Merge branch 'rickard-sverker/carrier-migration/OTP-10279' into maint

* rickard-sverker/carrier-migration/OTP-10279:
  erts: Document the +M<S>acul command line argument
  erts: Carrier pool information in allocator information
  erts: Use carrier pool for migration of carriers
  erts: Implement test case for carrier pool
  erts: Implement carrier pool
  erts: Fix type errors in info functions
  erts: Use Uint64 for call counts
  erts: Fix failing testcase alloc_SUITE:rbtree
  erts: Rename allocator aoffcbf to aoffcaobf
  erts: Remove unnecessary flag arguments in allocators
  erts: Remove SBMBC allocator
  erts: Add test for add_mbc and remove_mbc callbacks
  erts: Fix deallocation in removed carrier
  erts: Change naive list to rb-tree of carriers in AOFF allocator
  erts: Prepare aoff allocator for carrier migration
  erts: Make carrier header sizes customizable
  erts: Add "bestfit within carrier" for aoff allocator (aoffcbf)

1 files changed, 2036 insertions, 740 deletions

diff --git a/erts/emulator/beam/erl_alloc_util.c b/erts/emulator/beam/erl_alloc_util.c
index 53062979a6..b19e603a5f 100644
--- a/erts/emulator/beam/erl_alloc_util.c
+++ b/erts/emulator/beam/erl_alloc_util.c
@@ -71,21 +71,16 @@
 
 #define ALLOC_ZERO_EQ_NULL 0
 
+#ifndef ERTS_MSEG_FLG_2POW
+#  define ERTS_MSEG_FLG_2POW 0
+#endif
+#ifndef ERTS_MSEG_FLG_NONE
+#  define ERTS_MSEG_FLG_NONE 0
+#endif
+
 static int atoms_initialized = 0;
 static int initialized = 0;
 
-int erts_have_sbmbc_alloc;
-
-#if HAVE_ERTS_MSEG
-
-#define MSEG_UNIT_SHIFT         MSEG_ALIGN_BITS
-#define MSEG_UNIT_SZ            (1 << MSEG_UNIT_SHIFT)
-#define MSEG_UNIT_MASK		((~(UWord)0) << MSEG_UNIT_SHIFT)
-
-#define MSEG_UNIT_FLOOR(X)	((X) & MSEG_UNIT_MASK)
-#define MSEG_UNIT_CEILING(X)	MSEG_UNIT_FLOOR((X) + ~MSEG_UNIT_MASK)
-
-#endif
 
 #define INV_SYS_ALLOC_CARRIER_MASK	((UWord) (sys_alloc_carrier_size - 1))
 #define SYS_ALLOC_CARRIER_MASK		(~INV_SYS_ALLOC_CARRIER_MASK)
@@ -110,13 +105,12 @@ static Uint max_mseg_carriers;
 
 #define ONE_GIGA (1000000000)
 
-#define INC_CC(CC) ((CC).no == ONE_GIGA - 1				\
-		    ? ((CC).giga_no++, (CC).no = 0)			\
-		    : (CC).no++)
+#define ERTS_ALC_CC_GIGA_VAL(CC) ((CC) / ONE_GIGA)
+#define ERTS_ALC_CC_VAL(CC) ((CC) % ONE_GIGA)
+
+#define INC_CC(CC) ((CC)++)
 
-#define DEC_CC(CC) ((CC).no == 0					\
-		    ? ((CC).giga_no--, (CC).no = ONE_GIGA - 1)		\
-		    : (CC).no--)
+#define DEC_CC(CC) ((CC)--)
 
 /* Multi block carrier (MBC) memory layout in R16: 
 
@@ -173,14 +167,6 @@ MBC after deallocating first block:
 #define SET_BLK_SZ_FTR(B, SZ) \
   (((FreeBlkFtr_t *) (((char *) (B)) + (SZ)))[-1] = (SZ))
 
-#define THIS_FREE_BLK_HDR_FLG 	(((UWord) 1) << 0)
-#define PREV_FREE_BLK_HDR_FLG 	(((UWord) 1) << 1)
-#define LAST_BLK_HDR_FLG 	(((UWord) 1) << 2)
-
-/* Special flag combo for (allocated) SBC blocks 
-*/
-#define SBC_BLK_HDR_FLG (THIS_FREE_BLK_HDR_FLG | PREV_FREE_BLK_HDR_FLG | LAST_BLK_HDR_FLG)
-
 #define SET_MBC_ABLK_SZ(B, SZ) \
   (ASSERT(((SZ) & FLG_MASK) == 0), \
    (B)->bhdr = (((B)->bhdr) & ~MBC_ABLK_SZ_MASK) | (SZ))
@@ -222,18 +208,7 @@ MBC after deallocating first block:
      ASSERT(((UWord)(F) & (~FLG_MASK|THIS_FREE_BLK_HDR_FLG|PREV_FREE_BLK_HDR_FLG)) == THIS_FREE_BLK_HDR_FLG), \
      (B)->bhdr = ((Sz) | (F)), \
      (B)->u.carrier = (C))
-
-#  define ABLK_TO_MBC(B) \
-    (ASSERT(IS_MBC_BLK(B) && IS_ALLOCED_BLK(B)), \
-     (Carrier_t*)((MSEG_UNIT_FLOOR((UWord)(B)) - \
-		  (((B)->bhdr >> MBC_ABLK_OFFSET_SHIFT) << MSEG_UNIT_SHIFT))))
-
-#  define FBLK_TO_MBC(B) \
-    (ASSERT(IS_MBC_BLK(B) && IS_FREE_BLK(B)), \
-     (B)->u.carrier)
       
-#  define BLK_TO_MBC(B) (IS_FREE_BLK(B) ? FBLK_TO_MBC(B) : ABLK_TO_MBC(B))
-
 #  define IS_MBC_FIRST_ABLK(AP,B) \
   ((((UWord)(B) & ~MSEG_UNIT_MASK) == MBC_HEADER_SIZE(AP)) \
    && ((B)->bhdr & MBC_ABLK_OFFSET_MASK) == 0)
@@ -272,10 +247,6 @@ MBC after deallocating first block:
      (B)->bhdr = ((Sz) | (F)), \
      (B)->carrier = (C))
 
-#  define BLK_TO_MBC(B) ((B)->carrier)
-#  define ABLK_TO_MBC(B) BLK_TO_MBC(B)
-#  define FBLK_TO_MBC(B) BLK_TO_MBC(B)
-
 #  define IS_MBC_FIRST_BLK(AP,B) \
   ((char*)(B) == (char*)((B)->carrier) + MBC_HEADER_SIZE(AP))
 #  define IS_MBC_FIRST_ABLK(AP,B) IS_MBC_FIRST_BLK(AP,B)
@@ -300,8 +271,6 @@ MBC after deallocating first block:
   ((B)->bhdr & PREV_FREE_BLK_HDR_FLG)
 #define IS_PREV_BLK_ALLOCED(B) \
   (!IS_PREV_BLK_FREE((B)))
-#define IS_FREE_BLK(B) \
-  (ASSERT(!IS_SBC_BLK(B)), (B)->bhdr & THIS_FREE_BLK_HDR_FLG)
 #define IS_ALLOCED_BLK(B) \
   (!IS_FREE_BLK((B)))  
 #define IS_LAST_BLK(B) \
@@ -318,13 +287,6 @@ MBC after deallocating first block:
 #define GET_BLK_HDR_FLGS(B) \
   ((B)->bhdr & FLG_MASK)
 
-#define IS_SBC_BLK(B) \
-    (((B)->bhdr & FLG_MASK) == SBC_BLK_HDR_FLG)
-#define IS_MBC_BLK(B) \
-  (!IS_SBC_BLK((B)))
-
-#define MBC_BLK_SZ(B) (IS_FREE_BLK(B) ? MBC_FBLK_SZ(B) : MBC_ABLK_SZ(B))
-
 #define NXT_BLK(B) \
   (ASSERT(IS_MBC_BLK(B)), \
    (Block_t *) (((char *) (B)) + MBC_BLK_SZ((B))))
@@ -338,9 +300,96 @@ MBC after deallocating first block:
 
 /* Carriers ... */
 
-#define SBC_HEADER_SIZE	   (UNIT_CEILING(sizeof(Carrier_t) + ABLK_HDR_SZ) \
-			    - ABLK_HDR_SZ)
-#define MBC_HEADER_SIZE(AP) SBC_HEADER_SIZE
+/* #define ERTS_ALC_CPOOL_DEBUG */
+
+#if defined(DEBUG) && !defined(ERTS_ALC_CPOOL_DEBUG)
+#  define ERTS_ALC_CPOOL_DEBUG
+#endif
+
+#ifndef ERTS_SMP
+#  undef ERTS_ALC_CPOOL_DEBUG
+#endif
+
+#ifdef ERTS_ALC_CPOOL_DEBUG
+#  define ERTS_ALC_CPOOL_ASSERT(A)				\
+    ((void) ((A)						\
+	     ? 1						\
+	     : (erts_alcu_assert_failed(#A,			\
+					(char *) __FILE__,	\
+					__LINE__,		\
+					(char *) __func__),	\
+		0)))
+#else
+#  define ERTS_ALC_CPOOL_ASSERT(A) ((void) 1)
+#endif
+
+#ifdef ERTS_SMP
+#define ERTS_ALC_IS_CPOOL_ENABLED(A)	((A)->cpool.util_limit)
+#else
+#define ERTS_ALC_IS_CPOOL_ENABLED(A)	(0)
+#endif
+
+#ifdef ERTS_SMP
+
+#define ERTS_ALC_CPOOL_MAX_DISABLE_ABANDON		1000
+#define ERTS_ALC_CPOOL_ALLOC_OP_INC			8
+#define ERTS_ALC_CPOOL_FREE_OP_DEC			10
+
+#define ERTS_ALC_CPOOL_ALLOC_OP(A)						\
+do {										\
+    if ((A)->cpool.disable_abandon < ERTS_ALC_CPOOL_MAX_DISABLE_ABANDON) { 	\
+	(A)->cpool.disable_abandon += ERTS_ALC_CPOOL_ALLOC_OP_INC;		\
+	if ((A)->cpool.disable_abandon > ERTS_ALC_CPOOL_MAX_DISABLE_ABANDON)	\
+	    (A)->cpool.disable_abandon = ERTS_ALC_CPOOL_MAX_DISABLE_ABANDON;	\
+    }										\
+} while (0)
+
+
+#if ERTS_ALC_CPOOL_ALLOC_OP_INC >= ERTS_ALC_CPOOL_FREE_OP_DEC
+#  error "Implementation assume ERTS_ALC_CPOOL_ALLOC_OP_INC < ERTS_ALC_CPOOL_FREE_OP_DEC"
+#endif
+
+#define ERTS_ALC_CPOOL_REALLOC_OP(A)						\
+do {										\
+    if ((A)->cpool.disable_abandon) {						\
+	(A)->cpool.disable_abandon -= (ERTS_ALC_CPOOL_FREE_OP_DEC		\
+				       - ERTS_ALC_CPOOL_ALLOC_OP_INC);		\
+	if ((A)->cpool.disable_abandon < 0)					\
+	    (A)->cpool.disable_abandon = 0;					\
+    }										\
+} while (0)
+
+#define ERTS_ALC_CPOOL_FREE_OP(A)						\
+do {										\
+    if ((A)->cpool.disable_abandon) {						\
+	(A)->cpool.disable_abandon -= ERTS_ALC_CPOOL_FREE_OP_DEC;		\
+	if ((A)->cpool.disable_abandon < 0)					\
+	    (A)->cpool.disable_abandon = 0;					\
+    }										\
+} while (0)
+
+#else
+#define ERTS_ALC_CPOOL_ALLOC_OP(A)
+#define ERTS_ALC_CPOOL_REALLOC_OP(A)
+#define ERTS_ALC_CPOOL_FREE_OP(A)
+#endif
+
+#define ERTS_CRR_ALCTR_FLG_IN_POOL	(((erts_aint_t) 1) << 0)
+#define ERTS_CRR_ALCTR_FLG_BUSY		(((erts_aint_t) 1) << 1)
+
+#ifdef ERTS_SMP
+#define SBC_HEADER_SIZE	   						\
+    (UNIT_CEILING(sizeof(Carrier_t)					\
+		  - sizeof(ErtsAlcCPoolData_t)				\
+		  + ABLK_HDR_SZ)					\
+     - ABLK_HDR_SZ)
+#else
+#define SBC_HEADER_SIZE	   						\
+    (UNIT_CEILING(sizeof(Carrier_t)					\
+		  + ABLK_HDR_SZ)					\
+     - ABLK_HDR_SZ)
+#endif
+#define MBC_HEADER_SIZE(AP) ((AP)->mbc_header_size)
 
 
 #define MSEG_CARRIER_HDR_FLAG		(((UWord) 1) << 0)
@@ -352,7 +401,8 @@ MBC after deallocating first block:
 #define SCH_SBC				SBC_CARRIER_HDR_FLAG
 
 #define SET_CARRIER_HDR(C, Sz, F, AP) \
-  (ASSERT(((Sz) & FLG_MASK) == 0), (C)->chdr = ((Sz) | (F)), (C)->allctr = (AP))
+  (ASSERT(((Sz) & FLG_MASK) == 0), (C)->chdr = ((Sz) | (F)), \
+   erts_smp_atomic_init_nob(&(C)->allctr, (erts_aint_t) (AP)))
 
 #define BLK_TO_SBC(B) \
   ((Carrier_t *) (((char *) (B)) - SBC_HEADER_SIZE))
@@ -385,6 +435,7 @@ MBC after deallocating first block:
 #define CFLG_FORCE_SYS_ALLOC			(1 << 3)
 #define CFLG_FORCE_SIZE				(1 << 4)
 #define CFLG_MAIN_CARRIER			(1 << 5)
+#define CFLG_NO_CPOOL				(1 << 6)
 
 #ifdef ERTS_ALLOC_UTIL_HARD_DEBUG
 static void check_blk_carrier(Allctr_t *, Block_t *);
@@ -412,11 +463,7 @@ static void check_blk_carrier(Allctr_t *, Block_t *);
     ASSERT(((AP)->mbcs.curr.norm.sys_alloc.no				\
 	    && (AP)->mbcs.curr.norm.sys_alloc.size)			\
 	   || (!(AP)->mbcs.curr.norm.sys_alloc.no			\
-	       && !(AP)->mbcs.curr.norm.sys_alloc.size));		\
-    ASSERT(((AP)->sbmbcs.curr.small_block.no				\
-	    && (AP)->sbmbcs.curr.small_block.size)			\
-	   || (!(AP)->sbmbcs.curr.small_block.no			\
-	       && !(AP)->sbmbcs.curr.small_block.size))
+	       && !(AP)->mbcs.curr.norm.sys_alloc.size));
 
