aboutsummaryrefslogtreecommitdiffstats
path: root/erts/emulator/beam/erl_ao_firstfit_alloc.c
blob: 3f0ab33597bafec478ef1c7746db5ea856939ff9 (plain) (blame)
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
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
/*
 * %CopyrightBegin%
 * 
 * Copyright Ericsson AB 2003-2018. All Rights Reserved.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * %CopyrightEnd%
 */


/*
 * Description:	A family of "first fit" allocator strategies
 *              based on a Red-Black (binary search) Tree. The search,
 *              insert, and delete operations are all O(log n) operations
 *              on a Red-Black Tree.
 *              Red-Black Trees are described in "Introduction to Algorithms",
 *              by Thomas H. Cormen, Charles E. Leiserson, and Ronald L. Riverest.
 *
 *              This module is a callback-module for erl_alloc_util.c
 *
 * AOFF Algorithm:
 *              The tree nodes are ordered in address order.
 *              Every node also keeps the size of the largest block in its
 *              sub-tree ('max_sz'). By that we can start from root and keep
 *              left (for low addresses) while dismissing entire sub-trees with
 *              too small blocks.
 * Bestfit within carrier:
 *              The only difference for "bestfit within carrier" is the tree
 *              sorting order. Blocks within the same carrier are sorted
 *              wrt size instead of address. The 'max_sz' field is maintained
 *              in order to dismiss entire carriers with too small blocks. 
 * Age Order:
 *      	Carriers are ordered by creation time instead of address.
 *      	Oldest carrier with a large enough free block is chosen.
 *      	No age order supported for blocks.
 *
 * Authors: 	Rickard Green/Sverker Eriksson
 */


#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif
#include "global.h"
#define GET_ERL_AOFF_ALLOC_IMPL
#include "erl_ao_firstfit_alloc.h"

#ifdef DEBUG
# define IS_DEBUG 1
#if 0
#define HARD_DEBUG
#endif
#else
# define IS_DEBUG 0
#undef HARD_DEBUG
#endif

#define MIN_MBC_SZ		(16*1024)
#define MIN_MBC_FIRST_FREE_SZ	(4*1024)

#define TREE_NODE_FLG		(((Uint) 1) << 0)
#define RED_FLG			(((Uint) 1) << 1)
#ifdef HARD_DEBUG
#  define LEFT_VISITED_FLG	(((Uint) 1) << 2)
#  define RIGHT_VISITED_FLG	(((Uint) 1) << 3)
#endif
#ifdef DEBUG
#  define IS_BF_FLG	        (((Uint) 1) << 4)
#endif

#define IS_TREE_NODE(N)		(((AOFF_RBTree_t *) (N))->flags & TREE_NODE_FLG)
#define IS_LIST_ELEM(N)		(!IS_TREE_NODE(((AOFF_RBTree_t *) (N))))

#define SET_TREE_NODE(N)	(((AOFF_RBTree_t *) (N))->flags |= TREE_NODE_FLG)
#define SET_LIST_ELEM(N)	(((AOFF_RBTree_t *) (N))->flags &= ~TREE_NODE_FLG)

#define IS_RED(N)		(((AOFF_RBTree_t *) (N)) \
				 && ((AOFF_RBTree_t *) (N))->flags & RED_FLG)
#define IS_BLACK(N)		(!IS_RED(((AOFF_RBTree_t *) (N))))

#define SET_RED(N)		(((AOFF_RBTree_t *) (N))->flags |= RED_FLG)
#define SET_BLACK(N)		(((AOFF_RBTree_t *) (N))->flags &= ~RED_FLG)

#if 1
#define RBT_ASSERT	ASSERT
#else
#define RBT_ASSERT(x)
#endif

#define AOFF_BLK_SZ(B) MBC_FBLK_SZ(&(B)->hdr)

#define LIST_NEXT(N) (((AOFF_RBTree_t*)(N))->u.next)
#define LIST_PREV(N) (((AOFF_RBTree_t*)(N))->parent)

typedef struct AOFF_Carrier_t_ AOFF_Carrier_t;

struct AOFF_Carrier_t_ {
    Carrier_t crr;
    AOFF_RBTree_t rbt_node;     /* My node in the carrier tree */
    AOFF_RBTree_t* root;        /* Root of my block tree */
};
#define RBT_NODE_TO_MBC(PTR) ErtsContainerStruct((PTR), AOFF_Carrier_t, rbt_node)

/* 
   To support carrier migration we keep two kinds of rb-trees:
   1. One tree of carriers for each allocator instance.
   2. One tree of free blocks for each carrier. 
   Both trees use the same node structure AOFF_RBTree_t and implementation.
   Carrier nodes thus contain a phony Block_t header 'rbt_node.hdr'.
   The size value of such a phony block is the size of the largest free block in
   that carrier, i.e same as 'max_sz' of the root node of its block tree.  
*/

#ifdef HARD_DEBUG
#  define HARD_CHECK_IS_MEMBER(ROOT,NODE) ASSERT(rbt_is_member(ROOT,NODE))
#  define HARD_CHECK_TREE(CRR,ORDER,ROOT,SZ) check_tree(CRR, ORDER, ROOT, SZ)
static AOFF_RBTree_t * check_tree(Carrier_t*, enum AOFFSortOrder, AOFF_RBTree_t*, Uint);
#else
#  define HARD_CHECK_IS_MEMBER(ROOT,NODE)
#  define HARD_CHECK_TREE(CRR,ORDER,ROOT,SZ)
#endif


/* Calculate 'max_sz' of tree node x by only looking at 'max_sz' of the
 * direct children of x and the size x itself.
 */
static ERTS_INLINE Uint node_max_size(AOFF_RBTree_t *x)
{
    Uint sz = AOFF_BLK_SZ(x);
    if (x->left && x->left->max_sz > sz) {
	sz = x->left->max_sz;
    }
    if (x->right && x->right->max_sz > sz) {
	sz = x->right->max_sz;
    }
    return sz;
}

