 else if (p
->num_free_objects
== 0)
1323 /* Don't move it if it's already at the end. */
1324 if (p
!= G
.page_tails
[order
])
1326 /* Move p to the end of the list. */
1328 G
.page_tails
[order
]->next
= p
;
1330 /* Update the tail pointer... */
1331 G
.page_tails
[order
] = p
;
1333 /* ... and the head pointer, if necessary. */
1335 G
.pages
[order
] = next
;
1337 previous
->next
= next
;
1342 /* If we've fallen through to here, it's a page in the
1343 topmost context that is neither full nor empty. Such a
1344 page must precede pages at lesser context depth in the
1345 list, so move it to the head. */
1346 else if (p
!= G
.pages
[order
])
1348 previous
->next
= p
->next
;
1349 p
->next
= G
.pages
[order
];
1351 /* Are we moving the last element? */
1352 if (G
.page_tails
[order
] == p
)
1353 G
.page_tails
[order
] = previous
;
1362 /* Now, restore the in_use_p vectors for any pages from contexts
1363 other than the current one. */
1364 for (p
= G
.pages
[order
]; p
; p
= p
->next
)
1365 if (p
->context_depth
!= G
.context_depth
)
1366 ggc_recalculate_in_use_p (p
);
1371 /* Clobber all free objects. */
1378 for (order
= 2; order
< NUM_ORDERS
; order
++)
1380 size_t num_objects
= OBJECTS_PER_PAGE (order
);
1381 size_t size
= OBJECT_SIZE (order
);
1384 for (p
= G
.pages
[order
]; p
!= NULL
; p
= p
->next
)
1388 if (p
->context_depth
!= G
.context_depth
)
1389 /* Since we don't do any collection for pages in pushed
1390 contexts, there's no need to do any poisoning. And
1391 besides, the IN_USE_P array isn't valid until we pop
1395 for (i
= 0; i
< num_objects
; i
++)
1398 word
= i
/ HOST_BITS_PER_LONG
;
1399 bit
= i
% HOST_BITS_PER_LONG
;
1400 if (((p
->in_use_p
[word
] >> bit
) & 1) == 0)
1401 memset (p
->page
+ i
* size
, 0xa5, size
);
1408 /* Top level mark-and-sweep routine. */
1413 /* Avoid frequent unnecessary work by skipping collection if the
1414 total allocations haven't expanded much since the last
1416 #ifndef GGC_ALWAYS_COLLECT
1417 if (G
.allocated
< GGC_MIN_EXPAND_FOR_GC
* G
.allocated_last_gc
)
1421 timevar_push (TV_GC
);
1423 fprintf (stderr
, " {GC %luk -> ", (unsigned long) G
.allocated
/ 1024);
1425 /* Zero the total allocated bytes. This will be recalculated in the
1429 /* Release the pages we freed the last time we collected, but didn't
1430 reuse in the interim. */
1442 G
.allocated_last_gc
= G
.allocated
;
1443 if (G
.allocated_last_gc
< GGC_MIN_LAST_ALLOCATED
)
1444 G
.allocated_last_gc
= GGC_MIN_LAST_ALLOCATED
;
1446 timevar_pop (TV_GC
);
1449 fprintf (stderr
, "%luk}", (unsigned long) G
.allocated
/ 1024);
1452 /* Print allocation statistics. */
1453 #define SCALE(x) ((unsigned long) ((x) < 1024*10 \
1455 : ((x) < 1024*1024*10 \
1457 : (x) / (1024*1024))))
1458 #define LABEL(x) ((x) < 1024*10 ? ' ' : ((x) < 1024*1024*10 ? 'k' : 'M'))
1461 ggc_print_statistics ()
1463 struct ggc_statistics stats
;
1465 size_t total_overhead
= 0;
1467 /* Clear the statistics. */
1468 memset (&stats
, 0, sizeof (stats
));
1470 /* Make sure collection will really occur. */
1471 G
.allocated_last_gc
= 0;
1473 /* Collect and print the statistics common across collectors. */
1474 ggc_print_common_statistics (stderr
, &stats
);
1476 /* Release free pages so that we will not count the bytes allocated
1477 there as part of the total allocated memory. */
1480 /* Collect some information about the various sizes of
1482 fprintf (stderr
, "\n%-5s %10s %10s %10s\n",
1483 "Size", "Allocated", "Used", "Overhead");
1484 for (i
= 0; i
< NUM_ORDERS
; ++i
)
1491 /* Skip empty entries. */
1495 overhead
= allocated
= in_use
= 0;
1497 /* Figure out the total number of bytes allocated for objects of
1498 this size, and how many of them are actually in use. Also figure
1499 out how much memory the page table is using. */
1500 for (p
= G
.pages
[i
]; p
; p
= p
->next
)
1502 allocated
+= p
->bytes
;
1504 (OBJECTS_PER_PAGE (i
) - p
->num_free_objects
) * OBJECT_SIZE (i
);
1506 overhead
+= (sizeof (page_entry
) - sizeof (long)
1507 + BITMAP_SIZE (OBJECTS_PER_PAGE (i
) + 1));
1509 fprintf (stderr
, "%-5lu %10lu%c %10lu%c %10lu%c\n",
1510 (unsigned long) OBJECT_SIZE (i
),
1511 SCALE (allocated
), LABEL (allocated
),
1512 SCALE (in_use
), LABEL (in_use
),
1513 SCALE (overhead
), LABEL (overhead
));
1514 total_overhead
+= overhead
;
1516 fprintf (stderr
, "%-5s %10lu%c %10lu%c %10lu%c\n", "Total",
1517 SCALE (G
.bytes_mapped
), LABEL (G
.bytes_mapped
),
1518 SCALE (G
.allocated
), LABEL(G
.allocated
),
1519 SCALE (total_overhead
), LABEL (total_overhead
));