 #else
 #define DEBUG_CHECK_CARRIER_NO_SZ(AP)
@@ -487,17 +534,6 @@ do {									\
 			       + (AP)->mbcs.curr.norm.sys_alloc.size)
 
 
-#define STAT_SBMBC_ALLOC(AP, CSZ)					\
-do {									\
-    (AP)->sbmbcs.curr.small_block.no++;					\
-    (AP)->sbmbcs.curr.small_block.size += (CSZ);			\
-    if ((AP)->sbmbcs.max.no < (AP)->sbmbcs.curr.small_block.no)		\
-	(AP)->sbmbcs.max.no = (AP)->sbmbcs.curr.small_block.no;		\
-    if ((AP)->sbmbcs.max.size < (AP)->sbmbcs.curr.small_block.size)	\
-	(AP)->sbmbcs.max.size = (AP)->sbmbcs.curr.small_block.size;	\
-    DEBUG_CHECK_CARRIER_NO_SZ((AP));					\
-} while (0)
-
 #define STAT_MSEG_MBC_ALLOC(AP, CSZ)					\
 do {									\
     (AP)->mbcs.curr.norm.mseg.no++;					\
@@ -514,13 +550,19 @@ do {									\
     DEBUG_CHECK_CARRIER_NO_SZ((AP));					\
 } while (0)
 
-#define STAT_SBMBC_FREE(AP, CSZ)					\
+#define STAT_MBC_CPOOL_FETCH(AP, CRR)					\
 do {									\
-    ASSERT((AP)->sbmbcs.curr.small_block.no > 0);			\
-    (AP)->sbmbcs.curr.small_block.no--;					\
-    ASSERT((AP)->sbmbcs.curr.small_block.size >= (CSZ));		\
-    (AP)->sbmbcs.curr.small_block.size -= (CSZ);			\
-    DEBUG_CHECK_CARRIER_NO_SZ((AP));					\
+    UWord csz__ = CARRIER_SZ((CRR));					\
+    if (IS_MSEG_CARRIER((CRR)))						\
+	STAT_MSEG_MBC_ALLOC((AP), csz__);				\
+    else								\
+	STAT_SYS_ALLOC_MBC_ALLOC((AP), csz__);				\
+    (AP)->mbcs.blocks.curr.no += (CRR)->cpool.blocks;			\
+    if ((AP)->mbcs.blocks.max.no < (AP)->mbcs.blocks.curr.no)		\
+	(AP)->mbcs.blocks.max.no = (AP)->mbcs.blocks.curr.no;		\
+    (AP)->mbcs.blocks.curr.size += (CRR)->cpool.blocks_size;		\
+    if ((AP)->mbcs.blocks.max.size < (AP)->mbcs.blocks.curr.size)	\
+	(AP)->mbcs.blocks.max.size = (AP)->mbcs.blocks.curr.size;	\
 } while (0)
 
 #define STAT_MSEG_MBC_FREE(AP, CSZ)					\
@@ -541,28 +583,88 @@ do {									\
     DEBUG_CHECK_CARRIER_NO_SZ((AP));					\
 } while (0)
 
-#define STAT_MBC_BLK_ALLOC(AP, BSZ, FLGS)	       			\
+#define STAT_MBC_CPOOL_INSERT(AP, CRR)					\
+do {									\
+    UWord csz__ = CARRIER_SZ((CRR));					\
+    if (IS_MSEG_CARRIER((CRR)))						\
+	STAT_MSEG_MBC_FREE((AP), csz__);				\
+    else								\
+	STAT_SYS_ALLOC_MBC_FREE((AP), csz__);				\
+    ERTS_ALC_CPOOL_ASSERT((AP)->mbcs.blocks.curr.no			\
+			  >= (CRR)->cpool.blocks);			\
+    (AP)->mbcs.blocks.curr.no -= (CRR)->cpool.blocks;			\
+    ERTS_ALC_CPOOL_ASSERT((AP)->mbcs.blocks.curr.size 			\
+			  >= (CRR)->cpool.blocks_size);			\
+    (AP)->mbcs.blocks.curr.size -= (CRR)->cpool.blocks_size;		\
+} while (0)
+
+#ifdef ERTS_SMP
+#define STAT_MBC_BLK_ALLOC_CRR(CRR, BSZ)				\
+do {									\
+    (CRR)->cpool.blocks++;						\
+    (CRR)->cpool.blocks_size += (BSZ);					\
+} while (0)
+#else
+#define STAT_MBC_BLK_ALLOC_CRR(CRR, BSZ) ((void) (CRR)) /* Get rid of warning */
+#endif
+
+#define STAT_MBC_BLK_ALLOC(AP, CRR, BSZ, FLGS)	       			\
 do {									\
-    CarriersStats_t *cstats__ = (((FLGS) & ERTS_ALCU_FLG_SBMBC)		\
-				 ? &(AP)->sbmbcs			\
-				 : &(AP)->mbcs);			\
+    CarriersStats_t *cstats__ = &(AP)->mbcs;			        \
     cstats__->blocks.curr.no++;						\
     if (cstats__->blocks.max.no < cstats__->blocks.curr.no)		\
 	cstats__->blocks.max.no = cstats__->blocks.curr.no;		\
     cstats__->blocks.curr.size += (BSZ);				\
     if (cstats__->blocks.max.size < cstats__->blocks.curr.size)		\
 	cstats__->blocks.max.size = cstats__->blocks.curr.size;		\
+    STAT_MBC_BLK_ALLOC_CRR((CRR), (BSZ));				\
 } while (0)
 
-#define STAT_MBC_BLK_FREE(AP, BSZ, FLGS)				\
+static ERTS_INLINE int
+stat_cpool_mbc_blk_free(Allctr_t *allctr,
+			Carrier_t *crr,
+			Carrier_t **busy_pcrr_pp,
+			UWord blksz)
+{
+#ifdef ERTS_SMP
+
+    ERTS_ALC_CPOOL_ASSERT(crr->cpool.blocks > 0);
+    crr->cpool.blocks--;
+    ERTS_ALC_CPOOL_ASSERT(crr->cpool.blocks_size >= blksz);
+    crr->cpool.blocks_size -= blksz;
+
+    if (!busy_pcrr_pp || !*busy_pcrr_pp)
+	return 0;
+
+    ERTS_ALC_CPOOL_ASSERT(crr == *busy_pcrr_pp);
+
+#ifdef ERTS_ALC_CPOOL_DEBUG
+    ERTS_ALC_CPOOL_ASSERT(
+	erts_atomic_dec_read_nob(&allctr->cpool.stat.no_blocks) >= 0);
+    ERTS_ALC_CPOOL_ASSERT(
+	erts_atomic_add_read_nob(&allctr->cpool.stat.blocks_size,
+				 -((erts_aint_t) blksz)) >= 0);
+#else
+    erts_atomic_dec_nob(&allctr->cpool.stat.no_blocks);
+    erts_atomic_add_nob(&allctr->cpool.stat.blocks_size,
+			-((erts_aint_t) blksz));
+#endif
+
+    return 1;
+#else
+    return 0;
+#endif
+}
+
+#define STAT_MBC_BLK_FREE(AP, CRR, BPCRRPP, BSZ, FLGS)			\
 do {									\
-    CarriersStats_t *cstats__ = (((FLGS) & ERTS_ALCU_FLG_SBMBC)		\
-				 ? &(AP)->sbmbcs			\
-				 : &(AP)->mbcs);			\
-    ASSERT(cstats__->blocks.curr.no > 0);				\
-    cstats__->blocks.curr.no--;						\
-    ASSERT(cstats__->blocks.curr.size >= (BSZ));			\
-    cstats__->blocks.curr.size -= (BSZ);				\
+    if (!stat_cpool_mbc_blk_free((AP), (CRR), (BPCRRPP), (BSZ))) {	\
+	CarriersStats_t *cstats__ = &(AP)->mbcs;			\
+	ASSERT(cstats__->blocks.curr.no > 0);				\
+	cstats__->blocks.curr.no--;					\
+	ASSERT(cstats__->blocks.curr.size >= (BSZ));			\
+	cstats__->blocks.curr.size -= (BSZ);				\
+    }									\
 } while (0)
 
 /* Debug stuff... */
@@ -613,13 +715,42 @@ do {									\
 #define ERTS_ALCU_DBG_CHK_THR_ACCESS(A)
 #endif
 
-
 static void make_name_atoms(Allctr_t *allctr);
 
 static Block_t *create_carrier(Allctr_t *, Uint, UWord);
-static void destroy_carrier(Allctr_t *, Block_t *);
-static void mbc_free(Allctr_t *allctr, void *p);
+static void destroy_carrier(Allctr_t *, Block_t *, Carrier_t **);
+static void mbc_free(Allctr_t *allctr, void *p, Carrier_t **busy_pcrr_pp);
+static void dealloc_block(Allctr_t *, void *, int);
+
+/* internal data... */
+
+#if 0
+
+static ERTS_INLINE void *
+internal_alloc(UWord size)
+{
+    void *res = erts_sys_alloc(0, NULL, size);
+    if (!res)
+	erts_alloc_enomem(ERTS_ALC_T_UNDEF, size);
+    return res;
+}
 
+static ERTS_INLINE void *
+internal_realloc(void *ptr, UWord size)
+{
+    void *res = erts_sys_realloc(0, NULL, ptr, size);
+    if (!res)
+	erts_alloc_enomem(ERTS_ALC_T_UNDEF, size);
+    return res;
+}
+
+static ERTS_INLINE void
+internal_free(void *ptr)
+{
+    erts_sys_free(0, NULL, ptr);
+}
+
+#endif
 
 /* mseg ... */
 
@@ -781,10 +912,35 @@ unlink_carrier(CarrierList_t *cl, Carrier_t *crr)
     }
 }
 
-static Block_t *create_sbmbc(Allctr_t *allctr, Uint umem_sz);
-static void destroy_sbmbc(Allctr_t *allctr, Block_t *blk);
-static Block_t *create_carrier(Allctr_t *, Uint, UWord);
-static void destroy_carrier(Allctr_t *, Block_t *);
+#ifdef ERTS_SMP
+
+static ERTS_INLINE void
+clear_busy_pool_carrier(Allctr_t *allctr, Carrier_t *crr)
+{
+    if (crr) {
+	erts_aint_t max_size;
+	erts_aint_t new_val;
+
+	max_size = (erts_aint_t) allctr->largest_fblk_in_mbc(allctr, crr);
+	erts_atomic_set_nob(&crr->cpool.max_size, max_size);
+
+	new_val = (((erts_aint_t) allctr)|ERTS_CRR_ALCTR_FLG_IN_POOL);
+
+#ifdef ERTS_ALC_CPOOL_DEBUG
+	{
+	    erts_aint_t old_val = new_val|ERTS_CRR_ALCTR_FLG_BUSY;
+
+	    ERTS_ALC_CPOOL_ASSERT(old_val
+				  == erts_smp_atomic_xchg_relb(&crr->allctr,
+							       new_val));
+	}
+#else
+	erts_smp_atomic_set_relb(&crr->allctr, new_val);
+#endif
+    }
+}
+
+#endif
 
 #if 0
 #define ERTS_DBG_CHK_FIX_LIST(A, FIX, IX, B)			\
@@ -806,13 +962,154 @@ chk_fix_list(Allctr_t *allctr, ErtsAlcFixList_t *fix, int ix, int before)
 #define ERTS_DBG_CHK_FIX_LIST(A, FIX, IX, B)
 #endif
 
-erts_aint32_t
-erts_alcu_fix_alloc_shrink(Allctr_t *allctr, erts_aint32_t flgs)
+static void *mbc_alloc(Allctr_t *allctr, Uint size);
+
+#ifdef ERTS_SMP
+typedef struct {
+    ErtsAllctrDDBlock_t ddblock__; /* must be first */
+    ErtsAlcType_t fix_type;
+} ErtsAllctrFixDDBlock_t;
+#endif
+
+static ERTS_INLINE void
+dealloc_fix_block(Allctr_t *allctr,
+		  ErtsAlcType_t type,
+		  void *ptr,
+		  int dec_cc_on_redirect)
+{
+#ifdef ERTS_SMP
+    /* May be redirected... */
+    ((ErtsAllctrFixDDBlock_t *) ptr)->fix_type = type;
+#endif
+    dealloc_block(allctr, ptr, dec_cc_on_redirect);
+}
+
+static ERTS_INLINE void
+sched_fix_shrink(Allctr_t *allctr, int on)
+{
+    if (on && !allctr->fix_shrink_scheduled) {
+	allctr->fix_shrink_scheduled = 1;
+	erts_set_aux_work_timeout(allctr->ix,
+				  (ERTS_SSI_AUX_WORK_FIX_ALLOC_LOWER_LIM
+				   | ERTS_SSI_AUX_WORK_FIX_ALLOC_DEALLOC),
+				  1);
+    }
+    else if (!on && allctr->fix_shrink_scheduled) {
+	allctr->fix_shrink_scheduled = 0;
+	erts_set_aux_work_timeout(allctr->ix,
+				  (ERTS_SSI_AUX_WORK_FIX_ALLOC_LOWER_LIM
+				   | ERTS_SSI_AUX_WORK_FIX_ALLOC_DEALLOC),
+				  0);
+    }
+}
+
+static ERTS_INLINE void
+fix_cpool_check_shrink(Allctr_t *allctr,
+		       ErtsAlcType_t type,
+		       ErtsAlcFixList_t *fix,
+		       Carrier_t **busy_pcrr_pp)
+{
+    if (fix->u.cpool.shrink_list > 0) {
+	if (fix->list_size == 0)
+	    fix->u.cpool.shrink_list = 0;
+	else {
+	    void *p;
+#ifdef ERTS_SMP
+	    if (busy_pcrr_pp) {
+		clear_busy_pool_carrier(allctr, *busy_pcrr_pp);
+		*busy_pcrr_pp = NULL;
+	    }
+#endif
+	    fix->u.cpool.shrink_list--;
+	    p = fix->list;
+	    fix->list = *((void **) p);
+	    fix->list_size--;
+	    if (fix->u.cpool.min_list_size > fix->list_size)
+		fix->u.cpool.min_list_size = fix->list_size;
+
+	    fix->u.cpool.allocated--;
+	    dealloc_fix_block(allctr, type, p, 0);
+	}
+    }
+}
+
+static ERTS_INLINE void *
+fix_cpool_alloc(Allctr_t *allctr, ErtsAlcType_t type, Uint size)
+{
+    void *res;
+    ErtsAlcFixList_t *fix;
+
+    ASSERT(ERTS_ALC_N_MIN_A_FIXED_SIZE <= type
+	   && type <= ERTS_ALC_N_MAX_A_FIXED_SIZE);
+
+    fix = &allctr->fix[type - ERTS_ALC_N_MIN_A_FIXED_SIZE];
+
+    res = fix->list;
+    if (res) {
+	fix->list = *((void **) res);
+	fix->list_size--;
+	if (fix->u.cpool.min_list_size > fix->list_size)
+	    fix->u.cpool.min_list_size = fix->list_size;
+	fix->u.cpool.used++;
+	fix_cpool_check_shrink(allctr, type, fix, NULL);
+	return res;
+    }
+    if (size < 2*sizeof(UWord))
+	size += sizeof(UWord);
+    if (size >= allctr->sbc_threshold) {
+	Block_t *blk;
+	blk = create_carrier(allctr, size, CFLG_SBC);
+	res = blk ? BLK2UMEM(blk) : NULL;
+    }
+    else
+	res = mbc_alloc(allctr, size);
+    if (res) {
+	fix->u.cpool.used++;
+	fix->u.cpool.allocated++;
+    }
+    return res;
+}
+
+static ERTS_INLINE void
+fix_cpool_free(Allctr_t *allctr,
+	       ErtsAlcType_t type,
+	       void *p,
+	       Carrier_t **busy_pcrr_pp)
+{
+    ErtsAlcFixList_t *fix;
+
+    ASSERT(ERTS_ALC_N_MIN_A_FIXED_SIZE <= type
+	   && type <= ERTS_ALC_N_MAX_A_FIXED_SIZE);
+
+    fix = &allctr->fix[type - ERTS_ALC_N_MIN_A_FIXED_SIZE];
+    
+    fix->u.cpool.used--;
+
+    if ((!busy_pcrr_pp || !*busy_pcrr_pp)
+	&& !fix->u.cpool.shrink_list
+	&& fix->list_size < ERTS_ALCU_FIX_MAX_LIST_SZ) {
+	*((void **) p) = fix->list;
+	fix->list = p;
+	fix->list_size++;
+	sched_fix_shrink(allctr, 1);
+    }
+    else {
+	Block_t *blk = UMEM2BLK(p);
+	if (IS_SBC_BLK(blk))
+	    destroy_carrier(allctr, blk, NULL);
+	else
+	    mbc_free(allctr, p, busy_pcrr_pp);
+	fix->u.cpool.allocated--;
+	fix_cpool_check_shrink(allctr, type, fix, busy_pcrr_pp);
+    }
+}
+
+static ERTS_INLINE erts_aint32_t
+fix_cpool_alloc_shrink(Allctr_t *allctr, erts_aint32_t flgs)
 {
     int all_empty = 1;
     erts_aint32_t res = 0;
     int ix, o;
-    ErtsAlcFixList_t *fix = allctr->fix;
     int flush = flgs == 0;
 
