1 /* "Bag-of-pages" garbage collector for the GNU compiler.
2 Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004
3 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 2, or (at your option) any later
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to the Free
19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
24 #include "coretypes.h"
34 #ifdef ENABLE_VALGRIND_CHECKING
35 # ifdef HAVE_VALGRIND_MEMCHECK_H
36 # include <valgrind/memcheck.h>
37 # elif defined HAVE_MEMCHECK_H
38 # include <memcheck.h>
40 # include <valgrind.h>
43 /* Avoid #ifdef:s when we can help it. */
44 #define VALGRIND_DISCARD(x)
47 /* Prefer MAP_ANON(YMOUS) to /dev/zero, since we don't need to keep a
48 file open. Prefer either to valloc. */
50 # undef HAVE_MMAP_DEV_ZERO
52 # include <sys/mman.h>
54 # define MAP_FAILED -1
56 # if !defined (MAP_ANONYMOUS) && defined (MAP_ANON)
57 # define MAP_ANONYMOUS MAP_ANON
63 #ifdef HAVE_MMAP_DEV_ZERO
65 # include <sys/mman.h>
67 # define MAP_FAILED -1
74 #define USING_MALLOC_PAGE_GROUPS
79 This garbage-collecting allocator allocates objects on one of a set
80 of pages. Each page can allocate objects of a single size only;
81 available sizes are powers of two starting at four bytes. The size
82 of an allocation request is rounded up to the next power of two
83 (`order'), and satisfied from the appropriate page.
85 Each page is recorded in a page-entry, which also maintains an
86 in-use bitmap of object positions on the page. This allows the
87 allocation state of a particular object to be flipped without
88 touching the page itself.
90 Each page-entry also has a context depth, which is used to track
91 pushing and popping of allocation contexts. Only objects allocated
92 in the current (highest-numbered) context may be collected.
94 Page entries are arranged in an array of singly-linked lists. The
95 array is indexed by the allocation size, in bits, of the pages on
96 it; i.e. all pages on a list allocate objects of the same size.
97 Pages are ordered on the list such that all non-full pages precede
98 all full pages, with non-full pages arranged in order of decreasing
101 Empty pages (of all orders) are kept on a single page cache list,
102 and are considered first when new pages are required; they are
103 deallocated at the start of the next collection if they haven't
104 been recycled by then. */
106 /* Define GGC_DEBUG_LEVEL to print debugging information.
107 0: No debugging output.
108 1: GC statistics only.
109 2: Page-entry allocations/deallocations as well.
110 3: Object allocations as well.
111 4: Object marks as well. */
112 #define GGC_DEBUG_LEVEL (0)
114 #ifndef HOST_BITS_PER_PTR
115 #define HOST_BITS_PER_PTR HOST_BITS_PER_LONG
119 /* A two-level tree is used to look up the page-entry for a given
120 pointer. Two chunks of the pointer's bits are extracted to index
121 the first and second levels of the tree, as follows:
125 msb +----------------+----+------+------+ lsb
131 The bottommost HOST_PAGE_SIZE_BITS are ignored, since page-entry
132 pages are aligned on system page boundaries. The next most
133 significant PAGE_L2_BITS and PAGE_L1_BITS are the second and first
134 index values in the lookup table, respectively.
136 For 32-bit architectures and the settings below, there are no
137 leftover bits. For architectures with wider pointers, the lookup
138 tree points to a list of pages, which must be scanned to find the
141 #define PAGE_L1_BITS (8)
142 #define PAGE_L2_BITS (32 - PAGE_L1_BITS - G.lg_pagesize)
143 #define PAGE_L1_SIZE ((size_t) 1 << PAGE_L1_BITS)
144 #define PAGE_L2_SIZE ((size_t) 1 << PAGE_L2_BITS)
146 #define LOOKUP_L1(p) \
147 (((size_t) (p) >> (32 - PAGE_L1_BITS)) & ((1 << PAGE_L1_BITS) - 1))
149 #define LOOKUP_L2(p) \
150 (((size_t) (p) >> G.lg_pagesize) & ((1 << PAGE_L2_BITS) - 1))
152 /* The number of objects per allocation page, for objects on a page of
153 the indicated ORDER. */
154 #define OBJECTS_PER_PAGE(ORDER) objects_per_page_table[ORDER]
156 /* The number of objects in P. */
157 #define OBJECTS_IN_PAGE(P) ((P)->bytes / OBJECT_SIZE ((P)->order))
159 /* The size of an object on a page of the indicated ORDER. */
160 #define OBJECT_SIZE(ORDER) object_size_table[ORDER]
162 /* For speed, we avoid doing a general integer divide to locate the
163 offset in the allocation bitmap, by precalculating numbers M, S
164 such that (O * M) >> S == O / Z (modulo 2^32), for any offset O
165 within the page which is evenly divisible by the object size Z. */
166 #define DIV_MULT(ORDER) inverse_table[ORDER].mult
167 #define DIV_SHIFT(ORDER) inverse_table[ORDER].shift
168 #define OFFSET_TO_BIT(OFFSET, ORDER) \
169 (((OFFSET) * DIV_MULT (ORDER)) >> DIV_SHIFT (ORDER))
171 /* The number of extra orders, not corresponding to power-of-two sized
174 #define NUM_EXTRA_ORDERS ARRAY_SIZE (extra_order_size_table)
176 #define RTL_SIZE(NSLOTS) \
177 (RTX_HDR_SIZE + (NSLOTS) * sizeof (rtunion))
179 #define TREE_EXP_SIZE(OPS) \
180 (sizeof (struct tree_exp) + ((OPS) - 1) * sizeof (tree))
182 /* The Ith entry is the maximum size of an object to be stored in the
183 Ith extra order. Adding a new entry to this array is the *only*
184 thing you need to do to add a new special allocation size. */
186 static const size_t extra_order_size_table[] = {
187 sizeof (struct tree_decl),
188 sizeof (struct tree_list),
190 RTL_SIZE (2), /* MEM, PLUS, etc. */
191 RTL_SIZE (9), /* INSN */
194 /* The total number of orders. */
196 #define NUM_ORDERS (HOST_BITS_PER_PTR + NUM_EXTRA_ORDERS)
198 /* We use this structure to determine the alignment required for
199 allocations. For power-of-two sized allocations, that's not a
200 problem, but it does matter for odd-sized allocations. */
202 struct max_alignment {
210 /* The biggest alignment required. */
212 #define MAX_ALIGNMENT (offsetof (struct max_alignment, u))
214 /* Compute the smallest nonnegative number which when added to X gives
217 #define ROUND_UP_VALUE(x, f) ((f) - 1 - ((f) - 1 + (x)) % (f))
219 /* Compute the smallest multiple of F that is >= X. */
221 #define ROUND_UP(x, f) (CEIL (x, f) * (f))
223 /* The Ith entry is the number of objects on a page or order I. */
225 static unsigned objects_per_page_table[NUM_ORDERS];
227 /* The Ith entry is the size of an object on a page of order I. */
229 static size_t object_size_table[NUM_ORDERS];
231 /* The Ith entry is a pair of numbers (mult, shift) such that
232 ((k * mult) >> shift) mod 2^32 == (k / OBJECT_SIZE(I)) mod 2^32,
233 for all k evenly divisible by OBJECT_SIZE(I). */
240 inverse_table[NUM_ORDERS];
242 /* A page_entry records the status of an allocation page. This
243 structure is dynamically sized to fit the bitmap in_use_p. */
244 typedef struct page_entry
246 /* The next page-entry with objects of the same size, or NULL if
247 this is the last page-entry. */
248 struct page_entry *next;
250 /* The previous page-entry with objects of the same size, or NULL if
251 this is the first page-entry. The PREV pointer exists solely to
252 keep the cost of ggc_free managable. */
253 struct page_entry *prev;
255 /* The number of bytes allocated. (This will always be a multiple
256 of the host system page size.) */
259 /* The address at which the memory is allocated. */
262 #ifdef USING_MALLOC_PAGE_GROUPS
263 /* Back pointer to the page group this page came from. */
264 struct page_group *group;
267 /* This is the index in the by_depth varray where this page table
269 unsigned long index_by_depth;
271 /* Context depth of this page. */
272 unsigned short context_depth;
274 /* The number of free objects remaining on this page. */
275 unsigned short num_free_objects;
277 /* A likely candidate for the bit position of a free object for the
278 next allocation from this page. */
279 unsigned short next_bit_hint;
281 /* The lg of size of objects allocated from this page. */
284 /* A bit vector indicating whether or not objects are in use. The
285 Nth bit is one if the Nth object on this page is allocated. This
286 array is dynamically sized. */
287 unsigned long in_use_p[1];
290 #ifdef USING_MALLOC_PAGE_GROUPS
291 /* A page_group describes a large allocation from malloc, from which
292 we parcel out aligned pages. */
293 typedef struct page_group
295 /* A linked list of all extant page groups. */
296 struct page_group *next;
298 /* The address we received from malloc. */
301 /* The size of the block. */
304 /* A bitmask of pages in use. */
309 #if HOST_BITS_PER_PTR <= 32
311 /* On 32-bit hosts, we use a two level page table, as pictured above. */
312 typedef page_entry **page_table[PAGE_L1_SIZE];
316 /* On 64-bit hosts, we use the same two level page tables plus a linked
317 list that disambiguates the top 32-bits. There will almost always be
318 exactly one entry in the list. */
319 typedef struct page_table_chain
321 struct page_table_chain *next;
323 page_entry **table[PAGE_L1_SIZE];
328 /* The rest of the global variables. */
329 static struct globals
331 /* The Nth element in this array is a page with objects of size 2^N.
