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ocaml/byterun/major_gc.c

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C
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#include "config.h"
#include "fail.h"
#include "freelist.h"
#include "gc.h"
#include "gc_ctrl.h"
#include "major_gc.h"
#include "misc.h"
#include "mlvalues.h"
#include "roots.h"
#ifdef __STDC__
#include <limits.h>
#else
#ifdef SIXTYFOUR
#define LONG_MAX 0x7FFFFFFFFFFFFFFF
#else
#define LONG_MAX 0x7FFFFFFF
#endif
#endif
int percent_free;
long major_heap_increment;
char *heap_start, *heap_end;
page_table_entry *page_table;
asize_t page_table_size;
char *gc_sweep_hp;
int gc_phase;
static value *gray_vals;
value *gray_vals_cur, *gray_vals_end;
static asize_t gray_vals_size;
static int heap_is_pure; /* The heap is pure if the only gray objects
below [markhp] are also in [gray_vals]. */
unsigned long allocated_words;
unsigned long extra_heap_memory;
extern char *fl_merge; /* Defined in freelist.c. */
static char *markhp, *chunk, *limit;
static void realloc_gray_vals ()
{
value *new;
Assert (gray_vals_cur == gray_vals_end);
if (gray_vals_size < stat_heap_size / 128){
gc_message ("Growing gray_vals to %ldk\n",
(long) gray_vals_size * sizeof (value) / 512);
new = (value *) realloc ((char *) gray_vals,
2 * gray_vals_size * sizeof (value));
if (new == NULL){
gc_message ("No room for growing gray_vals\n", 0);
gray_vals_cur = gray_vals;
heap_is_pure = 0;
}else{
gray_vals = new;
gray_vals_cur = gray_vals + gray_vals_size;
gray_vals_size *= 2;
gray_vals_end = gray_vals + gray_vals_size;
}
}else{
gray_vals_cur = gray_vals + gray_vals_size / 2;
heap_is_pure = 0;
}
}
void darken (v)
value v;
{
if (Is_block (v) && Is_in_heap (v)) {
if (Tag_val(v) == Infix_tag) v -= Infix_offset_val(v);
if (Is_white_val (v)){
Hd_val (v) = Grayhd_hd (Hd_val (v));
*gray_vals_cur++ = v;
if (gray_vals_cur >= gray_vals_end) realloc_gray_vals ();
}
}
}
static void start_cycle ()
{
Assert (gray_vals_cur == gray_vals);
darken_all_roots();
gc_phase = Phase_mark;
markhp = NULL;
}
static void mark_slice (work)
long work;
{
value * gray_vals_ptr; /* Local copy of gray_vals_cur */
value v, child;
header_t hd;
mlsize_t size, i;
gray_vals_ptr = gray_vals_cur;
while (work > 0){
if (gray_vals_ptr > gray_vals){
v = *--gray_vals_ptr;
hd = Hd_val(v);
Assert (Is_gray_hd (hd));
Hd_val (v) = Blackhd_hd (hd);
size = Wosize_hd(hd);
if (Tag_hd (hd) < No_scan_tag){
for (i = 0; i < size; i++){
child = Field (v, i);
if (Is_block (child) && Is_in_heap (child)) {
hd = Hd_val(child);
if (Tag_hd(hd) == Infix_tag) {
child -= Infix_offset_val(child);
hd = Hd_val(child);
}
if (Is_white_hd (hd)){
Hd_val (child) = Grayhd_hd (hd);
*gray_vals_ptr++ = child;
if (gray_vals_ptr >= gray_vals_end) {
gray_vals_cur = gray_vals_ptr;
realloc_gray_vals ();
gray_vals_ptr = gray_vals_cur;
}
}
}
}
}
work -= Whsize_wosize(size);
}else if (markhp != NULL){
if (markhp == limit){
chunk = (((heap_chunk_head *) chunk) [-1]).next;
if (chunk == NULL){
markhp = NULL;
}else{
markhp = chunk;
limit = chunk + (((heap_chunk_head *) chunk) [-1]).size;
}
}else{
if (Is_gray_val (Val_hp (markhp))){
Assert (gray_vals_ptr == gray_vals);
*gray_vals_ptr++ = Val_hp (markhp);
}
markhp += Bhsize_hp (markhp);
}
}else if (!heap_is_pure){
heap_is_pure = 1;
chunk = heap_start;
markhp = chunk;
limit = chunk + (((heap_chunk_head *) chunk) [-1]).size;
}else{
/* Marking is done. */
gray_vals_cur = gray_vals_ptr;
gc_sweep_hp = heap_start;
fl_init_merge ();
gc_phase = Phase_sweep;
chunk = heap_start;
gc_sweep_hp = chunk;
limit = chunk + (((heap_chunk_head *) chunk) [-1]).size;
work = 0;
}
}
gray_vals_cur = gray_vals_ptr;
}
static void sweep_slice (work)
long work;
{
char *hp;
header_t hd;
while (work > 0){
if (gc_sweep_hp < limit){
hp = gc_sweep_hp;
hd = Hd_hp (hp);
work -= Whsize_hd (hd);
gc_sweep_hp += Bhsize_hd (hd);
switch (Color_hd (hd)){
case White:
if (Tag_hd (hd) == Final_tag){
Final_fun (Val_hp (hp)) (Val_hp (hp));
}
gc_sweep_hp = fl_merge_block (Bp_hp (hp));
break;
case Blue:
/* Only the blocks of the free-list are blue. See [freelist.c]. */
