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allchblk.c
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/*
* Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
* Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
* Copyright (c) 1998-1999 by Silicon Graphics. All rights reserved.
* Copyright (c) 1999 by Hewlett-Packard Company. All rights reserved.
* Copyright (c) 2008-2022 Ivan Maidanski
*
* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
* OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
*
* Permission is hereby granted to use or copy this program
* for any purpose, provided the above notices are retained on all copies.
* Permission to modify the code and to distribute modified code is granted,
* provided the above notices are retained, and a notice that the code was
* modified is included with the above copyright notice.
*/
#include "private/gc_priv.h"
#ifdef GC_USE_ENTIRE_HEAP
int GC_use_entire_heap = TRUE;
#else
int GC_use_entire_heap = FALSE;
#endif
/* Free heap blocks are kept on one of several free lists, depending on */
/* the size of the block. Each free list is doubly linked. Adjacent */
/* free blocks are coalesced. */
/* Largest block we will allocate starting on a black listed block. */
/* Must be >= HBLKSIZE. */
#define MAX_BLACK_LIST_ALLOC (2 * HBLKSIZE)
/* Sizes up to this many HBLKs each have their own free list. */
#define UNIQUE_THRESHOLD 32
/* Sizes of at least this many heap blocks are mapped to a single free */
/* list. */
#define HUGE_THRESHOLD 256
/* In between sizes map this many distinct sizes to a single bin. */
#define FL_COMPRESSION 8
#define N_HBLK_FLS \
((HUGE_THRESHOLD - UNIQUE_THRESHOLD) / FL_COMPRESSION + UNIQUE_THRESHOLD)
/* List of completely empty heap blocks. Linked through hb_next field */
/* of header structure associated with block. Remains externally */
/* visible as used by GNU GCJ currently. */
#ifndef GC_GCJ_SUPPORT
STATIC
#endif
struct hblk *GC_hblkfreelist[N_HBLK_FLS + 1] = { 0 };
GC_API void GC_CALL
GC_iterate_free_hblks(GC_walk_free_blk_fn fn, void *client_data)
{
int i;
for (i = 0; i <= N_HBLK_FLS; ++i) {
struct hblk *h;
for (h = GC_hblkfreelist[i]; h != NULL; h = HDR(h)->hb_next) {
fn(h, i, client_data);
}
}
}
/* Number of free bytes on each list. Remains visible to GCJ. */
#ifndef GC_GCJ_SUPPORT
STATIC
#endif
word GC_free_bytes[N_HBLK_FLS + 1] = { 0 };
/* Return the largest n such that the number of free bytes on lists */
/* n .. N_HBLK_FLS is greater or equal to GC_max_large_allocd_bytes */
/* minus GC_large_allocd_bytes. If there is no such n, return 0. */
GC_INLINE size_t
GC_enough_large_bytes_left(void)
{
size_t n;
word bytes = GC_large_allocd_bytes;
GC_ASSERT(GC_max_large_allocd_bytes <= GC_heapsize);
for (n = N_HBLK_FLS + 1; n > 0;) {
n--;
bytes += GC_free_bytes[n];
if (bytes >= GC_max_large_allocd_bytes)
break;
}
return n;
}
/* Map a number of blocks to the appropriate large block free-list index. */
STATIC size_t
GC_hblk_fl_from_blocks(size_t blocks_needed)
{
if (blocks_needed <= UNIQUE_THRESHOLD)
return blocks_needed;
if (blocks_needed >= HUGE_THRESHOLD)
return N_HBLK_FLS;
return (blocks_needed - UNIQUE_THRESHOLD) / FL_COMPRESSION
+ UNIQUE_THRESHOLD;
}
#define PHDR(hhdr) HDR((hhdr)->hb_prev)
#define NHDR(hhdr) HDR((hhdr)->hb_next)
#ifdef USE_MUNMAP
# define IS_MAPPED(hhdr) (((hhdr)->hb_flags & WAS_UNMAPPED) == 0)
#else
# define IS_MAPPED(hhdr) TRUE
#endif /* !USE_MUNMAP */
#if !defined(NO_DEBUGGING) || defined(GC_ASSERTIONS)
static void GC_CALLBACK
add_hb_sz(struct hblk *h, int i, void *total_free_ptr)
{
UNUSED_ARG(i);
*(word *)total_free_ptr += HDR(h)->hb_sz;
