430 lines
14 KiB
C
430 lines
14 KiB
C
/***********************************************************************/
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/* */
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/* Objective Caml */
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/* */
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/* Damien Doligez, projet Para, INRIA Rocquencourt */
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/* */
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/* Copyright 1996 Institut National de Recherche en Informatique et */
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/* en Automatique. All rights reserved. This file is distributed */
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/* under the terms of the GNU Library General Public License, with */
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/* the special exception on linking described in file ../LICENSE. */
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/* */
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/***********************************************************************/
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/* $Id$ */
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#include <limits.h>
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#include "compact.h"
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#include "custom.h"
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#include "config.h"
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#include "fail.h"
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#include "finalise.h"
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#include "freelist.h"
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#include "gc.h"
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#include "gc_ctrl.h"
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#include "major_gc.h"
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#include "misc.h"
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#include "mlvalues.h"
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#include "roots.h"
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#include "weak.h"
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unsigned long percent_free;
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long major_heap_increment;
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char *heap_start, *heap_end;
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page_table_entry *page_table;
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asize_t page_low, page_high;
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char *gc_sweep_hp;
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int gc_phase; /* always Phase_mark, Phase_sweep, or Phase_idle */
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static value *gray_vals;
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value *gray_vals_cur, *gray_vals_end;
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static asize_t gray_vals_size;
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static int heap_is_pure; /* The heap is pure if the only gray objects
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below [markhp] are also in [gray_vals]. */
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unsigned long allocated_words;
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double extra_heap_memory;
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extern char *fl_merge; /* Defined in freelist.c. */
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static char *markhp, *chunk, *limit;
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static int gc_subphase; /* Subphase_main, Subphase_weak, Subphase_final */
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#define Subphase_main 10
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#define Subphase_weak 11
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#define Subphase_final 12
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static value *weak_prev;
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static void realloc_gray_vals (void)
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{
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value *new;
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Assert (gray_vals_cur == gray_vals_end);
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if (gray_vals_size < stat_heap_size / 128){
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gc_message (0x08, "Growing gray_vals to %luk bytes\n",
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(long) gray_vals_size * sizeof (value) / 512);
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new = (value *) realloc ((char *) gray_vals,
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2 * gray_vals_size * sizeof (value));
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if (new == NULL){
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gc_message (0x08, "No room for growing gray_vals\n", 0);
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gray_vals_cur = gray_vals;
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heap_is_pure = 0;
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}else{
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gray_vals = new;
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gray_vals_cur = gray_vals + gray_vals_size;
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gray_vals_size *= 2;
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gray_vals_end = gray_vals + gray_vals_size;
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}
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}else{
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gray_vals_cur = gray_vals + gray_vals_size / 2;
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heap_is_pure = 0;
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}
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}
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void darken (value v, value *p /* not used */)
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{
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if (Is_block (v) && Is_in_heap (v)) {
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if (Tag_val(v) == Infix_tag) v -= Infix_offset_val(v);
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if (Is_white_val (v)){
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Hd_val (v) = Grayhd_hd (Hd_val (v));
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*gray_vals_cur++ = v;
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if (gray_vals_cur >= gray_vals_end) realloc_gray_vals ();
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}
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}
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}
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static void start_cycle (void)
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{
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Assert (gc_phase == Phase_idle);
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Assert (gray_vals_cur == gray_vals);
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gc_message (0x01, "Starting new major GC cycle\n", 0);
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darken_all_roots();
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gc_phase = Phase_mark;
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gc_subphase = Subphase_main;
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markhp = NULL;
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#ifdef DEBUG
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heap_check ();
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#endif
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}
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static void mark_slice (long work)
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{
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value *gray_vals_ptr; /* Local copy of gray_vals_cur */
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value v, child;
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header_t hd;
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mlsize_t size, i;
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gc_message (0x40, "Marking %ld words\n", work);
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gray_vals_ptr = gray_vals_cur;
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while (work > 0){
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if (gray_vals_ptr > gray_vals){
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v = *--gray_vals_ptr;
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hd = Hd_val(v);
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Assert (Is_gray_hd (hd));
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Hd_val (v) = Blackhd_hd (hd);
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size = Wosize_hd(hd);
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if (Tag_hd (hd) < No_scan_tag){
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for (i = 0; i < size; i++){
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child = Field (v, i);
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mark_again:
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if (Is_block (child) && Is_in_heap (child)) {
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hd = Hd_val(child);
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if (Tag_hd (hd) == Forward_tag){
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child = Forward_val (child);
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Field (v, i) = child;
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goto mark_again;
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}
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if (Tag_hd(hd) == Infix_tag) {
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child -= Infix_offset_val(child);
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hd = Hd_val(child);
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}
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if (Is_white_hd (hd)){
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Hd_val (child) = Grayhd_hd (hd);
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*gray_vals_ptr++ = child;
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if (gray_vals_ptr >= gray_vals_end) {
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gray_vals_cur = gray_vals_ptr;
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realloc_gray_vals ();
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gray_vals_ptr = gray_vals_cur;
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}
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}
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}
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}
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}
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work -= Whsize_wosize(size);
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}else if (markhp != NULL){
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if (markhp == limit){
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chunk = Chunk_next (chunk);
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if (chunk == NULL){
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markhp = NULL;
