New allocator: Address order first fit (aoff)

9 files changed, 1153 insertions, 35 deletions

diff --git a/erts/doc/src/erts_alloc.xml b/erts/doc/src/erts_alloc.xml
index 452e5d990e..90347824d5 100644
--- a/erts/doc/src/erts_alloc.xml
+++ b/erts/doc/src/erts_alloc.xml
@@ -180,6 +180,14 @@
           used. The time complexity is proportional to log N, where
           N is the number of free blocks.</p>
       </item>
+      <tag>Address order first fit</tag>
+      <item>
+        <p>Strategy: Find the block with the lowest address that satisfies the
+          requested block size.</p>
+        <p>Implementation: A balanced binary search tree is
+          used. The time complexity is proportional to log N, where
+          N is the number of free blocks.</p>
+      </item>
       <tag>Good fit</tag>
       <item>
         <p>Strategy: Try to find the best fit, but settle for the best fit
@@ -320,11 +328,11 @@
        subsystem identifier, only the specific allocator identified will be
        effected:</p>
     <taglist>
-      <tag><marker id="M_as"><c><![CDATA[+M<S>as bf|aobf|gf|af]]></c></marker></tag>
+      <tag><marker id="M_as"><c><![CDATA[+M<S>as bf|aobf|aoff|gf|af]]></c></marker></tag>
       <item>
        Allocation strategy. Valid strategies are <c>bf</c> (best fit),
-      <c>aobf</c> (address order best fit), <c>gf</c> (good fit),
-       and <c>af</c> (a fit). See 
+      <c>aobf</c> (address order best fit), <c>aoff</c> (address order first fit),
+      <c>gf</c> (good fit), and <c>af</c> (a fit). See 
       <seealso marker="#strategy">the description of allocation strategies</seealso> in "the <c>alloc_util</c> framework" section.</item>
       <tag><marker id="M_asbcst"><c><![CDATA[+M<S>asbcst <size>]]></c></marker></tag>
       <item>
diff --git a/erts/emulator/Makefile.in b/erts/emulator/Makefile.in
index d9362a2a8f..b658e79378 100644
--- a/erts/emulator/Makefile.in
+++ b/erts/emulator/Makefile.in
@@ -742,7 +742,7 @@ RUN_OBJS = \
 	$(OBJDIR)/erl_bif_re.o		$(OBJDIR)/erl_unicode.o \
 	$(OBJDIR)/packet_parser.o	$(OBJDIR)/safe_hash.o \
 	$(OBJDIR)/erl_zlib.o		$(OBJDIR)/erl_nif.o \
-	$(OBJDIR)/erl_bif_binary.o
+	$(OBJDIR)/erl_bif_binary.o      $(OBJDIR)/erl_ao_firstfit_alloc.o
 
 ifeq ($(TARGET),win32)
 DRV_OBJS = \
diff --git a/erts/emulator/beam/erl_alloc.c b/erts/emulator/beam/erl_alloc.c
index 840534ec5e..1aa5308a5f 100644
--- a/erts/emulator/beam/erl_alloc.c
+++ b/erts/emulator/beam/erl_alloc.c
@@ -50,6 +50,9 @@
 #include "erl_bestfit_alloc.h"
 #define GET_ERL_AF_ALLOC_IMPL
 #include "erl_afit_alloc.h"
+#define GET_ERL_AOFF_ALLOC_IMPL
+#include "erl_ao_firstfit_alloc.h"
+
 
 #define ERTS_ALC_DEFAULT_MAX_THR_PREF 16
 
@@ -85,6 +88,8 @@ typedef union {
     char align_bfa[ERTS_ALC_CACHE_LINE_ALIGN_SIZE(sizeof(BFAllctr_t))];
     AFAllctr_t afa;
     char align_afa[ERTS_ALC_CACHE_LINE_ALIGN_SIZE(sizeof(AFAllctr_t))];
+    AOFFAllctr_t aoffa;
+    char align_aoffa[ERTS_ALC_CACHE_LINE_ALIGN_SIZE(sizeof(AOFFAllctr_t))];
 } ErtsAllocatorState_t;
 
 static ErtsAllocatorState_t sbmbc_alloc_state;
@@ -122,7 +127,8 @@ static void *fix_core_alloc(Uint size)
 enum allctr_type {
     GOODFIT,
     BESTFIT,
-    AFIT
+    AFIT,
+    AOFIRSTFIT
 };
 