332 If there are any pages with free objects, they will be at the
333 head of the list. NULL if there are no page-entries for this
335 page_entry *pages[NUM_ORDERS];
337 /* The Nth element in this array is the last page with objects of
338 size 2^N. NULL if there are no page-entries for this object
340 page_entry *page_tails[NUM_ORDERS];
342 /* Lookup table for associating allocation pages with object addresses. */
345 /* The system's page size. */
349 /* Bytes currently allocated. */
352 /* Bytes currently allocated at the end of the last collection. */
353 size_t allocated_last_gc;
355 /* Total amount of memory mapped. */
358 /* Bit N set if any allocations have been done at context depth N. */
359 unsigned long context_depth_allocations;
361 /* Bit N set if any collections have been done at context depth N. */
362 unsigned long context_depth_collections;
364 /* The current depth in the context stack. */
365 unsigned short context_depth;
367 /* A file descriptor open to /dev/zero for reading. */
368 #if defined (HAVE_MMAP_DEV_ZERO)
372 /* A cache of free system pages. */
373 page_entry *free_pages;
375 #ifdef USING_MALLOC_PAGE_GROUPS
376 page_group *page_groups;
379 /* The file descriptor for debugging output. */
382 /* Current number of elements in use in depth below. */
383 unsigned int depth_in_use;
385 /* Maximum number of elements that can be used before resizing. */
386 unsigned int depth_max;
388 /* Each element of this arry is an index in by_depth where the given
389 depth starts. This structure is indexed by that given depth we
390 are interested in. */
393 /* Current number of elements in use in by_depth below. */
394 unsigned int by_depth_in_use;
396 /* Maximum number of elements that can be used before resizing. */
397 unsigned int by_depth_max;
399 /* Each element of this array is a pointer to a page_entry, all
400 page_entries can be found in here by increasing depth.
401 index_by_depth in the page_entry is the index into this data
402 structure where that page_entry can be found. This is used to
403 speed up finding all page_entries at a particular depth. */
404 page_entry **by_depth;
406 /* Each element is a pointer to the saved in_use_p bits, if any,
407 zero otherwise. We allocate them all together, to enable a
408 better runtime data access pattern. */
409 unsigned long **save_in_use;
411 #ifdef ENABLE_GC_ALWAYS_COLLECT
412 /* List of free objects to be verified as actually free on the
417 struct free_object *next;
421 #ifdef GATHER_STATISTICS
424 /* Total memory allocated with ggc_alloc. */
425 unsigned long long total_allocated;
426 /* Total overhead for memory to be allocated with ggc_alloc. */
427 unsigned long long total_overhead;
429 /* Total allocations and overhead for sizes less than 32, 64 and 128.
430 These sizes are interesting because they are typical cache line
433 unsigned long long total_allocated_under32;
434 unsigned long long total_overhead_under32;
436 unsigned long long total_allocated_under64;
437 unsigned long long total_overhead_under64;
439 unsigned long long total_allocated_under128;
440 unsigned long long total_overhead_under128;
442 /* The allocations for each of the allocation orders. */
443 unsigned long long total_allocated_per_order[NUM_ORDERS];
445 /* The overhead for each of the allocation orders. */
446 unsigned long long total_overhead_per_order[NUM_ORDERS];
451 /* The size in bytes required to maintain a bitmap for the objects
453 #define BITMAP_SIZE(Num_objects) \
454 (CEIL ((Num_objects), HOST_BITS_PER_LONG) * sizeof(long))
456 /* Allocate pages in chunks of this size, to throttle calls to memory
457 allocation routines. The first page is used, the rest go onto the
458 free list. This cannot be larger than HOST_BITS_PER_INT for the
459 in_use bitmask for page_group. */
460 #define GGC_QUIRE_SIZE 16
462 /* Initial guess as to how many page table entries we might need. */
463 #define INITIAL_PTE_COUNT 128
465 static int ggc_allocated_p (const void *);
466 static page_entry *lookup_page_table_entry (const void *);
467 static void set_page_table_entry (void *, page_entry *);
469 static char *alloc_anon (char *, size_t);
471 #ifdef USING_MALLOC_PAGE_GROUPS
472 static size_t page_group_index (char *, char *);
473 static void set_page_group_in_use (page_group *, char *);
474 static void clear_page_group_in_use (page_group *, char *);
476 static struct page_entry * alloc_page (unsigned);
477 static void free_page (struct page_entry *);
478 static void release_pages (void);
479 static void clear_marks (void);
480 static void sweep_pages (void);
481 static void ggc_recalculate_in_use_p (page_entry *);
482 static void compute_inverse (unsigned);
483 static inline void adjust_depth (void);
484 static void move_ptes_to_front (int, int);
486 void debug_print_page_list (int);
487 static void push_depth (unsigned int);
488 static void push_by_depth (page_entry *, unsigned long *);
489 struct alloc_zone *rtl_zone = NULL;
490 struct alloc_zone *tree_zone = NULL;
491 struct alloc_zone *garbage_zone = NULL;
493 /* Push an entry onto G.depth. */
496 push_depth (unsigned int i)
498 if (G.depth_in_use >= G.depth_max)
501 G.depth = xrealloc (G.depth, G.depth_max * sizeof (unsigned int));
503 G.depth[G.depth_in_use++] = i;
506 /* Push an entry onto G.by_depth and G.save_in_use. */
509 push_by_depth (page_entry *p, unsigned long *s)
511 if (G.by_depth_in_use >= G.by_depth_max)
514 G.by_depth = xrealloc (G.by_depth,
515 G.by_depth_max * sizeof (page_entry *));
516 G.save_in_use = xrealloc (G.save_in_use,
517 G.by_depth_max * sizeof (unsigned long *));
519 G.by_depth[G.by_depth_in_use] = p;
520 G.save_in_use[G.by_depth_in_use++] = s;
523 #if (GCC_VERSION < 3001)
524 #define prefetch(X) ((void) X)
526 #define prefetch(X) __builtin_prefetch (X)
529 #define save_in_use_p_i(__i) \
531 #define save_in_use_p(__p) \
532 (save_in_use_p_i (__p->index_by_depth))
534 /* Returns nonzero if P was allocated in GC'able memory. */
537 ggc_allocated_p (const void *p)
542 #if HOST_BITS_PER_PTR <= 32
545 page_table table = G.lookup;
546 size_t high_bits = (size_t) p & ~ (size_t) 0xffffffff;
551 if (table->high_bits == high_bits)
555 base = &table->table[0];
558 /* Extract the level 1 and 2 indices. */
562 return base[L1] && base[L1][L2];
565 /* Traverse the page table and find the entry for a page.