# if defined(CPPCHECK)
GC_noop1_ptr(h);
# endif
}
/* Should return the same value as GC_large_free_bytes. */
GC_INNER word
GC_compute_large_free_bytes(void)
{
word total_free = 0;
GC_iterate_free_hblks(add_hb_sz, &total_free);
return total_free;
}
#endif /* !NO_DEBUGGING || GC_ASSERTIONS */
#if !defined(NO_DEBUGGING)
static void GC_CALLBACK
print_hblkfreelist_item(struct hblk *h, int i, void *prev_index_ptr)
{
hdr *hhdr = HDR(h);
# if defined(CPPCHECK)
GC_noop1_ptr(h);
# endif
if (i != *(int *)prev_index_ptr) {
GC_printf("Free list %d (total size %lu):\n", i,
(unsigned long)GC_free_bytes[i]);
*(int *)prev_index_ptr = i;
}
GC_printf("\t%p size %lu %s black listed\n", (void *)h,
(unsigned long)hhdr->hb_sz,
GC_is_black_listed(h, HBLKSIZE) != NULL ? "start"
: GC_is_black_listed(h, hhdr->hb_sz) != NULL ? "partially"
: "not");
}
void
GC_print_hblkfreelist(void)
{
word total;
int prev_index = -1;
GC_iterate_free_hblks(print_hblkfreelist_item, &prev_index);
GC_printf("GC_large_free_bytes: %lu\n", (unsigned long)GC_large_free_bytes);
total = GC_compute_large_free_bytes();
if (total != GC_large_free_bytes)
GC_err_printf("GC_large_free_bytes INCONSISTENT!! Should be: %lu\n",
(unsigned long)total);
}
/* Return the free-list index on which the block described by the header */
/* appears, or -1 if it appears nowhere. */
static int
free_list_index_of(const hdr *wanted)
{
int i;
for (i = 0; i <= N_HBLK_FLS; ++i) {
const struct hblk *h;
const hdr *hhdr;
for (h = GC_hblkfreelist[i]; h != NULL; h = hhdr->hb_next) {
hhdr = HDR(h);
if (hhdr == wanted)
return i;
}
}
return -1;
}
GC_API void GC_CALL
GC_dump_regions(void)
{
size_t i;
for (i = 0; i < GC_n_heap_sects; ++i) {
ptr_t start = GC_heap_sects[i].hs_start;
size_t bytes = GC_heap_sects[i].hs_bytes;
ptr_t finish = start + bytes;
ptr_t p;
/* Merge in contiguous sections. */
while (i + 1 < GC_n_heap_sects
&& GC_heap_sects[i + 1].hs_start == finish) {
++i;
finish = GC_heap_sects[i].hs_start + GC_heap_sects[i].hs_bytes;
}
GC_printf("***Section from %p to %p\n", (void *)start, (void *)finish);
for (p = start; ADDR_LT(p, finish);) {
hdr *hhdr = HDR(p);
if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
GC_printf("\t%p Missing header!!(%p)\n", (void *)p, (void *)hhdr);
p += HBLKSIZE;
continue;
}
if (HBLK_IS_FREE(hhdr)) {
int correct_index
= (int)GC_hblk_fl_from_blocks(divHBLKSZ(hhdr->hb_sz));
int actual_index;
GC_printf("\t%p\tfree block of size 0x%lx bytes%s\n", (void *)p,
(unsigned long)hhdr->hb_sz,
IS_MAPPED(hhdr) ? "" : " (unmapped)");
actual_index = free_list_index_of(hhdr);
if (-1 == actual_index) {
GC_printf("\t\tBlock not on free list %d!!\n", correct_index);
} else if (correct_index != actual_index) {
GC_printf("\t\tBlock on list %d, should be on %d!!\n", actual_index,
correct_index);
}
p += hhdr->hb_sz;
} else {
GC_printf("\t%p\tused for blocks of size 0x%lx bytes\n", (void *)p,
(unsigned long)hhdr->hb_sz);
p += HBLKSIZE * OBJ_SZ_TO_BLOCKS(hhdr->hb_sz);
}
}
}
}
#endif /* NO_DEBUGGING */
/* Initialize hdr for a block containing the indicated size and */
/* kind of objects. Return FALSE on failure. */
static GC_bool
setup_header(hdr *hhdr, struct hblk *block, size_t lb_adjusted, int k,
unsigned flags)
{
const struct obj_kind *ok;
word descr;
GC_ASSERT(I_HOLD_LOCK());
GC_ASSERT(lb_adjusted >= ALIGNMENT);
#ifndef MARK_BIT_PER_OBJ
if (lb_adjusted > MAXOBJBYTES)
flags |= LARGE_BLOCK;
#endif
ok = &GC_obj_kinds[k];
#ifdef ENABLE_DISCLAIM
if (ok->ok_disclaim_proc)
flags |= HAS_DISCLAIM;
if (ok->ok_mark_unconditionally)
flags |= MARK_UNCONDITIONALLY;
#endif
/* Set size, kind and mark proc fields. */
