-
Notifications
You must be signed in to change notification settings - Fork 69
/
major_gc.c
1352 lines (1197 loc) · 42.6 KB
/
major_gc.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
/**************************************************************************/
/* */
/* 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
#include <limits.h>
#include <math.h>
#include "caml/compact.h"
#include "caml/custom.h"
#include "caml/config.h"
#include "caml/fail.h"
#include "caml/finalise.h"
#include "caml/freelist.h"
#include "caml/gc.h"
#include "caml/gc_ctrl.h"
#include "caml/major_gc.h"
#include "caml/misc.h"
#include "caml/mlvalues.h"
#include "caml/roots.h"
#include "caml/skiplist.h"
#include "caml/signals.h"
#include "caml/weak.h"
#include "caml/memprof.h"
#include "caml/eventlog.h"
#ifdef _MSC_VER
Caml_inline double fmin(double a, double b) {
return (a < b) ? a : b;
}
#endif
#define MARK_STACK_INIT_SIZE 2048
struct mark_stack {
mark_entry* stack;
uintnat count;
uintnat size;
};
uintnat caml_percent_free;
uintnat caml_major_heap_increment;
CAMLexport char *caml_heap_start;
char *caml_gc_sweep_hp;
int caml_gc_phase; /* always Phase_mark, Pase_clean,
Phase_sweep, or Phase_idle */
uintnat caml_allocated_words;
uintnat caml_dependent_size, caml_dependent_allocated;
double caml_extra_heap_resources;
uintnat caml_fl_wsz_at_phase_change = 0;
extern value caml_fl_merge; /* Defined in freelist.c. */
/* redarken_first_chunk is the first chunk needing redarkening, if NULL no
redarkening required */
static char *redarken_first_chunk = NULL;
static char *sweep_chunk;
static double p_backlog = 0.0; /* backlog for the gc speedup parameter */
int caml_gc_subphase; /* Subphase_{mark_roots,mark_main,mark_final} */
/**
Ephemerons:
During mark phase the list caml_ephe_list_head of ephemerons
is iterated by different pointers that follow the invariants:
caml_ephe_list_head ->* ephes_checked_if_pure ->* ephes_to_check ->* null
| | |
(1) (2) (3)
At the start of mark phase, (1) and (2) are empty.
In mark phase:
- the ephemerons in (1) have a data alive or none
(nb: new ephemerons are added in this part by weak.c)
- the ephemerons in (2) have at least a white key or are white
if ephe_list_pure is true, otherwise they are in an unknown state and
must be checked again.
- the ephemerons in (3) are in an unknown state and must be checked
At the end of mark phase, (3) is empty and ephe_list_pure is true.
The ephemeron in (1) and (2) will be cleaned (white keys and data
replaced by none or the ephemeron is removed from the list if it is white)
in clean phase.
In clean phase:
caml_ephe_list_head ->* ephes_to_check ->* null
| |
(1) (3)
In clean phase, (2) is not used, ephes_to_check is initialized at
caml_ephe_list_head:
- the ephemerons in (1) are clean.
- the ephemerons in (3) should be cleaned or removed if white.