566 Die (probably) if the object wasn't allocated via GC. */
568 static inline page_entry *
569 lookup_page_table_entry (const void *p)
574 #if HOST_BITS_PER_PTR <= 32
577 page_table table = G.lookup;
578 size_t high_bits = (size_t) p & ~ (size_t) 0xffffffff;
579 while (table->high_bits != high_bits)
581 base = &table->table[0];
584 /* Extract the level 1 and 2 indices. */
591 /* Set the page table entry for a page. */
594 set_page_table_entry (void *p, page_entry *entry)
599 #if HOST_BITS_PER_PTR <= 32
603 size_t high_bits = (size_t) p & ~ (size_t) 0xffffffff;
604 for (table = G.lookup; table; table = table->next)
605 if (table->high_bits == high_bits)
608 /* Not found -- allocate a new table. */
609 table = xcalloc (1, sizeof(*table));
610 table->next = G.lookup;
611 table->high_bits = high_bits;
614 base = &table->table[0];
617 /* Extract the level 1 and 2 indices. */
621 if (base[L1] == NULL)
622 base[L1] = xcalloc (PAGE_L2_SIZE, sizeof (page_entry *));
624 base[L1][L2] = entry;
627 /* Prints the page-entry for object size ORDER, for debugging. */
630 debug_print_page_list (int order)
633 printf ("Head=%p, Tail=%p:\n", (void *) G.pages[order],
634 (void *) G.page_tails[order]);
638 printf ("%p(%1d|%3d) -> ", (void *) p, p->context_depth,
639 p->num_free_objects);
647 /* Allocate SIZE bytes of anonymous memory, preferably near PREF,
648 (if non-null). The ifdef structure here is intended to cause a
649 compile error unless exactly one of the HAVE_* is defined. */
652 alloc_anon (char *pref ATTRIBUTE_UNUSED, size_t size)
654 #ifdef HAVE_MMAP_ANON
655 char *page = (char *) mmap (pref, size, PROT_READ | PROT_WRITE,
656 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
658 #ifdef HAVE_MMAP_DEV_ZERO
659 char *page = (char *) mmap (pref, size, PROT_READ | PROT_WRITE,
660 MAP_PRIVATE, G.dev_zero_fd, 0);
663 if (page == (char *) MAP_FAILED)
665 perror ("virtual memory exhausted");
666 exit (FATAL_EXIT_CODE);
669 /* Remember that we allocated this memory. */
670 G.bytes_mapped += size;
672 /* Pretend we don't have access to the allocated pages. We'll enable
673 access to smaller pieces of the area in ggc_alloc. Discard the
674 handle to avoid handle leak. */
675 VALGRIND_DISCARD (VALGRIND_MAKE_NOACCESS (page, size));
680 #ifdef USING_MALLOC_PAGE_GROUPS
681 /* Compute the index for this page into the page group. */
684 page_group_index (char *allocation, char *page)
686 return (size_t) (page - allocation) >> G.lg_pagesize;
689 /* Set and clear the in_use bit for this page in the page group. */
692 set_page_group_in_use (page_group *group, char *page)
694 group->in_use |= 1 << page_group_index (group->allocation, page);
698 clear_page_group_in_use (page_group *group, char *page)
700 group->in_use &= ~(1 << page_group_index (group->allocation, page));
704 /* Allocate a new page for allocating objects of size 2^ORDER,
705 and return an entry for it. The entry is not added to the
706 appropriate page_table list. */
708 static inline struct page_entry *
709 alloc_page (unsigned order)
711 struct page_entry *entry, *p, **pp;
715 size_t page_entry_size;
717 #ifdef USING_MALLOC_PAGE_GROUPS
721 num_objects = OBJECTS_PER_PAGE (order);
722 bitmap_size = BITMAP_SIZE (num_objects + 1);
723 page_entry_size = sizeof (page_entry) - sizeof (long) + bitmap_size;
724 entry_size = num_objects * OBJECT_SIZE (order);
725 if (entry_size < G.pagesize)
726 entry_size = G.pagesize;
731 /* Check the list of free pages for one we can use. */
732 for (pp = &G.free_pages, p = *pp; p; pp = &p->next, p = *pp)
733 if (p->bytes == entry_size)
738 /* Recycle the allocated memory from this page ... */
742 #ifdef USING_MALLOC_PAGE_GROUPS
746 /* ... and, if possible, the page entry itself. */
747 if (p->order == order)
750 memset (entry, 0, page_entry_size);
756 else if (entry_size == G.pagesize)
758 /* We want just one page. Allocate a bunch of them and put the
759 extras on the freelist. (Can only do this optimization with
760 mmap for backing store.) */
761 struct page_entry *e, *f = G.free_pages;
764 page = alloc_anon (NULL, G.pagesize * GGC_QUIRE_SIZE);
766 /* This loop counts down so that the chain will be in ascending
768 for (i = GGC_QUIRE_SIZE - 1; i >= 1; i--)
770 e = xcalloc (1, page_entry_size);
772 e->bytes = G.pagesize;
773 e->page = page + (i << G.lg_pagesize);
781 page = alloc_anon (NULL, entry_size);
783 #ifdef USING_MALLOC_PAGE_GROUPS
786 /* Allocate a large block of memory and serve out the aligned
787 pages therein. This results in much less memory wastage
788 than the traditional implementation of valloc. */
790 char *allocation, *a, *enda;
791 size_t alloc_size, head_slop, tail_slop;
792 int multiple_pages = (entry_size == G.pagesize);
795 alloc_size = GGC_QUIRE_SIZE * G.pagesize;
797 alloc_size = entry_size + G.pagesize - 1;
798 allocation = xmalloc (alloc_size);
800 page = (char *) (((size_t) allocation + G.pagesize - 1) & -G.pagesize);
801 head_slop = page - allocation;
803 tail_slop = ((size_t) allocation + alloc_size) & (G.pagesize - 1);
805 tail_slop = alloc_size - entry_size - head_slop;
806 enda = allocation + alloc_size - tail_slop;
808 /* We allocated N pages, which are likely not aligned, leaving
809 us with N-1 usable pages. We plan to place the page_group
810 structure somewhere in the slop. */
811 if (head_slop >= sizeof (page_group))
812 group = (page_group *)page - 1;
815 /* We magically got an aligned allocation. Too bad, we have
816 to waste a page anyway. */
820 tail_slop += G.pagesize;
822 if (tail_slop < sizeof (page_group))
824 group = (page_group *)enda;
825 tail_slop -= sizeof (page_group);
828 /* Remember that we allocated this memory. */
829 group->next = G.page_groups;
830 group->allocation = allocation;
831 group->alloc_size = alloc_size;
833 G.page_groups = group;
834 G.bytes_mapped += alloc_size;
836 /* If we allocated multiple pages, put the rest on the free list. */
839 struct page_entry *e, *f = G.free_pages;
840 for (a = enda - G.pagesize; a != page; a -= G.pagesize)
842 e = xcalloc (1, page_entry_size);
844 e->bytes = G.pagesize;
856 entry = xcalloc (1, page_entry_size);
858 entry->bytes = entry_size;
860 entry->context_depth = G.context_depth;
861 entry->order = order;
862 entry->num_free_objects = num_objects;
863 entry->next_bit_hint = 1;
865 G.context_depth_allocations |= (unsigned long)1 << G.context_depth;
867 #ifdef USING_MALLOC_PAGE_GROUPS
868 entry->group = group;
869 set_page_group_in_use (group, page);
872 /* Set the one-past-the-end in-use bit. This acts as a sentry as we
873 increment the hint. */
874 entry->in_use_p[num_objects / HOST_BITS_PER_LONG]
875 = (unsigned long) 1 << (num_objects % HOST_BITS_PER_LONG);
877 set_page_table_entry (page, entry);
879 if (GGC_DEBUG_LEVEL >= 2)
880 fprintf (G.debug_file,
881 "Allocating page at %p, object size=%lu, data %p-%p\n",
882 (void *) entry, (unsigned long) OBJECT_SIZE (order), page,
883 page + entry_size - 1);
888 /* Adjust the size of G.depth so that no index greater than the one
889 used by the top of the G.by_depth is used. */
896 if (G.by_depth_in_use)
898 top = G.by_depth[G.by_depth_in_use-1];
900 /* Peel back indices in depth that index into by_depth, so that
901 as new elements are added to by_depth, we note the indices
902 of those elements, if they are for new context depths. */
903 while (G.depth_in_use > (size_t)top->context_depth+1)
908 /* For a page that is no longer needed, put it on the free page list. */
911 free_page (page_entry *entry)
913 if (GGC_DEBUG_LEVEL >= 2)
914 fprintf (G.debug_file,
915 "Deallocating page at %p, data %p-%p\n", (void *) entry,
916 entry->page, entry->page + entry->bytes - 1);
918 /* Mark the page as inaccessible. Discard the handle to avoid handle
920 VALGRIND_DISCARD (VALGRIND_MAKE_NOACCESS (entry->page, entry->bytes));
922 set_page_table_entry (entry->page, NULL);
924 #ifdef USING_MALLOC_PAGE_GROUPS