hhdr->hb_sz = lb_adjusted;
hhdr->hb_obj_kind = (unsigned char)k;
hhdr->hb_flags = (unsigned char)flags;
hhdr->hb_block = block;
descr = ok->ok_descriptor;
#if ALIGNMENT > GC_DS_TAGS
/* An extra byte is not added in case of ignore-off-page */
/* allocated objects not smaller than HBLKSIZE. */
if (EXTRA_BYTES != 0 && (flags & IGNORE_OFF_PAGE) != 0 && k == NORMAL
&& lb_adjusted >= HBLKSIZE)
descr += ALIGNMENT; /* or set to 0 */
#endif
if (ok->ok_relocate_descr)
descr += lb_adjusted;
hhdr->hb_descr = descr;
#ifdef MARK_BIT_PER_OBJ
/* Set hb_inv_sz as portably as possible. We set it to the */
/* smallest value such that lb_adjusted * inv_sz >= 2**32. */
/* This may be more precision than necessary. */
if (lb_adjusted > MAXOBJBYTES) {
hhdr->hb_inv_sz = LARGE_INV_SZ;
} else {
unsigned32 inv_sz;
GC_ASSERT(lb_adjusted > 1);
# if CPP_WORDSZ > 32
inv_sz = (unsigned32)(((word)1 << 32) / lb_adjusted);
if (((inv_sz * (word)lb_adjusted) >> 32) == 0)
++inv_sz;
# else
inv_sz = (((unsigned32)1 << 31) / lb_adjusted) << 1;
while ((inv_sz * lb_adjusted) > lb_adjusted)
inv_sz++;
# endif
# if (CPP_WORDSZ == 32) && defined(__GNUC__)
GC_ASSERT(((1ULL << 32) + lb_adjusted - 1) / lb_adjusted == inv_sz);
# endif
hhdr->hb_inv_sz = inv_sz;
}
#else
{
size_t lg = BYTES_TO_GRANULES(lb_adjusted);
if (EXPECT(!GC_add_map_entry(lg), FALSE)) {
/* Make it look like a valid block. */
hhdr->hb_sz = HBLKSIZE;
hhdr->hb_descr = 0;
hhdr->hb_flags |= LARGE_BLOCK;
hhdr->hb_map = 0;
return FALSE;
}
hhdr->hb_map = GC_obj_map[(hhdr->hb_flags & LARGE_BLOCK) != 0 ? 0 : lg];
}
#endif
/* Clear mark bits. */
GC_clear_hdr_marks(hhdr);
hhdr->hb_last_reclaimed = (unsigned short)GC_gc_no;
return TRUE;
}
/* Remove hhdr from the free list (it is assumed to specified by index). */
STATIC void
GC_remove_from_fl_at(hdr *hhdr, size_t index)
{
GC_ASSERT(modHBLKSZ(hhdr->hb_sz) == 0);
if (hhdr->hb_prev == 0) {
GC_ASSERT(HDR(GC_hblkfreelist[index]) == hhdr);
GC_hblkfreelist[index] = hhdr->hb_next;
} else {
hdr *phdr;
GET_HDR(hhdr->hb_prev, phdr);
phdr->hb_next = hhdr->hb_next;
}
/* We always need index to maintain free counts. */
GC_ASSERT(GC_free_bytes[index] >= hhdr->hb_sz);
GC_free_bytes[index] -= hhdr->hb_sz;
if (0 != hhdr->hb_next) {
hdr *nhdr;
GC_ASSERT(!IS_FORWARDING_ADDR_OR_NIL(NHDR(hhdr)));
GET_HDR(hhdr->hb_next, nhdr);
nhdr->hb_prev = hhdr->hb_prev;
}
}
/* Remove hhdr from the appropriate free list (we assume it is on the */
/* size-appropriate free list). */
GC_INLINE void
GC_remove_from_fl(hdr *hhdr)
{
GC_remove_from_fl_at(hhdr, GC_hblk_fl_from_blocks(divHBLKSZ(hhdr->hb_sz)));
}
/* Return a pointer to the block ending just before h, if any. */
static struct hblk *
get_block_ending_at(struct hblk *h)
{
struct hblk *p = h - 1;
hdr *hhdr;
GET_HDR(p, hhdr);
if (hhdr != NULL) {
return GC_find_starting_hblk(p, &hhdr);
}
p = GC_prev_block(p);
if (p != NULL) {
hhdr = HDR(p);
if ((ptr_t)p + hhdr->hb_sz == (ptr_t)h) {
return p;
}
}
return NULL;
}
/* Return a pointer to the free block ending just before h, if any. */
STATIC struct hblk *
GC_free_block_ending_at(struct hblk *h)
{
struct hblk *p = get_block_ending_at(h);
if (p /* != NULL */) { /* CPPCHECK */
const hdr *hhdr = HDR(p);
if (HBLK_IS_FREE(hhdr)) {
return p;
}
}
return 0;
}
/* Add hhdr to the appropriate free list. */
/* We maintain individual free lists sorted by address. */
STATIC void
GC_add_to_fl(struct hblk *h, hdr *hhdr)
{
size_t index = GC_hblk_fl_from_blocks(divHBLKSZ(hhdr->hb_sz));
struct hblk *second = GC_hblkfreelist[index];
#if defined(GC_ASSERTIONS) && !defined(USE_MUNMAP)
{
struct hblk *next = (struct hblk *)((ptr_t)h + hhdr->hb_sz);