*/
static int ephe_list_pure;
/** The ephemerons is pure if since the start of its iteration
no value have been darkened. */
static value *ephes_checked_if_pure;
static value *ephes_to_check;
int caml_major_window = 1;
double caml_major_ring[Max_major_window] = { 0. };
int caml_major_ring_index = 0;
double caml_major_work_credit = 0.0;
double caml_gc_clock = 0.0;
#ifdef DEBUG
static unsigned long major_gc_counter = 0;
#endif
void (*caml_major_gc_hook)(void) = NULL;
/* This function prunes the mark stack if it's about to overflow. It does so
by building a skiplist of major heap chunks and then iterating through the
mark stack and setting redarken_start/redarken_end on each chunk to indicate
the range that requires redarkening. */
static void mark_stack_prune (struct mark_stack* stk)
{
int entry;
uintnat mark_stack_count = stk->count;
mark_entry* mark_stack = stk->stack;
char* heap_chunk = caml_heap_start;
struct skiplist chunk_sklist = SKIPLIST_STATIC_INITIALIZER;
do {
caml_skiplist_insert(&chunk_sklist, (uintnat)heap_chunk,
(uintnat)(heap_chunk+Chunk_size(heap_chunk)));
heap_chunk = Chunk_next(heap_chunk);
} while( heap_chunk != NULL );
for( entry = 0; entry < mark_stack_count ; entry++ ) {
mark_entry me = mark_stack[entry];
uintnat chunk_addr = 0, chunk_addr_below = 0;
if( caml_skiplist_find_below(&chunk_sklist, (uintnat)me.start,
&chunk_addr, &chunk_addr_below)
&& (uintnat)me.start < chunk_addr_below ) {
heap_chunk_head* ch = Chunk_head(chunk_addr);
if (ch->redarken_first.start > me.start)
ch->redarken_first = me;
if (ch->redarken_end < me.end)
ch->redarken_end = me.end;
if( redarken_first_chunk == NULL
|| redarken_first_chunk > (char*)chunk_addr ) {
redarken_first_chunk = (char*)chunk_addr;
}
}
}
caml_skiplist_empty(&chunk_sklist);
caml_gc_message(0x08, "Mark stack overflow.\n");
stk->count = 0;
}
static void realloc_mark_stack (struct mark_stack* stk)
{
mark_entry* new;
uintnat mark_stack_bsize = stk->size * sizeof(mark_entry);
if ( Wsize_bsize(mark_stack_bsize) < Caml_state->stat_heap_wsz / 64 ) {
caml_gc_message (0x08, "Growing mark stack to %"
ARCH_INTNAT_PRINTF_FORMAT "uk bytes\n",
(intnat) mark_stack_bsize * 2 / 1024);
new = (mark_entry*) caml_stat_resize_noexc ((char*) stk->stack,
2 * mark_stack_bsize);
if (new != NULL) {
stk->stack = new;
stk->size *= 2;
return;
}
}
caml_gc_message (0x08, "No room for growing mark stack. Pruning..\n");
mark_stack_prune(stk);
}
/* This function pushes the provided mark_entry [me] onto the current mark
stack [stk]. It first checks, if the block is small enough, whether there
are any fields we would actually do mark work on. If so then it enqueues
the entry. */
Caml_inline void mark_stack_push(struct mark_stack* stk, value block,
uintnat offset, intnat* work)
{
value v;
int i, block_wsz = Wosize_val(block), end;
mark_entry* me;
CAMLassert(Is_block(block) && Is_in_heap (block)
&& Is_black_val(block));
CAMLassert(Tag_val(block) != Infix_tag);
CAMLassert(Tag_val(block) < No_scan_tag);
#if defined(NO_NAKED_POINTERS) || defined(NAKED_POINTERS_CHECKER)
if (Tag_val(block) == Closure_tag) {
/* Skip the code pointers and integers at beginning of closure;
start scanning at the first word of the environment part. */
/* It might be the case that [mark_stack_push] has been called
while we are traversing a closure block but have not enough
budget to finish the block. In that specific case, we should not
update [m.offset] */
if (offset == 0)
offset = Start_env_closinfo(Closinfo_val(block));
CAMLassert(offset <= Wosize_val(block)
&& offset >= Start_env_closinfo(Closinfo_val(block)));
}
#endif
end = (block_wsz < 8 ? block_wsz : 8);
/* Optimisation to avoid pushing small, unmarkable objects such as [Some 42]
* into the mark stack. */
for (i = offset; i < end; i++) {
v = Field(block, i);
if (Is_block(v) && !Is_young(v))
/* found something to mark */
break;
}
if (i == block_wsz) {
/* nothing left to mark */
if( work != NULL ) {
/* we should take credit for it though */
*work -= Whsize_wosize(block_wsz - offset);
}
return;
}
if( work != NULL ) {
/* take credit for the work we skipped due to the optimisation.
