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freelist.c
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freelist.c
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/**************************************************************************/
/* */
/* OCaml */
/* */
/* Damien Doligez, projet Para, INRIA Rocquencourt */
/* */
/* Copyright 1996 Institut National de Recherche en Informatique et */
/* en Automatique. */
/* */
/* All rights reserved. This file is distributed under the terms of */
/* the GNU Lesser General Public License version 2.1, with the */
/* special exception on linking described in the file LICENSE. */
/* */
/**************************************************************************/
#define CAML_INTERNALS
#define FREELIST_DEBUG 0
#if FREELIST_DEBUG
#include <stdio.h>
#endif
#include <string.h>
#include "caml/config.h"
#include "caml/custom.h"
#include "caml/freelist.h"
#include "caml/gc.h"
#include "caml/gc_ctrl.h"
#include "caml/memory.h"
#include "caml/major_gc.h"
#include "caml/misc.h"
#include "caml/mlvalues.h"
#include "caml/eventlog.h"
/*************** declarations common to all policies ******************/
/* A block in a small free list is a [value] (integer representing a
pointer to the first word after the block's header). The end of the
list is NULL.
*/
#define Val_NULL ((value) NULL)
asize_t caml_fl_cur_wsz = 0; /* Number of words in the free set,
including headers but not fragments. */
value caml_fl_merge = Val_NULL; /* Current insertion pointer. Managed
jointly with [sweep_slice]. */
/* Next in list */
#define Next_small(v) Field ((v), 0)
/* Next in memory order */
Caml_inline value Next_in_mem (value v) {
return (value) &Field ((v), Whsize_val (v));
}
#ifdef CAML_INSTR
/* number of pointers followed to allocate from the free set */
uintnat caml_instr_alloc_jump = 0;
#define EV_ALLOC_JUMP(n) (caml_instr_alloc_jump += (n))
#endif /*CAML_INSTR*/
/********************* next-fit allocation policy *********************/
/* The free-list is kept sorted by increasing addresses.
This makes the merging of adjacent free blocks possible.
(See [nf_merge_block].)
*/
/* The sentinel can be located anywhere in memory, but it must not be
adjacent to any heap object. */
static struct {
value filler1; /* Make sure the sentinel is never adjacent to any block. */
header_t h;
value first_field;
value filler2; /* Make sure the sentinel is never adjacent to any block. */
} nf_sentinel = {0, Make_header (0, 0, Caml_blue), Val_NULL, 0};
#define Nf_head (Val_bp (&(nf_sentinel.first_field)))
static value nf_prev = Nf_head; /* Current allocation pointer. */
static value nf_last = Val_NULL; /* Last block in the list. Only valid
just after [nf_allocate] returns NULL. */
#if defined (DEBUG) || FREELIST_DEBUG
static void nf_check (void)
{
value cur;
int prev_found = 0, merge_found = 0;
uintnat size_found = 0;
cur = Next_small (Nf_head);
while (cur != Val_NULL){
size_found += Whsize_bp (cur);
CAMLassert (Is_in_heap (cur));
if (cur == nf_prev) prev_found = 1;
if (cur == caml_fl_merge) merge_found = 1;
cur = Next_small (cur);
}
CAMLassert (prev_found || nf_prev == Nf_head);
CAMLassert (merge_found || caml_fl_merge == Nf_head);
CAMLassert (size_found == caml_fl_cur_wsz);
}
#endif /* DEBUG || FREELIST_DEBUG */
/* [nf_allocate_block] is called by [nf_allocate]. Given a suitable free
block and the requested size, it allocates a new block from the free
block. There are three cases:
0. The free block has the requested size. Detach the block from the
free-list and return it.
1. The free block is 1 word longer than the requested size. Detach
the block from the free list. The remaining word cannot be linked:
turn it into an empty block (header only), and return the rest.
2. The free block is large enough. Split it in two and return the right
block.
In all cases, the allocated block is right-justified in the free block:
it is located in the high-address words of the free block, so that
the linking of the free-list does not change in case 2.