 struct au_init {
@@ -134,6 +140,7 @@ struct au_init {
 	GFAllctrInit_t	gf;
 	BFAllctrInit_t	bf;
 	AFAllctrInit_t	af;
+	AOFFAllctrInit_t aoff;
     } init;
     struct {
 	int mmbcs;
@@ -147,7 +154,8 @@ struct au_init {
     ERTS_DEFAULT_ALLCTR_INIT,		\
     ERTS_DEFAULT_GF_ALLCTR_INIT,	\
     ERTS_DEFAULT_BF_ALLCTR_INIT,	\
-    ERTS_DEFAULT_AF_ALLCTR_INIT		\
+    ERTS_DEFAULT_AF_ALLCTR_INIT,	\
+    ERTS_DEFAULT_AOFF_ALLCTR_INIT       \
 }
 
 typedef struct {
@@ -562,6 +570,7 @@ erts_alloc_init(int *argc, char **argv, ErtsAllocInitOpts *eaiop)
     erts_afalc_init();
     erts_bfalc_init();
     erts_gfalc_init();
+    erts_aoffalc_init();
 
     for (i = ERTS_ALC_A_MIN; i <= ERTS_ALC_A_MAX; i++) {
 	erts_allctrs[i].alloc		= NULL;
@@ -903,6 +912,12 @@ start_au_allocator(ErtsAlcType_t alctr_n,
 					   &init->init.af,
 					   &init->init.util);
 	    break;
+    	case AOFIRSTFIT:
+	    as = (void *) erts_aoffalc_start((AOFFAllctr_t *) as0,
+					     &init->init.aoff,
+					     &init->init.util);
+	    break;
+
 	default:
 	    as = NULL;
 	    ASSERT(0);
@@ -1097,6 +1112,9 @@ handle_au_arg(struct au_init *auip,
 	    else if (strcmp("af", alg) == 0) {
 		auip->atype = AFIT;
 	    }
+	    else if (strcmp("aoff", alg) == 0) {
+		auip->atype = AOFIRSTFIT;
+	    }
 	    else {
 		bad_value(param, sub_param + 1, alg);
 	    }
@@ -2982,6 +3000,7 @@ unsigned long erts_alc_test(unsigned long op,
     case 0x2:	return erts_bfalc_test(op, a1, a2);
     case 0x3:	return erts_afalc_test(op, a1, a2);
     case 0x4:	return erts_mseg_test(op,  a1, a2, a3);
+    case 0x5:	return erts_aoffalc_test(op, a1, a2);
     case 0xf:
 	switch (op) {
 	case 0xf00:
@@ -3061,6 +3080,14 @@ unsigned long erts_alc_test(unsigned long op,
 					  &init.init.af,
 					  &init.init.util);
 		break;
+	    case AOFIRSTFIT:
+		allctr = erts_aoffalc_start((AOFFAllctr_t *)
+					  erts_alloc(ERTS_ALC_T_UNDEF,
+						     sizeof(AOFFAllctr_t)),
+					  &init.init.aoff,
+					  &init.init.util);
+		break;
+
 	    default:
 		ASSERT(0);
 		allctr = NULL;
diff --git a/erts/emulator/beam/erl_ao_firstfit_alloc.c b/erts/emulator/beam/erl_ao_firstfit_alloc.c
new file mode 100644
index 0000000000..002852cdad
--- /dev/null
+++ b/erts/emulator/beam/erl_ao_firstfit_alloc.c
@@ -0,0 +1,972 @@
+/*
+ * %CopyrightBegin%
+ * 
+ * Copyright Ericsson AB 2003-2009. All Rights Reserved.
+ * 
+ * The contents of this file are subject to the Erlang Public License,
+ * Version 1.1, (the "License"); you may not use this file except in
+ * compliance with the License. You should have received a copy of the
+ * Erlang Public License along with this software. If not, it can be
+ * retrieved online at http://www.erlang.org/.
+ * 
+ * Software distributed under the License is distributed on an "AS IS"
+ * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+ * the License for the specific language governing rights and limitations
+ * under the License.
+ * 
+ * %CopyrightEnd%
+ */
+
+
+/*
+ * Description:	An "address order first fit" allocator
+ *              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
+ *
+ * Algorithm:   The tree nodes are free-blocks ordered in address order.
+ *              Every node also keeps the size of the largest block in its
+ *              sub-tree ('max_size'). By that we can start from root and keep
+ *              left (for low addresses) while dismissing entire sub-trees with
+ *              too small 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
+#if 0
+#define HARD_DEBUG
+#endif
+#else
+#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
+
+#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)
+
+#undef ASSERT
+#define ASSERT ASSERT_EXPR
+
+#if 1
+#define RBT_ASSERT	ASSERT
+#else
+#define RBT_ASSERT(x)
+#endif
+
+
+/* Types... */
+typedef struct AOFF_RBTree_t_ AOFF_RBTree_t;
+
+struct AOFF_RBTree_t_ {
+    Block_t hdr;
+    Uint flags;
+    AOFF_RBTree_t *parent;
+    AOFF_RBTree_t *left;
+    AOFF_RBTree_t *right;
+    Uint max_sz;  /* of all blocks in this sub-tree */
+};
+
+#ifdef HARD_DEBUG
+static AOFF_RBTree_t * check_tree(AOFF_RBTree_t* root, Uint);
+#endif
+
+
+/* Calculate 'max_size' of tree node x by only looking at the direct children
+ * of x and x itself.
+ */
+static ERTS_INLINE Uint node_max_size(AOFF_RBTree_t *x)
+{
+    Uint sz = 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_size' 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);
+}
+
+
+/* Prototypes of callback functions */
+static Block_t*	aoff_get_free_block(Allctr_t *, Uint, Block_t *, Uint, Uint32 flags);
+static void aoff_link_free_block(Allctr_t *, Block_t*, Uint32 flags);
+static void aoff_unlink_free_block(Allctr_t *allctr, Block_t *del, Uint32 flags);
+
+static Eterm info_options(Allctr_t *, char *, int *, void *, Uint **, Uint *);
+static void init_atoms(void);
+
+
+
+#ifdef DEBUG
+
+/* Destroy all tree fields */
+#define DESTROY_TREE_NODE(N)						\
+  sys_memset((void *) (((Block_t *) (N)) + 1),				\
+	     0xff,							\
+	     (sizeof(AOFF_RBTree_t) - sizeof(Block_t)))
+
+#else
+
+#define DESTROY_TREE_NODE(N)
+
+#endif
+
+
+static int atoms_initialized = 0;
+
+void
+erts_aoffalc_init(void)