we will take credit for the header later as part of marking. */
*work -= (i - offset);
}
offset = i;
if (stk->count == stk->size)
realloc_mark_stack(stk);
me = &stk->stack[stk->count++];
me->start = Op_val(block) + offset;
me->end = Op_val(block) + Wosize_val(block);
}
#if defined(NAKED_POINTERS_CHECKER) && defined(NATIVE_CODE)
static void is_naked_pointer_safe (value v, value *p);
#endif
void caml_darken (value v, value *p)
{
#ifdef NO_NAKED_POINTERS
if (Is_block(v) && !Is_young (v)) {
#else
if (Is_block(v) && Is_in_heap (v)) {
#endif
header_t h = Hd_val (v);
tag_t t = Tag_hd (h);
if (t == Infix_tag){
v -= Infix_offset_val(v);
h = Hd_val (v);
t = Tag_hd (h);
}
#ifdef NO_NAKED_POINTERS
/* We insist that naked pointers to outside the heap point to things that
look like values with headers coloured black. This is always
strictly necessary because the compactor relies on it. */
CAMLassert (Is_in_heap (v) || Is_black_hd (h));
#endif
CAMLassert (!Is_blue_hd (h));
if (Is_white_hd (h)){
ephe_list_pure = 0;
Hd_val (v) = Blackhd_hd (h);
if (t < No_scan_tag){
mark_stack_push(Caml_state->mark_stack, v, 0, NULL);
}
}
}
#if defined(NAKED_POINTERS_CHECKER) && defined(NATIVE_CODE)
else if (Is_block(v) && !Is_young(v)) {
is_naked_pointer_safe(v, p);
}
#endif
}
/* This function shrinks the mark stack back to the MARK_STACK_INIT_SIZE size
and is called at the end of a GC compaction to avoid a mark stack greater
than 1/32th of the heap. */
void caml_shrink_mark_stack () {
struct mark_stack* stk = Caml_state->mark_stack;
intnat init_stack_bsize = MARK_STACK_INIT_SIZE * sizeof(mark_entry);
mark_entry* shrunk_stack;
caml_gc_message (0x08, "Shrinking mark stack to %"
ARCH_INTNAT_PRINTF_FORMAT "uk bytes\n",
init_stack_bsize);
shrunk_stack = (mark_entry*) caml_stat_resize_noexc ((char*) stk->stack,
init_stack_bsize);
if (shrunk_stack != NULL) {
stk->stack = shrunk_stack;
stk->size = MARK_STACK_INIT_SIZE;
}else{
caml_gc_message (0x08, "Mark stack shrinking failed");
}
}
/* This function adds blocks in the passed heap chunk [heap_chunk] to
the mark stack. It returns 1 when the supplied chunk has no more
range to redarken. It returns 0 if there are still blocks in the
chunk that need redarkening because pushing them onto the stack
would make it grow more than a quarter full. This is to lower the
chance of triggering another overflow, which would be
wasteful. Subsequent calls will continue progress.
*/
static int redarken_chunk(char* heap_chunk, struct mark_stack* stk) {
heap_chunk_head* chunk = Chunk_head(heap_chunk);
mark_entry me = chunk->redarken_first;
header_t* end = (header_t*)chunk->redarken_end;
if (chunk->redarken_end <= me.start) return 1;
while (1) {
header_t* hp;
/* Skip a prefix of fields that need no marking */
CAMLassert(me.start <= me.end && (header_t*)me.end <= end);
while (me.start < me.end &&
(!Is_block(*me.start) || Is_young(*me.start))) {
me.start++;
}
/* Push to the mark stack (if anything's left) */
if (me.start < me.end) {
if (stk->count < stk->size/4) {
stk->stack[stk->count++] = me;
} else {
/* Only fill up a quarter of the mark stack, we can resume later
for more if we need to */
chunk->redarken_first = me;
return 0;
}
}
/* Find the next block that needs to be re-marked */