*/
static header_t *nf_allocate_block (mlsize_t wh_sz, value prev, value cur)
{
header_t h = Hd_bp (cur);
CAMLassert (Whsize_hd (h) >= wh_sz);
if (Wosize_hd (h) < wh_sz + 1){ /* Cases 0 and 1. */
caml_fl_cur_wsz -= Whsize_hd (h);
Next_small (prev) = Next_small (cur);
CAMLassert (Is_in_heap (Next_small (prev))
|| Next_small (prev) == Val_NULL);
if (caml_fl_merge == cur) caml_fl_merge = prev;
#ifdef DEBUG
nf_last = Val_NULL;
#endif
/* In case 1, the following creates the empty block correctly.
In case 0, it gives an invalid header to the block. The function
calling [nf_allocate] will overwrite it. */
Hd_op (cur) = Make_header (0, 0, Caml_white);
}else{ /* Case 2. */
caml_fl_cur_wsz -= wh_sz;
Hd_op (cur) = Make_header (Wosize_hd (h) - wh_sz, 0, Caml_blue);
}
nf_prev = prev;
return (header_t *) &Field (cur, Wosize_hd (h) - wh_sz);
}
static header_t *nf_allocate (mlsize_t wo_sz)
{
value cur = Val_NULL, prev;
CAMLassert (sizeof (char *) == sizeof (value));
CAMLassert (wo_sz >= 1);
CAMLassert (nf_prev != Val_NULL);
/* Search from [nf_prev] to the end of the list. */
prev = nf_prev;
cur = Next_small (prev);
while (cur != Val_NULL){
CAMLassert (Is_in_heap (cur));
if (Wosize_bp (cur) >= wo_sz){
return nf_allocate_block (Whsize_wosize (wo_sz), prev, cur);
}
prev = cur;
cur = Next_small (prev);
CAML_EVENTLOG_DO(EV_ALLOC_JUMP (1));
}
nf_last = prev;
/* Search from the start of the list to [nf_prev]. */
prev = Nf_head;
cur = Next_small (prev);
while (prev != nf_prev){
if (Wosize_bp (cur) >= wo_sz){
return nf_allocate_block (Whsize_wosize (wo_sz), prev, cur);
}
prev = cur;
cur = Next_small (prev);
CAML_EVENTLOG_DO(EV_ALLOC_JUMP (1));
}
/* No suitable block was found. */
return NULL;
}
/* Location of the last fragment seen by the sweeping code.
This is a pointer to the first word after the fragment, which is
the header of the next block.
Note that [last_fragment] doesn't point to the fragment itself,
but to the block after it.
*/
static header_t *nf_last_fragment;
static void nf_init_merge (void)
{
CAML_EV_ALLOC_FLUSH();
nf_last_fragment = NULL;
caml_fl_merge = Nf_head;
#ifdef DEBUG
nf_check ();
#endif
}
static void nf_init (void)
{
Next_small (Nf_head) = Val_NULL;
nf_prev = Nf_head;
caml_fl_cur_wsz = 0;
}
static void nf_reset (void)
{
nf_init ();
}
/* Note: the [limit] parameter is unused because we merge blocks one by one. */
static header_t *nf_merge_block (value bp, char *limit)
{
value prev, cur, adj;
header_t hd = Hd_val (bp);
mlsize_t prev_wosz;
caml_fl_cur_wsz += Whsize_hd (hd);
/* [merge_block] is now responsible for calling the finalization function. */
if (Tag_hd (hd) == Custom_tag){
void (*final_fun)(value) = Custom_ops_val(bp)->finalize;
if (final_fun != NULL) final_fun(bp);
}
#ifdef DEBUG
caml_set_fields (bp, 0, Debug_free_major);
#endif
prev = caml_fl_merge;
cur = Next_small (prev);
/* The sweep code makes sure that this is the right place to insert
this block: */
CAMLassert (Bp_val (prev) < Bp_val (bp) || prev == Nf_head);
CAMLassert (Bp_val (cur) > Bp_val (bp) || cur == Val_NULL);
/* If [last_fragment] and [bp] are adjacent, merge them. */
if (nf_last_fragment == Hp_val (bp)){
mlsize_t bp_whsz = Whsize_val (bp);
if (bp_whsz <= Max_wosize){
hd = Make_header (bp_whsz, 0, Caml_white);
bp = (value) nf_last_fragment;