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}else{
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markhp = chunk;
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limit = chunk + Chunk_size (chunk);
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}
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}else{
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if (Is_gray_val (Val_hp (markhp))){
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Assert (gray_vals_ptr == gray_vals);
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*gray_vals_ptr++ = Val_hp (markhp);
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}
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markhp += Bhsize_hp (markhp);
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}
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}else if (!heap_is_pure){
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heap_is_pure = 1;
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chunk = heap_start;
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markhp = chunk;
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limit = chunk + Chunk_size (chunk);
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}else if (gc_subphase == Subphase_main){
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/* The main marking phase is over. Start removing weak pointers to
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dead values. */
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gc_subphase = Subphase_weak;
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weak_prev = &weak_list_head;
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}else if (gc_subphase == Subphase_weak){
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value cur, curfield;
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mlsize_t sz, i;
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header_t hd;
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cur = *weak_prev;
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if (cur != (value) NULL){
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hd = Hd_val (cur);
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if (Color_hd (hd) == Caml_white){
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/* The whole array is dead, remove it from the list. */
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*weak_prev = Field (cur, 0);
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}else{
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sz = Wosize_hd (hd);
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for (i = 1; i < sz; i++){
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curfield = Field (cur, i);
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weak_again:
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if (curfield != 0 && Is_block (curfield) && Is_in_heap (curfield)
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&& Is_white_val (curfield)){
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if (Tag_val (curfield) == Forward_tag){
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curfield = Forward_val (curfield);
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Field (cur, i) = curfield;
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goto weak_again;
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}
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Field (cur, i) = 0;
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}
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}
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weak_prev = &Field (cur, 0);
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}
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work -= Whsize_hd (hd);
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}else{
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/* Subphase_weak is done. Handle finalised values. */
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gray_vals_cur = gray_vals_ptr;
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final_update ();
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gray_vals_ptr = gray_vals_cur;
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gc_subphase = Subphase_final;
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}
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}else{
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Assert (gc_subphase == Subphase_final);
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/* Initialise the sweep phase. */
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gray_vals_cur = gray_vals_ptr;
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gc_sweep_hp = heap_start;
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fl_init_merge ();
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gc_phase = Phase_sweep;
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chunk = heap_start;
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gc_sweep_hp = chunk;
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limit = chunk + Chunk_size (chunk);
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work = 0;
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}
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}
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gray_vals_cur = gray_vals_ptr;
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}
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static void sweep_slice (long work)
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{
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char *hp;
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header_t hd;
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gc_message (0x40, "Sweeping %ld words\n", work);
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while (work > 0){
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if (gc_sweep_hp < limit){
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hp = gc_sweep_hp;
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hd = Hd_hp (hp);
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work -= Whsize_hd (hd);
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gc_sweep_hp += Bhsize_hd (hd);
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switch (Color_hd (hd)){
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case Caml_white:
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if (Tag_hd (hd) == Custom_tag){
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void (*final_fun)(value) = Custom_ops_val(Val_hp(hp))->finalize;
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if (final_fun != NULL) final_fun(Val_hp(hp));
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}
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gc_sweep_hp = fl_merge_block (Bp_hp (hp));
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break;
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case Caml_blue:
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/* Only the blocks of the free-list are blue. See [freelist.c]. */
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fl_merge = Bp_hp (hp);
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break;
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default: /* gray or black */
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Assert (Color_hd (hd) == Caml_black);
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Hd_hp (hp) = Whitehd_hd (hd);
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break;
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}
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Assert (gc_sweep_hp <= limit);
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}else{
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chunk = Chunk_next (chunk);
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if (chunk == NULL){
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/* Sweeping is done. */
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++ stat_major_collections;
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work = 0;
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gc_phase = Phase_idle;
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}else{
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gc_sweep_hp = chunk;
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limit = chunk + Chunk_size (chunk);
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}
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}
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}
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}
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/* The main entry point for the GC. Called after each minor GC.
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[howmuch] is the amount of work to do, 0 to let the GC compute it.
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Return the computed amount of work to do.
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*/
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long major_collection_slice (long howmuch)
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{
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double p;
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long computed_work;
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/*
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Free memory at the start of the GC cycle (garbage + free list) (assumed):
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FM = stat_heap_size * percent_free / (100 + percent_free)
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Garbage at the start of the GC cycle:
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G = FM * 2/3
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Proportion of free memory consumed since the previous slice:
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PH = allocated_words / G
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= 3 * allocated_words * (100 + percent_free)
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/ (2 * stat_heap_size * percent_free)
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Proportion of extra-heap memory consumed since the previous slice:
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PE = extra_heap_memory
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Proportion of total work to do in this slice:
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P = max (PH, PE)
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Amount of marking work for the GC cycle:
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MW = stat_heap_size * 100 / (100 + percent_free)
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Amount of sweeping work for the GC cycle:
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SW = stat_heap_size
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Amount of marking work for this slice:
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MS = P * MW
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MS = P * stat_heap_size * 100 / (100 + percent_free)
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Amount of sweeping work for this slice:
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SS = P * SW
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SS = P * stat_heap_size
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This slice will either mark 2*MS words or sweep 2*SS words.