925 clear_page_group_in_use (entry->group, entry->page);
928 if (G.by_depth_in_use > 1)
930 page_entry *top = G.by_depth[G.by_depth_in_use-1];
932 /* If they are at the same depth, put top element into freed
934 if (entry->context_depth == top->context_depth)
936 int i = entry->index_by_depth;
938 G.save_in_use[i] = G.save_in_use[G.by_depth_in_use-1];
939 top->index_by_depth = i;
943 /* We cannot free a page from a context deeper than the
952 entry->next = G.free_pages;
953 G.free_pages = entry;
956 /* Release the free page cache to the system. */
962 page_entry *p, *next;
966 /* Gather up adjacent pages so they are unmapped together. */
977 while (p && p->page == start + len)
986 G.bytes_mapped -= len;
991 #ifdef USING_MALLOC_PAGE_GROUPS
995 /* Remove all pages from free page groups from the list. */
997 while ((p = *pp) != NULL)
998 if (p->group->in_use == 0)
1006 /* Remove all free page groups, and release the storage. */
1007 gp = &G.page_groups;
1008 while ((g = *gp) != NULL)
1012 G.bytes_mapped -= g->alloc_size;
1013 free (g->allocation);
1020 /* This table provides a fast way to determine ceil(log_2(size)) for
1021 allocation requests. The minimum allocation size is eight bytes. */
1023 static unsigned char size_lookup[257] =
1025 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4,
1026 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
1027 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
1028 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
1029 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
1030 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
1031 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
1032 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
1033 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1034 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1035 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1036 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1037 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1038 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1039 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1040 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
1044 /* Typed allocation function. Does nothing special in this collector. */
1047 ggc_alloc_typed (enum gt_types_enum type ATTRIBUTE_UNUSED, size_t size)
1049 return ggc_alloc (size);
1052 /* Zone allocation function. Does nothing special in this collector. */
1055 ggc_alloc_zone (size_t size, struct alloc_zone *zone ATTRIBUTE_UNUSED)
1057 return ggc_alloc (size);
1060 /* Allocate a chunk of memory of SIZE bytes. Its contents are undefined. */
1063 ggc_alloc (size_t size)
1065 size_t order, word, bit, object_offset, object_size;
1066 struct page_entry *entry;
1071 order = size_lookup[size];
1072 object_size = OBJECT_SIZE (order);
1077 while (size > (object_size = OBJECT_SIZE (order)))
1081 /* If there are non-full pages for this size allocation, they are at
1082 the head of the list. */
1083 entry = G.pages[order];
1085 /* If there is no page for this object size, or all pages in this
1086 context are full, allocate a new page. */
1087 if (entry == NULL || entry->num_free_objects == 0)
1089 struct page_entry *new_entry;
1090 new_entry = alloc_page (order);
1092 new_entry->index_by_depth = G.by_depth_in_use;
1093 push_by_depth (new_entry, 0);
1095 /* We can skip context depths, if we do, make sure we go all the
1096 way to the new depth. */
1097 while (new_entry->context_depth >= G.depth_in_use)
1098 push_depth (G.by_depth_in_use-1);
1100 /* If this is the only entry, it's also the tail. If it is not
1101 the only entry, then we must update the PREV pointer of the
1102 ENTRY (G.pages[order]) to point to our new page entry. */
1104 G.page_tails[order] = new_entry;
1106 entry->prev = new_entry;
1108 /* Put new pages at the head of the page list. By definition the
1109 entry at the head of the list always has a NULL pointer. */
1110 new_entry->next = entry;
1111 new_entry->prev = NULL;
1113 G.pages[order] = new_entry;
1115 /* For a new page, we know the word and bit positions (in the
1116 in_use bitmap) of the first available object -- they're zero. */
1117 new_entry->next_bit_hint = 1;
1124 /* First try to use the hint left from the previous allocation
1125 to locate a clear bit in the in-use bitmap. We've made sure
1126 that the one-past-the-end bit is always set, so if the hint
1127 has run over, this test will fail. */
1128 unsigned hint = entry->next_bit_hint;
1129 word = hint / HOST_BITS_PER_LONG;
1130 bit = hint % HOST_BITS_PER_LONG;
1132 /* If the hint didn't work, scan the bitmap from the beginning. */
1133 if ((entry->in_use_p[word] >> bit) & 1)
1136 while (~entry->in_use_p[word] == 0)
1138 while ((entry->in_use_p[word] >> bit) & 1)
1140 hint = word * HOST_BITS_PER_LONG + bit;
1143 /* Next time, try the next bit. */
1144 entry->next_bit_hint = hint + 1;
1146 object_offset = hint * object_size;
1149 /* Set the in-use bit. */
1150 entry->in_use_p[word] |= ((unsigned long) 1 << bit);
1152 /* Keep a running total of the number of free objects. If this page
1153 fills up, we may have to move it to the end of the list if the
1154 next page isn't full. If the next page is full, all subsequent
1155 pages are full, so there's no need to move it. */
1156 if (--entry->num_free_objects == 0
1157 && entry->next != NULL
1158 && entry->next->num_free_objects > 0)
1160 /* We have a new head for the list. */
1161 G.pages[order] = entry->next;
1163 /* We are moving ENTRY to the end of the page table list.
1164 The new page at the head of the list will have NULL in
1165 its PREV field and ENTRY will have NULL in its NEXT field. */
1166 entry->next->prev = NULL;
1169 /* Append ENTRY to the tail of the list. */
1170 entry->prev = G.page_tails[order];
1171 G.page_tails[order]->next = entry;
1172 G.page_tails[order] = entry;
1175 /* Calculate the object's address. */
1176 result = entry->page + object_offset;
1178 #ifdef ENABLE_GC_CHECKING
1179 /* Keep poisoning-by-writing-0xaf the object, in an attempt to keep the
1180 exact same semantics in presence of memory bugs, regardless of
1181 ENABLE_VALGRIND_CHECKING. We override this request below. Drop the
1182 handle to avoid handle leak. */
1183 VALGRIND_DISCARD (VALGRIND_MAKE_WRITABLE (result, object_size));
1185 /* `Poison' the entire allocated object, including any padding at
1187 memset (result, 0xaf, object_size);
1189 /* Make the bytes after the end of the object unaccessible. Discard the
1190 handle to avoid handle leak. */
1191 VALGRIND_DISCARD (VALGRIND_MAKE_NOACCESS ((char *) result + size,
1192 object_size - size));
1195 /* Tell Valgrind that the memory is there, but its content isn't
1196 defined. The bytes at the end of the object are still marked
1198 VALGRIND_DISCARD (VALGRIND_MAKE_WRITABLE (result, size));
1200 /* Keep track of how many bytes are being allocated. This
1201 information is used in deciding when to collect. */
1202 G.allocated += object_size;
1204 #ifdef GATHER_STATISTICS
1206 size_t overhead = object_size - size;
1208 G.stats.total_overhead += overhead;
1209 G.stats.total_allocated += object_size;
1210 G.stats.total_overhead_per_order[order] += overhead;
1211 G.stats.total_allocated_per_order[order] += object_size;
1215 G.stats.total_overhead_under32 += overhead;
1216 G.stats.total_allocated_under32 += object_size;
1220 G.stats.total_overhead_under64 += overhead;
1221 G.stats.total_allocated_under64 += object_size;
1225 G.stats.total_overhead_under128 += overhead;
1226 G.stats.total_allocated_under128 += object_size;
1231 if (GGC_DEBUG_LEVEL >= 3)
1232 fprintf (G.debug_file,
1233 "Allocating object, requested size=%lu, actual=%lu at %p on %p\n",
1234 (unsigned long) size, (unsigned long) object_size, result,
1240 /* If P is not marked, marks it and return false. Otherwise return true.