+{
+    atoms_initialized = 0;
+}
+
+Allctr_t *
+erts_aoffalc_start(AOFFAllctr_t *alc,
+		   AOFFAllctrInit_t* aoffinit,
+		   AllctrInit_t *init)
+{
+    AOFFAllctr_t nulled_state = {{0}};
+    /* {{0}} is used instead of {0}, 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 *) &nulled_state, sizeof(AOFFAllctr_t));
+
+    allctr->mbc_header_size		= sizeof(Carrier_t);
+    allctr->min_mbc_size		= MIN_MBC_SZ;
+    allctr->min_mbc_first_free_size	= MIN_MBC_FIRST_FREE_SZ;
+    allctr->min_block_size		= sizeof(AOFF_RBTree_t);
+
+    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		= NULL;
+    allctr->destroying_mbc		= NULL;
+    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;
+    lower_max_size(y, NULL);
+    DESTROY_TREE_NODE(x);
+}
+
+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 *del, Uint32 flags)
+{
+    AOFFAllctr_t *alc = (AOFFAllctr_t *) allctr;
+    AOFF_RBTree_t **root = ((flags & ERTS_ALCU_FLG_SBMBC)
+			    ? &alc->sbmbc_root : &alc->mbc_root);
+    Uint spliced_is_black;
+    AOFF_RBTree_t *x, *y, *z = (AOFF_RBTree_t *) del;
+    AOFF_RBTree_t null_x; /* null_x is used to get the fixup started when we
+			splice out a node without children. */
+
+    null_x.parent = NULL;
+
+#ifdef HARD_DEBUG
+    check_tree(*root, 0);
+#endif
+
+    /* 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 */
+	replace(root, z, y);
+    }
+
+    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);
+	}
+    }
+
+    DESTROY_TREE_NODE(del);
+
+#ifdef HARD_DEBUG
+    check_tree(*root, 0);
+#endif
+}
+
+static void
+aoff_link_free_block(Allctr_t *allctr, Block_t *block, Uint32 flags)
+{
+    AOFFAllctr_t *alc = (AOFFAllctr_t *) allctr;
+    AOFF_RBTree_t *blk = (AOFF_RBTree_t *) block;
+    AOFF_RBTree_t **root = ((flags & ERTS_ALCU_FLG_SBMBC)
+			    ? &alc->sbmbc_root : &alc->mbc_root);
+    Uint blk_sz = BLK_SZ(blk);
+
+#ifdef HARD_DEBUG
+    check_tree(*root, 0);
+#endif
+
+    blk->flags	= 0;
+    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) {
+	    if (x->max_sz < blk_sz) {
+		x->max_sz = blk_sz;
+	    }
+	    if (blk < x) {
+		if (!x->left) {
+		    blk->parent = x;
+		    x->left = blk;
+		    break;
+		}
+		x = x->left;
+	    }
+	    else {
+		if (!x->right) {
+		    blk->parent = x;
+		    x->right = blk;
+		    break;
+		}
+		x = x->right;
+	    }
+
+	}
+
+	/* Insert block into size tree */
+	RBT_ASSERT(blk->parent);
+
+	SET_RED(blk);
+	if (IS_RED(blk->parent))
+	    tree_insert_fixup(root, blk);
+    }
+
+#ifdef HARD_DEBUG
+    check_tree(*root, 0);
+#endif
+}
+
+static Block_t *
+aoff_get_free_block(Allctr_t *allctr, Uint size,
+		    Block_t *cand_blk, Uint cand_size, Uint32 flags)
+{
+    AOFFAllctr_t *alc = (AOFFAllctr_t *) allctr;
+    AOFF_RBTree_t *x = ((flags & ERTS_ALCU_FLG_SBMBC)
+		       ? alc->sbmbc_root : alc->mbc_root);
+    AOFF_RBTree_t *blk = NULL;
+#ifdef HARD_DEBUG
+    AOFF_RBTree_t* dbg_blk = check_tree(x, size);
+#endif
+
+    ASSERT(!cand_blk || cand_size >= size);
+
+    while (x) {
+	if (x->left && x->left->max_sz >= size) {
+	    x = x->left;
+	}
+	else if (BLK_SZ(x) >= size) {
+	    blk = x;
+	    break;
+	}
+	else {
+	    x = x->right;
+	}
+    }
+
+#ifdef HARD_DEBUG
+    ASSERT(blk == dbg_blk);
+#endif
+
+    if (!blk)
+	return NULL;
+
+    if (cand_blk && cand_blk < &blk->hdr) {
+	return NULL; /* cand_blk was better */
+    }
+
+    aoff_unlink_free_block(allctr, (Block_t *) blk, flags);
+
+    return (Block_t *) blk;
+}
+
+
+/*
+ * info_options()
+ */
+
+static struct {
+    Eterm as;
+    Eterm aoff;
+#ifdef DEBUG
+    Eterm end_of_atoms;
+#endif
+} am;
+
+static void ERTS_INLINE atom_init(Eterm *atom, char *name)
+{
+    *atom = am_atom_put(name, strlen(name));
+}
+#define AM_INIT(AM) atom_init(&am.AM, #AM)
+
+static void
+init_atoms(void)
+{
+#ifdef DEBUG
+    Eterm *atom;
+#endif
+
+    if (atoms_initialized)
+	return;
+
+#ifdef DEBUG
+    for (atom = (Eterm *) &am; atom <= &am.end_of_atoms; atom++) {
+	*atom = THE_NON_VALUE;
+    }
+#endif
+    AM_INIT(as);
+    AM_INIT(aoff);
+
+#ifdef DEBUG
+    for (atom = (Eterm *) &am; atom < &am.end_of_atoms; atom++) {
+	ASSERT(*atom != THE_NON_VALUE);
+    }
+#endif
+
+    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,
+	     int *print_to_p,
+	     void *print_to_arg,
+	     Uint **hpp,
+	     Uint *szp)
+{
+    Eterm res = THE_NON_VALUE;
+
+    if (print_to_p) {
+	erts_print(*print_to_p,
+		   print_to_arg,
+		   "%sas: %s\n",
+		   prefix,
+		   "aoff");
+    }
+
+    if (hpp || szp) {
+	
+	if (!atoms_initialized)
+	    erl_exit(1, "%s:%d: Internal error: Atoms not initialized",
+		     __FILE__, __LINE__);;
+
+	res = NIL;
+	add_2tup(hpp, szp, &res, am.as, am.aoff);
+    }
+
+    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()                                                    *
+\*                                                                           */
+
+unsigned long
+erts_aoffalc_test(unsigned long op, unsigned long a1, unsigned long a2)
+{
+    switch (op) {
+    case 0x500:	return (unsigned long) 0; /* IS_AOBF */
+    case 0x501:	return (unsigned long) ((AOFFAllctr_t *) a1)->mbc_root;