const hdr *nexthdr = HDR(next);
struct hblk *prev = GC_free_block_ending_at(h);
const hdr *prevhdr = HDR(prev);
GC_ASSERT(NULL == nexthdr || !HBLK_IS_FREE(nexthdr)
|| (GC_heapsize & SIGNB) != 0);
/* In the last case, blocks may be too large to be merged. */
GC_ASSERT(NULL == prev || !HBLK_IS_FREE(prevhdr)
|| (GC_heapsize & SIGNB) != 0);
}
#endif
GC_ASSERT(modHBLKSZ(hhdr->hb_sz) == 0);
GC_hblkfreelist[index] = h;
GC_free_bytes[index] += hhdr->hb_sz;
GC_ASSERT(GC_free_bytes[index] <= GC_large_free_bytes);
hhdr->hb_next = second;
hhdr->hb_prev = 0;
if (second /* != NULL */) { /* CPPCHECK */
hdr *second_hdr;
GET_HDR(second, second_hdr);
second_hdr->hb_prev = h;
}
hhdr->hb_flags |= FREE_BLK;
}
#define BLOCKS_MERGE_OVERFLOW(hhdr, nexthdr) \
((((hhdr)->hb_sz + (nexthdr)->hb_sz) & SIZET_SIGNB) != 0)
#ifdef USE_MUNMAP
# ifdef COUNT_UNMAPPED_REGIONS
/* GC_unmap_old will avoid creating more than this many unmapped regions, */
/* but an unmapped region may be split again so exceeding the limit. */
/* Return the change in number of unmapped regions if the block h swaps */
/* from its current state of mapped/unmapped to the opposite state. */
static int
calc_num_unmapped_regions_delta(struct hblk *h, hdr *hhdr)
{
struct hblk *prev = get_block_ending_at(h);
struct hblk *next;
GC_bool prev_unmapped = FALSE;
GC_bool next_unmapped = FALSE;
next = GC_next_block((struct hblk *)((ptr_t)h + hhdr->hb_sz), TRUE);
/* Ensure next is contiguous with h. */
if (next != HBLK_PAGE_ALIGNED((ptr_t)h + hhdr->hb_sz)) {
next = NULL;
}
if (prev != NULL) {
const hdr *prevhdr = HDR(prev);
prev_unmapped = !IS_MAPPED(prevhdr);
}
if (next != NULL) {
const hdr *nexthdr = HDR(next);
next_unmapped = !IS_MAPPED(nexthdr);
}
if (prev_unmapped && next_unmapped) {
/* If h unmapped, merge two unmapped regions into one. */
/* If h remapped, split one unmapped region into two. */
return IS_MAPPED(hhdr) ? -1 : 1;
}
if (!prev_unmapped && !next_unmapped) {
/* If h unmapped, create an isolated unmapped region. */
/* If h remapped, remove it. */
return IS_MAPPED(hhdr) ? 1 : -1;
}
/* If h unmapped, merge it with previous or next unmapped region. */
/* If h remapped, reduce either previous or next unmapped region. */
/* In either way, no change to the number of unmapped regions. */
return 0;
}
# endif /* COUNT_UNMAPPED_REGIONS */
/* Update GC_num_unmapped_regions assuming the block h changes */
/* from its current state of mapped/unmapped to the opposite state. */
GC_INLINE void
GC_adjust_num_unmapped(struct hblk *h, hdr *hhdr)
{
# ifdef COUNT_UNMAPPED_REGIONS
GC_num_unmapped_regions += calc_num_unmapped_regions_delta(h, hhdr);
# else
UNUSED_ARG(h);
UNUSED_ARG(hhdr);
# endif
}
/* Unmap blocks that haven't been recently touched. This is the only */
/* way blocks are ever unmapped. */
GC_INNER void
GC_unmap_old(unsigned threshold)
{
size_t i;
# ifdef COUNT_UNMAPPED_REGIONS
/* Skip unmapping if we have already exceeded the soft limit. */
/* This forgoes any opportunities to merge unmapped regions though. */
if (GC_num_unmapped_regions >= GC_UNMAPPED_REGIONS_SOFT_LIMIT)
return;
# endif
for (i = 0; i <= N_HBLK_FLS; ++i) {
struct hblk *h;
hdr *hhdr;
for (h = GC_hblkfreelist[i]; 0 != h; h = hhdr->hb_next) {
hhdr = HDR(h);
if (!IS_MAPPED(hhdr))
continue;
/* Check that the interval is not smaller than the threshold. */
/* The truncated counter value wrapping is handled correctly. */
if ((unsigned short)(GC_gc_no - hhdr->hb_last_reclaimed)
>= (unsigned short)threshold) {
# ifdef COUNT_UNMAPPED_REGIONS
/* Continue with unmapping the block only if it will not */
/* create too many unmapped regions, or if unmapping */