/* Set new possibly lower 'max_sz' of node and propagate change toward root
*/
static ERTS_INLINE void lower_max_size(AOFF_RBTree_t *node,
				       AOFF_RBTree_t* stop_at)
{
    AOFF_RBTree_t* x = node;    
    Uint old_max = x->max_sz;
    Uint new_max = node_max_size(x);

    if (new_max < old_max) {
	x->max_sz = new_max;
	while ((x=x->parent) != stop_at && x->max_sz == old_max) {		
	    x->max_sz = node_max_size(x);
	}
	ASSERT(x == stop_at || x->max_sz > old_max);
    }
    else ASSERT(new_max == old_max);
}

/*
 * Set possibly new larger 'max_sz' of node and propagate change toward root
 */
void erts_aoff_larger_max_size(AOFF_RBTree_t *node)
{
    AOFF_RBTree_t* x = node;
    const Uint new_sz = node->hdr.bhdr;

    ASSERT(!x->left  || x->left->max_sz  <= x->max_sz);
    ASSERT(!x->right || x->right->max_sz <= x->max_sz);

    while (new_sz > x->max_sz) {
        x->max_sz = new_sz;
        x = x->parent;
        if (!x)
            break;
    }
}

/* Compare nodes for both carrier and block trees */
static ERTS_INLINE SWord cmp_blocks(enum AOFFSortOrder order,
				    AOFF_RBTree_t* lhs, AOFF_RBTree_t* rhs)
{
    ASSERT(lhs != rhs);
    if (order == FF_AGEFF) {
	Sint64 diff = lhs->u.birth_time - rhs->u.birth_time;
 #ifdef ARCH_64
        if (diff)
            return diff;
 #else
        if (diff < 0)
            return -1;
        else if (diff > 0)
            return 1;
 #endif
    }
    else {
	ASSERT(order == FF_AOFF || FBLK_TO_MBC(&lhs->hdr) == FBLK_TO_MBC(&rhs->hdr));
	if (order != FF_AOFF) {
	    SWord diff = (SWord)AOFF_BLK_SZ(lhs) - (SWord)AOFF_BLK_SZ(rhs);
	    if (diff || order == FF_BF) return diff;
	}
    }
    return (char*)lhs - (char*)rhs;
}

/* Compare candidate block. Only for block tree */
static ERTS_INLINE SWord cmp_cand_blk(enum AOFFSortOrder order,
				      Block_t* cand_blk, AOFF_RBTree_t* rhs)
{
    ASSERT(order != FF_AGEFF);
    if (order != FF_AOFF) {
	if (BLK_TO_MBC(cand_blk) == FBLK_TO_MBC(&rhs->hdr)) {
	    SWord diff = (SWord)MBC_BLK_SZ(cand_blk) - (SWord)MBC_FBLK_SZ(&rhs->hdr);
	    if (diff || order == FF_BF) return diff;
	}
    }
    return (char*)cand_blk - (char*)rhs;
}


/* Prototypes of callback functions */
static Block_t*	aoff_get_free_block(Allctr_t *, Uint, Block_t *, Uint);
static void aoff_link_free_block(Allctr_t *, Block_t*);
static void aoff_unlink_free_block(Allctr_t *allctr, Block_t *del);
static void aoff_creating_mbc(Allctr_t*, Carrier_t*);
#ifdef DEBUG
static void aoff_destroying_mbc(Allctr_t*, Carrier_t*);
#endif
static void aoff_add_mbc(Allctr_t*, Carrier_t*);
static void aoff_remove_mbc(Allctr_t*, Carrier_t*);
static UWord aoff_largest_fblk_in_mbc(Allctr_t*, Carrier_t*);

/* Generic tree functions used by both carrier and block trees. */
static void rbt_delete(AOFF_RBTree_t** root, AOFF_RBTree_t* del);
static void rbt_insert(enum AOFFSortOrder, AOFF_RBTree_t** root, AOFF_RBTree_t* blk);
static AOFF_RBTree_t* rbt_search(AOFF_RBTree_t* root, Uint size);

static Eterm info_options(Allctr_t *, char *, fmtfn_t *, void *, Uint **, Uint *);
static void init_atoms(void);


static int atoms_initialized = 0;

#ifndef ERTS_HAVE_OS_MONOTONIC_TIME_SUPPORT
static erts_atomic64_t birth_time_counter;
#endif

void
erts_aoffalc_init(void)
{
    atoms_initialized = 0;
#ifndef ERTS_HAVE_OS_MONOTONIC_TIME_SUPPORT
    erts_atomic64_init_nob(&birth_time_counter, 0);
#endif
}

Allctr_t *
erts_aoffalc_start(AOFFAllctr_t *alc,
		   AOFFAllctrInit_t* aoffinit,
		   AllctrInit_t *init)
{
    struct {
	int dummy;
	AOFFAllctr_t allctr;
    } zero = {0};
    /* The struct with a dummy element first is used in order to avoid (an
       incorrect) gcc warning. gcc warns if {0} is used as initializer of
       a struct when the first member is a struct (not if, for example,
       the third member is a struct). */

    Allctr_t *allctr = (Allctr_t *) alc;

    sys_memcpy((void *) alc, (void *) &zero.allctr, sizeof(AOFFAllctr_t));

    alc->blk_order                      = aoffinit->blk_order;
    alc->crr_order                      = aoffinit->crr_order;
    allctr->mbc_header_size		= sizeof(AOFF_Carrier_t);
    allctr->min_mbc_size		= MIN_MBC_SZ;
    allctr->min_mbc_first_free_size	= MIN_MBC_FIRST_FREE_SZ;
    allctr->min_block_size = (aoffinit->blk_order == FF_BF
                              ? (offsetof(AOFF_RBTree_t, u.next)
                                 + ErtsSizeofMember(AOFF_RBTree_t, u.next))
                              : offsetof(AOFF_RBTree_t, u));

    allctr->vsn_str			= ERTS_ALC_AOFF_ALLOC_VSN_STR;