Hd_val (bp) = hd;
caml_fl_cur_wsz += Whsize_wosize (0);
}
}
/* If [bp] and [cur] are adjacent, remove [cur] from the free-list
and merge them. */
adj = Next_in_mem (bp);
if (adj == cur){
value next_cur = Next_small (cur);
mlsize_t cur_whsz = Whsize_val (cur);
if (Wosize_hd (hd) + cur_whsz <= Max_wosize){
Next_small (prev) = next_cur;
if (nf_prev == cur) nf_prev = prev;
hd = Make_header (Wosize_hd (hd) + cur_whsz, 0, Caml_blue);
Hd_val (bp) = hd;
adj = Next_in_mem (bp);
#ifdef DEBUG
nf_last = Val_NULL;
Next_small (cur) = (value) Debug_free_major;
Hd_val (cur) = Debug_free_major;
#endif
cur = next_cur;
}
}
/* If [prev] and [bp] are adjacent merge them, else insert [bp] into
the free-list if it is big enough. */
prev_wosz = Wosize_val (prev);
if (Next_in_mem (prev) == bp && prev_wosz + Whsize_hd (hd) < Max_wosize){
Hd_val (prev) = Make_header (prev_wosz + Whsize_hd (hd), 0, Caml_blue);
#ifdef DEBUG
Hd_val (bp) = Debug_free_major;
#endif
CAMLassert (caml_fl_merge == prev);
}else if (Wosize_hd (hd) != 0){
Hd_val (bp) = Bluehd_hd (hd);
Next_small (bp) = cur;
Next_small (prev) = bp;
caml_fl_merge = bp;
}else{
/* This is a fragment. Leave it in white but remember it for eventual
merging with the next block. */
nf_last_fragment = (header_t *) bp;
caml_fl_cur_wsz -= Whsize_wosize (0);
}
return Hp_val (adj);
}
/* This is a heap extension. We have to insert it in the right place
in the free-list.
[nf_add_blocks] can only be called right after a call to
[nf_allocate] that returned Val_NULL.
Most of the heap extensions are expected to be at the end of the
free list. (This depends on the implementation of [malloc].)
[bp] must point to a list of blocks chained by their field 0,
terminated by Val_NULL, and field 1 of the first block must point to
the last block.
*/
static void nf_add_blocks (value bp)
{
value cur = bp;
CAMLassert (nf_last != Val_NULL);
CAMLassert (Next_small (nf_last) == Val_NULL);
do {
caml_fl_cur_wsz += Whsize_bp (cur);
cur = Field(cur, 0);
} while (cur != Val_NULL);
if (Bp_val (bp) > Bp_val (nf_last)){
Next_small (nf_last) = bp;
if (nf_last == caml_fl_merge && (char *) bp < caml_gc_sweep_hp){
caml_fl_merge = Field (bp, 1);
}
}else{
value prev;
prev = Nf_head;
cur = Next_small (prev);
while (cur != Val_NULL && Bp_val (cur) < Bp_val (bp)){
CAMLassert (Bp_val (prev) < Bp_val (bp) || prev == Nf_head);
prev = cur;
cur = Next_small (prev);
}
CAMLassert (Bp_val (prev) < Bp_val (bp) || prev == Nf_head);
CAMLassert (Bp_val (cur) > Bp_val (bp) || cur == Val_NULL);
Next_small (Field (bp, 1)) = cur;
Next_small (prev) = bp;
/* When inserting blocks between [caml_fl_merge] and [caml_gc_sweep_hp],
we must advance [caml_fl_merge] to the new block, so that [caml_fl_merge]
is always the last free-list block before [caml_gc_sweep_hp]. */
if (prev == caml_fl_merge && (char *) bp < caml_gc_sweep_hp){
caml_fl_merge = Field (bp, 1);
}
}
}
static void nf_make_free_blocks
(value *p, mlsize_t size, int do_merge, int color)
{
mlsize_t sz;
while (size > 0){
if (size > Whsize_wosize (Max_wosize)){
sz = Whsize_wosize (Max_wosize);
}else{
sz = size;
}
*(header_t *)p = Make_header (Wosize_whsize (sz), 0, color);
if (do_merge) nf_merge_block (Val_hp (p), NULL);
size -= sz;
p += sz;
}
}