fl_merge = Bp_hp (hp);
break;
default: /* Gray or Black */
Assert(Color_hd(hd) == Black);
Hd_hp (hp) = Whitehd_hd (hd);
break;
}
Assert (gc_sweep_hp <= limit);
}else{
chunk = (((heap_chunk_head *) chunk) [-1]).next;
if (chunk == NULL){
/* Sweeping is done. Start the next cycle. */
++ stat_major_collections;
work = 0;
start_cycle ();
}else{
gc_sweep_hp = chunk;
limit = chunk + (((heap_chunk_head *) chunk) [-1]).size;
}
}
}
}
void major_collection_slice ()
{
/* Free memory at the start of the GC cycle:
FM = stat_heap_size * percent_free / 100 * 2/3
Proportion of free memory consumed since the previous slice:
PH = allocated_words / FM
Proportion of extra-heap memory consumed since the previous slice:
PE = extra_heap_memory / stat_heap_size
Proportion of total work to do in this slice:
P = PH + PE
Amount of marking work for the GC cycle:
MW = stat_heap_size * (100 - percent_free) / 100
Amount of sweeping work for the GC cycle:
SW = stat_heap_size
Amount of marking work for this slice:
MS = MW * 2 * P
MS = 2 * (100 - percent_free)
* (allocated_words * 3 / percent_free / 2
+ 100 * extra_heap_memory)
Amount of sweeping work for this slice:
SS = SW * 2 * P
SS = 2 * 100
* (allocated_words * 3 / percent_free / 2
+ 100 * extra_heap_memory)
This slice will either mark MS words or sweep SS words.
*/
#define Margin 100 /* Make it a little faster to be on the safe side. */
if (gc_phase == Phase_mark){
mark_slice (2 * (100 - percent_free)
* (allocated_words * 3 / percent_free / 2
+ 100 * extra_heap_memory)
+ Margin);
gc_message ("!", 0);
}else{
Assert (gc_phase == Phase_sweep);
sweep_slice (200 * (allocated_words * 3 / percent_free / 2
+ 100 * extra_heap_memory)
+ Margin);
gc_message ("$", 0);
}
stat_major_words += allocated_words;
allocated_words = 0;
extra_heap_memory = 0;
}
/* The minor heap must be empty when this function is called. */
void finish_major_cycle ()
{
if (gc_phase == Phase_mark) mark_slice (LONG_MAX);
Assert (gc_phase == Phase_sweep);
sweep_slice (LONG_MAX);
stat_major_words += allocated_words;
allocated_words = 0;
}
asize_t round_heap_chunk_size (request)
asize_t request;
{ Assert (major_heap_increment >= Heap_chunk_min);
if (request < major_heap_increment){
Assert (major_heap_increment % Page_size == 0);
return major_heap_increment;
}else if (request <= Heap_chunk_max){
return ((request + Page_size - 1) >> Page_log) << Page_log;
}else{
raise_out_of_memory ();
}
}
void init_major_heap (heap_size)
asize_t heap_size;
{
asize_t i;
stat_heap_size = round_heap_chunk_size (heap_size);
Assert (stat_heap_size % Page_size == 0);
heap_start = aligned_malloc (stat_heap_size + sizeof (heap_chunk_head),
sizeof (heap_chunk_head));
if (heap_start == NULL)
fatal_error ("Fatal error: not enough memory for the initial heap.\n");
heap_start += sizeof (heap_chunk_head);
Assert ((unsigned long) heap_start % Page_size == 0);
(((heap_chunk_head *) heap_start) [-1]).size = stat_heap_size;
(((heap_chunk_head *) heap_start) [-1]).next = NULL;
heap_end = heap_start + stat_heap_size;
Assert ((unsigned long) heap_end % Page_size == 0);
page_table_size = 4 * stat_heap_size / Page_size;
page_table =
(page_table_entry *) malloc (page_table_size * sizeof(page_table_entry));
if (page_table == NULL){
fatal_error ("Fatal error: not enough memory for the initial heap.\n");
}
for (i = 0; i < page_table_size; i++){
page_table [i] = Not_in_heap;
}
for (i = Page (heap_start); i < Page (heap_end); i++){
page_table [i] = In_heap;
}
Hd_hp (heap_start) = Make_header (Wosize_bhsize (stat_heap_size), 0, Blue);
fl_init_merge ();
fl_merge_block (Bp_hp (heap_start));
/* We start the major GC in the marking phase, just after the roots have been
darkened. (Since there are no roots, we don't have to darken anything.) */
gc_phase = Phase_mark;
gray_vals_size = 2048;
gray_vals = (value *) malloc (gray_vals_size * sizeof (value));
gray_vals_cur = gray_vals;
gray_vals_end = gray_vals + gray_vals_size;
heap_is_pure = 1;
allocated_words = 0;
extra_heap_memory = 0;
}
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