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*/
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#define Margin 100 /* Make it a little faster to be on the safe side. */
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if (gc_phase == Phase_idle) start_cycle ();
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p = 1.5 * allocated_words * (100 + percent_free)
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/ stat_heap_size / percent_free;
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if (p < extra_heap_memory) p = extra_heap_memory;
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gc_message (0x40, "allocated_words = %lu\n", allocated_words);
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gc_message (0x40, "extra_heap_memory = %luu\n",
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(unsigned long) (extra_heap_memory * 1000000));
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gc_message (0x40, "amount of work to do = %luu\n",
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(unsigned long) (p * 1000000));
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if (gc_phase == Phase_mark){
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computed_work = (long) (p * stat_heap_size * 100 / (100+percent_free));
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}else{
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computed_work = (long) (p * stat_heap_size);
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}
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computed_work += Margin;
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gc_message (0x40, "ordered work = %ld words\n", howmuch);
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gc_message (0x40, "computed work = %ld words\n", computed_work);
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if (howmuch == 0) howmuch = computed_work;
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if (gc_phase == Phase_mark){
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mark_slice (howmuch);
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gc_message (0x02, "!", 0);
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}else{
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Assert (gc_phase == Phase_sweep);
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sweep_slice (howmuch);
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gc_message (0x02, "$", 0);
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}
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if (gc_phase == Phase_idle) compact_heap_maybe ();
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stat_major_words += allocated_words;
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allocated_words = 0;
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extra_heap_memory = 0.0;
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return computed_work;
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}
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/* The minor heap must be empty when this function is called;
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the minor heap is empty when this function returns.
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*/
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/* This does not call compact_heap_maybe because the estimations of
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free and live memory are only valid for a cycle done incrementally.
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Besides, this function is called by compact_heap_maybe.
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*/
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void finish_major_cycle (void)
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{
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if (gc_phase == Phase_idle) start_cycle ();
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while (gc_phase == Phase_mark) mark_slice (LONG_MAX);
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Assert (gc_phase == Phase_sweep);
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while (gc_phase == Phase_sweep) sweep_slice (LONG_MAX);
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Assert (gc_phase == Phase_idle);
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stat_major_words += allocated_words;
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allocated_words = 0;
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}
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asize_t round_heap_chunk_size (asize_t request)
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{ Assert (major_heap_increment >= Heap_chunk_min);
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if (request < major_heap_increment){
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Assert (major_heap_increment % Page_size == 0);
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return major_heap_increment;
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}else if (request <= Heap_chunk_max){
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return ((request + Page_size - 1) >> Page_log) << Page_log;
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}else{
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raise_out_of_memory ();
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/* not reached */ return 0;
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}
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}
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void init_major_heap (asize_t heap_size)
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{
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asize_t i;
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void *block;
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asize_t page_table_size;
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page_table_entry *page_table_block;
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stat_heap_size = round_heap_chunk_size (heap_size);
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stat_top_heap_size = stat_heap_size;
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Assert (stat_heap_size % Page_size == 0);
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heap_start = aligned_malloc (stat_heap_size + sizeof (heap_chunk_head),
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sizeof (heap_chunk_head), &block);
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if (heap_start == NULL)
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fatal_error ("Fatal error: not enough memory for the initial heap.\n");
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heap_start += sizeof (heap_chunk_head);
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Assert ((unsigned long) heap_start % Page_size == 0);
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Chunk_size (heap_start) = stat_heap_size;
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Chunk_next (heap_start) = NULL;
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Chunk_block (heap_start) = block;
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heap_end = heap_start + stat_heap_size;
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Assert ((unsigned long) heap_end % Page_size == 0);
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page_low = Page (heap_start);
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page_high = Page (heap_end);
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page_table_size = page_high - page_low;
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page_table_block =
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(page_table_entry *) malloc (page_table_size * sizeof (page_table_entry));
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if (page_table_block == NULL){
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fatal_error ("Fatal error: not enough memory for the initial heap.\n");
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}
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page_table = page_table_block - page_low;
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for (i = Page (heap_start); i < Page (heap_end); i++){
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page_table [i] = In_heap;
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}
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Hd_hp (heap_start) = Make_header (Wosize_bhsize(stat_heap_size),0,Caml_blue);
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fl_init_merge ();
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fl_merge_block (Bp_hp (heap_start));
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gc_phase = Phase_idle;
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gray_vals_size = 2048;
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gray_vals = (value *) malloc (gray_vals_size * sizeof (value));
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if (gray_vals == NULL)
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fatal_error ("Fatal error: not enough memory for the initial heap.\n");
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gray_vals_cur = gray_vals;
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gray_vals_end = gray_vals + gray_vals_size;
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heap_is_pure = 1;
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allocated_words = 0;
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extra_heap_memory = 0.0;
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}
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