1241 P must have been allocated by the GC allocator; it mustn't point to
1242 static objects, stack variables, or memory allocated with malloc. */
1245 ggc_set_mark (const void *p)
1251 /* Look up the page on which the object is alloced. If the object
1252 wasn't allocated by the collector, we'll probably die. */
1253 entry = lookup_page_table_entry (p);
1254 #ifdef ENABLE_CHECKING
1259 /* Calculate the index of the object on the page; this is its bit
1260 position in the in_use_p bitmap. */
1261 bit = OFFSET_TO_BIT (((const char *) p) - entry->page, entry->order);
1262 word = bit / HOST_BITS_PER_LONG;
1263 mask = (unsigned long) 1 << (bit % HOST_BITS_PER_LONG);
1265 /* If the bit was previously set, skip it. */
1266 if (entry->in_use_p[word] & mask)
1269 /* Otherwise set it, and decrement the free object count. */
1270 entry->in_use_p[word] |= mask;
1271 entry->num_free_objects -= 1;
1273 if (GGC_DEBUG_LEVEL >= 4)
1274 fprintf (G.debug_file, "Marking %p\n", p);
1279 /* Return 1 if P has been marked, zero otherwise.
1280 P must have been allocated by the GC allocator; it mustn't point to
1281 static objects, stack variables, or memory allocated with malloc. */
1284 ggc_marked_p (const void *p)
1290 /* Look up the page on which the object is alloced. If the object
1291 wasn't allocated by the collector, we'll probably die. */
1292 entry = lookup_page_table_entry (p);
1293 #ifdef ENABLE_CHECKING
1298 /* Calculate the index of the object on the page; this is its bit
1299 position in the in_use_p bitmap. */
1300 bit = OFFSET_TO_BIT (((const char *) p) - entry->page, entry->order);
1301 word = bit / HOST_BITS_PER_LONG;
1302 mask = (unsigned long) 1 << (bit % HOST_BITS_PER_LONG);
1304 return (entry->in_use_p[word] & mask) != 0;
1307 /* Return the size of the gc-able object P. */
1310 ggc_get_size (const void *p)
1312 page_entry *pe = lookup_page_table_entry (p);
1313 return OBJECT_SIZE (pe->order);
1316 /* Release the memory for object P. */
1321 page_entry *pe = lookup_page_table_entry (p);
1322 size_t order = pe->order;
1323 size_t size = OBJECT_SIZE (order);
1325 if (GGC_DEBUG_LEVEL >= 3)
1326 fprintf (G.debug_file,
1327 "Freeing object, actual size=%lu, at %p on %p\n",
1328 (unsigned long) size, p, (void *) pe);
1330 #ifdef ENABLE_GC_CHECKING
1331 /* Poison the data, to indicate the data is garbage. */
1332 VALGRIND_DISCARD (VALGRIND_MAKE_WRITABLE (p, size));
1333 memset (p, 0xa5, size);
1335 /* Let valgrind know the object is free. */
1336 VALGRIND_DISCARD (VALGRIND_MAKE_NOACCESS (p, size));
1338 #ifdef ENABLE_GC_ALWAYS_COLLECT
1339 /* In the completely-anal-checking mode, we do *not* immediately free
1340 the data, but instead verify that the data is *actually* not
1341 reachable the next time we collect. */
1343 struct free_object *fo = xmalloc (sizeof (struct free_object));
1345 fo->next = G.free_object_list;
1346 G.free_object_list = fo;
1350 unsigned int bit_offset, word, bit;
1352 G.allocated -= size;
1354 /* Mark the object not-in-use. */
1355 bit_offset = OFFSET_TO_BIT (((const char *) p) - pe->page, order);
1356 word = bit_offset / HOST_BITS_PER_LONG;
1357 bit = bit_offset % HOST_BITS_PER_LONG;
1358 pe->in_use_p[word] &= ~(1UL << bit);
1360 if (pe->num_free_objects++ == 0)
1364 /* If the page is completely full, then it's supposed to
1365 be after all pages that aren't. Since we've freed one
1366 object from a page that was full, we need to move the
1367 page to the head of the list.
1369 PE is the node we want to move. Q is the previous node
1370 and P is the next node in the list. */
1372 if (q && q->num_free_objects == 0)
1378 /* If PE was at the end of the list, then Q becomes the
1379 new end of the list. If PE was not the end of the
1380 list, then we need to update the PREV field for P. */
1382 G.page_tails[order] = q;
1386 /* Move PE to the head of the list. */
1387 pe->next = G.pages[order];
1389 G.pages[order]->prev = pe;
1390 G.pages[order] = pe;
1393 /* Reset the hint bit to point to the only free object. */
1394 pe->next_bit_hint = bit_offset;
1400 /* Subroutine of init_ggc which computes the pair of numbers used to
1401 perform division by OBJECT_SIZE (order) and fills in inverse_table[].
1403 This algorithm is taken from Granlund and Montgomery's paper
1404 "Division by Invariant Integers using Multiplication"
1405 (Proc. SIGPLAN PLDI, 1994), section 9 (Exact division by
1409 compute_inverse (unsigned order)
1414 size = OBJECT_SIZE (order);
1416 while (size % 2 == 0)
1423 while (inv * size != 1)
1424 inv = inv * (2 - inv*size);
1426 DIV_MULT (order) = inv;
1427 DIV_SHIFT (order) = e;
1430 /* Initialize the ggc-mmap allocator. */
1436 G.pagesize = getpagesize();
1437 G.lg_pagesize = exact_log2 (G.pagesize);
1439 #ifdef HAVE_MMAP_DEV_ZERO
1440 G.dev_zero_fd = open ("/dev/zero", O_RDONLY);
1441 if (G.dev_zero_fd == -1)
1442 internal_error ("open /dev/zero: %m");
1446 G.debug_file = fopen ("ggc-mmap.debug", "w");
1448 G.debug_file = stdout;
1452 /* StunOS has an amazing off-by-one error for the first mmap allocation
1453 after fiddling with RLIMIT_STACK. The result, as hard as it is to
1454 believe, is an unaligned page allocation, which would cause us to
1455 hork badly if we tried to use it. */
1457 char *p = alloc_anon (NULL, G.pagesize);
1458 struct page_entry *e;
1459 if ((size_t)p & (G.pagesize - 1))
1461 /* How losing. Discard this one and try another. If we still
1462 can't get something useful, give up. */
1464 p = alloc_anon (NULL, G.pagesize);
1465 if ((size_t)p & (G.pagesize - 1))
1469 /* We have a good page, might as well hold onto it... */
1470 e = xcalloc (1, sizeof (struct page_entry));
1471 e->bytes = G.pagesize;
1473 e->next = G.free_pages;
1478 /* Initialize the object size table. */
1479 for (order = 0; order < HOST_BITS_PER_PTR; ++order)
1480 object_size_table[order] = (size_t) 1 << order;
1481 for (order = HOST_BITS_PER_PTR; order < NUM_ORDERS; ++order)
1483 size_t s = extra_order_size_table[order - HOST_BITS_PER_PTR];
1485 /* If S is not a multiple of the MAX_ALIGNMENT, then round it up
1486 so that we're sure of getting aligned memory. */
1487 s = ROUND_UP (s, MAX_ALIGNMENT);
1488 object_size_table[order] = s;
1491 /* Initialize the objects-per-page and inverse tables. */
1492 for (order = 0; order < NUM_ORDERS; ++order)
1494 objects_per_page_table[order] = G.pagesize / OBJECT_SIZE (order);
1495 if (objects_per_page_table[order] == 0)
1496 objects_per_page_table[order] = 1;
1497 compute_inverse (order);
1500 /* Reset the size_lookup array to put appropriately sized objects in
1501 the special orders. All objects bigger than the previous power
1502 of two, but no greater than the special size, should go in the
1504 for (order = HOST_BITS_PER_PTR; order < NUM_ORDERS; ++order)
1509 o = size_lookup[OBJECT_SIZE (order)];