    /* Callback functions */

    allctr->get_free_block		= aoff_get_free_block;
    allctr->link_free_block		= aoff_link_free_block;
    allctr->unlink_free_block           = aoff_unlink_free_block;
    allctr->info_options		= info_options;

    allctr->get_next_mbc_size		= NULL;
    allctr->creating_mbc		= aoff_creating_mbc;
#ifdef DEBUG
    allctr->destroying_mbc		= aoff_destroying_mbc;
#else
    allctr->destroying_mbc		= NULL;
#endif
    allctr->add_mbc                     = aoff_add_mbc;
    allctr->remove_mbc                  = aoff_remove_mbc;
    allctr->largest_fblk_in_mbc         = aoff_largest_fblk_in_mbc;
    allctr->init_atoms			= init_atoms;

#ifdef ERTS_ALLOC_UTIL_HARD_DEBUG
    allctr->check_block			= NULL;
    allctr->check_mbc			= NULL;
#endif

    allctr->atoms_initialized		= 0;

    if (!erts_alcu_start(allctr, init))
	return NULL;

    return allctr;
}

/*
 * Red-Black Tree operations needed
 */

static ERTS_INLINE void
left_rotate(AOFF_RBTree_t **root, AOFF_RBTree_t *x)
{
    AOFF_RBTree_t *y = x->right;
    x->right = y->left;
    if (y->left)
	y->left->parent = x;
    y->parent = x->parent;
    if (!y->parent) {
	RBT_ASSERT(*root == x);
	*root = y;
    }
    else if (x == x->parent->left)
	x->parent->left = y;
    else {
	RBT_ASSERT(x == x->parent->right);
	x->parent->right = y;
    }
    y->left = x;
    x->parent = y;

    y->max_sz = x->max_sz;
    x->max_sz = node_max_size(x); 
    ASSERT(y->max_sz >= x->max_sz);
}

static ERTS_INLINE void
right_rotate(AOFF_RBTree_t **root, AOFF_RBTree_t *x)
{
    AOFF_RBTree_t *y = x->left;
    x->left = y->right;
    if (y->right)
	y->right->parent = x;
    y->parent = x->parent;
    if (!y->parent) {
	RBT_ASSERT(*root == x);
	*root = y;
    }
    else if (x == x->parent->right)
	x->parent->right = y;
    else {
	RBT_ASSERT(x == x->parent->left);
	x->parent->left = y;
    }
    y->right = x;
    x->parent = y;
    y->max_sz = x->max_sz;
    x->max_sz = node_max_size(x);    
    ASSERT(y->max_sz >= x->max_sz);
}


/*
 * Replace node x with node y
 * NOTE: block header of y is not changed
 */
static ERTS_INLINE void
replace(AOFF_RBTree_t **root, AOFF_RBTree_t *x, AOFF_RBTree_t *y)
{

    if (!x->parent) {
	RBT_ASSERT(*root == x);
	*root = y;
    }
    else if (x == x->parent->left)
	x->parent->left = y;
    else {
	RBT_ASSERT(x == x->parent->right);
	x->parent->right = y;
    }
    if (x->left) {
	RBT_ASSERT(x->left->parent == x);
	x->left->parent = y;
    }
    if (x->right) {
	RBT_ASSERT(x->right->parent == x);
	x->right->parent = y;
    }

    y->flags	= x->flags;
    y->parent	= x->parent;
    y->right	= x->right;
    y->left	= x->left;
    y->max_sz   = x->max_sz;
}

static void
tree_insert_fixup(AOFF_RBTree_t** root, AOFF_RBTree_t *blk)
{
    AOFF_RBTree_t *x = blk, *y;

    /*
     * Rearrange the tree so that it satisfies the Red-Black Tree properties
     */

    RBT_ASSERT(x != *root && IS_RED(x->parent));
    do {

	/*
	 * x and its parent are both red. Move the red pair up the tree
	 * until we get to the root or until we can separate them.
	 */

	RBT_ASSERT(IS_RED(x));
	RBT_ASSERT(IS_BLACK(x->parent->parent));
	RBT_ASSERT(x->parent->parent);

	if (x->parent == x->parent->parent->left) {
	    y = x->parent->parent->right;
	    if (IS_RED(y)) {
		SET_BLACK(y);
		x = x->parent;
		SET_BLACK(x);
		x = x->parent;
		SET_RED(x);
	    }
	    else {

		if (x == x->parent->right) {
		    x = x->parent;
		    left_rotate(root, x);
		}

		RBT_ASSERT(x == x->parent->parent->left->left);
		RBT_ASSERT(IS_RED(x));
		RBT_ASSERT(IS_RED(x->parent));
		RBT_ASSERT(IS_BLACK(x->parent->parent));
		RBT_ASSERT(IS_BLACK(y));

		SET_BLACK(x->parent);
		SET_RED(x->parent->parent);
		right_rotate(root, x->parent->parent);

		RBT_ASSERT(x == x->parent->left);
		RBT_ASSERT(IS_RED(x));
		RBT_ASSERT(IS_RED(x->parent->right));
		RBT_ASSERT(IS_BLACK(x->parent));
		break;
	    }
	}
	else {
	    RBT_ASSERT(x->parent == x->parent->parent->right);
	    y = x->parent->parent->left;
	    if (IS_RED(y)) {
		SET_BLACK(y);
		x = x->parent;
		SET_BLACK(x);
		x = x->parent;
		SET_RED(x);
	    }
	    else {

		if (x == x->parent->left) {
		    x = x->parent;
		    right_rotate(root, x);
		}

		RBT_ASSERT(x == x->parent->parent->right->right);
		RBT_ASSERT(IS_RED(x));
		RBT_ASSERT(IS_RED(x->parent));
		RBT_ASSERT(IS_BLACK(x->parent->parent));
		RBT_ASSERT(IS_BLACK(y));

		SET_BLACK(x->parent);
		SET_RED(x->parent->parent);
		left_rotate(root, x->parent->parent);