 #ifdef USE_THREADS
@@ -821,56 +1118,204 @@ erts_alcu_fix_alloc_shrink(Allctr_t *allctr, erts_aint32_t flgs)
 #endif
 
     for (ix = 0; ix < ERTS_ALC_NO_FIXED_SIZES; ix++) {
+	ErtsAlcFixList_t *fix = &allctr->fix[ix];
+	ErtsAlcType_t type;
 	ERTS_DBG_CHK_FIX_LIST(allctr, fix, ix, 1);
-	if (flgs & ERTS_SSI_AUX_WORK_FIX_ALLOC_LOWER_LIM) {
-	    fix[ix].limit = fix[ix].max_used;
-	    if (fix[ix].limit < fix[ix].used)
-		fix[ix].limit = fix[ix].used;
-	    fix[ix].max_used = fix[ix].used;
-	    ASSERT(fix[ix].limit >= 0);
-
-	}
-	if (flush) {
-	    fix[ix].limit = 0;
-	    fix[ix].max_used = fix[ix].used;
-	    ASSERT(fix[ix].limit >= 0);
+	if (flush)
+	    fix->u.cpool.shrink_list = fix->list_size;
+	else if (flgs & ERTS_SSI_AUX_WORK_FIX_ALLOC_LOWER_LIM) {
+	    fix->u.cpool.shrink_list = fix->u.cpool.min_list_size;
+	    fix->u.cpool.min_list_size = fix->list_size;
 	}
+	type = (ErtsAlcType_t) (ix + ERTS_ALC_N_MIN_A_FIXED_SIZE);
 	for (o = 0; o < ERTS_ALC_FIX_MAX_SHRINK_OPS || flush; o++) {
-	    Block_t *blk;
 	    void *ptr;
 
-	    if (!flush && fix[ix].limit >= fix[ix].allocated)
+	    if (fix->u.cpool.shrink_list == 0)
 		break;
-	    if (fix[ix].list_size == 0)
+	    if (fix->list_size == 0) {
+		fix->u.cpool.shrink_list = 0;
 		break;
-	    ptr = fix[ix].list;
-	    fix[ix].list = *((void **) ptr);
-	    fix[ix].list_size--;	    
+	    }
+	    ptr = fix->list;
+	    fix->list = *((void **) ptr);
+	    fix->list_size--;
+	    fix->u.cpool.shrink_list--;
+	    fix->u.cpool.allocated--;
+	    dealloc_fix_block(allctr, type, ptr, 0);
+	}
+	if (fix->u.cpool.min_list_size > fix->list_size)
+	    fix->u.cpool.min_list_size = fix->list_size;
+	if (fix->list_size != 0) {
+	    if (fix->u.cpool.shrink_list > 0)
+		res |= ERTS_SSI_AUX_WORK_FIX_ALLOC_DEALLOC;
+	    all_empty = 0;
+	}
+    }
+
+    if (all_empty)
+	sched_fix_shrink(allctr, 0);
+
+#ifdef USE_THREADS
+    if (allctr->thread_safe)
+	erts_mtx_unlock(&allctr->mutex);
+#endif
 
-	    blk = UMEM2BLK(ptr);
+    return res;
+}
 
+static ERTS_INLINE void *
+fix_nocpool_alloc(Allctr_t *allctr, ErtsAlcType_t type, Uint size)
+{
+    ErtsAlcFixList_t *fix;
+    void *res;
+
+    ASSERT(ERTS_ALC_N_MIN_A_FIXED_SIZE <= type
+	   && type <= ERTS_ALC_N_MAX_A_FIXED_SIZE);
+
+    fix = &allctr->fix[type - ERTS_ALC_N_MIN_A_FIXED_SIZE];
+
+    ERTS_DBG_CHK_FIX_LIST(allctr, fix, ix, 1);
+    fix->u.nocpool.used++;
+    res = fix->list;
+    if (res) {
+	fix->list_size--;
+	fix->list = *((void **) res);
+	if (fix->list && fix->u.nocpool.allocated > fix->u.nocpool.limit) {
+	    Block_t *blk;
+	    void *p = fix->list;
+	    fix->list = *((void **) p);
+	    fix->list_size--;
+	    blk = UMEM2BLK(p);
 	    if (IS_SBC_BLK(blk))
-		destroy_carrier(allctr, blk);
+		destroy_carrier(allctr, blk, NULL);
 	    else
-		mbc_free(allctr, ptr);
+		mbc_free(allctr, p, NULL);
+	    fix->u.nocpool.allocated--;
+	}
+	ERTS_DBG_CHK_FIX_LIST(allctr, fix, ix, 0);
+	return res;
+    }
+    if (size < 2*sizeof(UWord))
+	size += sizeof(UWord);
+    if (fix->u.nocpool.limit < fix->u.nocpool.used)
+	fix->u.nocpool.limit = fix->u.nocpool.used;
+    if (fix->u.nocpool.max_used < fix->u.nocpool.used)
+	fix->u.nocpool.max_used = fix->u.nocpool.used;
+    fix->u.nocpool.allocated++;
 
-	    fix[ix].allocated--;
+    if (size >= allctr->sbc_threshold) {
+	Block_t *blk;
+	blk = create_carrier(allctr, size, CFLG_SBC);
+	res = blk ? BLK2UMEM(blk) : NULL;
+    }
+    else
+	res = mbc_alloc(allctr, size);
+
+    if (!res) {
+	fix->u.nocpool.allocated--;
+	fix->u.nocpool.used--;
+    }
+    return res;
+}
+
+static ERTS_INLINE void
+fix_nocpool_free(Allctr_t *allctr,
+		 ErtsAlcType_t type,
+		 void *p)
+{
+    Block_t *blk;
+    ErtsAlcFixList_t *fix;
+
+    ASSERT(ERTS_ALC_N_MIN_A_FIXED_SIZE <= type
+	   && type <= ERTS_ALC_N_MAX_A_FIXED_SIZE);
+
+    fix = &allctr->fix[type - ERTS_ALC_N_MIN_A_FIXED_SIZE];
+
+    ERTS_DBG_CHK_FIX_LIST(allctr, fix, ix, 1);
+    fix->u.nocpool.used--;
+    if (fix->u.nocpool.allocated < fix->u.nocpool.limit
+	&& fix->list_size < ERTS_ALCU_FIX_MAX_LIST_SZ) {
+	*((void **) p) = fix->list;
+	fix->list = p;
+	fix->list_size++;
+	sched_fix_shrink(allctr, 1);
+	ERTS_DBG_CHK_FIX_LIST(allctr, fix, ix, 0);
+	return;
+    }
+    fix->u.nocpool.allocated--;
+    if (fix->list && fix->u.nocpool.allocated > fix->u.nocpool.limit) {
+	blk = UMEM2BLK(p);
+	if (IS_SBC_BLK(blk))
+	    destroy_carrier(allctr, blk, NULL);
+	else
+	    mbc_free(allctr, p, NULL);
+	p = fix->list;
+	fix->list = *((void **) p);
+	fix->list_size--;
+	fix->u.nocpool.allocated--;
+    }
+
+    blk = UMEM2BLK(p);
+    if (IS_SBC_BLK(blk))
+	destroy_carrier(allctr, blk, NULL);
+    else
+	mbc_free(allctr, p, NULL);
+    ERTS_DBG_CHK_FIX_LIST(allctr, fix, ix, 0);
+}
+
+static ERTS_INLINE erts_aint32_t
+fix_nocpool_alloc_shrink(Allctr_t *allctr, erts_aint32_t flgs)
+{
+    int all_empty = 1;
+    erts_aint32_t res = 0;
+    int ix, o;
+    int flush = flgs == 0;
+
+#ifdef USE_THREADS
+    if (allctr->thread_safe)
+	erts_mtx_lock(&allctr->mutex);
+#endif
+
+    for (ix = 0; ix < ERTS_ALC_NO_FIXED_SIZES; ix++) {
+	ErtsAlcFixList_t *fix = &allctr->fix[ix];
+	ERTS_DBG_CHK_FIX_LIST(allctr, fix, ix, 1);
+	if (flgs & ERTS_SSI_AUX_WORK_FIX_ALLOC_LOWER_LIM) {
+	    fix->u.nocpool.limit = fix->u.nocpool.max_used;
+	    if (fix->u.nocpool.limit < fix->u.nocpool.used)
+		fix->u.nocpool.limit = fix->u.nocpool.used;
+	    fix->u.nocpool.max_used = fix->u.nocpool.used;
+	    ASSERT(fix->u.nocpool.limit >= 0);
+
+	}
+	if (flush) {
+	    fix->u.nocpool.limit = 0;
+	    fix->u.nocpool.max_used = fix->u.nocpool.used;
+	    ASSERT(fix->u.nocpool.limit >= 0);
 	}
-	if (fix[ix].list_size != 0) {
-	    if (fix[ix].limit < fix[ix].allocated)
+	for (o = 0; o < ERTS_ALC_FIX_MAX_SHRINK_OPS || flush; o++) {
+	    void *ptr;
+
+	    if (!flush && fix->u.nocpool.limit >= fix->u.nocpool.allocated)
+		break;
+	    if (fix->list_size == 0)
+		break;
+	    ptr = fix->list;
+	    fix->list = *((void **) ptr);
+	    fix->list_size--;
+	    dealloc_block(allctr, ptr, 0);
+	    fix->u.nocpool.allocated--;
+	}
+	if (fix->list_size != 0) {
+	    if (fix->u.nocpool.limit < fix->u.nocpool.allocated)
 		res |= ERTS_SSI_AUX_WORK_FIX_ALLOC_DEALLOC;
 	    all_empty = 0;
 	}
 	ERTS_DBG_CHK_FIX_LIST(allctr, fix, ix, 0);
     }
 
-    if (all_empty && allctr->fix_shrink_scheduled) {
-	allctr->fix_shrink_scheduled = 0;
-	erts_set_aux_work_timeout(allctr->ix,
-				  (ERTS_SSI_AUX_WORK_FIX_ALLOC_LOWER_LIM
-				   | ERTS_SSI_AUX_WORK_FIX_ALLOC_DEALLOC),
-				  0);
-    }
+    if (all_empty)
+	sched_fix_shrink(allctr, 0);
 
 #ifdef USE_THREADS
     if (allctr->thread_safe)
@@ -880,13 +1325,18 @@ erts_alcu_fix_alloc_shrink(Allctr_t *allctr, erts_aint32_t flgs)
     return res;
 }
 
-#ifdef ERTS_SMP
+erts_aint32_t
+erts_alcu_fix_alloc_shrink(Allctr_t *allctr, erts_aint32_t flgs)
+{
+    if (ERTS_ALC_IS_CPOOL_ENABLED(allctr))
+	return fix_cpool_alloc_shrink(allctr, flgs);
+    else
+	return fix_nocpool_alloc_shrink(allctr, flgs);
+}
 
-typedef struct {
-    ErtsAllctrDDBlock_t ddblock__; /* must be first */
-    ErtsAlcType_t fix_type;
-}ErtsAllctrFixDDBlock_t;
+static void dealloc_carrier(Allctr_t *allctr, Carrier_t *crr, Uint mseg_flags);
 
+#ifdef ERTS_SMP
 
 static ERTS_INLINE Allctr_t*
 get_pref_allctr(void *extra)
@@ -902,6 +1352,9 @@ get_pref_allctr(void *extra)
     return tspec->allctr[pref_ix];
 }
 