hp = (header_t*)me.end;
CAMLassert(hp <= end);
while (hp < end) {
value v = Val_hp(hp);
if (Tag_val(v) < No_scan_tag && Is_black_val(v))
break;
hp = (header_t*)(Op_val(v) + Wosize_val(v));
}
if (hp == end)
break;
/* Found a block */
me.start = Op_hp(hp);
me.end = me.start + Wosize_hp(hp);
if (Tag_hp(hp) == Closure_tag) {
me.start += Start_env_closinfo(Closinfo_val(Val_hp(hp)));
}
}
chunk->redarken_first.start =
(value*)(heap_chunk + Chunk_size(heap_chunk));
chunk->redarken_first.end = chunk->redarken_first.start;
chunk->redarken_end = (value*)heap_chunk;
return 1;
}
static void start_cycle (void)
{
CAMLassert (caml_gc_phase == Phase_idle);
CAMLassert (Caml_state->mark_stack->count == 0);
CAMLassert (redarken_first_chunk == NULL);
caml_gc_message (0x01, "Starting new major GC cycle\n");
caml_darken_all_roots_start ();
caml_gc_phase = Phase_mark;
caml_gc_subphase = Subphase_mark_roots;
ephe_list_pure = 1;
ephes_checked_if_pure = &caml_ephe_list_head;
ephes_to_check = &caml_ephe_list_head;
#ifdef DEBUG
++ major_gc_counter;
caml_heap_check ();
#endif
}
static void init_sweep_phase(void)
{
/* Phase_clean is done. */
/* Initialise the sweep phase. */
caml_gc_sweep_hp = caml_heap_start;
caml_fl_init_merge ();
caml_gc_phase = Phase_sweep;
sweep_chunk = caml_heap_start;
caml_gc_sweep_hp = sweep_chunk;
caml_fl_wsz_at_phase_change = caml_fl_cur_wsz;
if (caml_major_gc_hook) (*caml_major_gc_hook)();
}
/* auxiliary function of mark_ephe_aux */
Caml_inline void mark_ephe_darken(struct mark_stack* stk, value v, mlsize_t i,
int in_ephemeron, int *slice_pointers,
intnat *work)
{
value child;
header_t chd;
child = Field (v, i);
#ifdef NO_NAKED_POINTERS
if (Is_block (child) && ! Is_young (child)) {
#else
if (Is_block (child) && Is_in_heap (child)) {
#endif
CAML_EVENTLOG_DO (++ *slice_pointers);
chd = Hd_val (child);
if (Tag_hd (chd) == Forward_tag){
value f = Forward_val (child);
if ((in_ephemeron && Is_long(f)) ||
(Is_block (f)
&& (!Is_in_value_area(f) || Tag_val (f) == Forward_tag
|| Tag_val (f) == Lazy_tag
#ifdef FLAT_FLOAT_ARRAY
|| Tag_val (f) == Double_tag
#endif
))){
/* Do not short-circuit the pointer. */
}else{
/* The variable child is not changed because it must be mark alive */
Field (v, i) = f;
if (Is_block (f) && Is_young (f) && !Is_young (child)){
if(in_ephemeron) {
add_to_ephe_ref_table (Caml_state->ephe_ref_table, v, i);
} else {
add_to_ref_table (Caml_state->ref_table, &Field (v, i));
}
}
}
}
else if (Tag_hd(chd) == Infix_tag) {
child -= Infix_offset_val(child);
chd = Hd_val(child);
}
#ifdef NO_NAKED_POINTERS
/* See [caml_darken] for a description of this assertion. */
CAMLassert (Is_in_heap (child) || Is_black_hd (chd));
#endif
if (Is_white_hd (chd)){
ephe_list_pure = 0;
Hd_val (child) = Blackhd_hd (chd);
if( Tag_hd(chd) < No_scan_tag ) {
mark_stack_push(stk, child, 0, work);
} else {
*work -= Whsize_hd (chd);
}
}
}
#if defined(NAKED_POINTERS_CHECKER) && defined(NATIVE_CODE)
else if (Is_block(child) && ! Is_young(child)) {
is_naked_pointer_safe(child, &Field (v, i));
}
#endif
}
static void mark_ephe_aux (struct mark_stack *stk, intnat *work,
int *slice_pointers)
{
value v, data, key;
header_t hd;
mlsize_t size, i;
v = *ephes_to_check;
hd = Hd_val(v);
CAMLassert(Tag_val (v) == Abstract_tag);