		RBT_ASSERT(x == x->parent->right);
		RBT_ASSERT(IS_RED(x));
		RBT_ASSERT(IS_RED(x->parent->left));
		RBT_ASSERT(IS_BLACK(x->parent));
		break;
	    }
	}
    } while (x != *root && IS_RED(x->parent));

    SET_BLACK(*root);
}

static void
aoff_unlink_free_block(Allctr_t *allctr, Block_t *blk)
{
    AOFFAllctr_t* alc = (AOFFAllctr_t*)allctr;
    AOFF_RBTree_t* del = (AOFF_RBTree_t*)blk;
    AOFF_Carrier_t *crr = (AOFF_Carrier_t*) FBLK_TO_MBC(&del->hdr);

    ASSERT(crr->rbt_node.hdr.bhdr == crr->root->max_sz);
    HARD_CHECK_TREE(&crr->crr, alc->blk_order, crr->root, 0);

    if (alc->blk_order == FF_BF) {
	ASSERT(del->flags & IS_BF_FLG);
	if (IS_LIST_ELEM(del)) {
	    /* Remove from list */
	    ASSERT(LIST_PREV(del));
	    ASSERT(LIST_PREV(del)->flags & IS_BF_FLG);
	    LIST_NEXT(LIST_PREV(del)) = LIST_NEXT(del);
	    if (LIST_NEXT(del)) {
		ASSERT(LIST_NEXT(del)->flags & IS_BF_FLG);
		LIST_PREV(LIST_NEXT(del)) = LIST_PREV(del);
	    }
	    return;
	}
	else if (LIST_NEXT(del)) {
	    /* Replace tree node by next element in list... */
	    
	    ASSERT(AOFF_BLK_SZ(LIST_NEXT(del)) == AOFF_BLK_SZ(del));
	    ASSERT(IS_LIST_ELEM(LIST_NEXT(del)));
	    
	    replace(&crr->root, (AOFF_RBTree_t*)del, LIST_NEXT(del));
	    
	    HARD_CHECK_TREE(&crr->crr, alc->blk_order, crr->root, 0);
	    return;
	}
    }

    rbt_delete(&crr->root, (AOFF_RBTree_t*)del);

    HARD_CHECK_TREE(&crr->crr, alc->blk_order, crr->root, 0);

    /* Update the carrier tree with a potentially new (lower) max_sz
     */    
    if (crr->root) {
	if (crr->rbt_node.hdr.bhdr == crr->root->max_sz) {
	    return;
	}
	ASSERT(crr->rbt_node.hdr.bhdr > crr->root->max_sz);
	crr->rbt_node.hdr.bhdr = crr->root->max_sz; 
    }
    else {
	crr->rbt_node.hdr.bhdr = 0;
    }
    lower_max_size(&crr->rbt_node, NULL);
}


static void
rbt_delete(AOFF_RBTree_t** root, AOFF_RBTree_t* del)
{
    Uint spliced_is_black;
    AOFF_RBTree_t *x, *y, *z = del;
    AOFF_RBTree_t null_x; /* null_x is used to get the fixup started when we
			splice out a node without children. */

    HARD_CHECK_IS_MEMBER(*root, del);

    null_x.parent = NULL;

    /* Remove node from tree... */

    /* Find node to splice out */
    if (!z->left || !z->right)
	y = z;
    else
	/* Set y to z:s successor */
	for(y = z->right; y->left; y = y->left);
    /* splice out y */
    x = y->left ? y->left : y->right;
    spliced_is_black = IS_BLACK(y);
    if (x) {
	x->parent = y->parent;
    }
    else if (spliced_is_black) {
	x = &null_x;
	x->flags = 0;
	SET_BLACK(x);
	x->right = x->left = NULL;
	x->max_sz = 0;
	x->parent = y->parent;
	y->left = x;
    }

    if (!y->parent) {
	RBT_ASSERT(*root == y);
	*root = x;
    }
    else {
	if (y == y->parent->left) {
	    y->parent->left = x;
	}
	else {
	    RBT_ASSERT(y == y->parent->right);
	    y->parent->right = x;
	}
	if (y->parent != z) {
	    lower_max_size(y->parent, (y==z ? NULL : z));
	}
    }
    if (y != z) {
	/* We spliced out the successor of z; replace z by the successor */
	ASSERT(z != &null_x);
	replace(root, z, y);
	lower_max_size(y, NULL);
    }

    if (spliced_is_black) {
	/* We removed a black node which makes the resulting tree
	   violate the Red-Black Tree properties. Fixup tree... */

	while (IS_BLACK(x) && x->parent) {

	    /*
	     * x has an "extra black" which we move up the tree
	     * until we reach the root or until we can get rid of it.
	     *
	     * y is the sibbling of x
	     */

	    if (x == x->parent->left) {
		y = x->parent->right;
		RBT_ASSERT(y);
		if (IS_RED(y)) {
		    RBT_ASSERT(y->right);
		    RBT_ASSERT(y->left);
		    SET_BLACK(y);
		    RBT_ASSERT(IS_BLACK(x->parent));
		    SET_RED(x->parent);
		    left_rotate(root, x->parent);
		    y = x->parent->right;
		}
		RBT_ASSERT(y);
		RBT_ASSERT(IS_BLACK(y));
		if (IS_BLACK(y->left) && IS_BLACK(y->right)) {
		    SET_RED(y);
		    x = x->parent;
		}
		else {
		    if (IS_BLACK(y->right)) {
			SET_BLACK(y->left);
			SET_RED(y);
			right_rotate(root, y);
			y = x->parent->right;
		    }
		    RBT_ASSERT(y);
		    if (IS_RED(x->parent)) {