/******************** first-fit allocation policy *********************/
#define FLP_MAX 1000
static value flp [FLP_MAX];
static int flp_size = 0;
static value beyond = Val_NULL;
/* The sentinel can be located anywhere in memory, but it must not be
adjacent to any heap object. */
static struct {
value filler1; /* Make sure the sentinel is never adjacent to any block. */
header_t h;
value first_field;
value filler2; /* Make sure the sentinel is never adjacent to any block. */
} ff_sentinel = {0, Make_header (0, 0, Caml_blue), Val_NULL, 0};
#define Ff_head (Val_bp (&(ff_sentinel.first_field)))
static value ff_last = Val_NULL; /* Last block in the list. Only valid
just after [ff_allocate] returns NULL. */
#if defined (DEBUG) || FREELIST_DEBUG
static void ff_check (void)
{
value cur;
int flp_found = 0, merge_found = 0;
uintnat size_found = 0;
int sz = 0;
cur = Next_small (Ff_head);
while (cur != Val_NULL){
size_found += Whsize_bp (cur);
CAMLassert (Is_in_heap (cur));
if (Wosize_bp (cur) > sz){
sz = Wosize_bp (cur);
if (flp_found < flp_size){
CAMLassert (Next_small (flp[flp_found]) == cur);
++ flp_found;
}else{
CAMLassert (beyond == Val_NULL
|| Bp_val (cur) >= Bp_val (Next_small (beyond)));
}
}
if (cur == caml_fl_merge) merge_found = 1;
cur = Next_small (cur);
}
CAMLassert (flp_found == flp_size);
CAMLassert (merge_found || caml_fl_merge == Ff_head);
CAMLassert (size_found == caml_fl_cur_wsz);
}
#endif /* DEBUG || FREELIST_DEBUG */
/* [ff_allocate_block] is called by [ff_allocate]. Given a suitable free
block and the requested size, it allocates a new block from the free
block. There are three cases:
0. The free block has the requested size. Detach the block from the
free-list and return it.
1. The free block is 1 word longer than the requested size. Detach
the block from the free list. The remaining word cannot be linked:
turn it into an empty block (header only), and return the rest.
2. The free block is large enough. Split it in two and return the right
block.
In all cases, the allocated block is right-justified in the free block:
it is located in the high-address words of the free block, so that
the linking of the free-list does not change in case 2.
*/
static header_t *ff_allocate_block (mlsize_t wh_sz, int flpi, value prev,
value cur)
{
header_t h = Hd_bp (cur);
CAMLassert (Whsize_hd (h) >= wh_sz);
if (Wosize_hd (h) < wh_sz + 1){ /* Cases 0 and 1. */
caml_fl_cur_wsz -= Whsize_hd (h);
Next_small (prev) = Next_small (cur);
CAMLassert (Is_in_heap (Next_small (prev))
|| Next_small (prev) == Val_NULL);
if (caml_fl_merge == cur) caml_fl_merge = prev;
#ifdef DEBUG
ff_last = Val_NULL;
#endif
/* In case 1, the following creates the empty block correctly.
In case 0, it gives an invalid header to the block. The function
calling [ff_allocate] will overwrite it. */
Hd_op (cur) = Make_header (0, 0, Caml_white);
if (flpi + 1 < flp_size && flp[flpi + 1] == cur){
flp[flpi + 1] = prev;
}else if (flpi == flp_size - 1){
beyond = (prev == Ff_head) ? Val_NULL : prev;
-- flp_size;
}
}else{ /* Case 2. */
caml_fl_cur_wsz -= wh_sz;
Hd_op (cur) = Make_header (Wosize_hd (h) - wh_sz, 0, Caml_blue);
}
return (header_t *) &Field (cur, Wosize_hd (h) - wh_sz);
}
static header_t *ff_allocate (mlsize_t wo_sz)
{
value cur = Val_NULL, prev;
header_t *result;