1510 for (i = OBJECT_SIZE (order); size_lookup [i] == o; --i)
1511 size_lookup[i] = order;
1516 G.depth = xmalloc (G.depth_max * sizeof (unsigned int));
1518 G.by_depth_in_use = 0;
1519 G.by_depth_max = INITIAL_PTE_COUNT;
1520 G.by_depth = xmalloc (G.by_depth_max * sizeof (page_entry *));
1521 G.save_in_use = xmalloc (G.by_depth_max * sizeof (unsigned long *));
1524 /* Start a new GGC zone. */
1527 new_ggc_zone (const char *name ATTRIBUTE_UNUSED)
1532 /* Destroy a GGC zone. */
1534 destroy_ggc_zone (struct alloc_zone *zone ATTRIBUTE_UNUSED)
1538 /* Increment the `GC context'. Objects allocated in an outer context
1539 are never freed, eliminating the need to register their roots. */
1542 ggc_push_context (void)
1547 if (G.context_depth >= HOST_BITS_PER_LONG)
1551 /* Merge the SAVE_IN_USE_P and IN_USE_P arrays in P so that IN_USE_P
1552 reflects reality. Recalculate NUM_FREE_OBJECTS as well. */
1555 ggc_recalculate_in_use_p (page_entry *p)
1560 /* Because the past-the-end bit in in_use_p is always set, we
1561 pretend there is one additional object. */
1562 num_objects = OBJECTS_IN_PAGE (p) + 1;
1564 /* Reset the free object count. */
1565 p->num_free_objects = num_objects;
1567 /* Combine the IN_USE_P and SAVE_IN_USE_P arrays. */
1569 i < CEIL (BITMAP_SIZE (num_objects),
1570 sizeof (*p->in_use_p));
1575 /* Something is in use if it is marked, or if it was in use in a
1576 context further down the context stack. */
1577 p->in_use_p[i] |= save_in_use_p (p)[i];
1579 /* Decrement the free object count for every object allocated. */
1580 for (j = p->in_use_p[i]; j; j >>= 1)
1581 p->num_free_objects -= (j & 1);
1584 if (p->num_free_objects >= num_objects)
1588 /* Decrement the `GC context'. All objects allocated since the
1589 previous ggc_push_context are migrated to the outer context. */
1592 ggc_pop_context (void)
1594 unsigned long omask;
1595 unsigned int depth, i, e;
1596 #ifdef ENABLE_CHECKING
1600 depth = --G.context_depth;
1601 omask = (unsigned long)1 << (depth + 1);
1603 if (!((G.context_depth_allocations | G.context_depth_collections) & omask))
1606 G.context_depth_allocations |= (G.context_depth_allocations & omask) >> 1;
1607 G.context_depth_allocations &= omask - 1;
1608 G.context_depth_collections &= omask - 1;
1610 /* The G.depth array is shortened so that the last index is the
1611 context_depth of the top element of by_depth. */
1612 if (depth+1 < G.depth_in_use)
1613 e = G.depth[depth+1];
1615 e = G.by_depth_in_use;
1617 /* We might not have any PTEs of depth depth. */
1618 if (depth < G.depth_in_use)
1621 /* First we go through all the pages at depth depth to
1622 recalculate the in use bits. */
1623 for (i = G.depth[depth]; i < e; ++i)
1627 #ifdef ENABLE_CHECKING
1630 /* Check that all of the pages really are at the depth that
1632 if (p->context_depth != depth)
1634 if (p->index_by_depth != i)
1638 prefetch (&save_in_use_p_i (i+8));
1639 prefetch (&save_in_use_p_i (i+16));
1640 if (save_in_use_p_i (i))
1643 ggc_recalculate_in_use_p (p);
1644 free (save_in_use_p_i (i));
1645 save_in_use_p_i (i) = 0;
1650 /* Then, we reset all page_entries with a depth greater than depth
1652 for (i = e; i < G.by_depth_in_use; ++i)
1654 page_entry *p = G.by_depth[i];
1656 /* Check that all of the pages really are at the depth we
1658 #ifdef ENABLE_CHECKING
1659 if (p->context_depth <= depth)
1661 if (p->index_by_depth != i)
1664 p->context_depth = depth;
1669 #ifdef ENABLE_CHECKING
1670 for (order = 2; order < NUM_ORDERS; order++)
1674 for (p = G.pages[order]; p != NULL; p = p->next)
1676 if (p->context_depth > depth)
1678 else if (p->context_depth == depth && save_in_use_p (p))
1685 /* Unmark all objects. */
1692 for (order = 2; order < NUM_ORDERS; order++)
1696 for (p = G.pages[order]; p != NULL; p = p->next)
1698 size_t num_objects = OBJECTS_IN_PAGE (p);
1699 size_t bitmap_size = BITMAP_SIZE (num_objects + 1);
1701 #ifdef ENABLE_CHECKING
1702 /* The data should be page-aligned. */
1703 if ((size_t) p->page & (G.pagesize - 1))
1707 /* Pages that aren't in the topmost context are not collected;
1708 nevertheless, we need their in-use bit vectors to store GC
1709 marks. So, back them up first. */
1710 if (p->context_depth < G.context_depth)
1712 if (! save_in_use_p (p))
1713 save_in_use_p (p) = xmalloc (bitmap_size);
1714 memcpy (save_in_use_p (p), p->in_use_p, bitmap_size);
1717 /* Reset reset the number of free objects and clear the
1718 in-use bits. These will be adjusted by mark_obj. */
1719 p->num_free_objects = num_objects;
1720 memset (p->in_use_p, 0, bitmap_size);
1722 /* Make sure the one-past-the-end bit is always set. */
1723 p->in_use_p[num_objects / HOST_BITS_PER_LONG]
1724 = ((unsigned long) 1 << (num_objects % HOST_BITS_PER_LONG));
1729 /* Free all empty pages. Partially empty pages need no attention
1730 because the `mark' bit doubles as an `unused' bit. */
1737 for (order = 2; order < NUM_ORDERS; order++)
1739 /* The last page-entry to consider, regardless of entries
1740 placed at the end of the list. */
1741 page_entry * const last = G.page_tails[order];
1744 size_t live_objects;
1745 page_entry *p, *previous;
1755 page_entry *next = p->next;
1757 /* Loop until all entries have been examined. */
1760 num_objects = OBJECTS_IN_PAGE (p);
1762 /* Add all live objects on this page to the count of
1763 allocated memory. */
1764 live_objects = num_objects - p->num_free_objects;
1766 G.allocated += OBJECT_SIZE (order) * live_objects;
1768 /* Only objects on pages in the topmost context should get
1770 if (p->context_depth < G.context_depth)
1773 /* Remove the page if it's empty. */
1774 else if (live_objects == 0)
1776 /* If P was the first page in the list, then NEXT
1777 becomes the new first page in the list, otherwise
1778 splice P out of the forward pointers. */
1780 G.pages[order] = next;
1782 previous->next = next;
1784 /* Splice P out of the back pointers too. */
1786 next->prev = previous;
1788 /* Are we removing the last element? */
1789 if (p == G.page_tails[order])
1790 G.page_tails[order] = previous;
1795 /* If the page is full, move it to the end. */
1796 else if (p->num_free_objects == 0)
1798 /* Don't move it if it's already at the end. */
1799 if (p != G.page_tails[order])
1801 /* Move p to the end of the list. */
1803 p->prev = G.page_tails[order];
1804 G.page_tails[order]->next = p;
1806 /* Update the tail pointer... */
1807 G.page_tails[order] = p;
1809 /* ... and the head pointer, if necessary. */
1811 G.pages[order] = next;
1813 previous->next = next;
1815 /* And update the backpointer in NEXT if necessary. */
1817 next->prev = previous;
1823 /* If we've fallen through to here, it's a page in the
1824 topmost context that is neither full nor empty. Such a
1825 page must precede pages at lesser context depth in the
1826 list, so move it to the head. */