data = Field(v,CAML_EPHE_DATA_OFFSET);
if ( data != caml_ephe_none &&
Is_block (data) &&
#ifdef NO_NAKED_POINTERS
!Is_young(data) &&
#else
Is_in_heap (data) &&
#endif
Is_white_val (data)){
int alive_data = 1;
/* The liveness of the ephemeron is one of the condition */
if (Is_white_hd (hd)) alive_data = 0;
/* The liveness of the keys not caml_ephe_none is the other condition */
size = Wosize_hd (hd);
for (i = CAML_EPHE_FIRST_KEY; alive_data && i < size; i++){
key = Field (v, i);
ephemeron_again:
if (key != caml_ephe_none &&
Is_block (key) &&
#ifdef NO_NAKED_POINTERS
!Is_young(key)
#else
Is_in_heap(key)
#endif
){
if (Tag_val (key) == Forward_tag){
value f = Forward_val (key);
if (Is_long (f) ||
(Is_block (f) &&
(!Is_in_value_area(f) || Tag_val (f) == Forward_tag
|| Tag_val (f) == Lazy_tag
#ifdef FLAT_FLOAT_ARRAY
|| Tag_val (f) == Double_tag
#endif
))){
/* Do not short-circuit the pointer. */
}else{
Field (v, i) = key = f;
goto ephemeron_again;
}
}
if (Is_white_val (key)){
alive_data = 0;
}
}
}
*work -= Whsize_wosize(i);
if (alive_data){
mark_ephe_darken(stk, v, CAML_EPHE_DATA_OFFSET, /*in_ephemeron=*/1,
slice_pointers, work);
} else { /* not triggered move to the next one */
ephes_to_check = &Field(v,CAML_EPHE_LINK_OFFSET);
return;
}
} else { /* a simily weak pointer or an already alive data */
*work -= 1;
}
/* all keys black or data none or black
move the ephemerons from (3) to the end of (1) */
if ( ephes_checked_if_pure == ephes_to_check ) {
/* corner case and optim */
ephes_checked_if_pure = &Field(v,CAML_EPHE_LINK_OFFSET);
ephes_to_check = ephes_checked_if_pure;
} else {
/* - remove v from the list (3) */
*ephes_to_check = Field(v,CAML_EPHE_LINK_OFFSET);
/* - insert it at the end of (1) */
Field(v,CAML_EPHE_LINK_OFFSET) = *ephes_checked_if_pure;
*ephes_checked_if_pure = v;
ephes_checked_if_pure = &Field(v,CAML_EPHE_LINK_OFFSET);
}
}
#define Pb_size (1 << 8)
#define Pb_min 64
#define Pb_mask (Pb_size - 1)
Caml_inline void prefetch_block(value v)
{
/* Prefetch a block so that scanning it later avoids cache misses.
We will access at least the header, but we don't yet know how
many of the fields we will access - the block might be already
marked, not scannable, or very short. The compromise here is to
prefetch the header and the first few fields.
We issue two prefetches, with the second being a few words ahead
of the first. Most of the time, these will land in the same
cacheline, be coalesced by hardware, and so not cost any more
than a single prefetch. Two memory operations are issued only
when the two prefetches land in different cachelines.
In the case where the block is not already in cache, and yet is
already marked, not markable, or extremely short, then we waste
somewhere between 1/8-1/2 of a prefetch operation (in expectation,
depending on alignment, word size, and cache line size), which is
cheap enough to make this worthwhile. */
caml_prefetch(Hp_val(v));
caml_prefetch(&Field(v, 3));
}
Caml_inline uintnat rotate1(uintnat x)
{
return (x << ((sizeof x)*8 - 1)) | (x >> 1);
}
Caml_noinline static intnat do_some_marking
#ifndef CAML_INSTR
(intnat work)
#else
(intnat work, int* pslice_fields, int* pslice_pointers)
#endif
{
uintnat pb_enqueued = 0, pb_dequeued = 0;
int darkened_anything = 0;