int i;
mlsize_t sz, prevsz;
CAMLassert (sizeof (char *) == sizeof (value));
CAMLassert (wo_sz >= 1);
/* Search in the flp array. */
for (i = 0; i < flp_size; i++){
sz = Wosize_bp (Next_small (flp[i]));
if (sz >= wo_sz){
#if FREELIST_DEBUG
if (i > 5) fprintf (stderr, "FLP: found at %d size=%d\n", i, wo_sz);
#endif
result = ff_allocate_block (Whsize_wosize (wo_sz), i, flp[i],
Next_small (flp[i]));
goto update_flp;
}
}
/* Extend the flp array. */
if (flp_size == 0){
prev = Ff_head;
prevsz = 0;
}else{
prev = Next_small (flp[flp_size - 1]);
prevsz = Wosize_bp (prev);
if (beyond != Val_NULL) prev = beyond;
}
while (flp_size < FLP_MAX){
cur = Next_small (prev);
if (cur == Val_NULL){
ff_last = prev;
beyond = (prev == Ff_head) ? Val_NULL : prev;
return NULL;
}else{
sz = Wosize_bp (cur);
if (sz > prevsz){
flp[flp_size] = prev;
++ flp_size;
if (sz >= wo_sz){
beyond = cur;
i = flp_size - 1;
#if FREELIST_DEBUG
if (flp_size > 5){
fprintf (stderr, "FLP: extended to %d\n", flp_size);
}
#endif
result = ff_allocate_block (Whsize_wosize (wo_sz), flp_size - 1,
prev, cur);
goto update_flp;
}
prevsz = sz;
}
}
prev = cur;
}
beyond = cur;
/* The flp table is full. Do a slow first-fit search. */
#if FREELIST_DEBUG
fprintf (stderr, "FLP: table is full -- slow first-fit\n");
#endif
if (beyond != Val_NULL){
prev = beyond;
}else{
prev = flp[flp_size - 1];
}
prevsz = Wosize_bp (Next_small (flp[FLP_MAX-1]));
CAMLassert (prevsz < wo_sz);
cur = Next_small (prev);
while (cur != Val_NULL){
CAMLassert (Is_in_heap (cur));
sz = Wosize_bp (cur);
if (sz < prevsz){
beyond = cur;
}else if (sz >= wo_sz){
return ff_allocate_block (Whsize_wosize (wo_sz), flp_size, prev, cur);
}
prev = cur;
cur = Next_small (prev);
}
ff_last = prev;
return NULL;
update_flp: /* (i, sz) */
/* The block at [i] was removed or reduced. Update the table. */
CAMLassert (0 <= i && i < flp_size + 1);
if (i < flp_size){
if (i > 0){
prevsz = Wosize_bp (Next_small (flp[i-1]));
}else{
prevsz = 0;
}
if (i == flp_size - 1){
if (Wosize_bp (Next_small (flp[i])) <= prevsz){
beyond = Next_small (flp[i]);
-- flp_size;
}else{
beyond = Val_NULL;
}
}else{
value buf [FLP_MAX];
int j = 0;
mlsize_t oldsz = sz;
prev = flp[i];
while (prev != flp[i+1] && j < FLP_MAX - i){
cur = Next_small (prev);
sz = Wosize_bp (cur);
if (sz > prevsz){
buf[j++] = prev;
prevsz = sz;
if (sz >= oldsz){
CAMLassert (sz == oldsz);
break;
}
}
prev = cur;
}
#if FREELIST_DEBUG
if (j > 2) fprintf (stderr, "FLP: update; buf size = %d\n", j);
#endif
if (FLP_MAX >= flp_size + j - 1){
if (j != 1){
memmove (&flp[i+j], &flp[i+1], sizeof (value) * (flp_size-i-1));
}
if (j > 0) memmove (&flp[i], &buf[0], sizeof (value) * j);
flp_size += j - 1;
}else{
if (FLP_MAX > i + j){
if (j != 1){
memmove (&flp[i+j], &flp[i+1], sizeof (value) * (FLP_MAX-i-j));
}
if (j > 0) memmove (&flp[i], &buf[0], sizeof (value) * j);
}else{
if (i != FLP_MAX){
memmove (&flp[i], &buf[0], sizeof (value) * (FLP_MAX - i));
}
}
flp_size = FLP_MAX - 1;
beyond = Next_small (flp[FLP_MAX - 1]);
}
}
}
return result;
}
/* Location of the last fragment seen by the sweeping code.
This is a pointer to the first word after the fragment, which is
the header of the next block.
Note that [ff_last_fragment] doesn't point to the fragment itself,
but to the block after it.