			SET_BLACK(x->parent);
			SET_RED(y);
		    }
		    RBT_ASSERT(y->right);
		    SET_BLACK(y->right);
		    left_rotate(root, x->parent);
		    x = *root;
		    break;
		}
	    }
	    else {
		RBT_ASSERT(x == x->parent->right);
		y = x->parent->left;
		RBT_ASSERT(y);
		if (IS_RED(y)) {
		    RBT_ASSERT(y->right);
		    RBT_ASSERT(y->left);
		    SET_BLACK(y);
		    RBT_ASSERT(IS_BLACK(x->parent));
		    SET_RED(x->parent);
		    right_rotate(root, x->parent);
		    y = x->parent->left;
		}
		RBT_ASSERT(y);
		RBT_ASSERT(IS_BLACK(y));
		if (IS_BLACK(y->right) && IS_BLACK(y->left)) {
		    SET_RED(y);
		    x = x->parent;
		}
		else {
		    if (IS_BLACK(y->left)) {
			SET_BLACK(y->right);
			SET_RED(y);
			left_rotate(root, y);
			y = x->parent->left;
		    }
		    RBT_ASSERT(y);
		    if (IS_RED(x->parent)) {
			SET_BLACK(x->parent);
			SET_RED(y);
		    }
		    RBT_ASSERT(y->left);
		    SET_BLACK(y->left);
		    right_rotate(root, x->parent);
		    x = *root;
		    break;
		}
	    }
	}
	SET_BLACK(x);

	if (null_x.parent) {
	    if (null_x.parent->left == &null_x)
		null_x.parent->left = NULL;
	    else {
		RBT_ASSERT(null_x.parent->right == &null_x);
		null_x.parent->right = NULL;
	    }
	    RBT_ASSERT(!null_x.left);
	    RBT_ASSERT(!null_x.right);
	}
	else if (*root == &null_x) {
	    *root = NULL;
	    RBT_ASSERT(!null_x.left);
	    RBT_ASSERT(!null_x.right);
	}
    }
}

static void
aoff_link_free_block(Allctr_t *allctr, Block_t *block)
{
    AOFFAllctr_t* alc = (AOFFAllctr_t*) allctr;
    AOFF_RBTree_t *blk = (AOFF_RBTree_t *) block;
    AOFF_RBTree_t *crr_node;
    AOFF_Carrier_t *blk_crr = (AOFF_Carrier_t*) FBLK_TO_MBC(block);
    Uint blk_sz = AOFF_BLK_SZ(blk);

    ASSERT(allctr == ERTS_ALC_CARRIER_TO_ALLCTR(&blk_crr->crr));
    ASSERT(blk_crr->rbt_node.hdr.bhdr == (blk_crr->root ? blk_crr->root->max_sz : 0));
    HARD_CHECK_TREE(&blk_crr->crr, alc->blk_order, blk_crr->root, 0);

    rbt_insert(alc->blk_order, &blk_crr->root, blk);

    /*
     * Update carrier tree with a potentially new (larger) max_sz
     */
    crr_node = &blk_crr->rbt_node;
    if (blk_sz > crr_node->hdr.bhdr) {
        ASSERT(blk_sz == blk_crr->root->max_sz);
        crr_node->hdr.bhdr = blk_sz;
        while (blk_sz > crr_node->max_sz) {
            crr_node->max_sz = blk_sz;
            crr_node = crr_node->parent;
            if (!crr_node) break;
        }
    }
    HARD_CHECK_TREE(NULL, alc->crr_order, alc->mbc_root, 0);
}

static void
rbt_insert(enum AOFFSortOrder order, AOFF_RBTree_t** root, AOFF_RBTree_t* blk)
{
    Uint blk_sz = AOFF_BLK_SZ(blk);

#ifdef DEBUG
    blk->flags  = (order == FF_BF) ? IS_BF_FLG : 0;
#else
    blk->flags  = 0; 
#endif
    blk->left	= NULL;
    blk->right	= NULL;
    blk->max_sz = blk_sz;

    if (!*root) {
	blk->parent = NULL;
	SET_BLACK(blk);
	*root = blk;
    }
    else {
	AOFF_RBTree_t *x = *root;
	while (1) {
	    SWord diff; 
	    if (x->max_sz < blk_sz) {
		x->max_sz = blk_sz;
	    }
	    diff = cmp_blocks(order, blk, x);
	    if (diff < 0) {
		if (!x->left) {
		    blk->parent = x;
		    x->left = blk;
		    break;
		}
		x = x->left;
	    }
	    else if (diff > 0) {
		if (!x->right) {
		    blk->parent = x;
		    x->right = blk;
		    break;
		}
		x = x->right;
	    }
	    else {
		ASSERT(order == FF_BF);
		ASSERT(blk->flags & IS_BF_FLG);			    
		ASSERT(x->flags & IS_BF_FLG);			    
		SET_LIST_ELEM(blk);
		LIST_NEXT(blk) = LIST_NEXT(x);
		LIST_PREV(blk) = x;
		if (LIST_NEXT(x))
		    LIST_PREV(LIST_NEXT(x)) = blk;
		LIST_NEXT(x) = blk;
		return;
	    }
	}

	/* Insert block into size tree */
	RBT_ASSERT(blk->parent);

	SET_RED(blk);
	if (IS_RED(blk->parent))
	    tree_insert_fixup(root, blk);
    }
    if (order == FF_BF) {
	SET_TREE_NODE(blk);
	LIST_NEXT(blk) = NULL;
    }
}

static AOFF_RBTree_t*
rbt_search(AOFF_RBTree_t* root, Uint size)
{
    AOFF_RBTree_t* x = root;

    ASSERT(x);
    for (;;) {
	if (x->left && x->left->max_sz >= size) {
	    x = x->left;
	}
	else if (AOFF_BLK_SZ(x) >= size) {
	    return x;
	}
	else {
	    x = x->right;
	    if (!x) {
		return NULL;
	    }
	}
    }
}