+    case 0x502:	return (unsigned long) ((AOFF_RBTree_t *) a1)->parent;
+    case 0x503:	return (unsigned long) ((AOFF_RBTree_t *) a1)->left;
+    case 0x504:	return (unsigned long) ((AOFF_RBTree_t *) a1)->right;
+    case 0x506:	return (unsigned long) IS_BLACK((AOFF_RBTree_t *) a1);
+    case 0x508: return (unsigned long) 1; /* IS_AOFF */
+    case 0x509: return (unsigned long) ((AOFF_RBTree_t *) a1)->max_sz;
+    default:	ASSERT(0); return ~((unsigned long) 0);
+    }
+}
+
+
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *\
+ * Debug functions                                                           *
+\*                                                                           */
+
+
+#ifdef HARD_DEBUG
+
+#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(AOFF_RBTree_t* root, Uint size)
+{
+    AOFF_RBTree_t *res = NULL;
+    Sint blacks;
+    Sint curr_blacks;
+    AOFF_RBTree_t *x;
+
+#ifdef PRINT_TREE
+    print_tree(root);
+#endif
+
+    if (!root)
+	return res;
+
+    x = root;
+    ASSERT(IS_BLACK(x));
+    ASSERT(!x->parent);
+    curr_blacks = 1;
+    blacks = -1;
+
+    while (x) {
+	if (!IS_LEFT_VISITED(x)) {
+	    SET_LEFT_VISITED(x);
+	    if (x->left) {
+		x = x->left;
+		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;
+		if (IS_BLACK(x))
+		    curr_blacks++;
+		continue;
+	    }
+	    else {
+		if (blacks < 0)
+		    blacks = curr_blacks;
+		ASSERT(blacks == curr_blacks);
+	    }
+	}
+
+
+	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(x->left < x);
+	    ASSERT(x->left->max_sz <= x->max_sz);	    
+	}
+
+	if (x->right) {
+	    ASSERT(x->right->parent == x);
+	    ASSERT(x->right > x);
+	    ASSERT(x->right->max_sz <= x->max_sz);	    
+	}
+	ASSERT(x->max_sz >= BLK_SZ(x));
+	ASSERT(x->max_sz == 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 && BLK_SZ(x) >= size) {
+	    if (!res || x < res) {
+		res = x;
+	    }
+	}
+
+	UNSET_LEFT_VISITED(x);
+	UNSET_RIGHT_VISITED(x);
+	if (IS_BLACK(x))
+	    curr_blacks--;
+	x = x->parent;
+
+    }
+
+    ASSERT(curr_blacks == 0);
+
+    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=%lu\r\n",
+		IS_BLACK(x) ? "BLACK" : "RED",
+		BLK_SZ(x), (Uint)x, 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 */
+
diff --git a/erts/emulator/beam/erl_ao_firstfit_alloc.h b/erts/emulator/beam/erl_ao_firstfit_alloc.h
new file mode 100644
index 0000000000..0bf0ec8cee
--- /dev/null
+++ b/erts/emulator/beam/erl_ao_firstfit_alloc.h
@@ -0,0 +1,60 @@
+/*
+ * %CopyrightBegin%
+ * 
+ * Copyright Ericsson AB 2003-2009. All Rights Reserved.
+ * 
+ * The contents of this file are subject to the Erlang Public License,
+ * Version 1.1, (the "License"); you may not use this file except in
+ * compliance with the License. You should have received a copy of the
+ * Erlang Public License along with this software. If not, it can be
+ * retrieved online at http://www.erlang.org/.
+ * 
+ * Software distributed under the License is distributed on an "AS IS"
+ * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+ * the License for the specific language governing rights and limitations
+ * under the License.
+ * 
+ * %CopyrightEnd%
+ */
+
+
+#ifndef ERL_AO_FIRSTFIT_ALLOC__
+#define ERL_AO_FIRSTFIT_ALLOC__
+
+#include "erl_alloc_util.h"
+
+#define ERTS_ALC_AOFF_ALLOC_VSN_STR "0.9"
+
+typedef struct AOFFAllctr_t_ AOFFAllctr_t;
+
+typedef struct {
+    int dummy;
+} AOFFAllctrInit_t;
+
+#define ERTS_DEFAULT_AOFF_ALLCTR_INIT {0/*dummy*/}
+
+void erts_aoffalc_init(void);
+Allctr_t *erts_aoffalc_start(AOFFAllctr_t *, AOFFAllctrInit_t*, AllctrInit_t *);
+
+#endif /* #ifndef ERL_AO_FIRSTFIT_ALLOC__ */
+
+
+
+#if defined(GET_ERL_AOFF_ALLOC_IMPL) && !defined(ERL_AOFF_ALLOC_IMPL__)
+#define ERL_AOFF_ALLOC_IMPL__
+
+#define GET_ERL_ALLOC_UTIL_IMPL
+#include "erl_alloc_util.h"
+
+
+struct AOFFAllctr_t_ {
+    Allctr_t		allctr; /* Has to be first! */
+
+    struct AOFF_RBTree_t_* mbc_root;
+    struct AOFF_RBTree_t_* sbmbc_root;
+};
+
+unsigned long erts_aoffalc_test(unsigned long, unsigned long, unsigned long);
+
+#endif /* #if defined(GET_ERL_AOFF_ALLOC_IMPL)
+	      && !defined(ERL_AOFF_ALLOC_IMPL__) */
diff --git a/erts/emulator/beam/erl_bestfit_alloc.c b/erts/emulator/beam/erl_bestfit_alloc.c
index d9b1170a3d..5e3032ddaa 100644
--- a/erts/emulator/beam/erl_bestfit_alloc.c
+++ b/erts/emulator/beam/erl_bestfit_alloc.c
@@ -979,6 +979,7 @@ erts_bfalc_test(unsigned long op, unsigned long a1, unsigned long a2)
     case 0x205:	return (unsigned long) ((RBTreeList_t *) a1)->next;
     case 0x206:	return (unsigned long) IS_BLACK((RBTree_t *) a1);
     case 0x207:	return (unsigned long) IS_TREE_NODE((RBTree_t *) a1);
+    case 0x208:	return (unsigned long) 0; /* IS_AOFF */
     default:	ASSERT(0); return ~((unsigned long) 0);
     }
 }
diff --git a/erts/emulator/test/alloc_SUITE_data/allocator_test.h b/erts/emulator/test/alloc_SUITE_data/allocator_test.h
index b869a4079c..8b34375980 100644
--- a/erts/emulator/test/alloc_SUITE_data/allocator_test.h
+++ b/erts/emulator/test/alloc_SUITE_data/allocator_test.h
@@ -82,15 +82,17 @@ typedef void* erts_cond;
 #define NO_OF_BKTS		((Ulong)	ALC_TEST0(0x102))
 #define FIND_BKT(A, I)		((int)		ALC_TEST2(0x103, (A), (I)))
 