*/
static header_t *ff_last_fragment;
static void ff_init_merge (void)
{
CAML_EV_ALLOC_FLUSH();
ff_last_fragment = NULL;
caml_fl_merge = Ff_head;
#ifdef DEBUG
ff_check ();
#endif
}
static void ff_truncate_flp (value changed)
{
if (changed == Ff_head){
flp_size = 0;
beyond = Val_NULL;
}else{
while (flp_size > 0 &&
Bp_val (Next_small (flp[flp_size - 1])) >= Bp_val (changed))
-- flp_size;
if (Bp_val (beyond) >= Bp_val (changed)) beyond = Val_NULL;
}
}
static void ff_init (void)
{
Next_small (Ff_head) = Val_NULL;
ff_truncate_flp (Ff_head);
caml_fl_cur_wsz = 0;
}
static void ff_reset (void)
{
ff_init ();
}
/* Note: the [limit] parameter is unused because we merge blocks one by one. */
static header_t *ff_merge_block (value bp, char *limit)
{
value prev, cur, adj;
header_t hd = Hd_val (bp);
mlsize_t prev_wosz;
caml_fl_cur_wsz += Whsize_hd (hd);
/* [merge_block] is now responsible for calling the finalization function. */
if (Tag_hd (hd) == Custom_tag){
void (*final_fun)(value) = Custom_ops_val(bp)->finalize;
if (final_fun != NULL) final_fun(bp);
}
#ifdef DEBUG
caml_set_fields (bp, 0, Debug_free_major);
#endif
prev = caml_fl_merge;
cur = Next_small (prev);
/* The sweep code makes sure that this is the right place to insert
this block: */
CAMLassert (Bp_val (prev) < Bp_val (bp) || prev == Ff_head);
CAMLassert (Bp_val (cur) > Bp_val (bp) || cur == Val_NULL);
ff_truncate_flp (prev);
/* If [ff_last_fragment] and [bp] are adjacent, merge them. */
if (ff_last_fragment == Hp_bp (bp)){
mlsize_t bp_whsz = Whsize_val (bp);
if (bp_whsz <= Max_wosize){
hd = Make_header (bp_whsz, 0, Caml_white);
bp = (value) ff_last_fragment;
Hd_val (bp) = hd;
caml_fl_cur_wsz += Whsize_wosize (0);
}
}
/* If [bp] and [cur] are adjacent, remove [cur] from the free-list
and merge them. */
adj = Next_in_mem (bp);
if (adj == cur){
value next_cur = Next_small (cur);
mlsize_t cur_whsz = Whsize_val (cur);
if (Wosize_hd (hd) + cur_whsz <= Max_wosize){
Next_small (prev) = next_cur;
hd = Make_header (Wosize_hd (hd) + cur_whsz, 0, Caml_blue);
Hd_val (bp) = hd;
adj = Next_in_mem (bp);
#ifdef DEBUG
ff_last = Val_NULL;
Next_small (cur) = (value) Debug_free_major;
Hd_val (cur) = Debug_free_major;
#endif
cur = next_cur;
}
}
/* If [prev] and [bp] are adjacent merge them, else insert [bp] into
the free-list if it is big enough. */
prev_wosz = Wosize_val (prev);
if (Next_in_mem (prev) == bp && prev_wosz + Whsize_hd (hd) < Max_wosize){
Hd_val (prev) = Make_header (prev_wosz + Whsize_hd (hd), 0, Caml_blue);
#ifdef DEBUG
Hd_val (bp) = Debug_free_major;
#endif
CAMLassert (caml_fl_merge == prev);
}else if (Wosize_hd (hd) != 0){
Hd_val (bp) = Bluehd_hd (hd);
Next_small (bp) = cur;
Next_small (prev) = bp;
caml_fl_merge = bp;
}else{
/* This is a fragment. Leave it in white but remember it for eventual
merging with the next block. */
ff_last_fragment = (header_t *) bp;
caml_fl_cur_wsz -= Whsize_wosize (0);
}
return Hp_val (adj);
}
/* This is a heap extension. We have to insert it in the right place
in the free-list.
[ff_add_blocks] can only be called right after a call to
[ff_allocate] that returned Val_NULL.
Most of the heap extensions are expected to be at the end of the
free list. (This depends on the implementation of [malloc].)
[bp] must point to a list of blocks chained by their field 0,
terminated by Val_NULL, and field 1 of the first block must point to
the last block.