+#define ERTS_ALC_TS_PREF_LOCK_IF_USED	(1)
+#define ERTS_ALC_TS_PREF_LOCK_NO	(0)
+
 /* SMP note:
  * get_used_allctr() must be safe WITHOUT locking the allocator while
  * concurrent threads may be updating adjacent blocks.
@@ -910,22 +1363,85 @@ get_pref_allctr(void *extra)
  * the "PREV_FREE" flag bit. 
  */
 static ERTS_INLINE Allctr_t*
-get_used_allctr(void *extra, void *p, UWord *sizep)
+get_used_allctr(Allctr_t *pref_allctr, int pref_lock, void *p, UWord *sizep,
+		Carrier_t **busy_pcrr_pp)
 {
     Block_t* blk = UMEM2BLK(p);
-    Carrier_t* crr;
+    Carrier_t *crr;
+    erts_aint_t iallctr;
+    Allctr_t *used_allctr;
+
+    *busy_pcrr_pp = NULL;
 
     if (IS_SBC_BLK(blk)) {
 	crr = BLK_TO_SBC(blk);
 	if (sizep)
 	    *sizep = SBC_BLK_SZ(blk) - ABLK_HDR_SZ;  
+	iallctr = erts_smp_atomic_read_dirty(&crr->allctr);
     }
     else {
 	crr = ABLK_TO_MBC(blk);
+
 	if (sizep)
 	    *sizep = MBC_ABLK_SZ(blk) - ABLK_HDR_SZ;
+	if (!ERTS_ALC_IS_CPOOL_ENABLED(pref_allctr))
+	    iallctr = erts_smp_atomic_read_dirty(&crr->allctr);
+	else {
+	    int locked_pref_allctr = 0;
+	    iallctr = erts_smp_atomic_read_ddrb(&crr->allctr);
+
+	    if (ERTS_ALC_TS_PREF_LOCK_IF_USED == pref_lock
+		&& pref_allctr->thread_safe) {
+		used_allctr = (Allctr_t *) (iallctr & ~FLG_MASK);
+		if (pref_allctr == used_allctr) {
+		    erts_mtx_lock(&pref_allctr->mutex);
+		    locked_pref_allctr = 1;
+		}
+	    }
+
+	    while ((iallctr & ((~FLG_MASK)|ERTS_CRR_ALCTR_FLG_IN_POOL))
+		   == (((erts_aint_t) pref_allctr)|ERTS_CRR_ALCTR_FLG_IN_POOL)) {
+		erts_aint_t act;
+
+		ERTS_ALC_CPOOL_ASSERT(!(iallctr & ERTS_CRR_ALCTR_FLG_BUSY));
+		act = erts_smp_atomic_cmpxchg_ddrb(&crr->allctr,
+						   iallctr|ERTS_CRR_ALCTR_FLG_BUSY,
+						   iallctr);
+		if (act == iallctr) {
+		    *busy_pcrr_pp = crr;
+		    break;
+		}
+		iallctr = act;
+	    }
+
+	    used_allctr = (Allctr_t *) (iallctr & ~FLG_MASK);
+
+	    if (ERTS_ALC_TS_PREF_LOCK_IF_USED == pref_lock) {
+		if (locked_pref_allctr && used_allctr != pref_allctr) {
+		    /* Was taken out of pool; now owned by someone else */
+		    erts_mtx_unlock(&pref_allctr->mutex);
+		}
+	    }
+
+	    ERTS_ALC_CPOOL_ASSERT(
+		(((iallctr & ~FLG_MASK) == (erts_aint_t) pref_allctr)
+		 ? (((iallctr & FLG_MASK) == ERTS_CRR_ALCTR_FLG_IN_POOL)
+		    || ((iallctr & FLG_MASK) == 0))
+		 : 1));
+
+	    return used_allctr;
+	}
+    }
+
+    used_allctr = (Allctr_t *) (iallctr & ~FLG_MASK);
+
+    if (ERTS_ALC_TS_PREF_LOCK_IF_USED == pref_lock
+	&& used_allctr == pref_allctr
+	&& pref_allctr->thread_safe) {
+	erts_mtx_lock(&pref_allctr->mutex);
     }
-    return crr->allctr;
+
+    return used_allctr;
 }
 
 static void
@@ -1020,7 +1536,7 @@ check_insert_marker(ErtsAllctrDDQueue_t *ddq, erts_aint_t ilast)
 }
 
 static ERTS_INLINE int
-ddq_enqueue(ErtsAlcType_t type, ErtsAllctrDDQueue_t *ddq, void *ptr, int cinit)
+ddq_enqueue(ErtsAllctrDDQueue_t *ddq, void *ptr, int cinit)
 {
     int last_elem;
     int um_refc_ix = 0;
@@ -1121,6 +1637,59 @@ store_earliest_thr_prgr(ErtsThrPrgrVal *prev_val, ErtsAllctrDDQueue_t *ddq)
     }
 }
 
+static void
+check_pending_dealloc_carrier(Allctr_t *allctr,
+			      int *need_thr_progress,
+			      ErtsThrPrgrVal *thr_prgr_p,
+			      int *need_more_work);
+
+static void
+handle_delayed_fix_dealloc(Allctr_t *allctr, void *ptr)
+{
+    ErtsAlcType_t type;
+
+    type = ((ErtsAllctrFixDDBlock_t *) ptr)->fix_type;
+
+    ASSERT(ERTS_ALC_N_MIN_A_FIXED_SIZE <= type
+	   && type <= ERTS_ALC_N_MAX_A_FIXED_SIZE);
+
+    if (!ERTS_ALC_IS_CPOOL_ENABLED(allctr))
+	fix_nocpool_free(allctr, type, ptr);
+    else {
+	Block_t *blk = UMEM2BLK(ptr);
+	Carrier_t *busy_pcrr_p;
+	Allctr_t *used_allctr;
+
+	if (IS_SBC_BLK(blk)) {
+	    busy_pcrr_p = NULL;
+	    goto doit;
+	}
+
+	used_allctr = get_used_allctr(allctr, ERTS_ALC_TS_PREF_LOCK_NO, ptr,
+				      NULL, &busy_pcrr_p);
+	if (used_allctr == allctr) {
+	doit:
+	    fix_cpool_free(allctr, type, ptr, &busy_pcrr_p);
+	    clear_busy_pool_carrier(allctr, busy_pcrr_p);
+	}
+	else {
+	    /* Carrier migrated; need to redirect block to new owner... */
+	    int cinit = used_allctr->dd.ix - allctr->dd.ix;
+
+	    ERTS_ALC_CPOOL_ASSERT(!busy_pcrr_p);
+
+	    DEC_CC(allctr->calls.this_free);
+
+	    ((ErtsAllctrFixDDBlock_t *) ptr)->fix_type = type;
+	    if (ddq_enqueue(&used_allctr->dd.q, ptr, cinit))
+		erts_alloc_notify_delayed_dealloc(used_allctr->ix);
+	}
+    }
+}
+
+static void
+schedule_dealloc_carrier(Allctr_t *allctr, Carrier_t *crr);
+
 static ERTS_INLINE int
 handle_delayed_dealloc(Allctr_t *allctr,
 		       int allctr_locked,
@@ -1152,7 +1721,6 @@ handle_delayed_dealloc(Allctr_t *allctr,
     while (1) {
 	Block_t *blk;
 	void *ptr;
-	int ix;
 
 	if (use_limit && ++ops > ops_limit) {
 	    if (ddq->head.first != ddq->head.unref_end) {
@@ -1181,52 +1749,29 @@ handle_delayed_dealloc(Allctr_t *allctr,
 
 	res = 1;
 
-	INC_CC(allctr->calls.this_free);
-
-	if (fix) {
-	    ErtsAlcType_t type;
-
-	    type = ((ErtsAllctrFixDDBlock_t*) ptr)->fix_type;
-	    ix = type - ERTS_ALC_N_MIN_A_FIXED_SIZE;
-	    ERTS_DBG_CHK_FIX_LIST(allctr, fix, ix, 1);
-	    fix[ix].used--;
-	    if (fix[ix].allocated < fix[ix].limit
-		&& fix[ix].list_size < ERTS_ALCU_FIX_MAX_LIST_SZ) {
-		*((void **) ptr) = fix[ix].list;
-		fix[ix].list = ptr;
-		fix[ix].list_size++;
-		if (!allctr->fix_shrink_scheduled) {
-		    allctr->fix_shrink_scheduled = 1;
-		    erts_set_aux_work_timeout(
-			allctr->ix,
-			(ERTS_SSI_AUX_WORK_FIX_ALLOC_LOWER_LIM
-			 | ERTS_SSI_AUX_WORK_FIX_ALLOC_DEALLOC),
-			1);
-		}
-		ERTS_DBG_CHK_FIX_LIST(allctr, fix, ix, 0);
-		continue;
-	    }
-	    fix[ix].allocated--;
-	    if (fix[ix].list && fix[ix].allocated > fix[ix].limit) {
-		blk = UMEM2BLK(ptr);
-		if (IS_SBC_BLK(blk))
-		    destroy_carrier(allctr, blk);
-		else
-		    mbc_free(allctr, ptr);
-		ptr = fix[ix].list;
-		fix[ix].list = *((void **) ptr);
-		fix[ix].list_size--;
-		fix[ix].allocated--;
-	    }
+	blk = UMEM2BLK(ptr);
+	if (IS_FREE_LAST_MBC_BLK(blk)) {
+	    /*
+	     * A multiblock carrier that previously has been migrated away
+	     * from us and now is back to be deallocated...
+	     *
+	     * Note that we cannot use FBLK_TO_MBC(blk) since it
+	     * data has been overwritten by the queue.
+	     */
+	    Carrier_t *crr = FIRST_BLK_TO_MBC(allctr, blk);
+	    ERTS_ALC_CPOOL_ASSERT(ERTS_ALC_IS_CPOOL_ENABLED(allctr));
+	    ERTS_ALC_CPOOL_ASSERT(allctr == crr->cpool.orig_allctr);
+	    schedule_dealloc_carrier(allctr, crr);
 	}
+	else {
 
-	blk = UMEM2BLK(ptr);
+	    INC_CC(allctr->calls.this_free);
 
-	if (IS_SBC_BLK(blk))
-	    destroy_carrier(allctr, blk);
-	else
-	    mbc_free(allctr, ptr);
-	ERTS_DBG_CHK_FIX_LIST(allctr, fix, ix, 0);
+	    if (fix)
+		handle_delayed_fix_dealloc(allctr, ptr);
+	    else
+		dealloc_block(allctr, ptr, 1);
+	}
     }
 
     if (need_thr_progress && !(need_thr_prgr | need_mr_wrk)) {
@@ -1236,6 +1781,12 @@ handle_delayed_dealloc(Allctr_t *allctr,
 	    store_earliest_thr_prgr(thr_prgr_p, ddq);
     }
 
+    if (ERTS_ALC_IS_CPOOL_ENABLED(allctr))
+	check_pending_dealloc_carrier(allctr,
+				      need_thr_progress,
+				      thr_prgr_p,
+				      need_more_work);
+
     if (allctr->thread_safe && !allctr_locked)
 	erts_mtx_unlock(&allctr->mutex);
    return res;
@@ -1250,13 +1801,59 @@ enqueue_dealloc_other_instance(ErtsAlcType_t type,
     if (allctr->fix)
 	((ErtsAllctrFixDDBlock_t*) ptr)->fix_type = type;
 
-    if (ddq_enqueue(type, &allctr->dd.q, ptr, cinit))
+    if (ddq_enqueue(&allctr->dd.q, ptr, cinit))
 	erts_alloc_notify_delayed_dealloc(allctr->ix);
 }
 
 #endif
 
 #ifdef ERTS_SMP
+static void
+set_new_allctr_abandon_limit(Allctr_t *allctr);
+static void
+abandon_carrier(Allctr_t *allctr, Carrier_t *crr);
+
+
+static ERTS_INLINE void
+check_abandon_carrier(Allctr_t *allctr, Block_t *fblk, Carrier_t **busy_pcrr_pp)
+{
+    Carrier_t *crr;
+
+    if (busy_pcrr_pp && *busy_pcrr_pp)
+	return;
+
+    if (!ERTS_ALC_IS_CPOOL_ENABLED(allctr))
+	return;
+
+    allctr->cpool.check_limit_count--;
+    if (--allctr->cpool.check_limit_count <= 0)
+	set_new_allctr_abandon_limit(allctr);
+
+    if (!erts_thr_progress_is_managed_thread())
+	return;
+
+    if (allctr->cpool.disable_abandon)
+	return;
+
+    if (allctr->mbcs.blocks.curr.size > allctr->cpool.abandon_limit)
+	return;
+
+
+    crr = FBLK_TO_MBC(fblk);
+
+    if (allctr->main_carrier == crr)
+	return;
+
+    if (crr->cpool.blocks_size > crr->cpool.abandon_limit)
+	return;
+
+    if (crr->cpool.thr_prgr != ERTS_THR_PRGR_INVALID
+	&& !erts_thr_progress_has_reached(crr->cpool.thr_prgr))
+	return;
+
+    abandon_carrier(allctr, crr);
+}
+
 void
 erts_alcu_check_delayed_dealloc(Allctr_t *allctr,
 				int limit,
@@ -1274,78 +1871,88 @@ erts_alcu_check_delayed_dealloc(Allctr_t *allctr,
 }
 #endif
 
-#define ERTS_ALCU_HANDLE_DD_IN_OP(Allctr, Locked) \
-    handle_delayed_dealloc((Allctr), (Locked), 1, \
+#define ERTS_ALCU_HANDLE_DD_IN_OP(Allctr, Locked)			\
+    handle_delayed_dealloc((Allctr), (Locked), 1, 			\
 			   ERTS_ALCU_DD_OPS_LIM_LOW, NULL, NULL, NULL)
 
+static void
+dealloc_block(Allctr_t *allctr, void *ptr, int dec_cc_on_redirect)
+{
+    Block_t *blk = UMEM2BLK(ptr);
+
+    ERTS_SMP_LC_ASSERT(!allctr->thread_safe
+		       || erts_lc_mtx_is_locked(&allctr->mutex));
+
+    if (IS_SBC_BLK(blk))
+	destroy_carrier(allctr, blk, NULL);
+#ifndef ERTS_SMP
+    else
+	mbc_free(allctr, ptr, NULL);
+#else
+    else if (!ERTS_ALC_IS_CPOOL_ENABLED(allctr))
+	mbc_free(allctr, ptr, NULL);
+    else {
+	Carrier_t *busy_pcrr_p;
+	Allctr_t *used_allctr;
+	used_allctr = get_used_allctr(allctr, ERTS_ALC_TS_PREF_LOCK_NO, ptr,
+				      NULL, &busy_pcrr_p);
+	if (used_allctr == allctr) {
+	    mbc_free(allctr, ptr, &busy_pcrr_p);
+	    clear_busy_pool_carrier(allctr, busy_pcrr_p);
+	}
+	else {
+	    /* Carrier migrated; need to redirect block to new owner... */
+	    int cinit = used_allctr->dd.ix - allctr->dd.ix;
+
+	    ERTS_ALC_CPOOL_ASSERT(!busy_pcrr_p);
+
+	    if (dec_cc_on_redirect)
+		DEC_CC(allctr->calls.this_free);
+	    if (ddq_enqueue(&used_allctr->dd.q, ptr, cinit))
+		erts_alloc_notify_delayed_dealloc(used_allctr->ix);
+	}
+    }
+#endif
+}
+
 /* Multi block carrier alloc/realloc/free ... */
 
 /* NOTE! mbc_alloc() may in case of memory shortage place the requested
  * block in a sbc.
  */
 static ERTS_INLINE void *
-mbc_alloc_block(Allctr_t *allctr, Uint size, Uint *blk_szp, Uint32 *alcu_flgsp)
+mbc_alloc_block(Allctr_t *allctr, Uint size, Uint *blk_szp)
 {
     Block_t *blk;
     Uint get_blk_sz;
-    Uint sbmbct;
 