1827 else if (p != G.pages[order])
1829 previous->next = p->next;
1831 /* Update the backchain in the next node if it exists. */
1833 p->next->prev = previous;
1835 /* Move P to the head of the list. */
1836 p->next = G.pages[order];
1838 G.pages[order]->prev = p;
1840 /* Update the head pointer. */
1843 /* Are we moving the last element? */
1844 if (G.page_tails[order] == p)
1845 G.page_tails[order] = previous;
1854 /* Now, restore the in_use_p vectors for any pages from contexts
1855 other than the current one. */
1856 for (p = G.pages[order]; p; p = p->next)
1857 if (p->context_depth != G.context_depth)
1858 ggc_recalculate_in_use_p (p);
1862 #ifdef ENABLE_GC_CHECKING
1863 /* Clobber all free objects. */
1870 for (order = 2; order < NUM_ORDERS; order++)
1872 size_t size = OBJECT_SIZE (order);
1875 for (p = G.pages[order]; p != NULL; p = p->next)
1880 if (p->context_depth != G.context_depth)
1881 /* Since we don't do any collection for pages in pushed
1882 contexts, there's no need to do any poisoning. And
1883 besides, the IN_USE_P array isn't valid until we pop
1887 num_objects = OBJECTS_IN_PAGE (p);
1888 for (i = 0; i < num_objects; i++)
1891 word = i / HOST_BITS_PER_LONG;
1892 bit = i % HOST_BITS_PER_LONG;
1893 if (((p->in_use_p[word] >> bit) & 1) == 0)
1895 char *object = p->page + i * size;
1897 /* Keep poison-by-write when we expect to use Valgrind,
1898 so the exact same memory semantics is kept, in case
1899 there are memory errors. We override this request
1901 VALGRIND_DISCARD (VALGRIND_MAKE_WRITABLE (object, size));
1902 memset (object, 0xa5, size);
1904 /* Drop the handle to avoid handle leak. */
1905 VALGRIND_DISCARD (VALGRIND_MAKE_NOACCESS (object, size));
1912 #define poison_pages()
1915 #ifdef ENABLE_GC_ALWAYS_COLLECT
1916 /* Validate that the reportedly free objects actually are. */
1919 validate_free_objects (void)
1921 struct free_object *f, *next, *still_free = NULL;
1923 for (f = G.free_object_list; f ; f = next)
1925 page_entry *pe = lookup_page_table_entry (f->object);
1928 bit = OFFSET_TO_BIT ((char *)f->object - pe->page, pe->order);
1929 word = bit / HOST_BITS_PER_LONG;
1930 bit = bit % HOST_BITS_PER_LONG;
1933 /* Make certain it isn't visible from any root. Notice that we
1934 do this check before sweep_pages merges save_in_use_p. */
1935 if (pe->in_use_p[word] & (1UL << bit))
1938 /* If the object comes from an outer context, then retain the
1939 free_object entry, so that we can verify that the address
1940 isn't live on the stack in some outer context. */
1941 if (pe->context_depth != G.context_depth)
1943 f->next = still_free;
1950 G.free_object_list = still_free;
1953 #define validate_free_objects()
1956 /* Top level mark-and-sweep routine. */
1961 /* Avoid frequent unnecessary work by skipping collection if the
1962 total allocations haven't expanded much since the last
1964 float allocated_last_gc =
1965 MAX (G.allocated_last_gc, (size_t)PARAM_VALUE (GGC_MIN_HEAPSIZE) * 1024);
1967 float min_expand = allocated_last_gc * PARAM_VALUE (GGC_MIN_EXPAND) / 100;
1969 if (G.allocated < allocated_last_gc + min_expand)
1972 timevar_push (TV_GC);
1974 fprintf (stderr, " {GC %luk -> ", (unsigned long) G.allocated / 1024);
1975 if (GGC_DEBUG_LEVEL >= 2)
1976 fprintf (G.debug_file, "BEGIN COLLECTING\n");
1978 /* Zero the total allocated bytes. This will be recalculated in the
1982 /* Release the pages we freed the last time we collected, but didn't
1983 reuse in the interim. */
1986 /* Indicate that we've seen collections at this context depth. */
1987 G.context_depth_collections = ((unsigned long)1 << (G.context_depth + 1)) - 1;
1992 validate_free_objects ();
1995 G.allocated_last_gc = G.allocated;
1997 timevar_pop (TV_GC);
2000 fprintf (stderr, "%luk}", (unsigned long) G.allocated / 1024);
2001 if (GGC_DEBUG_LEVEL >= 2)
2002 fprintf (G.debug_file, "END COLLECTING\n");
2005 /* Print allocation statistics. */
2006 #define SCALE(x) ((unsigned long) ((x) < 1024*10 \
2008 : ((x) < 1024*1024*10 \
2010 : (x) / (1024*1024))))
2011 #define LABEL(x) ((x) < 1024*10 ? ' ' : ((x) < 1024*1024*10 ? 'k' : 'M'))
2014 ggc_print_statistics (void)
2016 struct ggc_statistics stats;
2018 size_t total_overhead = 0;
2020 /* Clear the statistics. */
2021 memset (&stats, 0, sizeof (stats));
2023 /* Make sure collection will really occur. */
2024 G.allocated_last_gc = 0;
2026 /* Collect and print the statistics common across collectors. */
2027 ggc_print_common_statistics (stderr, &stats);
2029 /* Release free pages so that we will not count the bytes allocated
2030 there as part of the total allocated memory. */
2033 /* Collect some information about the various sizes of
2036 "Memory still allocated at the end of the compilation process\n");
2037 fprintf (stderr, "%-5s %10s %10s %10s\n",
2038 "Size", "Allocated", "Used", "Overhead");
2039 for (i = 0; i < NUM_ORDERS; ++i)
2046 /* Skip empty entries. */
2050 overhead = allocated = in_use = 0;
2052 /* Figure out the total number of bytes allocated for objects of
2053 this size, and how many of them are actually in use. Also figure
2054 out how much memory the page table is using. */
2055 for (p = G.pages[i]; p; p = p->next)
2057 allocated += p->bytes;
2059 (OBJECTS_IN_PAGE (p) - p->num_free_objects) * OBJECT_SIZE (i);
2061 overhead += (sizeof (page_entry) - sizeof (long)
2062 + BITMAP_SIZE (OBJECTS_IN_PAGE (p) + 1));
2064 fprintf (stderr, "%-5lu %10lu%c %10lu%c %10lu%c\n",
2065 (unsigned long) OBJECT_SIZE (i),
2066 SCALE (allocated), LABEL (allocated),
2067 SCALE (in_use), LABEL (in_use),
2068 SCALE (overhead), LABEL (overhead));
2069 total_overhead += overhead;
2071 fprintf (stderr, "%-5s %10lu%c %10lu%c %10lu%c\n", "Total",
2072 SCALE (G.bytes_mapped), LABEL (G.bytes_mapped),
2073 SCALE (G.allocated), LABEL(G.allocated),
2074 SCALE (total_overhead), LABEL (total_overhead));
2076 #ifdef GATHER_STATISTICS
2078 fprintf (stderr, "\nTotal allocations and overheads during the compilation process\n");
2080 fprintf (stderr, "Total Overhead: %10lld\n",
2081 G.stats.total_overhead);
2082 fprintf (stderr, "Total Allocated: %10lld\n",
2083 G.stats.total_allocated);
2085 fprintf (stderr, "Total Overhead under 32B: %10lld\n",
2086 G.stats.total_overhead_under32);
2087 fprintf (stderr, "Total Allocated under 32B: %10lld\n",
2088 G.stats.total_allocated_under32);
2089 fprintf (stderr, "Total Overhead under 64B: %10lld\n",
2090 G.stats.total_overhead_under64);
2091 fprintf (stderr, "Total Allocated under 64B: %10lld\n",
2092 G.stats.total_allocated_under64);
2093 fprintf (stderr, "Total Overhead under 128B: %10lld\n",
2094 G.stats.total_overhead_under128);
2095 fprintf (stderr, "Total Allocated under 128B: %10lld\n",
2096 G.stats.total_allocated_under128);
2098 for (i = 0; i < NUM_ORDERS; i++)