Carrier_t* aoff_lookup_pooled_mbc(Allctr_t* allctr, Uint size)
{
    AOFF_RBTree_t* node;

    if (!allctr->cpool.pooled_tree)
	return NULL;
    node = rbt_search(allctr->cpool.pooled_tree, size);
    return node ? ErtsContainerStruct(node, Carrier_t, cpool.pooled) : NULL;
}

static Block_t *
aoff_get_free_block(Allctr_t *allctr, Uint size,
		    Block_t *cand_blk, Uint cand_size)
{
    AOFFAllctr_t *alc = (AOFFAllctr_t *) allctr;
    AOFF_RBTree_t *crr_node = alc->mbc_root;
    AOFF_Carrier_t* crr;
    AOFF_RBTree_t *blk = NULL;
#ifdef HARD_DEBUG
    AOFF_RBTree_t* dbg_blk;
#endif
    
    ASSERT(!cand_blk || cand_size >= size);

    /* Get first-fit carrier
     */
    if (!crr_node || !(blk=rbt_search(crr_node, size))) {
	return NULL;
    }
    crr = RBT_NODE_TO_MBC(blk);

    /* Get block within carrier tree
     */
#ifdef HARD_DEBUG
    dbg_blk = HARD_CHECK_TREE(&crr->crr, alc->blk_order, crr->root, size);
#endif

    blk = rbt_search(crr->root, size);
    ASSERT(blk);

#ifdef HARD_DEBUG
    ASSERT(blk == dbg_blk);
#endif

    if (!blk)
	return NULL;

    if (cand_blk && cmp_cand_blk(alc->blk_order, cand_blk, blk) < 0) {
	return NULL; /* cand_blk was better */
    }

    aoff_unlink_free_block(allctr, (Block_t *) blk);

    return (Block_t *) blk;
}

static ERTS_INLINE Sint64 get_birth_time(void)
{
#ifdef ERTS_HAVE_OS_MONOTONIC_TIME_SUPPORT
    return (Sint64) erts_os_monotonic_time();
#else
    return (Sint64) erts_atomic64_inc_read_nob(&birth_time_counter);
#endif
}

static void aoff_creating_mbc(Allctr_t *allctr, Carrier_t *carrier)
{
    AOFFAllctr_t *alc = (AOFFAllctr_t *) allctr;
    AOFF_Carrier_t *crr = (AOFF_Carrier_t*) carrier;
    AOFF_RBTree_t **root = &alc->mbc_root;

    HARD_CHECK_TREE(NULL, alc->crr_order, *root, 0);

    crr->rbt_node.hdr.bhdr = 0;
    if (alc->crr_order == FF_AGEFF || IS_DEBUG) {
        Sint64 bt = get_birth_time();
        crr->rbt_node.u.birth_time = bt;
        crr->crr.cpool.pooled.u.birth_time = bt;
    }
    rbt_insert(alc->crr_order, root, &crr->rbt_node);

    /* aoff_link_free_block will add free block later */
    crr->root = NULL;

    HARD_CHECK_TREE(NULL, alc->crr_order, *root, 0);
}

#define IS_CRR_IN_TREE(CRR,ROOT) \
    ((CRR)->rbt_node.parent || (ROOT) == &(CRR)->rbt_node)

#ifdef DEBUG
static void aoff_destroying_mbc(Allctr_t *allctr, Carrier_t *carrier)
{
    AOFFAllctr_t *alc = (AOFFAllctr_t *) allctr;
    AOFF_Carrier_t *crr = (AOFF_Carrier_t*) carrier;

    ASSERT(!IS_CRR_IN_TREE(crr, alc->mbc_root));
}
#endif

static void aoff_add_mbc(Allctr_t *allctr, Carrier_t *carrier)
{
    AOFFAllctr_t *alc = (AOFFAllctr_t *) allctr;
    AOFF_Carrier_t *crr = (AOFF_Carrier_t*) carrier;
    AOFF_RBTree_t **root = &alc->mbc_root;

    ASSERT(!IS_CRR_IN_TREE(crr, *root));
    HARD_CHECK_TREE(NULL, alc->crr_order, *root, 0);   

    rbt_insert(alc->crr_order, root, &crr->rbt_node);

    HARD_CHECK_TREE(NULL, alc->crr_order, *root, 0);
}

void aoff_add_pooled_mbc(Allctr_t *allctr, Carrier_t *crr)
{
    AOFFAllctr_t *alc = (AOFFAllctr_t *) allctr;
    AOFF_RBTree_t **root = &allctr->cpool.pooled_tree;

    ASSERT(allctr == crr->cpool.orig_allctr);
    HARD_CHECK_TREE(NULL, 0, *root, 0);

    /* Link carrier in address order tree
     */
    rbt_insert(alc->crr_order, root, &crr->cpool.pooled);

    HARD_CHECK_TREE(NULL, 0, *root, 0);
}

static void aoff_remove_mbc(Allctr_t *allctr, Carrier_t *carrier)
{
    AOFF_RBTree_t **root = &((AOFFAllctr_t*)allctr)->mbc_root;
    AOFF_Carrier_t *crr = (AOFF_Carrier_t*)carrier;

    ASSERT(allctr == ERTS_ALC_CARRIER_TO_ALLCTR(carrier));

    if (!IS_CRR_IN_TREE(crr,*root))
	return;

    HARD_CHECK_TREE(NULL, alc->crr_order, *root, 0);

    rbt_delete(root, &crr->rbt_node);
    crr->rbt_node.parent = NULL;
    crr->rbt_node.left = NULL;
    crr->rbt_node.right = NULL;
    crr->rbt_node.max_sz = crr->rbt_node.hdr.bhdr;

    HARD_CHECK_TREE(NULL, alc->crr_order, *root, 0);
}

void aoff_remove_pooled_mbc(Allctr_t *allctr, Carrier_t *crr)
{
    ASSERT(allctr == crr->cpool.orig_allctr);

    HARD_CHECK_TREE(NULL, 0, allctr->cpool.pooled_tree, 0);

    rbt_delete(&allctr->cpool.pooled_tree, &crr->cpool.pooled);
#ifdef DEBUG
    crr->cpool.pooled.parent = NULL;
    crr->cpool.pooled.left = NULL;
    crr->cpool.pooled.right = NULL;
    crr->cpool.pooled.max_sz = 0;
#endif
    HARD_CHECK_TREE(NULL, 0, allctr->cpool.pooled_tree, 0);