-/* From erl_bestfit_alloc.c */
-#define IS_AOBF(A)		((Ulong)	ALC_TEST1(0x200, (A)))
-#define RBT_ROOT(A)		((RBT_t *)	ALC_TEST1(0x201, (A)))
-#define RBT_PARENT(T)		((RBT_t *)	ALC_TEST1(0x202, (T)))
-#define RBT_LEFT(T)		((RBT_t *)	ALC_TEST1(0x203, (T)))
-#define RBT_RIGHT(T)		((RBT_t *)	ALC_TEST1(0x204, (T)))
-#define RBT_NEXT(T)		((RBTL_t *)	ALC_TEST1(0x205, (T)))
-#define RBT_IS_BLACK(T)		((Ulong)	ALC_TEST1(0x206, (T)))
-#define RBT_IS_TREE(T)		((Ulong)	ALC_TEST1(0x207, (T)))
+/* From erl_bestfit_alloc.c and erl_ao_firstfit_alloc.c */
+#define IS_AOBF(A)		((Ulong)	ALC_TEST1(RBT_OP(0), (A)))
+#define RBT_ROOT(A)		((RBT_t *)	ALC_TEST1(RBT_OP(1), (A)))
+#define RBT_PARENT(T)		((RBT_t *)	ALC_TEST1(RBT_OP(2), (T)))
+#define RBT_LEFT(T)		((RBT_t *)	ALC_TEST1(RBT_OP(3), (T)))
+#define RBT_RIGHT(T)		((RBT_t *)	ALC_TEST1(RBT_OP(4), (T)))
+#define RBT_NEXT(T)		((RBTL_t *)	ALC_TEST1(RBT_OP(5), (T)))
+#define RBT_IS_BLACK(T)		((Ulong)	ALC_TEST1(RBT_OP(6), (T)))
+#define RBT_IS_TREE(T)		((Ulong)	ALC_TEST1(RBT_OP(7), (T)))
+#define IS_AOFF(A)		((Ulong)	ALC_TEST1(RBT_OP(8), (A)))
+#define RBT_MAX_SZ(T)		((Ulong)	ALC_TEST1(RBT_OP(9), (T)))
 