value pb[Pb_size];
uintnat min_pb = Pb_min; /* keep pb at least this full */
/* These global values are cached in locals,
so that they can be stored in registers */
struct mark_stack stk = *Caml_state->mark_stack;
uintnat young_start = (uintnat)Val_hp(Caml_state->young_start);
uintnat half_young_len =
((uintnat)Caml_state->young_end - (uintnat)Caml_state->young_start) >> 1;
#define Is_block_and_not_young(v) \
(((intnat)rotate1((uintnat)v - young_start)) >= (intnat)half_young_len)
#ifdef NO_NAKED_POINTERS
#define Is_major_block(v) Is_block_and_not_young(v)
#else
#define Is_major_block(v) (Is_block_and_not_young(v) && Is_in_heap(v))
#endif
#ifdef CAML_INSTR
int slice_fields = 0, slice_pointers = 0;
#endif
while (1) {
value *scan, *obj_end, *scan_end;
intnat scan_len;
if (pb_enqueued > pb_dequeued + min_pb) {
/* Dequeue from prefetch buffer */
value block = pb[(pb_dequeued++) & Pb_mask];
header_t hd = Hd_val(block);
if (Tag_hd(hd) == Infix_tag) {
block -= Infix_offset_val(block);
hd = Hd_val(block);
}
#ifdef NO_NAKED_POINTERS
/* See [caml_darken] for a description of this assertion. */
CAMLassert (Is_in_heap (block) || Is_black_hd (hd));
#endif
CAMLassert(Is_white_hd(hd) || Is_black_hd(hd));
if (!Is_white_hd (hd)) {
/* Already black, nothing to do */
continue;
}
hd = Blackhd_hd (hd);
Hd_val (block) = hd;
darkened_anything = 1;
work--; /* header word */
if (Tag_hd (hd) >= No_scan_tag) {
/* Nothing to scan here */
work -= Wosize_hd (hd);
continue;
}
scan = Op_val(block);
obj_end = scan + Wosize_hd(hd);
if (Tag_hd (hd) == Closure_tag) {
uintnat env_offset = Start_env_closinfo(Closinfo_val(block));
work -= env_offset;
scan += env_offset;
}
} else if (work <= 0 || stk.count == 0) {
if (min_pb > 0) {
/* Dequeue from pb even when close to empty, because
we have nothing else to do */
min_pb = 0;
continue;
} else {
/* Couldn't find work with min_pb == 0, so there's nothing to do */
break;
}
} else {
mark_entry m = stk.stack[--stk.count];
scan = m.start;
obj_end = m.end;
}
scan_len = obj_end - scan;
if (work < scan_len) {
scan_len = work;
if (scan_len < 0) scan_len = 0;
}
work -= scan_len;
scan_end = scan + scan_len;
for (; scan < scan_end; scan++) {
value v = *scan;
#ifdef CAML_INSTR
slice_fields ++;
#endif
if (Is_major_block(v)) {
#ifdef CAML_INSTR
slice_pointers ++;
#endif
if (pb_enqueued == pb_dequeued + Pb_size) {
/* Prefetch buffer is full */
work += scan_end - scan; /* scanning work not done */
break;
}
prefetch_block(v);
pb[(pb_enqueued++) & Pb_mask] = v;
}
#if defined(NAKED_POINTERS_CHECKER) && defined(NATIVE_CODE)
else if (Is_block_and_not_young (v) && !Is_in_heap (v)){
is_naked_pointer_safe (v, scan);
}
#endif
}
if (scan < obj_end) {
/* Didn't finish scanning this object, either because work <= 0,
or the prefetch buffer filled up. Leave the rest on the stack. */
mark_entry m = { scan, obj_end };
caml_prefetch(scan+1);
if (stk.count == stk.size) {
*Caml_state->mark_stack = stk;
realloc_mark_stack(Caml_state->mark_stack);
stk = *Caml_state->mark_stack;
}
CAML_EVENTLOG_DO({
if (work <= 0 && pb_enqueued == pb_dequeued) {
CAML_EV_COUNTER(EV_C_MAJOR_MARK_SLICE_REMAIN, obj_end - scan);
}
});
stk.stack[stk.count++] = m;
/* We may have just discovered more work when we were about to run out.