*/
static void ff_add_blocks (value bp)
{
value cur = bp;
CAMLassert (ff_last != Val_NULL);
CAMLassert (Next_small (ff_last) == Val_NULL);
do {
caml_fl_cur_wsz += Whsize_bp (cur);
cur = Field(cur, 0);
} while (cur != Val_NULL);
if (Bp_val (bp) > Bp_val (ff_last)){
Next_small (ff_last) = bp;
if (ff_last == caml_fl_merge && (char *) bp < caml_gc_sweep_hp){
caml_fl_merge = Field (bp, 1);
}
if (flp_size < FLP_MAX){
flp [flp_size++] = ff_last;
}
}else{
value prev;
prev = Ff_head;
cur = Next_small (prev);
while (cur != Val_NULL && Bp_val (cur) < Bp_val (bp)){
CAMLassert (Bp_val (prev) < Bp_val (bp) || prev == Ff_head);
/* XXX TODO: extend flp on the fly */
prev = cur;
cur = Next_small (prev);
}
CAMLassert (Bp_val (prev) < Bp_val (bp) || prev == Ff_head);
CAMLassert (Bp_val (cur) > Bp_val (bp) || cur == Val_NULL);
Next_small (Field (bp, 1)) = cur;
Next_small (prev) = bp;
/* When inserting blocks between [caml_fl_merge] and [caml_gc_sweep_hp],
we must advance [caml_fl_merge] to the new block, so that [caml_fl_merge]
is always the last free-list block before [caml_gc_sweep_hp]. */
if (prev == caml_fl_merge && (char *) bp < caml_gc_sweep_hp){
caml_fl_merge = Field (bp, 1);
}
ff_truncate_flp (bp);
}
}
static void ff_make_free_blocks
(value *p, mlsize_t size, int do_merge, int color)
{
mlsize_t sz;
while (size > 0){
if (size > Whsize_wosize (Max_wosize)){
sz = Whsize_wosize (Max_wosize);
}else{
sz = size;
}
*(header_t *)p = Make_header (Wosize_whsize (sz), 0, color);
if (do_merge) ff_merge_block (Val_hp (p), NULL);
size -= sz;
p += sz;
}
}
/********************* best-fit allocation policy *********************/
/* quick-fit + FIFO-ordered best fit (Wilson's nomenclature)
We use Standish's data structure (a tree of doubly-linked lists)
with a splay tree (Sleator & Tarjan).
*/
/* [BF_NUM_SMALL] must be at least 4 for this code to work
and at least 5 for good performance on typical OCaml programs.
For portability reasons, BF_NUM_SMALL cannot be more than 32.
*/
#define BF_NUM_SMALL 16
/* Note that indexing into [bf_small_fl] starts at 1, so the first entry
in this array is unused.
*/
static struct {
value free;
value *merge;
} bf_small_fl [BF_NUM_SMALL + 1];
static int bf_small_map = 0;
/* Small free blocks have only one pointer to the next block.
Large free blocks have 5 fields:
tree fields:
- isnode flag
- left child
- right child
list fields:
- next
- prev
*/
typedef struct large_free_block {
int isnode;
struct large_free_block *left;
struct large_free_block *right;
struct large_free_block *prev;
struct large_free_block *next;
} large_free_block;
Caml_inline mlsize_t bf_large_wosize (struct large_free_block *n) {
return Wosize_val((value)(n));
}
static struct large_free_block *bf_large_tree;
static struct large_free_block *bf_large_least;
/* [bf_large_least] is either NULL or a pointer to the smallest (leftmost)
block in the tree. In this latter case, the block must be alone in its
doubly-linked list (i.e. have [isnode] true and [prev] and [next]
both pointing back to this block)
*/
/* Auxiliary functions for bitmap */
/* Find first (i.e. least significant) bit set in a word. */
#ifdef HAS_FFS
#include <strings.h>
#elif defined(HAS_BITSCANFORWARD)
#include <intrin.h>
Caml_inline int ffs (int x)
{
unsigned long index;
unsigned char result;
result = _BitScanForward (&index, (unsigned long) x);