/* reduces the number of regions. */
int delta = calc_num_unmapped_regions_delta(h, hhdr);
GC_signed_word regions = GC_num_unmapped_regions + delta;
if (delta >= 0 && regions >= GC_UNMAPPED_REGIONS_SOFT_LIMIT) {
GC_COND_LOG_PRINTF("Unmapped regions limit reached!\n");
return;
}
GC_num_unmapped_regions = regions;
# endif
GC_unmap((ptr_t)h, hhdr->hb_sz);
hhdr->hb_flags |= WAS_UNMAPPED;
}
}
}
}
/* Merge all unmapped blocks that are adjacent to other free */
/* blocks. This may involve remapping, since all blocks are either */
/* fully mapped or fully unmapped. */
GC_INNER void
GC_merge_unmapped(void)
{
size_t i;
for (i = 0; i <= N_HBLK_FLS; ++i) {
struct hblk *h = GC_hblkfreelist[i];
while (h != NULL) {
struct hblk *next;
hdr *hhdr, *nexthdr;
size_t size, next_size;
GET_HDR(h, hhdr);
size = hhdr->hb_sz;
next = (struct hblk *)((ptr_t)h + size);
GET_HDR(next, nexthdr);
/* Coalesce with successor, if possible. */
if (NULL == nexthdr || !HBLK_IS_FREE(nexthdr)
|| BLOCKS_MERGE_OVERFLOW(hhdr, nexthdr)) {
/* Not mergeable with the successor. */
h = hhdr->hb_next;
continue;
}
next_size = nexthdr->hb_sz;
/* Note that we usually try to avoid adjacent free blocks */
/* that are either both mapped or both unmapped. But that */
/* isn't guaranteed to hold since we remap blocks when we */
/* split them, and don't merge at that point. It may also */
/* not hold if the merged block would be too big. */
if (IS_MAPPED(hhdr) && !IS_MAPPED(nexthdr)) {
/* Make both consistent, so that we can merge. */
if (size > next_size) {
GC_adjust_num_unmapped(next, nexthdr);
GC_remap((ptr_t)next, next_size);
} else {
GC_adjust_num_unmapped(h, hhdr);
GC_unmap((ptr_t)h, size);
GC_unmap_gap((ptr_t)h, size, (ptr_t)next, next_size);
hhdr->hb_flags |= WAS_UNMAPPED;
}
} else if (IS_MAPPED(nexthdr) && !IS_MAPPED(hhdr)) {
if (size > next_size) {
GC_adjust_num_unmapped(next, nexthdr);
GC_unmap((ptr_t)next, next_size);
GC_unmap_gap((ptr_t)h, size, (ptr_t)next, next_size);
} else {
GC_adjust_num_unmapped(h, hhdr);
GC_remap((ptr_t)h, size);
hhdr->hb_flags &= (unsigned char)~WAS_UNMAPPED;
hhdr->hb_last_reclaimed = nexthdr->hb_last_reclaimed;
}
} else if (!IS_MAPPED(hhdr) && !IS_MAPPED(nexthdr)) {
/* Unmap any gap in the middle. */
GC_unmap_gap((ptr_t)h, size, (ptr_t)next, next_size);
}
/* If they are both unmapped, we merge, but leave unmapped. */
GC_remove_from_fl_at(hhdr, i);
GC_remove_from_fl(nexthdr);
hhdr->hb_sz += nexthdr->hb_sz;
GC_remove_header(next);
GC_add_to_fl(h, hhdr);
/* Start over at the beginning of list. */
h = GC_hblkfreelist[i];
}
}
}
#endif /* USE_MUNMAP */
/* Return a pointer to a block starting at h of length bytes. Memory */
/* for the block is mapped. Remove the block from its free list, and */
/* return the remainder (if any) to its appropriate free list. */
/* May fail by returning 0. The header for the returned block must */
/* be set up by the caller. If the return value is not 0, then hhdr is */
/* the header for it. */
STATIC struct hblk *
GC_get_first_part(struct hblk *h, hdr *hhdr, size_t size_needed, size_t index)
{
size_t total_size;
struct hblk *rest;
hdr *rest_hdr;
GC_ASSERT(I_HOLD_LOCK());
GC_ASSERT(modHBLKSZ(size_needed) == 0);
total_size = hhdr->hb_sz;
GC_ASSERT(modHBLKSZ(total_size) == 0);
GC_remove_from_fl_at(hhdr, index);
if (total_size == size_needed)
return h;
rest = (struct hblk *)((ptr_t)h + size_needed);
rest_hdr = GC_install_header(rest);
if (EXPECT(NULL == rest_hdr, FALSE)) {
/* FIXME: This is likely to be very bad news ... */
WARN("Header allocation failed: dropping block\n", 0);
return NULL;
}
rest_hdr->hb_block = rest;
rest_hdr->hb_sz = total_size - size_needed;