     ASSERT(size);
     ASSERT(size < allctr->sbc_threshold);
 
     *blk_szp = get_blk_sz = UMEMSZ2BLKSZ(allctr, size);
 
-    sbmbct = allctr->sbmbc_threshold;
-    if (sbmbct) {
-	if (get_blk_sz < sbmbct) {
-	    *alcu_flgsp |= ERTS_ALCU_FLG_SBMBC;
-	    if (get_blk_sz + allctr->min_block_size > sbmbct) {
-		/* Since we use block size to determine if blocks are
-		   located in sbmbc or not... */
-		get_blk_sz += allctr->min_block_size;
-	    }
-	}
-    }
-
-#ifdef ERTS_SMP
-    if (allctr->dd.use)
-	ERTS_ALCU_HANDLE_DD_IN_OP(allctr, 1);
-#endif
-
-    blk = (*allctr->get_free_block)(allctr, get_blk_sz, NULL, 0, *alcu_flgsp);
-
-#ifdef ERTS_SMP
-    if (!blk && allctr->dd.use) {
-	if (ERTS_ALCU_HANDLE_DD_IN_OP(allctr, 1))
-	    blk = (*allctr->get_free_block)(allctr, get_blk_sz, NULL, 0,
-					    *alcu_flgsp);
-    }
-#endif
+    blk = (*allctr->get_free_block)(allctr, get_blk_sz, NULL, 0);
 
     if (!blk) {
-	if ((*alcu_flgsp) & ERTS_ALCU_FLG_SBMBC) 
-	    blk = create_sbmbc(allctr, get_blk_sz);
-	else {
-	    blk = create_carrier(allctr, get_blk_sz, CFLG_MBC);
+	blk = create_carrier(allctr, get_blk_sz, CFLG_MBC);
 #if !HALFWORD_HEAP && !HAVE_SUPER_ALIGNED_MB_CARRIERS
-	    if (!blk) {
-		/* Emergency! We couldn't create the carrier as we wanted.
-		   Try to place it in a sys_alloced sbc. */
-		blk = create_carrier(allctr,
-				     size,
-				     (CFLG_SBC
-				      | CFLG_FORCE_SIZE
-				      | CFLG_FORCE_SYS_ALLOC));
-	    }
-#endif
+	if (!blk) {
+	    /* Emergency! We couldn't create the carrier as we wanted.
+	       Try to place it in a sys_alloced sbc. */
+	    blk = create_carrier(allctr,
+				 size,
+				 (CFLG_SBC
+				  | CFLG_FORCE_SIZE
+				  | CFLG_FORCE_SYS_ALLOC));
 	}
+#endif
     }
 
 #ifdef ERTS_ALLOC_UTIL_HARD_DEBUG
     if (IS_MBC_BLK(blk)) {
-	(*allctr->link_free_block)(allctr, blk, *alcu_flgsp);
+	(*allctr->link_free_block)(allctr, blk);
 	HARD_CHECK_BLK_CARRIER(allctr, blk);
-	(*allctr->unlink_free_block)(allctr, blk, *alcu_flgsp);
+	(*allctr->unlink_free_block)(allctr, blk);
     }
 #endif
 
@@ -1359,8 +1966,7 @@ mbc_alloc_finalize(Allctr_t *allctr,
 		   UWord flags,
 		   Carrier_t *crr,
 		   Uint want_blk_sz,
-		   int valid_blk_info,
-		   Uint32 alcu_flgs)
+		   int valid_blk_info)
 {
     Uint blk_sz;
     Uint nxt_blk_sz;
@@ -1392,7 +1998,7 @@ mbc_alloc_finalize(Allctr_t *allctr,
 		SET_PREV_BLK_FREE(allctr, nxt_nxt_blk);
 	    }
 	}
-	(*allctr->link_free_block)(allctr, nxt_blk, alcu_flgs);
+	(*allctr->link_free_block)(allctr, nxt_blk);
 
 	ASSERT(IS_NOT_LAST_BLK(blk));
 	ASSERT(IS_FREE_BLK(nxt_blk));
@@ -1433,7 +2039,8 @@ mbc_alloc_finalize(Allctr_t *allctr,
 	ASSERT(ABLK_TO_MBC(blk) == crr);
     }
 
-    STAT_MBC_BLK_ALLOC(allctr, blk_sz, alcu_flgs);
+    ERTS_ALC_CPOOL_ALLOC_OP(allctr);
+    STAT_MBC_BLK_ALLOC(allctr, crr, blk_sz, alcu_flgs);
 
     ASSERT(IS_ALLOCED_BLK(blk));
     ASSERT(blk_sz == MBC_BLK_SZ(blk));
@@ -1453,8 +2060,7 @@ mbc_alloc(Allctr_t *allctr, Uint size)
 {
     Block_t *blk;
     Uint blk_sz;
-    Uint32 alcu_flgs = 0;
-    blk = mbc_alloc_block(allctr, size, &blk_sz, &alcu_flgs);
+    blk = mbc_alloc_block(allctr, size, &blk_sz);
     if (!blk)
 	return NULL;
     if (IS_MBC_BLK(blk))
@@ -1464,35 +2070,34 @@ mbc_alloc(Allctr_t *allctr, Uint size)
 			   GET_BLK_HDR_FLGS(blk),
 			   FBLK_TO_MBC(blk),
 			   blk_sz,
-			   1,
-			   alcu_flgs);
+			   1);
     return BLK2UMEM(blk);
 }
 
 static void
-mbc_free(Allctr_t *allctr, void *p)
+mbc_free(Allctr_t *allctr, void *p, Carrier_t **busy_pcrr_pp)
 {
     Uint is_first_blk;
     Uint is_last_blk;
-    Uint32 alcu_flgs = 0;
     Uint blk_sz;
     Block_t *blk;
     Block_t *nxt_blk;
-
+    Carrier_t *crr;
 
     ASSERT(p);
 
     blk = UMEM2BLK(p);
     blk_sz = MBC_ABLK_SZ(blk);
-    if (blk_sz < allctr->sbmbc_threshold)
-	alcu_flgs |= ERTS_ALCU_FLG_SBMBC;
 
     ASSERT(IS_MBC_BLK(blk));
     ASSERT(blk_sz >= allctr->min_block_size);
 
     HARD_CHECK_BLK_CARRIER(allctr, blk);
 
-    STAT_MBC_BLK_FREE(allctr, blk_sz, alcu_flgs);
+    crr = ABLK_TO_MBC(blk);
+
+    ERTS_ALC_CPOOL_FREE_OP(allctr);
+    STAT_MBC_BLK_FREE(allctr, crr, busy_pcrr_pp, blk_sz, alcu_flgs);
 
     is_first_blk = IS_MBC_FIRST_ABLK(allctr, blk);
     is_last_blk = IS_LAST_BLK(blk);
@@ -1501,7 +2106,7 @@ mbc_free(Allctr_t *allctr, void *p)
 	ASSERT(!is_first_blk); 
 	/* Coalesce with previous block... */
 	blk = PREV_BLK(blk);
-	(*allctr->unlink_free_block)(allctr, blk, alcu_flgs);
+	(*allctr->unlink_free_block)(allctr, blk);
 
 	blk_sz += MBC_FBLK_SZ(blk);
 	is_first_blk = IS_MBC_FIRST_FBLK(allctr, blk);
@@ -1517,7 +2122,7 @@ mbc_free(Allctr_t *allctr, void *p)
 	nxt_blk = BLK_AFTER(blk, blk_sz);
 	if (IS_FREE_BLK(nxt_blk)) {
 	    /* Coalesce with next block... */
-	    (*allctr->unlink_free_block)(allctr, nxt_blk, alcu_flgs);
+	    (*allctr->unlink_free_block)(allctr, nxt_blk);
 	    blk_sz += MBC_FBLK_SZ(nxt_blk);
 	    SET_MBC_FBLK_SZ(blk, blk_sz);
 
@@ -1550,19 +2155,20 @@ mbc_free(Allctr_t *allctr, void *p)
     if (is_first_blk
 	&& is_last_blk
 	&& allctr->main_carrier != FIRST_BLK_TO_MBC(allctr, blk)) {
-	if (alcu_flgs & ERTS_ALCU_FLG_SBMBC)
-	    destroy_sbmbc(allctr, blk);
-	else
-	    destroy_carrier(allctr, blk);
+	destroy_carrier(allctr, blk, busy_pcrr_pp);
     }
     else {
-	(*allctr->link_free_block)(allctr, blk, alcu_flgs);
+	(*allctr->link_free_block)(allctr, blk);
 	HARD_CHECK_BLK_CARRIER(allctr, blk);
+#ifdef ERTS_SMP
+	check_abandon_carrier(allctr, blk, busy_pcrr_pp);
+#endif
     }
 }
 
 static void *
-mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
+mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs,
+	    Carrier_t **busy_pcrr_pp)
 {
     void *new_p;
     Uint old_blk_sz;
@@ -1576,11 +2182,6 @@ mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
     Uint is_last_blk;
 #endif /* #ifndef MBC_REALLOC_ALWAYS_MOVES */
 
-#ifdef ERTS_SMP
-    if (allctr->dd.use)
-	ERTS_ALCU_HANDLE_DD_IN_OP(allctr, 1);
-#endif
-
     ASSERT(p);
     ASSERT(size);
     ASSERT(size < allctr->sbc_threshold);
@@ -1594,13 +2195,13 @@ mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
     if (alcu_flgs & ERTS_ALCU_FLG_FAIL_REALLOC_MOVE)
 	return NULL;
 #else /* !MBC_REALLOC_ALWAYS_MOVES */
+
+#ifdef ERTS_SMP
+    if (busy_pcrr_pp && *busy_pcrr_pp)
+	goto realloc_move; /* Don't want to use carrier in pool */
+#endif
+
     get_blk_sz = blk_sz = UMEMSZ2BLKSZ(allctr, size);
-    if ((alcu_flgs & ERTS_ALCU_FLG_SBMBC)
-	&& (blk_sz + allctr->min_block_size > allctr->sbmbc_threshold)) {
-	/* Since we use block size to determine if blocks are
-	   located in sbmbc or not... */
-	get_blk_sz = blk_sz + allctr->min_block_size;
-    }
 
     ASSERT(IS_ALLOCED_BLK(blk));
     ASSERT(IS_MBC_BLK(blk));
@@ -1648,8 +2249,7 @@ mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
 	    new_blk = (*allctr->get_free_block)(allctr,
 						get_blk_sz,
 						cand_blk,
-						cand_blk_sz,
-						alcu_flgs);
+						cand_blk_sz);
 	    if (new_blk || cand_blk != blk)
 		goto move_into_new_blk;
 	}
@@ -1671,8 +2271,11 @@ mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
 
 	nxt_blk = BLK_AFTER(blk, blk_sz);
 
-	STAT_MBC_BLK_FREE(allctr, old_blk_sz, alcu_flgs);
-	STAT_MBC_BLK_ALLOC(allctr, blk_sz, alcu_flgs);
+	crr = ABLK_TO_MBC(blk);
+
+	ERTS_ALC_CPOOL_REALLOC_OP(allctr);
+	STAT_MBC_BLK_FREE(allctr, crr, NULL, old_blk_sz, alcu_flgs);
+	STAT_MBC_BLK_ALLOC(allctr, crr, blk_sz, alcu_flgs);
 
 	ASSERT(MBC_BLK_SZ(blk) >= allctr->min_block_size);
 
@@ -1680,7 +2283,7 @@ mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
 	    if (IS_FREE_BLK(nxt_nxt_blk)) {
 		/* Coalesce with next free block... */
 		nxt_blk_sz += MBC_FBLK_SZ(nxt_nxt_blk);
-		(*allctr->unlink_free_block)(allctr, nxt_nxt_blk, alcu_flgs);
+		(*allctr->unlink_free_block)(allctr, nxt_nxt_blk);
 
 		is_last_blk = GET_LAST_BLK_HDR_FLG(nxt_nxt_blk);
 	    }
@@ -1690,12 +2293,11 @@ mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
 	    SET_BLK_SZ_FTR(nxt_blk, nxt_blk_sz);
 	}
 
-	crr = ABLK_TO_MBC(blk);
 	SET_MBC_FBLK_HDR(nxt_blk, nxt_blk_sz,
 			SBH_THIS_FREE | (is_last_blk ? SBH_LAST_BLK : 0),
 			crr);
 
-	(*allctr->link_free_block)(allctr, nxt_blk, alcu_flgs);
+	(*allctr->link_free_block)(allctr, nxt_blk);
 
 
 	ASSERT(IS_ALLOCED_BLK(blk));
@@ -1718,6 +2320,10 @@ mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
 		    
 	HARD_CHECK_BLK_CARRIER(allctr, blk);
 
+#ifdef ERTS_SMP
+	check_abandon_carrier(allctr, nxt_blk, NULL);
+#endif
+
 	return p;
     }
 
@@ -1727,11 +2333,12 @@ mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
 	nxt_blk = BLK_AFTER(blk, old_blk_sz);
 	nxt_blk_sz = MBC_BLK_SZ(nxt_blk);
 	if (IS_FREE_BLK(nxt_blk) && get_blk_sz <= old_blk_sz + nxt_blk_sz) {
+	    Carrier_t* crr = ABLK_TO_MBC(blk);
 	    /* Grow into next block... */
 
 	    HARD_CHECK_BLK_CARRIER(allctr, blk);
 
-	    (*allctr->unlink_free_block)(allctr, nxt_blk, alcu_flgs);
+	    (*allctr->unlink_free_block)(allctr, nxt_blk);
 	    nxt_blk_sz -= blk_sz - old_blk_sz;
 
 	    is_last_blk = IS_LAST_BLK(nxt_blk);
@@ -1756,7 +2363,6 @@ mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
 		}
 	    }
 	    else {
-		Carrier_t* crr = ABLK_TO_MBC(blk);
 		SET_MBC_ABLK_SZ(blk, blk_sz);
 
 		nxt_blk = BLK_AFTER(blk, blk_sz);
@@ -1767,15 +2373,15 @@ mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
 		else
 		    SET_BLK_SZ_FTR(nxt_blk, nxt_blk_sz);
 
-		(*allctr->link_free_block)(allctr, nxt_blk, alcu_flgs);
+		(*allctr->link_free_block)(allctr, nxt_blk);
 
 		ASSERT(IS_FREE_BLK(nxt_blk));
 		ASSERT(FBLK_TO_MBC(nxt_blk) == crr);
 	    }
 
-	    STAT_MBC_BLK_FREE(allctr, old_blk_sz, alcu_flgs);
-	    STAT_MBC_BLK_ALLOC(allctr, blk_sz, alcu_flgs);
-
+	    ERTS_ALC_CPOOL_REALLOC_OP(allctr);
+	    STAT_MBC_BLK_FREE(allctr, crr, NULL, old_blk_sz, alcu_flgs);
+	    STAT_MBC_BLK_ALLOC(allctr, crr, blk_sz, alcu_flgs);
 