 /* From erl_mseg.c */
 #define HAVE_MSEG()		((int)		ALC_TEST0(0x400))
diff --git a/erts/emulator/test/alloc_SUITE_data/coalesce.c b/erts/emulator/test/alloc_SUITE_data/coalesce.c
index c84da97d35..6f35d3279b 100644
--- a/erts/emulator/test/alloc_SUITE_data/coalesce.c
+++ b/erts/emulator/test/alloc_SUITE_data/coalesce.c
@@ -267,7 +267,7 @@ void
 testcase_run(TestCaseState_t *tcs)
 {
     char *argv_org[] = {"-tmmbcs1024", "-tsbct2048", "-trmbcmt100", "-tas", NULL, NULL};
-    char *alg[] = {"af", "gf", "bf", "aobf", NULL};
+    char *alg[] = {"af", "gf", "bf", "aobf", "aoff", NULL};
     int i;
 
     for (i = 0; alg[i]; i++) {
diff --git a/erts/emulator/test/alloc_SUITE_data/rbtree.c b/erts/emulator/test/alloc_SUITE_data/rbtree.c
index c97e0aac1a..4e7f821baf 100644
--- a/erts/emulator/test/alloc_SUITE_data/rbtree.c
+++ b/erts/emulator/test/alloc_SUITE_data/rbtree.c
@@ -34,6 +34,14 @@ typedef struct {
 #define PRINT_TREE
 #endif
 