return result ? (int) index + 1 : 0;
}
#else
Caml_inline int ffs (int x)
{
/* adapted from Hacker's Delight */
int bnz, b0, b1, b2, b3, b4;
CAMLassert ((x & 0xFFFFFFFF) == x);
x = x & -x;
bnz = x != 0;
b4 = !!(x & 0xFFFF0000) << 4;
b3 = !!(x & 0xFF00FF00) << 3;
b2 = !!(x & 0xF0F0F0F0) << 2;
b1 = !!(x & 0xCCCCCCCC) << 1;
b0 = !!(x & 0xAAAAAAAA);
return bnz + b0 + b1 + b2 + b3 + b4;
}
#endif /* HAS_FFS or HAS_BITSCANFORWARD */
/* Indexing starts at 1 because that's the minimum block size. */
Caml_inline void set_map (int index)
{
bf_small_map |= (1 << (index - 1));
}
Caml_inline void unset_map (int index)
{
bf_small_map &= ~(1 << (index - 1));
}
/* debug functions for checking the data structures */
#if defined (DEBUG) || FREELIST_DEBUG
static mlsize_t bf_check_cur_size = 0;
static asize_t bf_check_subtree (large_free_block *p)
{
mlsize_t wosz;
large_free_block *cur, *next;
asize_t total_size = 0;
if (p == NULL) return 0;
wosz = bf_large_wosize(p);
CAMLassert (p->isnode == 1);
total_size += bf_check_subtree (p->left);
CAMLassert (wosz > BF_NUM_SMALL);
CAMLassert (wosz > bf_check_cur_size);
bf_check_cur_size = wosz;
cur = p;
while (1){
CAMLassert (bf_large_wosize (cur) == wosz);
CAMLassert (Color_val ((value) cur) == Caml_blue);
CAMLassert ((cur == p && cur->isnode == 1) || cur->isnode == 0);
total_size += Whsize_wosize (wosz);
next = cur->next;
CAMLassert (next->prev == cur);
if (next == p) break;
cur = next;
}
total_size += bf_check_subtree (p->right);
return total_size;
}
static void bf_check (void)
{
mlsize_t i;
asize_t total_size = 0;
int map = 0;
/* check free lists */
CAMLassert (BF_NUM_SMALL <= 8 * sizeof (int));
for (i = 1; i <= BF_NUM_SMALL; i++){
value b;
int col = 0;
int merge_found = 0;
if (bf_small_fl[i].merge == &bf_small_fl[i].free){
merge_found = 1;
}else{
CAMLassert (caml_gc_phase != Phase_sweep
|| caml_fl_merge == Val_NULL
|| bf_small_fl[i].merge < &Next_small(caml_fl_merge));
}
CAMLassert (*bf_small_fl[i].merge == Val_NULL
|| Color_val (*bf_small_fl[i].merge) == Caml_blue);
if (bf_small_fl[i].free != Val_NULL) map |= 1 << (i-1);
for (b = bf_small_fl[i].free; b != Val_NULL; b = Next_small (b)){
if (bf_small_fl[i].merge == &Next_small (b)) merge_found = 1;
CAMLassert (Wosize_val (b) == i);
total_size += Whsize_wosize (i);
if (Color_val (b) == Caml_blue){
col = 1;
CAMLassert (Next_small (b) == Val_NULL
|| Bp_val (Next_small (b)) > Bp_val (b));
}else{
CAMLassert (col == 0);
CAMLassert (Color_val (b) == Caml_white);
}
}
if (caml_gc_phase == Phase_sweep) CAMLassert (merge_found);
}
CAMLassert (map == bf_small_map);
/* check [caml_fl_merge] */
CAMLassert (caml_gc_phase != Phase_sweep
|| caml_fl_merge == Val_NULL
|| Hp_val (caml_fl_merge) < (header_t *) caml_gc_sweep_hp);
/* check the tree */
bf_check_cur_size = 0;
total_size += bf_check_subtree (bf_large_tree);
/* check the total free set size */
CAMLassert (total_size == caml_fl_cur_wsz);
/* check the smallest-block pointer */
if (bf_large_least != NULL){
large_free_block *x = bf_large_tree;
while (x->left != NULL) x = x->left;
CAMLassert (x == bf_large_least);
CAMLassert (x->isnode == 1);
CAMLassert (x->prev == x);
CAMLassert (x->next == x);
}
}
#endif /* DEBUG || FREELIST_DEBUG */
#if FREELIST_DEBUG
#define FREELIST_DEBUG_bf_check() bf_check ()
#else
#define FREELIST_DEBUG_bf_check()
#endif