 	    ASSERT(IS_ALLOCED_BLK(blk));
 	    ASSERT(blk_sz == MBC_BLK_SZ(blk));
@@ -1828,13 +2434,16 @@ mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
 
     if (cand_blk_sz < get_blk_sz) {
 	/* We wont fit in cand_blk get a new one */
+#ifdef ERTS_SMP
+    realloc_move:
+#endif
 #endif /* !MBC_REALLOC_ALWAYS_MOVES */
 
 	new_p = mbc_alloc(allctr, size);
 	if (!new_p)
 	    return NULL;
 	sys_memcpy(new_p, p, MIN(size, old_blk_sz - ABLK_HDR_SZ));
-	mbc_free(allctr, p);
+	mbc_free(allctr, p, busy_pcrr_pp);
 
 	return new_p;
 
@@ -1847,8 +2456,7 @@ mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
 	new_blk = (*allctr->get_free_block)(allctr,
 					    get_blk_sz,
 					    cand_blk,
-					    cand_blk_sz,
-					    alcu_flgs);
+					    cand_blk_sz);
     move_into_new_blk:
 	/*
 	 * new_blk, and cand_blk have to be correctly set
@@ -1862,11 +2470,10 @@ mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
 			       GET_BLK_HDR_FLGS(new_blk),
 			       FBLK_TO_MBC(new_blk),
 			       blk_sz,
-			       1,
-			       alcu_flgs);
+			       1);
 	    new_p = BLK2UMEM(new_blk);
 	    sys_memcpy(new_p, p, MIN(size, old_blk_sz - ABLK_HDR_SZ));
-	    mbc_free(allctr, p);
+	    mbc_free(allctr, p, NULL);
 	    return new_p;
 	}
 	else {
@@ -1886,7 +2493,7 @@ mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
 
 	    HARD_CHECK_BLK_CARRIER(allctr, blk);
 
-	    (*allctr->unlink_free_block)(allctr, new_blk, alcu_flgs); /* prev */
+	    (*allctr->unlink_free_block)(allctr, new_blk); /* prev */
 
 	    if (is_last_blk) 
 		new_blk_flgs |= LAST_BLK_HDR_FLG;
@@ -1895,7 +2502,7 @@ mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
 		if (IS_FREE_BLK(nxt_blk)) {
 		    new_blk_flgs |= GET_LAST_BLK_HDR_FLG(nxt_blk);
 		    new_blk_sz += MBC_FBLK_SZ(nxt_blk);
-		    (*allctr->unlink_free_block)(allctr, nxt_blk, alcu_flgs);
+		    (*allctr->unlink_free_block)(allctr, nxt_blk);
 		}
 	    }
 
@@ -1920,10 +2527,10 @@ mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
 			       new_blk_flgs,
 			       crr,
 			       blk_sz,
-			       0,
-			       alcu_flgs);
+			       0);
 
-	    STAT_MBC_BLK_FREE(allctr, old_blk_sz, alcu_flgs);
+	    ERTS_ALC_CPOOL_FREE_OP(allctr);
+	    STAT_MBC_BLK_FREE(allctr, crr, NULL, old_blk_sz, alcu_flgs);
 
 	    return new_p;
 	}
@@ -1931,6 +2538,635 @@ mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
 #endif /* !MBC_REALLOC_ALWAYS_MOVES */
 }
 