Reset min_pb so that we try to refill the buffer again. */
min_pb = Pb_min;
}
}
CAMLassert(pb_enqueued == pb_dequeued);
*Caml_state->mark_stack = stk;
if (darkened_anything)
ephe_list_pure = 0;
#ifdef CAML_INSTR
*pslice_fields += slice_fields;
*pslice_pointers += slice_pointers;
#endif
return work;
}
static void mark_slice (intnat work)
{
#ifdef CAML_INSTR
int slice_fields = 0; /** eventlog counters */
#endif /*CAML_INSTR*/
int slice_pointers = 0;
struct mark_stack* stk = Caml_state->mark_stack;
caml_gc_message (0x40, "Marking %"ARCH_INTNAT_PRINTF_FORMAT"d words\n", work);
caml_gc_message (0x40, "Subphase = %d\n", caml_gc_subphase);
while (1){
#ifndef CAML_INSTR
work = do_some_marking(work);
#else
work = do_some_marking(work, &slice_fields, &slice_pointers);
#endif
if (work <= 0)
break;
CAMLassert (stk->count == 0);
if( redarken_first_chunk != NULL ) {
/* There are chunks that need to be redarkened because we
overflowed our mark stack */
if( redarken_chunk(redarken_first_chunk, stk) ) {
redarken_first_chunk = Chunk_next(redarken_first_chunk);
}
} else if (caml_gc_subphase == Subphase_mark_roots) {
CAML_EV_BEGIN(EV_MAJOR_MARK_ROOTS);
work = caml_darken_all_roots_slice (work);
CAML_EV_END(EV_MAJOR_MARK_ROOTS);
if (work > 0){
caml_gc_subphase = Subphase_mark_main;
}
} else if (*ephes_to_check != (value) NULL) {
/* Continue to scan the list of ephe */
mark_ephe_aux(stk,&work,&slice_pointers);
} else if (!ephe_list_pure){
/* We must scan again the list because some value have been darken */
ephe_list_pure = 1;
ephes_to_check = ephes_checked_if_pure;
}else{
switch (caml_gc_subphase){
case Subphase_mark_main: {
/* Subphase_mark_main is done.
Mark finalised values. */
CAML_EV_BEGIN(EV_MAJOR_MARK_MAIN);
caml_final_update_mark_phase ();
/* Complete the marking */
ephes_to_check = ephes_checked_if_pure;
CAML_EV_END(EV_MAJOR_MARK_MAIN);
caml_gc_subphase = Subphase_mark_final;
}
break;
case Subphase_mark_final: {
/** The set of unreachable value will not change anymore for
this cycle. Start clean phase. */
CAML_EV_BEGIN(EV_MAJOR_MARK_FINAL);
caml_gc_phase = Phase_clean;
caml_final_update_clean_phase ();
caml_memprof_update_clean_phase ();
if (caml_ephe_list_head != (value) NULL){
/* Initialise the clean phase. */
ephes_to_check = &caml_ephe_list_head;
} else {
/* Initialise the sweep phase. */
init_sweep_phase();
}
work = 0;
CAML_EV_END(EV_MAJOR_MARK_FINAL);
}
break;
default: CAMLassert (0);
}
}
}
CAML_EV_COUNTER(EV_C_MAJOR_MARK_SLICE_FIELDS, slice_fields);
CAML_EV_COUNTER(EV_C_MAJOR_MARK_SLICE_POINTERS, slice_pointers);
}
/* Clean ephemerons */
static void clean_slice (intnat work)
{
value v;
caml_gc_message (0x40, "Cleaning %"
ARCH_INTNAT_PRINTF_FORMAT "d words\n", work);
while (work > 0){
v = *ephes_to_check;
if (v != (value) NULL){
if (Is_white_val (v)){
/* The whole array is dead, remove it from the list. */
*ephes_to_check = Field (v, CAML_EPHE_LINK_OFFSET);
work -= 1;
}else{
caml_ephe_clean(v);
ephes_to_check = &Field (v, CAML_EPHE_LINK_OFFSET);
work -= Whsize_val (v);
}
}else{ /* End of list reached */
/* Phase_clean is done. */
/* Initialise the sweep phase. */
init_sweep_phase();
work = 0;
}
}
}
static void sweep_slice (intnat work)
{
char *hp, *sweep_hp, *limit;
header_t hd;
caml_gc_message (0x40, "Sweeping %"
ARCH_INTNAT_PRINTF_FORMAT "d words\n", work);
sweep_hp = caml_gc_sweep_hp;
limit = sweep_chunk + Chunk_size(sweep_chunk);
while (work > 0){
if (sweep_hp < limit){
caml_prefetch(sweep_hp + 4000);
hp = sweep_hp;
hd = Hd_hp (hp);
work -= Whsize_hd (hd);
sweep_hp += Bhsize_hd (hd);
switch (Color_hd (hd)){