rest_hdr->hb_flags = 0;
#ifdef GC_ASSERTIONS
/* Mark h not free, to avoid assertion about adjacent free blocks. */
hhdr->hb_flags &= (unsigned char)~FREE_BLK;
#endif
GC_add_to_fl(rest, rest_hdr);
return h;
}
/* Split the block. hbp is a free block; last_hbp points at an address */
/* inside it; a new header for last_hbp is assumed to be already set */
/* up. Fix up the header of hbp to reflect the fact that it is being */
/* split, move it to the appropriate free list. last_hbp replaces hbp */
/* in the original free list. last_hdr is not completely filled in, */
/* since it is about to be allocated. It may in fact end up on the */
/* wrong free list for its size. That is not a disaster, since */
/* last_hbp is to be allocated by our caller. (Hence adding it to */
/* a free list is silly. But this path is hopefully rare enough that */
/* it does not matter. The code is cleaner this way.) */
STATIC void
GC_split_block(struct hblk *hbp, hdr *hhdr, struct hblk *last_hbp,
hdr *last_hdr, size_t index /* of free list */)
{
size_t h_size = (size_t)((ptr_t)last_hbp - (ptr_t)hbp);
struct hblk *prev = hhdr->hb_prev;
struct hblk *next = hhdr->hb_next;
/* Replace hbp with last_hbp on its free list. */
last_hdr->hb_prev = prev;
last_hdr->hb_next = next;
last_hdr->hb_sz = hhdr->hb_sz - h_size;
last_hdr->hb_flags = 0;
if (prev /* != NULL */) { /* CPPCHECK */
HDR(prev)->hb_next = last_hbp;
} else {
GC_hblkfreelist[index] = last_hbp;
}
if (next /* != NULL */) {
HDR(next)->hb_prev = last_hbp;
}
GC_ASSERT(GC_free_bytes[index] > h_size);
GC_free_bytes[index] -= h_size;
#ifdef USE_MUNMAP
hhdr->hb_last_reclaimed = (unsigned short)GC_gc_no;
#endif
hhdr->hb_sz = h_size;
GC_add_to_fl(hbp, hhdr);
last_hdr->hb_flags |= FREE_BLK;
}
STATIC struct hblk *GC_allochblk_nth(size_t lb_adjusted, int k, unsigned flags,
size_t index, int may_split,
size_t align_m1);
#ifdef USE_MUNMAP
# define AVOID_SPLIT_REMAPPED 2
#endif
GC_INNER struct hblk *
GC_allochblk(size_t lb_adjusted, int k,
unsigned flags /* IGNORE_OFF_PAGE or 0 */, size_t align_m1)
{
size_t blocks, start_list;
struct hblk *result;
int may_split;
size_t split_limit; /* highest index of free list whose blocks we split */
GC_ASSERT(I_HOLD_LOCK());
GC_ASSERT((lb_adjusted & (GC_GRANULE_BYTES - 1)) == 0);
blocks = OBJ_SZ_TO_BLOCKS_CHECKED(lb_adjusted);
if (EXPECT(SIZET_SAT_ADD(blocks * HBLKSIZE, align_m1) >= (GC_SIZE_MAX >> 1),
FALSE))
return NULL; /* overflow */
start_list = GC_hblk_fl_from_blocks(blocks);
/* Try for an exact match first. */
result
= GC_allochblk_nth(lb_adjusted, k, flags, start_list, FALSE, align_m1);
if (result != NULL)
return result;
may_split = TRUE;
if (GC_use_entire_heap || GC_dont_gc
|| GC_heapsize - GC_large_free_bytes < GC_requested_heapsize
|| GC_incremental || !GC_should_collect()) {
/* Should use more of the heap, even if it requires splitting. */
split_limit = N_HBLK_FLS;
} else if (GC_finalizer_bytes_freed > (GC_heapsize >> 4)) {
/* If we are deallocating lots of memory from finalizers, */
/* fail and collect sooner rather than later. */
split_limit = 0;
} else {
/* If we have enough large blocks left to cover any */
/* previous request for large blocks, we go ahead */
/* and split. Assuming a steady state, that should */
/* be safe. It means that we can use the full */
/* heap if we allocate only small objects. */
split_limit = GC_enough_large_bytes_left();
#ifdef USE_MUNMAP
if (split_limit > 0)
may_split = AVOID_SPLIT_REMAPPED;
#endif
}
if (start_list < UNIQUE_THRESHOLD && 0 == align_m1) {
/* No reason to try start_list again, since all blocks are exact */
/* matches. */
++start_list;