+#ifdef ERTS_SMP
+
+#define ERTS_ALC_MAX_DEALLOC_CARRIER		10
+#define ERTS_ALC_CPOOL_MAX_FETCH_INSPECT	10
+#define ERTS_ALC_CPOOL_CHECK_LIMIT_COUNT	100
+#define ERTS_ALC_CPOOL_MAX_NO_CARRIERS		5
+#define ERTS_ALC_CPOOL_INSERT_ALLOWED_OFFSET	100
+#define ERTS_ALC_CPOOL_MAX_FAILED_STAT_READS	3
+
+#define ERTS_ALC_CPOOL_PTR_MOD_MRK		(((erts_aint_t) 1) << 0)
+#define ERTS_ALC_CPOOL_PTR_DEL_MRK		(((erts_aint_t) 1) << 1)
+
+#define ERTS_ALC_CPOOL_PTR_MRKS \
+    (ERTS_ALC_CPOOL_PTR_MOD_MRK | ERTS_ALC_CPOOL_PTR_DEL_MRK)
+
+/*
+ * When setting multiple mod markers we always
+ * set mod markers in pointer order and always
+ * on next pointers before prev pointers.
+ */
+
+typedef union {
+    ErtsAlcCPoolData_t sentinel;
+    char align__[ERTS_ALC_CACHE_LINE_ALIGN_SIZE(sizeof(ErtsAlcCPoolData_t))];
+} ErtsAlcCrrPool_t;
+
+#if ERTS_ALC_A_INVALID != 0
+#  error "Carrier pool implementation assumes ERTS_ALC_A_INVALID == 0"
+#endif
+#if ERTS_ALC_A_MIN <= ERTS_ALC_A_INVALID
+#  error "Carrier pool implementation assumes ERTS_ALC_A_MIN > ERTS_ALC_A_INVALID"
+#endif
+
+/*
+ * The pool is only allowed to be manipulated by managed
+ * threads except in the alloc_SUITE:cpool case. In this
+ * test case carrier_pool[ERTS_ALC_A_INVALID] will be
+ * used.
+ */
+
+static ErtsAlcCrrPool_t carrier_pool[ERTS_ALC_A_MAX+1] erts_align_attribute(ERTS_CACHE_LINE_SIZE);
+
+#define ERTS_ALC_CPOOL_MAX_BACKOFF (1 << 8)
+
+static int
+backoff(int n)
+{
+    int i;
+
+    for (i = 0; i < n; i++)
+	ERTS_SPIN_BODY;
+
+    if (n >= ERTS_ALC_CPOOL_MAX_BACKOFF)
+	return ERTS_ALC_CPOOL_MAX_BACKOFF;
+    else
+	return n << 1;
+}
+
+static int
+cpool_dbg_is_in_pool(Allctr_t *allctr, Carrier_t *crr)
+{
+    ErtsAlcCPoolData_t *sentinel = &carrier_pool[allctr->alloc_no].sentinel;
+    ErtsAlcCPoolData_t *cpdp = sentinel;
+    Carrier_t *tmp_crr;
+
+    while (1) {
+	cpdp = (ErtsAlcCPoolData_t *) (erts_atomic_read_ddrb(&cpdp->next) & ~FLG_MASK);
+	if (cpdp == sentinel)
+	    return 0;
+	tmp_crr = (Carrier_t *) (((char *) cpdp) - offsetof(Carrier_t, cpool));
+	if (tmp_crr == crr)
+	    return 1;
+    }
+}
+
+static int
+cpool_is_empty(Allctr_t *allctr)
+{
+    ErtsAlcCPoolData_t *sentinel = &carrier_pool[allctr->alloc_no].sentinel;
+    return ((erts_atomic_read_rb(&sentinel->next) == (erts_aint_t) sentinel)
+	    && (erts_atomic_read_rb(&sentinel->prev) == (erts_aint_t) sentinel));
+}
+
+static ERTS_INLINE ErtsAlcCPoolData_t *
+cpool_aint2cpd(erts_aint_t aint)
+{
+    return (ErtsAlcCPoolData_t *) (aint & ~ERTS_ALC_CPOOL_PTR_MRKS);
+}
+
+static ERTS_INLINE erts_aint_t
+cpool_read(erts_atomic_t *aptr)
+{
+    return erts_atomic_read_acqb(aptr);
+}
+
+static ERTS_INLINE void
+cpool_init(erts_atomic_t *aptr, erts_aint_t val)
+{
+    erts_atomic_set_nob(aptr, val);
+}
+
+static ERTS_INLINE void
+cpool_set_mod_marked(erts_atomic_t *aptr, erts_aint_t new, erts_aint_t old)
+{
+#ifdef ERTS_ALC_CPOOL_DEBUG
+    erts_aint_t act = erts_atomic_xchg_relb(aptr, new);
+    ERTS_ALC_CPOOL_ASSERT(act == (old | ERTS_ALC_CPOOL_PTR_MOD_MRK));
+#else
+    erts_atomic_set_relb(aptr, new);
+#endif
+}
+
+
+static ERTS_INLINE erts_aint_t
+cpool_try_mod_mark_exp(erts_atomic_t *aptr, erts_aint_t exp)
+{
+    ERTS_ALC_CPOOL_ASSERT((exp & ERTS_ALC_CPOOL_PTR_MOD_MRK) == 0);
+    return erts_atomic_cmpxchg_nob(aptr, exp | ERTS_ALC_CPOOL_PTR_MOD_MRK, exp);
+}
+
+static ERTS_INLINE erts_aint_t
+cpool_mod_mark_exp(erts_atomic_t *aptr, erts_aint_t exp)
+{
+    int b;
+    erts_aint_t act;
+    ERTS_ALC_CPOOL_ASSERT((exp & ERTS_ALC_CPOOL_PTR_MOD_MRK) == 0);
+    while (1) {
+	act = erts_atomic_cmpxchg_nob(aptr,
+				      exp | ERTS_ALC_CPOOL_PTR_MOD_MRK,
+				      exp);
+	if (act == exp)
+	    return exp;
+	b = 1;
+	do {
+	    if ((act & ~ERTS_ALC_CPOOL_PTR_MOD_MRK) != exp)
+		return act;
+	    b = backoff(b);
+	    act = erts_atomic_read_nob(aptr);
+	} while (act != exp);
+    }
+}
+
+static ERTS_INLINE erts_aint_t
+cpool_mod_mark(erts_atomic_t *aptr)
+{
+    int b;
+    erts_aint_t act, exp;
+    act = cpool_read(aptr);
+    while (1) {
+	b = 1;
+	while (act & ERTS_ALC_CPOOL_PTR_MOD_MRK) {
+	    b = backoff(b);
+	    act = erts_atomic_read_nob(aptr);
+	}
+	exp = act;
+	act = erts_atomic_cmpxchg_acqb(aptr,
+				       exp | ERTS_ALC_CPOOL_PTR_MOD_MRK,
+				       exp);
+	if (act == exp)
+	    return exp;
+    }
+}
+
+static void
+cpool_insert(Allctr_t *allctr, Carrier_t *crr)
+{
+    ErtsAlcCPoolData_t *cpd1p, *cpd2p;
+    erts_aint_t val;
+    ErtsAlcCPoolData_t *sentinel = &carrier_pool[allctr->alloc_no].sentinel;
+
+    ERTS_ALC_CPOOL_ASSERT(allctr->alloc_no == ERTS_ALC_A_INVALID /* testcase */
+			  || erts_thr_progress_is_managed_thread());
+    ERTS_ALC_CPOOL_ASSERT(erts_smp_atomic_read_nob(&crr->allctr)
+			  == (erts_aint_t) allctr);
+
+    erts_atomic_add_nob(&allctr->cpool.stat.blocks_size,
+			(erts_aint_t) crr->cpool.blocks_size);
+    erts_atomic_add_nob(&allctr->cpool.stat.no_blocks,
+			(erts_aint_t) crr->cpool.blocks);
+    erts_atomic_add_nob(&allctr->cpool.stat.carriers_size,
+			(erts_aint_t) CARRIER_SZ(crr));
+    erts_atomic_inc_nob(&allctr->cpool.stat.no_carriers);
+
+    erts_smp_atomic_set_nob(&crr->allctr,
+			    ((erts_aint_t) allctr)|ERTS_CRR_ALCTR_FLG_IN_POOL);
+
+    /*
+     * We search in 'next' direction and begin by passing
+     * one element before trying to insert. This in order to
+     * avoid contention with threads fetching elements.
+     */
+
+    val = cpool_read(&sentinel->next);
+
+    /* Find a predecessor to be, and set mod marker on its next ptr */
+
+    while (1) {
+	cpd1p = cpool_aint2cpd(val);
+	if (cpd1p == sentinel) {
+	    val = cpool_mod_mark(&cpd1p->next);
+	    break;
+	}
+	val = cpool_read(&cpd1p->next);
+	if (!(val & ERTS_ALC_CPOOL_PTR_MRKS)) {
+	    erts_aint_t tmp = cpool_try_mod_mark_exp(&cpd1p->next, val);
+	    if (tmp == val) {
+		val = tmp;
+		break;
+	    }
+	    val = tmp;
+	}
+    }
+
+    /* Set mod marker on prev ptr of the to be successor */
+
+    cpd2p = cpool_aint2cpd(val);
+
+    cpool_init(&crr->cpool.next, (erts_aint_t) cpd2p);
+    cpool_init(&crr->cpool.prev, (erts_aint_t) cpd1p);
+
+    val = (erts_aint_t) cpd1p;
+
+    while (1) {
+	int b;
+	erts_aint_t tmp;
+
+	tmp = cpool_mod_mark_exp(&cpd2p->prev, val);
+	if (tmp == val)
+	    break;
+	b = 1;
+	do {
+	    b = backoff(b);
+	    tmp = cpool_read(&cpd2p->prev);
+	} while (tmp != val);
+    }
+
+    /* Write pointers to this element in successor and predecessor */
+
+    cpool_set_mod_marked(&cpd1p->next,
+			 (erts_aint_t) &crr->cpool,
+			 (erts_aint_t) cpd2p);
+    cpool_set_mod_marked(&cpd2p->prev,
+			 (erts_aint_t) &crr->cpool,
+			 (erts_aint_t) cpd1p);
+}
+
+static void
+cpool_delete(Allctr_t *allctr, Allctr_t *prev_allctr, Carrier_t *crr)
+{
+    ErtsAlcCPoolData_t *cpd1p, *cpd2p;
+    erts_aint_t val;
+#ifdef ERTS_ALC_CPOOL_DEBUG
+    ErtsAlcCPoolData_t *sentinel = &carrier_pool[allctr->alloc_no].sentinel;
+#endif
+
+    ERTS_ALC_CPOOL_ASSERT(allctr->alloc_no == ERTS_ALC_A_INVALID /* testcase */
+			  || erts_thr_progress_is_managed_thread());
+    ERTS_ALC_CPOOL_ASSERT(sentinel != &crr->cpool);
+
+    /* Set mod marker on next ptr of our predecessor */
+
+    val = (erts_aint_t) &crr->cpool;
+    while (1) {
+	erts_aint_t tmp;
+	cpd1p = cpool_aint2cpd(cpool_read(&crr->cpool.prev));
+	tmp = cpool_mod_mark_exp(&cpd1p->next, val);
+	if (tmp == val)
+	    break;
+    }
+
+    /* Set mod marker on our next ptr */
+
+    val = cpool_mod_mark(&crr->cpool.next);
+
+    /* Set mod marker on the prev ptr of our successor */
+
+    cpd2p = cpool_aint2cpd(val);
+
+    val = (erts_aint_t) &crr->cpool;
+
+    while (1) {
+	int b;
+	erts_aint_t tmp;
+
+	tmp = cpool_mod_mark_exp(&cpd2p->prev, val);
+	if (tmp == val)
+	    break;
+	b = 1;
+	do {
+	    b = backoff(b);
+	    tmp = cpool_read(&cpd2p->prev);
+	} while (tmp != val);
+    }
+
+    /* Set mod marker on our prev ptr */
+
+    val = (erts_aint_t) cpd1p;
+
+    while (1) {
+	int b;
+	erts_aint_t tmp;
+
+	tmp = cpool_mod_mark_exp(&crr->cpool.prev, val);
+	if (tmp == val)
+	    break;
+	b = 1;
+	do {
+	    b = backoff(b);
+	    tmp = cpool_read(&cpd2p->prev);
+	} while (tmp != val);
+    }
+
+    /* Write pointers past this element in predecessor and successor */
+
+    cpool_set_mod_marked(&cpd1p->next,
+			 (erts_aint_t) cpd2p,
+			 (erts_aint_t) &crr->cpool);
+    cpool_set_mod_marked(&cpd2p->prev,
+			 (erts_aint_t) cpd1p,
+			 (erts_aint_t) &crr->cpool);
+
+    /* Repleace mod markers with delete markers on this element */
+    cpool_set_mod_marked(&crr->cpool.next,
+			 ((erts_aint_t) cpd2p) | ERTS_ALC_CPOOL_PTR_DEL_MRK,
+			 ((erts_aint_t) cpd2p) | ERTS_ALC_CPOOL_PTR_MOD_MRK);
+    cpool_set_mod_marked(&crr->cpool.prev,
+			 ((erts_aint_t) cpd1p) | ERTS_ALC_CPOOL_PTR_DEL_MRK,
+			 ((erts_aint_t) cpd1p) | ERTS_ALC_CPOOL_PTR_MOD_MRK);
+
+    crr->cpool.thr_prgr = erts_thr_progress_later(NULL);
+
+    erts_atomic_add_nob(&prev_allctr->cpool.stat.blocks_size,
+			-((erts_aint_t) crr->cpool.blocks_size));
+    erts_atomic_add_nob(&prev_allctr->cpool.stat.no_blocks,
+			-((erts_aint_t) crr->cpool.blocks));
+    erts_atomic_add_nob(&prev_allctr->cpool.stat.carriers_size,
+			-((erts_aint_t) CARRIER_SZ(crr)));
+    erts_atomic_dec_wb(&prev_allctr->cpool.stat.no_carriers);
+
+}
+
+static Carrier_t *
+cpool_fetch(Allctr_t *allctr, UWord size)
+{
+    int i;
+    Carrier_t *crr;
+    ErtsAlcCPoolData_t *cpdp;
+    ErtsAlcCPoolData_t *sentinel = &carrier_pool[allctr->alloc_no].sentinel;
+
+    ERTS_ALC_CPOOL_ASSERT(allctr->alloc_no == ERTS_ALC_A_INVALID /* testcase */
+			  || erts_thr_progress_is_managed_thread());
+
+    i = 0;
+
+    /* First; check our own pending dealloc carrier list... */
+    crr = allctr->cpool.dc_list.last;
+    while (crr && i < ERTS_ALC_CPOOL_MAX_FETCH_INSPECT) {
+	if (erts_atomic_read_nob(&crr->cpool.max_size) >= size) {
+	    unlink_carrier(&allctr->cpool.dc_list, crr);
+#ifdef ERTS_ALC_CPOOL_DEBUG
+	    ERTS_ALC_CPOOL_ASSERT(erts_smp_atomic_xchg_nob(&crr->allctr,
+							   ((erts_aint_t) allctr))
+				  == (((erts_aint_t) allctr) & ~FLG_MASK));
+#else
+	    erts_smp_atomic_set_nob(&crr->allctr, ((erts_aint_t) allctr));
+#endif
+	    return crr;
+	}
+	crr = crr->prev;
+	i++;
+    }
+
+    /* ... then the pool ... */
+
+    /*
+     * We search in 'prev' direction and begin by passing
+     * one element before trying to fetch. This in order to
+     * avoid contention with threads inserting elements.
+     */
+
+    cpdp = cpool_aint2cpd(cpool_read(&sentinel->prev));
+    if (cpdp == sentinel)
+	return NULL;
+
+    while (i < ERTS_ALC_CPOOL_MAX_FETCH_INSPECT) {
+	erts_aint_t exp;
+	cpdp = cpool_aint2cpd(cpool_read(&cpdp->prev));
+	if (cpdp == sentinel) {
+	    cpdp = cpool_aint2cpd(cpool_read(&cpdp->prev));
+	    if (cpdp == sentinel)
+		return NULL;
+	    i = ERTS_ALC_CPOOL_MAX_FETCH_INSPECT; /* Last one to inspect */
+	}
+	crr = (Carrier_t *) (((char *) cpdp) - offsetof(Carrier_t, cpool));
+	exp = erts_smp_atomic_read_rb(&crr->allctr);
+	if (((exp & (ERTS_CRR_ALCTR_FLG_IN_POOL|ERTS_CRR_ALCTR_FLG_BUSY))
+	     == ERTS_CRR_ALCTR_FLG_IN_POOL)
+	    && (erts_atomic_read_nob(&cpdp->max_size) >= size)) {
+	    erts_aint_t act;
+	    /* Try to fetch it... */
+	    act = erts_smp_atomic_cmpxchg_mb(&crr->allctr,
+					     (erts_aint_t) allctr,
+					     exp);
+	    if (act == exp) {
+		cpool_delete(allctr, ((Allctr_t *) (act & ~FLG_MASK)), crr);
+		return crr;
+	    }
+	}
+	i++;
+    }
+    return NULL;
+}
+
+static void
+check_pending_dealloc_carrier(Allctr_t *allctr,
+			      int *need_thr_progress,
+			      ErtsThrPrgrVal *thr_prgr_p,
+			      int *need_more_work)
+{
+    Carrier_t *crr = allctr->cpool.dc_list.first;
+
+    if (crr) {
+	ErtsThrPrgrVal current = erts_thr_progress_current();
+	int i = 0;
+
+	do {
+	    Carrier_t *dcrr;
+
+	    if (!erts_thr_progress_has_reached_this(current, crr->cpool.thr_prgr))
+		break;
+
+	    dcrr = crr;
+	    crr = crr->next;
+	    dealloc_carrier(allctr, dcrr, ERTS_MSEG_FLG_2POW);
+	    i++;
+	} while (crr && i < ERTS_ALC_MAX_DEALLOC_CARRIER);
+
+	allctr->cpool.dc_list.first = crr;
+	if (!crr)
+	    allctr->cpool.dc_list.last = NULL;
+	else {
+	    crr->prev = NULL;
+
+	    if (need_more_work) {
+		ERTS_ALC_CPOOL_ASSERT(need_thr_progress && thr_prgr_p);
+		if (erts_thr_progress_has_reached_this(current, crr->cpool.thr_prgr))
+		    *need_more_work = 1;
+		else {
+		    *need_thr_progress = 1;
+		    if (*thr_prgr_p == ERTS_THR_PRGR_INVALID
+			|| erts_thr_progress_cmp(crr->cpool.thr_prgr,
+						 *thr_prgr_p) < 0) {
+			*thr_prgr_p = crr->cpool.thr_prgr;
+		    }
+		}
+	    }
+	}
+    }
+}
+
+static void
+schedule_dealloc_carrier(Allctr_t *allctr, Carrier_t *crr)
+{
+    Allctr_t *used_allctr;
+    int check_pending_dealloc;
+    erts_aint_t max_size;
+
+    if (!ERTS_ALC_IS_CPOOL_ENABLED(allctr)) {
+	dealloc_carrier(allctr, crr, ERTS_MSEG_FLG_2POW);
+	return;
+    }
+
+    used_allctr = crr->cpool.orig_allctr;
+
+    if (allctr != used_allctr) {
+	Block_t *blk = MBC_TO_FIRST_BLK(allctr, crr);
+	int cinit = used_allctr->dd.ix - allctr->dd.ix;
+
+	/*
+	 * Receiver will recognize that this is a carrier to
+	 * deallocate since the block is an mbc block that
+	 * is free and last in carrier...
+	 */
+	ERTS_ALC_CPOOL_ASSERT(IS_FREE_LAST_MBC_BLK(blk));
+
+	ERTS_ALC_CPOOL_ASSERT(IS_MBC_FIRST_ABLK(allctr, blk));
+	ERTS_ALC_CPOOL_ASSERT(crr == FBLK_TO_MBC(blk));
+	ERTS_ALC_CPOOL_ASSERT(crr == FIRST_BLK_TO_MBC(used_allctr, blk));
+
+	if (ddq_enqueue(&used_allctr->dd.q, BLK2UMEM(blk), cinit))
+	    erts_alloc_notify_delayed_dealloc(used_allctr->ix);
+	return;
+    }
+
+    if (crr->cpool.thr_prgr == ERTS_THR_PRGR_INVALID
+	|| erts_thr_progress_has_reached(crr->cpool.thr_prgr)) {
+	dealloc_carrier(allctr, crr, ERTS_MSEG_FLG_2POW);
+	return;
+    }
+
+    max_size = (erts_aint_t) allctr->largest_fblk_in_mbc(allctr, crr);
+    erts_atomic_set_nob(&crr->cpool.max_size, max_size);
+
+    crr->next = NULL;
+    crr->prev = allctr->cpool.dc_list.last;
+    if (allctr->cpool.dc_list.last) {
+	check_pending_dealloc = 1;
+	allctr->cpool.dc_list.last->next = crr;
+    }
+    else {
+	check_pending_dealloc = 0;
+	allctr->cpool.dc_list.first = crr;
+    }
+    allctr->cpool.dc_list.last = crr;
+    if (check_pending_dealloc)
+	check_pending_dealloc_carrier(allctr, NULL, NULL, NULL);
+    erts_alloc_ensure_handle_delayed_dealloc_call(allctr->ix);
+}
+
+static ERTS_INLINE void
+cpool_init_carrier_data(Allctr_t *allctr, Carrier_t *crr)
+{
+    erts_atomic_init_nob(&crr->cpool.next, ERTS_AINT_NULL);
+    erts_atomic_init_nob(&crr->cpool.prev, ERTS_AINT_NULL);
+    crr->cpool.orig_allctr = allctr;
+    crr->cpool.thr_prgr = ERTS_THR_PRGR_INVALID;
+    erts_atomic_init_nob(&crr->cpool.max_size, 0);
+    crr->cpool.blocks = 0;
+    crr->cpool.blocks_size = 0;
+    if (!ERTS_ALC_IS_CPOOL_ENABLED(allctr))
+	crr->cpool.abandon_limit = 0;
+    else {
+	UWord csz = CARRIER_SZ(crr);
+	UWord limit = csz*allctr->cpool.util_limit;
+	if (limit > csz)
+	    limit /= 100;
+	else
+	    limit = (csz/100)*allctr->cpool.util_limit;
+	crr->cpool.abandon_limit = limit;
+    }
+}
+
+static void
+set_new_allctr_abandon_limit(Allctr_t *allctr)
+{
+    UWord limit;
+    UWord csz;
+
+    allctr->cpool.check_limit_count = ERTS_ALC_CPOOL_CHECK_LIMIT_COUNT;
+
+    csz = allctr->mbcs.curr.norm.mseg.size;
+    csz += allctr->mbcs.curr.norm.sys_alloc.size;
+
+    limit = csz*allctr->cpool.util_limit;
+    if (limit > csz)
+	limit /= 100;
+    else
+	limit = (csz/100)*allctr->cpool.util_limit;
+
+    allctr->cpool.abandon_limit = limit;
+}
+
+static void
+abandon_carrier(Allctr_t *allctr, Carrier_t *crr)
+{
+    erts_aint_t max_size;
+
+    STAT_MBC_CPOOL_INSERT(allctr, crr);
+
+    unlink_carrier(&allctr->mbc_list, crr);
+
+    allctr->remove_mbc(allctr, crr);
+
+    max_size = (erts_aint_t) allctr->largest_fblk_in_mbc(allctr, crr);
+    erts_atomic_set_nob(&crr->cpool.max_size, max_size);
+
+    cpool_insert(allctr, crr);
+
+    set_new_allctr_abandon_limit(allctr);
+}
+
+static void
+cpool_read_stat(Allctr_t *allctr, UWord *nocp, UWord *cszp, UWord *nobp, UWord *bszp)
+{
+    int i;
+    UWord noc = 0, csz = 0, nob = 0, bsz = 0;
+
+    /*
+     * We try to get consistent values, but after
+     * ERTS_ALC_CPOOL_MAX_FAILED_STAT_READS failed
+     * tries we give up and present what we got...
+     */
+    for (i = 0; i <= ERTS_ALC_CPOOL_MAX_FAILED_STAT_READS; i++) {
+	UWord tnoc, tcsz, tnob, tbsz;
+
+	tnoc = (UWord) (nocp
+			? erts_atomic_read_nob(&allctr->cpool.stat.no_carriers)
+			: 0);
+	tcsz = (UWord) (cszp
+			? erts_atomic_read_nob(&allctr->cpool.stat.carriers_size)
+			: 0);
+	tnob = (UWord) (nobp
+			? erts_atomic_read_nob(&allctr->cpool.stat.no_blocks)
+			: 0);
+	tbsz = (UWord) (bszp
+			? erts_atomic_read_nob(&allctr->cpool.stat.blocks_size)
+			: 0);
+	if (tnoc == noc && tcsz == csz && tnob == nob && tbsz == bsz)
+	    break;
+	noc = tnoc;
+	csz = tcsz;
+	nob = tnob;
+	bsz = tbsz;
+	ERTS_THR_READ_MEMORY_BARRIER;
+    }
+
+    if (nocp)
+	*nocp = noc;
+    if (cszp)
+	*cszp = csz;
+    if (nobp)
+	*nobp = nob;
+    if (bszp)
+	*bszp = bsz;
+}
+
+
+#endif /* ERTS_SMP */
+
 #ifdef DEBUG
 