}


static UWord aoff_largest_fblk_in_mbc(Allctr_t* allctr, Carrier_t* carrier)
{
    AOFF_Carrier_t *crr = (AOFF_Carrier_t*) carrier;

    ASSERT(allctr == ERTS_ALC_CARRIER_TO_ALLCTR(carrier));
    ASSERT(crr->rbt_node.hdr.bhdr == (crr->root ? crr->root->max_sz : 0));
    return crr->rbt_node.hdr.bhdr;
}

/*
 * info_options()
 */

static const char* flavor_str[2][3] = {
    {"ageffcaoff", "ageffcaobf", "ageffcbf"},
    {      "aoff",  "aoffcaobf",  "aoffcbf"}
};
static Eterm flavor_atoms[2][3];

static struct {
    Eterm as;
} am;

static void ERTS_INLINE atom_init(Eterm *atom, const char *name)
{
    *atom = am_atom_put(name, sys_strlen(name));
}
#define AM_INIT(AM) atom_init(&am.AM, #AM)

static void
init_atoms(void)
{
    int i, j;

    if (atoms_initialized)
	return;

    AM_INIT(as);

    for (i = 0; i < 2; i++)
        for (j = 0; j < 3; j++)
            atom_init(&flavor_atoms[i][j], flavor_str[i][j]);

    atoms_initialized = 1;
}


#define bld_uint	erts_bld_uint
#define bld_cons	erts_bld_cons
#define bld_tuple	erts_bld_tuple

static ERTS_INLINE void
add_2tup(Uint **hpp, Uint *szp, Eterm *lp, Eterm el1, Eterm el2)
{
    *lp = bld_cons(hpp, szp, bld_tuple(hpp, szp, 2, el1, el2), *lp);
}

static Eterm
info_options(Allctr_t *allctr,
	     char *prefix,
	     fmtfn_t *print_to_p,
	     void *print_to_arg,
	     Uint **hpp,
	     Uint *szp)
{
    AOFFAllctr_t* alc = (AOFFAllctr_t*) allctr;
    Eterm res = THE_NON_VALUE;

    ASSERT(alc->crr_order >= 0 && alc->crr_order <= 1);
    ASSERT(alc->blk_order >= 1 && alc->blk_order <= 3);

    if (print_to_p) {
	erts_print(*print_to_p,
		   print_to_arg,
		   "%sas: %s\n",
		   prefix,
		   flavor_str[alc->crr_order][alc->blk_order-1]);
    }

    if (hpp || szp) {
	
	if (!atoms_initialized)
	    erts_exit(ERTS_ERROR_EXIT, "%s:%d: Internal error: Atoms not initialized",
		     __FILE__, __LINE__);;

	res = NIL;
	add_2tup(hpp, szp, &res, am.as,
                 flavor_atoms[alc->crr_order][alc->blk_order-1]);
    }

    return res;
}


/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *\
 * NOTE:  erts_aoffalc_test() is only supposed to be used for testing.       *
 *                                                                           *
 * Keep alloc_SUITE_data/allocator_test.h updated if changes are made        *
 * to erts_aoffalc_test()                                                    *
\*                                                                           */

UWord
erts_aoffalc_test(UWord op, UWord a1, UWord a2)
{
    switch (op) {
    case 0x500: return (UWord) ((AOFFAllctr_t *) a1)->blk_order == FF_AOBF;
    case 0x501: {
	AOFF_RBTree_t *node = ((AOFFAllctr_t *) a1)->mbc_root; 
	Uint size = (Uint) a2;
	node = node ? rbt_search(node, size) : NULL;
	return (UWord) (node ? RBT_NODE_TO_MBC(node)->root : NULL);
    }
    case 0x502:	return (UWord) ((AOFF_RBTree_t *) a1)->parent;
    case 0x503:	return (UWord) ((AOFF_RBTree_t *) a1)->left;
    case 0x504:	return (UWord) ((AOFF_RBTree_t *) a1)->right;
    case 0x505:	return (UWord) LIST_NEXT(a1);
    case 0x506:	return (UWord) IS_BLACK((AOFF_RBTree_t *) a1);
    case 0x507:	return (UWord) IS_TREE_NODE((AOFF_RBTree_t *) a1);
    case 0x508: return (UWord) 0; /* IS_BF_ALGO */
    case 0x509: return (UWord) ((AOFF_RBTree_t *) a1)->max_sz;
    case 0x50a: return (UWord) ((AOFFAllctr_t *) a1)->blk_order == FF_BF;
    case 0x50b:	return (UWord) LIST_PREV(a1);
    default:	ASSERT(0); return ~((UWord) 0);
    }
}


/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *\
 * Debug functions                                                           *
\*                                                                           */


#ifdef HARD_DEBUG
static int rbt_is_member(AOFF_RBTree_t* root, AOFF_RBTree_t* node)
{
    while (node != root) {
        if (!node->parent || (node->parent->left != node &&
                              node->parent->right != node)) {
            return 0;
        }
	node = node->parent;
    }    
    return 1;
}

#define IS_LEFT_VISITED(FB)	((FB)->flags & LEFT_VISITED_FLG)
#define IS_RIGHT_VISITED(FB)	((FB)->flags & RIGHT_VISITED_FLG)

#define SET_LEFT_VISITED(FB)	((FB)->flags |= LEFT_VISITED_FLG)
#define SET_RIGHT_VISITED(FB)	((FB)->flags |= RIGHT_VISITED_FLG)

#define UNSET_LEFT_VISITED(FB)	((FB)->flags &= ~LEFT_VISITED_FLG)
#define UNSET_RIGHT_VISITED(FB)	((FB)->flags &= ~RIGHT_VISITED_FLG)