}
for (; start_list <= split_limit; ++start_list) {
result = GC_allochblk_nth(lb_adjusted, k, flags, start_list, may_split,
align_m1);
if (result != NULL)
break;
}
return result;
}
/* Number of warnings suppressed so far. */
STATIC long GC_large_alloc_warn_suppressed = 0;
/* Counter of the cases when found block by GC_allochblk_nth is */
/* blacklisted completely. */
STATIC unsigned GC_drop_blacklisted_count = 0;
#define ALIGN_PAD_SZ(p, align_m1) \
(((align_m1) + 1 - (size_t)ADDR(p)) & (align_m1))
static GC_bool
next_hblk_fits_better(const hdr *hhdr, size_t size_avail, size_t size_needed,
size_t align_m1)
{
const hdr *nexthdr;
size_t next_size;
size_t next_ofs;
struct hblk *next_hbp = hhdr->hb_next;
if (NULL == next_hbp)
return FALSE; /* no next block */
GET_HDR(next_hbp, nexthdr);
next_size = nexthdr->hb_sz;
if (size_avail <= next_size)
return FALSE; /* not enough size */
next_ofs = ALIGN_PAD_SZ(next_hbp, align_m1);
return next_size >= size_needed + next_ofs
&& !GC_is_black_listed(next_hbp + divHBLKSZ(next_ofs), size_needed);
}
static struct hblk *
find_nonbl_hblk(struct hblk *last_hbp, size_t size_remain,
size_t eff_size_needed, size_t align_m1)
{
ptr_t search_end
= PTR_ALIGN_DOWN((ptr_t)last_hbp + size_remain, align_m1 + 1);
do {
struct hblk *next_hbp;
last_hbp += divHBLKSZ(ALIGN_PAD_SZ(last_hbp, align_m1));
next_hbp = GC_is_black_listed(last_hbp, eff_size_needed);
if (NULL == next_hbp)
return last_hbp; /* not black-listed */
last_hbp = next_hbp;
} while (ADDR_GE(search_end, (ptr_t)last_hbp));
return NULL;
}
/* Allocate and drop the block in small chunks, to maximize the chance */
/* that we will recover some later. hhdr should correspond to hbp. */
static void
drop_hblk_in_chunks(size_t n, struct hblk *hbp, hdr *hhdr)
{
size_t total_size = hhdr->hb_sz;
const struct hblk *limit = hbp + divHBLKSZ(total_size);
GC_ASSERT(HDR(hbp) == hhdr);
GC_ASSERT(modHBLKSZ(total_size) == 0 && total_size > 0);
GC_large_free_bytes -= total_size;
GC_bytes_dropped += total_size;
GC_remove_from_fl_at(hhdr, n);
do {
(void)setup_header(hhdr, hbp, HBLKSIZE, PTRFREE, 0); /* cannot fail */
if (GC_debugging_started)
BZERO(hbp, HBLKSIZE);
hbp++;
if (ADDR_GE(hbp, limit))
break;
hhdr = GC_install_header(hbp);
} while (EXPECT(hhdr != NULL, TRUE)); /* no header allocation failure? */
}
#if defined(MPROTECT_VDB) && defined(DONT_PROTECT_PTRFREE)
static GC_bool
is_hblks_mix_in_page(struct hblk *hbp, GC_bool is_ptrfree)
{
struct hblk *h = HBLK_PAGE_ALIGNED(hbp);
size_t i, cnt = divHBLKSZ(GC_page_size);
/* Iterate over blocks in the page to check if all the */
/* occupied blocks are pointer-free if we are going to */
/* allocate a pointer-free one, and vice versa. */
for (i = 0; i < cnt; i++) {
hdr *hhdr;
GET_HDR(&h[i], hhdr);
if (NULL == hhdr)
continue;
(void)GC_find_starting_hblk(&h[i], &hhdr);
if (!HBLK_IS_FREE(hhdr)) {
/* It is OK to check only the first found occupied block. */
return IS_PTRFREE(hhdr) != is_ptrfree;
}
}
return FALSE; /* all blocks are free */
}
#endif /* MPROTECT_VDB && DONT_PROTECT_PTRFREE */
/* The same as GC_allochblk, but with search restricted to the index-th */
/* free list. flags should be IGNORE_OFF_PAGE or zero; may_split */
/* indicates whether it is OK to split larger blocks; size is in bytes. */
/* If may_split is set to AVOID_SPLIT_REMAPPED, then memory remapping */
/* followed by splitting should be generally avoided. Rounded-up */
/* lb_adjusted plus align_m1 value should be less than GC_SIZE_MAX / 2. */
STATIC struct hblk *
GC_allochblk_nth(size_t lb_adjusted, int k, unsigned flags, size_t index,
int may_split, size_t align_m1)
{