+/* Ugly hack to steer the test code towards the right allocator */
+#define RBT_OP(CMD) (current_rbt_type_op_base + (CMD))
+static enum {
+    BESTFIT_OP_BASE = 0x200,
+    AO_FIRSTFIT_OP_BASE = 0x500
+}current_rbt_type_op_base;
+
+
 #ifdef PRINT_TREE
 
 #define INDENT_STEP 5
@@ -65,12 +73,11 @@ print_tree_aux(TestCaseState_t *tcs, RBT_t *x, int indent)
 
 
 static void
-print_tree(TestCaseState_t *tcs, RBT_t *root, int aobf)
+print_tree(TestCaseState_t *tcs, RBT_t *root)
 {
-    char *type = aobf ? "Size-Adress" : "Size";
-    testcase_printf(tcs, " --- %s tree begin ---\r\n", type);
+    testcase_printf(tcs, " --- Tree begin ---\r\n");
     print_tree_aux(tcs, root, 0);
-    testcase_printf(tcs, " --- %s tree end ---\r\n", type);
+    testcase_printf(tcs, " --- Tree end ---\r\n");
 }
 
 #endif
@@ -78,7 +85,8 @@ print_tree(TestCaseState_t *tcs, RBT_t *root, int aobf)
 static RBT_t *
 check_tree(TestCaseState_t *tcs, Allctr_t *alc, Ulong size)
 {
-    int i, max_i, address_order;
+    enum { BF, AOBF, AOFF }type;
+    int i, max_i;
     char stk[128];
     RBT_t *root, *x, *y, *res;
     Ulong x_sz, y_sz, is_x_black;
@@ -86,11 +94,14 @@ check_tree(TestCaseState_t *tcs, Allctr_t *alc, Ulong size)
 
     res = NULL;
 
-    address_order = IS_AOBF(alc);
+    if      (IS_AOBF(alc)) type = AOBF;
+    else if (IS_AOFF(alc)) type = AOFF;
+    else type = BF;
+
     root = RBT_ROOT(alc);
 
 #ifdef PRINT_TREE
-    print_tree(tcs, root, address_order);
+    print_tree(tcs, root);
 #endif
 
     max_i = i = -1;
@@ -165,12 +176,18 @@ check_tree(TestCaseState_t *tcs, Allctr_t *alc, Ulong size)
 	if (y) {
 	    y_sz = BLK_SZ(y);
 	    ASSERT(tcs, RBT_PARENT(y) == x);
-	    if (address_order) {
+	    switch (type) {
+	    case AOBF:
 		ASSERT(tcs, y_sz < x_sz || (y_sz == x_sz && y < x));
-	    }
-	    else {
+		break;
+	    case BF:
 		ASSERT(tcs, RBT_IS_TREE(y));
 		ASSERT(tcs, y_sz < x_sz);
+		break;
+	    case AOFF:
+		ASSERT(tcs, y < x);
+		ASSERT(tcs, RBT_MAX_SZ(y) <= RBT_MAX_SZ(x));
+		break;
 	    }
 	}
 