#if 0
#  define PRINT_TREE
#else
#  undef PRINT_TREE
#endif

#ifdef PRINT_TREE
static void print_tree(AOFF_RBTree_t*);
#endif

/*
 * Checks that the order between parent and children are correct,
 * and that the Red-Black Tree properies are satisfied. if size > 0,
 * check_tree() returns the node that satisfies "address order first fit"
 *
 * The Red-Black Tree properies are:
 *   1. Every node is either red or black.
 *   2. Every leaf (NIL) is black.
 *   3. If a node is red, then both its children are black.
 *   4. Every simple path from a node to a descendant leaf
 *      contains the same number of black nodes.
 *
 *   + own.max_size == MAX(own.size, left.max_size, right.max_size)
 */

static AOFF_RBTree_t *
check_tree(Carrier_t* within_crr, enum AOFFSortOrder order, AOFF_RBTree_t* root, Uint size)
{
    AOFF_RBTree_t *res = NULL;
    Sint blacks;
    Sint curr_blacks;
    AOFF_RBTree_t *x;
    Carrier_t* crr;
    Uint depth, max_depth, node_cnt;

#ifdef PRINT_TREE
    print_tree(root);
#endif
    ASSERT((within_crr && order >= FF_AOFF) ||
           (!within_crr && order <= FF_AOFF));

    if (!root)
	return res;

    x = root;
    ASSERT(IS_BLACK(x));
    ASSERT(!x->parent);
    curr_blacks = 1;
    blacks = -1;
    depth = 1;
    max_depth = 0;
    node_cnt = 0;

    while (x) {
	if (!IS_LEFT_VISITED(x)) {
	    SET_LEFT_VISITED(x);
	    if (x->left) {
		x = x->left;
		++depth;
		if (IS_BLACK(x))
		    curr_blacks++;
		continue;
	    }
	    else {
		if (blacks < 0)
		    blacks = curr_blacks;
		ASSERT(blacks == curr_blacks);
	    }
	}

	if (!IS_RIGHT_VISITED(x)) {
	    SET_RIGHT_VISITED(x);
	    if (x->right) {
		x = x->right;
		++depth;
		if (IS_BLACK(x))
		    curr_blacks++;
		continue;
	    }
	    else {
		if (blacks < 0)
		    blacks = curr_blacks;
		ASSERT(blacks == curr_blacks);
	    }
	}

	++node_cnt;
	if (depth > max_depth)
	    max_depth = depth;

	if (within_crr) {
	    crr = FBLK_TO_MBC(&x->hdr);
	    ASSERT(crr == within_crr);
	    ASSERT((char*)x > (char*)crr);
	    ASSERT(((char*)x + AOFF_BLK_SZ(x)) <= ((char*)crr + CARRIER_SZ(crr)));

	}
	if (order == FF_BF) {
	    AOFF_RBTree_t* y = x;
	    AOFF_RBTree_t* nxt = LIST_NEXT(y);
	    ASSERT(IS_TREE_NODE(x));
	    while (nxt) {
		ASSERT(IS_LIST_ELEM(nxt));
		ASSERT(AOFF_BLK_SZ(nxt) == AOFF_BLK_SZ(x));
		ASSERT(FBLK_TO_MBC(&nxt->hdr) == within_crr);
		ASSERT(LIST_PREV(nxt) == y);
		y = nxt;
		nxt = LIST_NEXT(nxt);
	    }
	}

	if (IS_RED(x)) {
	    ASSERT(IS_BLACK(x->right));
	    ASSERT(IS_BLACK(x->left));
	}

	ASSERT(x->parent || x == root);

	if (x->left) {
	    ASSERT(x->left->parent == x);
	    ASSERT(cmp_blocks(order, x->left, x) < 0);
	    ASSERT(x->left->max_sz <= x->max_sz);	    
	}

	if (x->right) {
	    ASSERT(x->right->parent == x);
	    ASSERT(cmp_blocks(order, x->right, x) > 0);
	    ASSERT(x->right->max_sz <= x->max_sz);	    
	}
	ASSERT(x->max_sz >= AOFF_BLK_SZ(x));
	ASSERT(x->max_sz == AOFF_BLK_SZ(x)
	       || x->max_sz == (x->left ? x->left->max_sz : 0)
	       || x->max_sz == (x->right ? x->right->max_sz : 0));

	if (size && AOFF_BLK_SZ(x) >= size) {
	    if (!res || cmp_blocks(order, x, res) < 0) {
		res = x;
	    }
	}

	UNSET_LEFT_VISITED(x);
	UNSET_RIGHT_VISITED(x);
	if (IS_BLACK(x))
	    curr_blacks--;
	x = x->parent;
	--depth;
    }
    ASSERT(depth == 0 || (!root && depth==1)); 
    ASSERT(curr_blacks == 0);
    ASSERT((1 << (max_depth/2)) <= node_cnt);

    UNSET_LEFT_VISITED(root);
    UNSET_RIGHT_VISITED(root);

    return res;

}


#ifdef PRINT_TREE
#define INDENT_STEP 2

#include <stdio.h>

static void
print_tree_aux(AOFF_RBTree_t *x, int indent)
{
    int i;

    if (x) {
	print_tree_aux(x->right, indent + INDENT_STEP);
	for (i = 0; i < indent; i++) {
	    putc(' ', stderr);
	}
	fprintf(stderr, "%s: sz=%lu addr=0x%lx max_size=%u\r\n",
		IS_BLACK(x) ? "BLACK" : "RED",
		AOFF_BLK_SZ(x), (Uint)x, (unsigned)x->max_sz);
	print_tree_aux(x->left,  indent + INDENT_STEP);
    }
}


static void
print_tree(AOFF_RBTree_t* root)
{
    fprintf(stderr, " --- AOFF tree begin ---\r\n");
    print_tree_aux(root, 0);
    fprintf(stderr, " --- AOFF tree end ---\r\n");
}

#endif /* PRINT_TREE */

#endif /* HARD_DEBUG */