case Caml_white:
caml_gc_sweep_hp = sweep_hp;
sweep_hp = (char *) caml_fl_merge_block (Val_hp (hp), limit);
break;
case Caml_blue:
/* Only the blocks of the free-list are blue. See [freelist.c]. */
caml_fl_merge = (value) Bp_hp (hp);
break;
default: /* gray or black */
CAMLassert (Color_hd (hd) == Caml_black);
Hd_hp (hp) = Whitehd_hd (hd);
break;
}
CAMLassert (sweep_hp <= limit);
}else{
sweep_chunk = Chunk_next (sweep_chunk);
if (sweep_chunk == NULL){
/* Sweeping is done. */
caml_gc_sweep_hp = sweep_hp;
++ Caml_state->stat_major_collections;
work = 0;
caml_gc_phase = Phase_idle;
caml_request_minor_gc ();
}else{
sweep_hp = sweep_chunk;
limit = sweep_chunk + Chunk_size (sweep_chunk);
}
}
}
caml_gc_sweep_hp = sweep_hp;
}
/* The main entry point for the major GC. Called about once for each
minor GC. [howmuch] is the amount of work to do:
-1 if the GC is triggered automatically
0 to let the GC compute the amount of work
[n] to make the GC do enough work to (on average) free [n] words
*/
void caml_major_collection_slice (intnat howmuch)
{
double p, dp, filt_p, spend;
intnat computed_work;
int i;
/*
Free memory at the start of the GC cycle (garbage + free list) (assumed):
FM = Caml_state->stat_heap_wsz * caml_percent_free
/ (100 + caml_percent_free)
Assuming steady state and enforcing a constant allocation rate, then
FM is divided in 2/3 for garbage and 1/3 for free list.
G = 2 * FM / 3
G is also the amount of memory that will be used during this cycle
(still assuming steady state).
Proportion of G consumed since the previous slice:
PH = caml_allocated_words / G
= caml_allocated_words * 3 * (100 + caml_percent_free)
/ (2 * Caml_state->stat_heap_wsz * caml_percent_free)
Proportion of extra-heap resources consumed since the previous slice:
PE = caml_extra_heap_resources
Proportion of total work to do in this slice:
P = max (PH, PE)
Here, we insert a time-based filter on the P variable to avoid large
latency spikes in the GC, so the P below is a smoothed-out version of
the P above.
Amount of marking work for the GC cycle:
MW = Caml_state->stat_heap_wsz * 100 / (100 + caml_percent_free)
+ caml_incremental_roots_count
Amount of sweeping work for the GC cycle:
SW = Caml_state->stat_heap_wsz
In order to finish marking with a non-empty free list, we will
use 40% of the time for marking, and 60% for sweeping.
Let MT be the time spent marking, ST the time spent sweeping, and TT
the total time for this cycle. We have:
MT = 40/100 * TT
ST = 60/100 * TT
Amount of time to spend on this slice:
T = P * TT = P * MT / (40/100) = P * ST / (60/100)
Since we must do MW work in MT time or SW work in ST time, the amount
of work for this slice is:
MS = P * MW / (40/100) if marking
SS = P * SW / (60/100) if sweeping
Amount of marking work for a marking slice:
MS = P * MW / (40/100)
MS = P * (Caml_state->stat_heap_wsz * 250
/ (100 + caml_percent_free)
+ 2.5 * caml_incremental_roots_count)
Amount of sweeping work for a sweeping slice:
SS = P * SW / (60/100)
SS = P * Caml_state->stat_heap_wsz * 5 / 3
This slice will either mark MS words or sweep SS words.
*/
if (caml_major_slice_begin_hook != NULL) (*caml_major_slice_begin_hook) ();
p = (double) caml_allocated_words * 3.0 * (100 + caml_percent_free)
/ Caml_state->stat_heap_wsz / caml_percent_free / 2.0;
if (caml_dependent_size > 0){
dp = (double) caml_dependent_allocated * (100 + caml_percent_free)
/ caml_dependent_size / caml_percent_free;
}else{
dp = 0.0;
}
if (p < dp) p = dp;
if (p < caml_extra_heap_resources) p = caml_extra_heap_resources;
p += p_backlog;
p_backlog = 0.0;
if (p > 0.3){