@@ -178,16 +195,22 @@ check_tree(TestCaseState_t *tcs, Allctr_t *alc, Ulong size)
 	if (y) {
 	    y_sz = BLK_SZ(y);
 	    ASSERT(tcs, RBT_PARENT(y) == x);
-	    if (address_order) {
+	    switch (type) {
+	    case AOBF:
 		ASSERT(tcs, y_sz > x_sz || (y_sz == x_sz && y > x));
-	    }
-	    else {
+		break;
+	    case BF:
 		ASSERT(tcs, RBT_IS_TREE(y));
 		ASSERT(tcs, y_sz > x_sz);
+		break;
+	    case AOFF:
+		ASSERT(tcs, y > x);
+		ASSERT(tcs, RBT_MAX_SZ(y) <= RBT_MAX_SZ(x));
+		break;
 	    }
 	}
 
-	if (!address_order) {
+	if (type == BF) {
 	    Ulong l_sz;
 	    RBTL_t *l = RBT_NEXT(x);
 	    for (l = RBT_NEXT(x); l; l = RBT_NEXT(l)) {
@@ -202,13 +225,20 @@ check_tree(TestCaseState_t *tcs, Allctr_t *alc, Ulong size)
 		res = x;
 	    else {
 		y_sz = BLK_SZ(res);
-		if (address_order) {
+		switch (type) {
+		case AOBF:
 		    if (x_sz < y_sz || (x_sz == y_sz && x < res))
 			res = x;
-		}
-		else {
-		    if (!res || x_sz < y_sz)
+		    break;
+		case BF:
+		    if (x_sz < y_sz)
 			res = x;
+		    break;
+		case AOFF:
+		    if (x < res) {
+			res = x;
+		    }
+		    break;
 		}
 	    }
 	}
@@ -257,7 +287,7 @@ static void
 test_it(TestCaseState_t *tcs)
 {
     int i;
-    Allctr_t a = ((rbtree_test_data *) tcs->extra)->allocator;
+    Allctr_t* a = ((rbtree_test_data *) tcs->extra)->allocator;
     void **blk = ((rbtree_test_data *) tcs->extra)->blk;
     void **fence = ((rbtree_test_data *) tcs->extra)->fence;
     Ulong min_blk_sz;
@@ -338,6 +368,7 @@ testcase_run(TestCaseState_t *tcs)
 {
     char *argv1[] = {"-tasbf", NULL};
     char *argv2[] = {"-tasaobf", NULL};
+    char *argv3[] = {"-tasaoff", NULL};
     Allctr_t *a;
     rbtree_test_data *td;
 
@@ -355,6 +386,7 @@ testcase_run(TestCaseState_t *tcs)
 
     testcase_printf(tcs, "Starting test of best fit...\n");
 
+    current_rbt_type_op_base = BESTFIT_OP_BASE;
     td->allocator = a = START_ALC("rbtree_bf_", 0, argv1);
 
     ASSERT(tcs, a);
@@ -371,6 +403,7 @@ testcase_run(TestCaseState_t *tcs)
 
     testcase_printf(tcs, "Starting test of address order best fit...\n");
 
+    current_rbt_type_op_base = BESTFIT_OP_BASE;
     td->allocator = a = START_ALC("rbtree_aobf_", 0, argv2);
 
     ASSERT(tcs, a);
@@ -383,4 +416,19 @@ testcase_run(TestCaseState_t *tcs)
 
     testcase_printf(tcs, "Address order best fit test succeeded!\n");
 
+    /* Address order first fit... */
+
+    testcase_printf(tcs, "Starting test of address order first fit...\n");
+
+    current_rbt_type_op_base = AO_FIRSTFIT_OP_BASE;
+    td->allocator = a = START_ALC("rbtree_aoff_", 0, argv3);
+
+    ASSERT(tcs, a);
+
+    test_it(tcs);
+
+    STOP_ALC(a);
+    td->allocator = NULL;
+
+    testcase_printf(tcs, "Address order first fit test succeeded!\n");
 }