2099 if (G.stats.total_allocated_per_order[i])
2101 fprintf (stderr, "Total Overhead page size %7d: %10lld\n",
2102 OBJECT_SIZE (i), G.stats.total_overhead_per_order[i]);
2103 fprintf (stderr, "Total Allocated page size %7d: %10lld\n",
2104 OBJECT_SIZE (i), G.stats.total_allocated_per_order[i]);
2112 struct ggc_pch_ondisk
2114 unsigned totals[NUM_ORDERS];
2116 size_t base[NUM_ORDERS];
2117 size_t written[NUM_ORDERS];
2120 struct ggc_pch_data *
2123 return xcalloc (sizeof (struct ggc_pch_data), 1);
2127 ggc_pch_count_object (struct ggc_pch_data *d, void *x ATTRIBUTE_UNUSED,
2128 size_t size, bool is_string ATTRIBUTE_UNUSED)
2133 order = size_lookup[size];
2137 while (size > OBJECT_SIZE (order))
2141 d->d.totals[order]++;
2145 ggc_pch_total_size (struct ggc_pch_data *d)
2150 for (i = 0; i < NUM_ORDERS; i++)
2151 a += ROUND_UP (d->d.totals[i] * OBJECT_SIZE (i), G.pagesize);
2156 ggc_pch_this_base (struct ggc_pch_data *d, void *base)
2158 size_t a = (size_t) base;
2161 for (i = 0; i < NUM_ORDERS; i++)
2164 a += ROUND_UP (d->d.totals[i] * OBJECT_SIZE (i), G.pagesize);
2170 ggc_pch_alloc_object (struct ggc_pch_data *d, void *x ATTRIBUTE_UNUSED,
2171 size_t size, bool is_string ATTRIBUTE_UNUSED)
2177 order = size_lookup[size];
2181 while (size > OBJECT_SIZE (order))
2185 result = (char *) d->base[order];
2186 d->base[order] += OBJECT_SIZE (order);
2191 ggc_pch_prepare_write (struct ggc_pch_data *d ATTRIBUTE_UNUSED,
2192 FILE *f ATTRIBUTE_UNUSED)
2194 /* Nothing to do. */
2198 ggc_pch_write_object (struct ggc_pch_data *d ATTRIBUTE_UNUSED,
2199 FILE *f, void *x, void *newx ATTRIBUTE_UNUSED,
2200 size_t size, bool is_string ATTRIBUTE_UNUSED)
2203 static const char emptyBytes[256];
2206 order = size_lookup[size];
2210 while (size > OBJECT_SIZE (order))
2214 if (fwrite (x, size, 1, f) != 1)
2215 fatal_error ("can't write PCH file: %m");
2217 /* If SIZE is not the same as OBJECT_SIZE(order), then we need to pad the
2218 object out to OBJECT_SIZE(order). This happens for strings. */
2220 if (size != OBJECT_SIZE (order))
2222 unsigned padding = OBJECT_SIZE(order) - size;
2224 /* To speed small writes, we use a nulled-out array that's larger
2225 than most padding requests as the source for our null bytes. This
2226 permits us to do the padding with fwrite() rather than fseek(), and
2227 limits the chance the the OS may try to flush any outstanding
2229 if (padding <= sizeof(emptyBytes))
2231 if (fwrite (emptyBytes, 1, padding, f) != padding)
2232 fatal_error ("can't write PCH file");
2236 /* Larger than our buffer? Just default to fseek. */
2237 if (fseek (f, padding, SEEK_CUR) != 0)
2238 fatal_error ("can't write PCH file");
2242 d->written[order]++;
2243 if (d->written[order] == d->d.totals[order]
2244 && fseek (f, ROUND_UP_VALUE (d->d.totals[order] * OBJECT_SIZE (order),
2247 fatal_error ("can't write PCH file: %m");
2251 ggc_pch_finish (struct ggc_pch_data *d, FILE *f)
2253 if (fwrite (&d->d, sizeof (d->d), 1, f) != 1)
2254 fatal_error ("can't write PCH file: %m");
2258 /* Move the PCH PTE entries just added to the end of by_depth, to the
2262 move_ptes_to_front (int count_old_page_tables, int count_new_page_tables)
2266 /* First, we swap the new entries to the front of the varrays. */
2267 page_entry **new_by_depth;
2268 unsigned long **new_save_in_use;
2270 new_by_depth = xmalloc (G.by_depth_max * sizeof (page_entry *));
2271 new_save_in_use = xmalloc (G.by_depth_max * sizeof (unsigned long *));
2273 memcpy (&new_by_depth[0],
2274 &G.by_depth[count_old_page_tables],
2275 count_new_page_tables * sizeof (void *));
2276 memcpy (&new_by_depth[count_new_page_tables],
2278 count_old_page_tables * sizeof (void *));
2279 memcpy (&new_save_in_use[0],
2280 &G.save_in_use[count_old_page_tables],
2281 count_new_page_tables * sizeof (void *));
2282 memcpy (&new_save_in_use[count_new_page_tables],
2284 count_old_page_tables * sizeof (void *));
2287 free (G.save_in_use);
2289 G.by_depth = new_by_depth;
2290 G.save_in_use = new_save_in_use;
2292 /* Now update all the index_by_depth fields. */
2293 for (i = G.by_depth_in_use; i > 0; --i)
2295 page_entry *p = G.by_depth[i-1];
2296 p->index_by_depth = i-1;
2299 /* And last, we update the depth pointers in G.depth. The first
2300 entry is already 0, and context 0 entries always start at index
2301 0, so there is nothing to update in the first slot. We need a
2302 second slot, only if we have old ptes, and if we do, they start
2303 at index count_new_page_tables. */
2304 if (count_old_page_tables)
2305 push_depth (count_new_page_tables);
2309 ggc_pch_read (FILE *f, void *addr)
2311 struct ggc_pch_ondisk d;
2314 unsigned long count_old_page_tables;
2315 unsigned long count_new_page_tables;
2317 count_old_page_tables = G.by_depth_in_use;
2319 /* We've just read in a PCH file. So, every object that used to be
2320 allocated is now free. */
2322 #ifdef ENABLE_GC_CHECKING
2326 /* No object read from a PCH file should ever be freed. So, set the
2327 context depth to 1, and set the depth of all the currently-allocated
2328 pages to be 1 too. PCH pages will have depth 0. */
2329 if (G.context_depth != 0)
2331 G.context_depth = 1;
2332 for (i = 0; i < NUM_ORDERS; i++)
2335 for (p = G.pages[i]; p != NULL; p = p->next)
2336 p->context_depth = G.context_depth;
2339 /* Allocate the appropriate page-table entries for the pages read from
2341 if (fread (&d, sizeof (d), 1, f) != 1)
2342 fatal_error ("can't read PCH file: %m");
2344 for (i = 0; i < NUM_ORDERS; i++)
2346 struct page_entry *entry;
2352 if (d.totals[i] == 0)
2355 bytes = ROUND_UP (d.totals[i] * OBJECT_SIZE (i), G.pagesize);
2356 num_objs = bytes / OBJECT_SIZE (i);
2357 entry = xcalloc (1, (sizeof (struct page_entry)
2359 + BITMAP_SIZE (num_objs + 1)));
2360 entry->bytes = bytes;
2362 entry->context_depth = 0;
2364 entry->num_free_objects = 0;
2368 j + HOST_BITS_PER_LONG <= num_objs + 1;
2369 j += HOST_BITS_PER_LONG)
2370 entry->in_use_p[j / HOST_BITS_PER_LONG] = -1;
2371 for (; j < num_objs + 1; j++)
2372 entry->in_use_p[j / HOST_BITS_PER_LONG]
2373 |= 1L << (j % HOST_BITS_PER_LONG);
2375 for (pte = entry->page;
2376 pte < entry->page + entry->bytes;
2378 set_page_table_entry (pte, entry);
2380 if (G.page_tails[i] != NULL)
2381 G.page_tails[i]->next = entry;
2384 G.page_tails[i] = entry;
2386 /* We start off by just adding all the new information to the
2387 end of the varrays, later, we will move the new information
2388 to the front of the varrays, as the PCH page tables are at
2390 push_by_depth (entry, 0);
2393 /* Now, we update the various data structures that speed page table
2395 count_new_page_tables = G.by_depth_in_use - count_old_page_tables;
2397 move_ptes_to_front (count_old_page_tables, count_new_page_tables);
2399 /* Update the statistics. */
2400 G.allocated = G.allocated_last_gc = offs - (char *)addr;