struct hblk *hbp, *last_hbp;
/* The header corresponding to hbp. */
hdr *hhdr;
/* Number of bytes in requested objects. */
size_t size_needed = (lb_adjusted + HBLKSIZE - 1) & ~(HBLKSIZE - 1);
GC_ASSERT(I_HOLD_LOCK());
GC_ASSERT(((align_m1 + 1) & align_m1) == 0 && lb_adjusted > 0);
GC_ASSERT(0 == align_m1 || modHBLKSZ(align_m1 + 1) == 0);
retry:
/* Search for a big enough block in free list. */
for (hbp = GC_hblkfreelist[index];; hbp = hhdr->hb_next) {
size_t size_avail; /* bytes available in this block */
size_t align_ofs;
if (hbp /* != NULL */) {
/* CPPCHECK */
} else {
return NULL;
}
GET_HDR(hbp, hhdr); /* set hhdr value */
size_avail = hhdr->hb_sz;
if (!may_split && size_avail != size_needed)
continue;
align_ofs = ALIGN_PAD_SZ(hbp, align_m1);
if (size_avail < size_needed + align_ofs)
continue; /* the block is too small */
if (size_avail != size_needed) {
/* If the next heap block is obviously better, go on. */
/* This prevents us from disassembling a single large */
/* block to get tiny blocks. */
if (next_hblk_fits_better(hhdr, size_avail, size_needed, align_m1))
continue;
}
#if defined(MPROTECT_VDB) && defined(DONT_PROTECT_PTRFREE)
/* Avoid write-protecting pointer-free blocks (only the */
/* case if page size is larger than the block size). */
GC_ASSERT(GC_page_size != 0);
if (GC_page_size != HBLKSIZE
&& (!GC_incremental /* not enabled yet */
|| GC_incremental_protection_needs() != GC_PROTECTS_NONE)
&& is_hblks_mix_in_page(hbp, k == PTRFREE))
continue;
#endif
if (IS_UNCOLLECTABLE(k)
|| (k == PTRFREE && size_needed <= MAX_BLACK_LIST_ALLOC)) {
last_hbp = hbp + divHBLKSZ(align_ofs);
break;
}
last_hbp = find_nonbl_hblk(
hbp, size_avail - size_needed,
(flags & IGNORE_OFF_PAGE) != 0 ? HBLKSIZE : size_needed, align_m1);
/* Is non-blacklisted part of enough size? */
if (last_hbp != NULL) {
#ifdef USE_MUNMAP
/* Avoid remapping followed by splitting. */
if (may_split == AVOID_SPLIT_REMAPPED && last_hbp != hbp
&& !IS_MAPPED(hhdr))
continue;
#endif
break;
}
/* The block is completely blacklisted. If so, we need to */
/* drop some such blocks, since otherwise we spend all our */
/* time traversing them if pointer-free blocks are unpopular. */
/* A dropped block will be reconsidered at next GC. */
if (size_needed == HBLKSIZE && 0 == align_m1 && !GC_find_leak
&& IS_MAPPED(hhdr) && (++GC_drop_blacklisted_count & 3) == 0) {
const struct hblk *prev = hhdr->hb_prev;
drop_hblk_in_chunks(index, hbp, hhdr);
if (NULL == prev)
goto retry;
/* Restore hhdr to point at free block. */
hhdr = HDR(prev);
continue;
}
if (size_needed > BL_LIMIT && size_avail - size_needed > BL_LIMIT) {
/* Punt, since anything else risks unreasonable heap growth. */
if (++GC_large_alloc_warn_suppressed >= GC_large_alloc_warn_interval) {
WARN("Repeated allocation of very large block"
" (appr. size %" WARN_PRIuPTR " KiB):\n"
"\tMay lead to memory leak and poor performance\n",
size_needed >> 10);
GC_large_alloc_warn_suppressed = 0;
}
last_hbp = hbp + divHBLKSZ(align_ofs);
break;
}
}
GC_ASSERT((ADDR(last_hbp) & align_m1) == 0);
if (last_hbp != hbp) {
hdr *last_hdr = GC_install_header(last_hbp);
if (EXPECT(NULL == last_hdr, FALSE))
return NULL;
/* Make sure it's mapped before we mangle it. */
#ifdef USE_MUNMAP
if (!IS_MAPPED(hhdr)) {
GC_adjust_num_unmapped(hbp, hhdr);
GC_remap((ptr_t)hbp, hhdr->hb_sz);
hhdr->hb_flags &= (unsigned char)~WAS_UNMAPPED;
}
#endif
/* Split the block at last_hbp. */
GC_split_block(hbp, hhdr, last_hbp, last_hdr, index);
/* We must now allocate last_hbp, since it may be on the */
/* wrong free list. */
hbp = last_hbp;
hhdr = last_hdr;
}
GC_ASSERT(hhdr->hb_sz >= size_needed);