 #if HAVE_ERTS_MSEG
@@ -1974,81 +3210,6 @@ static void CHECK_1BLK_CARRIER(Allctr_t* A, int SBC, int MSEGED, Carrier_t* C,
 #endif
 
 static Block_t *
-create_sbmbc(Allctr_t *allctr, Uint umem_sz)
-{
-    Block_t *blk;
-    Uint blk_sz;
-    Uint crr_sz = allctr->sbmbc_size;
-    Carrier_t *crr;
-
-#if HALFWORD_HEAP
-    if (allctr->mseg_opt.low_mem)
-	crr = erts_alloc(ERTS_ALC_T_SBMBC_LOW, crr_sz);
-    else
-#endif
-	crr = erts_alloc(ERTS_ALC_T_SBMBC, crr_sz);
-
-    INC_CC(allctr->calls.sbmbc_alloc);
-    SET_CARRIER_HDR(crr, crr_sz, SCH_SYS_ALLOC|SCH_MBC, allctr);
-
-    blk = MBC_TO_FIRST_BLK(allctr, crr);
-
-    blk_sz = UNIT_FLOOR(crr_sz - MBC_HEADER_SIZE(allctr));
-
-    SET_MBC_FBLK_HDR(blk, blk_sz, SBH_THIS_FREE|SBH_LAST_BLK, crr);
-
-    link_carrier(&allctr->sbmbc_list, crr);
-
-    STAT_SBMBC_ALLOC(allctr, crr_sz);
-    CHECK_1BLK_CARRIER(allctr, 0, 0, crr, crr_sz, blk, blk_sz);
-    if (allctr->creating_mbc)
-	(*allctr->creating_mbc)(allctr, crr, ERTS_ALCU_FLG_SBMBC);
-
-    DEBUG_SAVE_ALIGNMENT(crr);
-    return blk;
-}
-
-static void
-destroy_sbmbc(Allctr_t *allctr, Block_t *blk)
-{
-    Uint crr_sz;
-    Carrier_t *crr;
-
-    ASSERT(IS_MBC_BLK(blk));
-    ASSERT(IS_MBC_FIRST_FBLK(allctr, blk));
-
-    crr = FIRST_BLK_TO_MBC(allctr, blk);
-    crr_sz = CARRIER_SZ(crr);
-
-#ifdef DEBUG
-    if (!allctr->stopped) {
-	ASSERT(IS_LAST_BLK(blk));
-
-#ifdef ERTS_ALLOC_UTIL_HARD_DEBUG
-	(*allctr->link_free_block)(allctr, blk, ERTS_ALCU_FLG_SBMBC);
-	HARD_CHECK_BLK_CARRIER(allctr, blk);
-	(*allctr->unlink_free_block)(allctr, blk, ERTS_ALCU_FLG_SBMBC);
-#endif
-    }
-#endif
-
-    STAT_SBMBC_FREE(allctr, crr_sz);
-
-    unlink_carrier(&allctr->sbmbc_list, crr);
-    if (allctr->destroying_mbc)
-	(*allctr->destroying_mbc)(allctr, crr, ERTS_ALCU_FLG_SBMBC);
-
-    INC_CC(allctr->calls.sbmbc_free);
-
-#if HALFWORD_HEAP
-    if (allctr->mseg_opt.low_mem)
-	erts_free(ERTS_ALC_T_SBMBC_LOW, crr);
-    else
-#endif
-	erts_free(ERTS_ALC_T_SBMBC, crr);
-}
-
-static Block_t *
 create_carrier(Allctr_t *allctr, Uint umem_sz, UWord flags)
 {
     Block_t *blk;
@@ -2077,6 +3238,24 @@ create_carrier(Allctr_t *allctr, Uint umem_sz, UWord flags)
 
     blk_sz = UMEMSZ2BLKSZ(allctr, umem_sz);
 
+#ifdef ERTS_SMP
+    allctr->cpool.disable_abandon = ERTS_ALC_CPOOL_MAX_DISABLE_ABANDON;
+
+    if ((flags & (CFLG_MBC|CFLG_NO_CPOOL)) == CFLG_MBC
+	&& ERTS_ALC_IS_CPOOL_ENABLED(allctr)
+	&& erts_thr_progress_is_managed_thread()) {
+	crr = cpool_fetch(allctr, blk_sz);
+	if (crr) {
+	    STAT_MBC_CPOOL_FETCH(allctr, crr);
+	    link_carrier(&allctr->mbc_list, crr);
+	    (*allctr->add_mbc)(allctr, crr);
+	    blk = (*allctr->get_free_block)(allctr, blk_sz, NULL, 0);
+	    ASSERT(blk);
+	    return blk;
+	}
+    }
+#endif
+
 #if HAVE_ERTS_MSEG
 
     if (flags & CFLG_FORCE_SYS_ALLOC)
@@ -2204,11 +3383,15 @@ create_carrier(Allctr_t *allctr, Uint umem_sz, UWord flags)
 	    allctr->main_carrier = crr;
 	}
 
+#ifdef ERTS_SMP
+	cpool_init_carrier_data(allctr, crr);
+#endif
+
 	link_carrier(&allctr->mbc_list, crr);
 
 	CHECK_1BLK_CARRIER(allctr, 0, is_mseg, crr, crr_sz, blk, blk_sz);
 	if (allctr->creating_mbc)
-	    (*allctr->creating_mbc)(allctr, crr, 0);
+	    (*allctr->creating_mbc)(allctr, crr);
 
     }
 
@@ -2352,14 +3535,21 @@ resize_carrier(Allctr_t *allctr, Block_t *old_blk, Uint umem_sz, UWord flags)
 }
 
 static void
-destroy_carrier(Allctr_t *allctr, Block_t *blk)
+dealloc_carrier(Allctr_t *allctr, Carrier_t *crr, Uint mseg_flags)
 {
-    Uint crr_sz;
-    Carrier_t *crr;
 #if HAVE_ERTS_MSEG
-    Uint is_mseg = 0;
-    Uint mseg_flags = ERTS_MSEG_FLG_NONE;
+    if (IS_MSEG_CARRIER(crr))
+	alcu_mseg_dealloc(allctr, crr, CARRIER_SZ(crr), mseg_flags);
+    else
 #endif
+	alcu_sys_free(allctr, crr);
+}
+
+static void
+destroy_carrier(Allctr_t *allctr, Block_t *blk, Carrier_t **busy_pcrr_pp)
+{
+    Uint crr_sz;
+    Carrier_t *crr;
 
     if (IS_SBC_BLK(blk)) {
 	Uint blk_sz = SBC_BLK_SZ(blk);
@@ -2372,7 +3562,6 @@ destroy_carrier(Allctr_t *allctr, Block_t *blk)
 
 #if HAVE_ERTS_MSEG
 	if (IS_MSEG_CARRIER(crr)) {
-	    is_mseg++;
 	    ASSERT(crr_sz % MSEG_UNIT_SZ == 0);
 	    STAT_MSEG_SBC_FREE(allctr, crr_sz, blk_sz);
 	}
@@ -2382,6 +3571,7 @@ destroy_carrier(Allctr_t *allctr, Block_t *blk)
 
 	unlink_carrier(&allctr->sbc_list, crr);
 
+	dealloc_carrier(allctr, crr, ERTS_MSEG_FLG_NONE);
     }
     else {
 	ASSERT(IS_MBC_FIRST_FBLK(allctr, blk));
@@ -2400,30 +3590,36 @@ destroy_carrier(Allctr_t *allctr, Block_t *blk)
 	}
 #endif
 
-#if HAVE_ERTS_MSEG
-	if (IS_MSEG_CARRIER(crr)) {
-	    is_mseg++;
-	    ASSERT(crr_sz % MSEG_UNIT_SZ == 0);
-	    STAT_MSEG_MBC_FREE(allctr, crr_sz);
-	    mseg_flags = ERTS_MSEG_FLG_2POW;
+	if (allctr->destroying_mbc)
+	    (*allctr->destroying_mbc)(allctr, crr);
+
+#ifdef ERTS_SMP
+	if (busy_pcrr_pp && *busy_pcrr_pp) {
+	    ERTS_ALC_CPOOL_ASSERT(*busy_pcrr_pp == crr);
+	    *busy_pcrr_pp = NULL;
+	    cpool_delete(allctr, allctr, crr);
 	}
 	else
 #endif
-	    STAT_SYS_ALLOC_MBC_FREE(allctr, crr_sz);
+	{
+	    unlink_carrier(&allctr->mbc_list, crr);
+#if HAVE_ERTS_MSEG
+	    if (IS_MSEG_CARRIER(crr)) {
+		ASSERT(crr_sz % MSEG_UNIT_SZ == 0);
+		STAT_MSEG_MBC_FREE(allctr, crr_sz);
+	    }
+	    else
+#endif
+		STAT_SYS_ALLOC_MBC_FREE(allctr, crr_sz);
+	}
 
-	unlink_carrier(&allctr->mbc_list, crr);
-	if (allctr->destroying_mbc)
-	    (*allctr->destroying_mbc)(allctr, crr, 0);
+#ifdef ERTS_SMP
+	schedule_dealloc_carrier(allctr, crr);
+#else
+	dealloc_carrier(allctr, crr, ERTS_MSEG_FLG_2POW);
+#endif
     }
 
-
-#if HAVE_ERTS_MSEG
-    if (is_mseg) {
-	alcu_mseg_dealloc(allctr, crr, crr_sz, mseg_flags);
-    }
-    else
-#endif
-	alcu_sys_free(allctr, crr);
 }
 
 
@@ -2457,19 +3653,19 @@ static struct {
     Eterm lmbcs;
     Eterm smbcs;
     Eterm mbcgs;
-    Eterm sbmbcs;
-    Eterm sbmbct;
+    Eterm acul;
 
 #if HAVE_ERTS_MSEG
     Eterm mmc;
 #endif
     Eterm ycs;
 
-    /* Eterm sbmbcs; */
-
     Eterm fix_types;
 
     Eterm mbcs;
+#ifdef ERTS_SMP
+    Eterm mbcs_pool;
+#endif
     Eterm sbcs;
 
     Eterm sys_alloc_carriers_size;
@@ -2494,8 +3690,6 @@ static struct {
     Eterm mseg_dealloc;
     Eterm mseg_realloc;
 #endif
-    Eterm sbmbc_alloc;
-    Eterm sbmbc_free;
 #ifdef DEBUG
     Eterm end_of_atoms;
 #endif
@@ -2551,19 +3745,19 @@ init_atoms(Allctr_t *allctr)
 	AM_INIT(lmbcs);
 	AM_INIT(smbcs);
 	AM_INIT(mbcgs);
-	AM_INIT(sbmbcs);
-	AM_INIT(sbmbct);
+	AM_INIT(acul);
 
 #if HAVE_ERTS_MSEG
 	AM_INIT(mmc);
 #endif
 	AM_INIT(ycs);
 
-	/*AM_INIT(sbmbcs);*/
-
 	AM_INIT(fix_types);
 
 	AM_INIT(mbcs);
+#ifdef ERTS_SMP
+	AM_INIT(mbcs_pool);
+#endif
 	AM_INIT(sbcs);
 
 	AM_INIT(sys_alloc_carriers_size);
@@ -2588,8 +3782,6 @@ init_atoms(Allctr_t *allctr)
 	AM_INIT(mseg_dealloc);
 	AM_INIT(mseg_realloc);
 #endif
-	AM_INIT(sbmbc_free);
-	AM_INIT(sbmbc_alloc);
 
 #ifdef DEBUG
 	for (atom = (Eterm *) &am; atom < &am.end_of_atoms; atom++) {
@@ -2637,19 +3829,22 @@ ensure_atoms_initialized(Allctr_t *allctr)
  * that would fit a small when size check is done may need to be built
  * as a big when the actual build is performed. Caller is required to
  * HRelease after build.
+ *
+ * Note, bld_unstable_uint() should have been called bld_unstable_uword()
+ * but we do not want to rename it...
  */
 static ERTS_INLINE Eterm
-bld_unstable_uint(Uint **hpp, Uint *szp, Uint ui)
+bld_unstable_uint(Uint **hpp, Uint *szp, UWord ui)
 {
     Eterm res = THE_NON_VALUE;
     if (szp)
-	*szp += BIG_UINT_HEAP_SIZE;
+	*szp += BIG_UWORD_HEAP_SIZE(~((UWord) 0));
     if (hpp) {
 	if (IS_USMALL(0, ui))
 	    res = make_small(ui);
 	else {
-	    res = uint_to_big(ui, *hpp);
-	    *hpp += BIG_UINT_HEAP_SIZE;
+	    res = uword_to_big(ui, *hpp);
+	    *hpp += BIG_UWORD_HEAP_SIZE(ui);
 	}
     }
     return res;
@@ -2675,8 +3870,24 @@ add_4tup(Uint **hpp, Uint *szp, Eterm *lp,
 	bld_cons(hpp, szp, bld_tuple(hpp, szp, 4, el1, el2, el3, el4), *lp);
 }
 
+static ERTS_INLINE void
+add_fix_types(Allctr_t *allctr, int internal, Uint **hpp, Uint *szp,
+	      Eterm *lp, Eterm fix)
+{
+    if (allctr->fix) {
+	if (!ERTS_ALC_IS_CPOOL_ENABLED(allctr))
+	    add_2tup(hpp, szp, lp, am.fix_types, fix);
+	else if (internal)
+	    add_3tup(hpp, szp, lp,
+		     am.fix_types,
+		     erts_bld_uword(hpp, szp, ~((UWord) 0)),
+		     fix);
+    }
+}
+
 static Eterm
 sz_info_fix(Allctr_t *allctr,
+	    int internal,
 	    int *print_to_p,
 	    void *print_to_arg,
 	    Uint **hpp,
@@ -2684,36 +3895,67 @@ sz_info_fix(Allctr_t *allctr,
 {
     Eterm res;
     int ix;
-    ErtsAlcFixList_t *fix = allctr->fix;
 
-    ASSERT(fix);
+    ASSERT(allctr->fix);
 
     res = NIL;
 
-    for (ix = ERTS_ALC_NO_FIXED_SIZES-1; ix >= 0; ix--) {
-	ErtsAlcType_t n = ix + ERTS_ALC_N_MIN_A_FIXED_SIZE;
-	Uint alloced = (fix[ix].type_size * fix[ix].allocated);
-	Uint used = fix[ix].type_size*fix[ix].used;
-
-	if (print_to_p) {
-	    int to = *print_to_p;
-	    void *arg = print_to_arg;
-	    erts_print(to,
-		       arg,
-		       "fix type: %s %bpu %bpu\n",
-		       (char *) ERTS_ALC_N2TD(n),
-		       alloced,
-		       used);
-	}
+    if (ERTS_ALC_IS_CPOOL_ENABLED(allctr)) {
+
+	if (internal) {
+	    for (ix = ERTS_ALC_NO_FIXED_SIZES-1; ix >= 0; ix--) {
+		ErtsAlcFixList_t *fix = &allctr->fix[ix];
+		UWord alloced = fix->type_size * fix->u.cpool.allocated;
+		UWord used = fix->type_size * fix->u.cpool.used;
+
+		if (print_to_p) {
+		    int to = *print_to_p;
+		    void *arg = print_to_arg;
+		    erts_print(to,
+			       arg,
+			       "fix type internal: %s %bpu %bpu\n",
+			       (char *) ERTS_ALC_N2TD(ERTS_ALC_N_MIN_A_FIXED_SIZE
+						      + ix),
+			       alloced,
+			       used);
+		}
 
-	if (hpp || szp) {
-	    add_3tup(hpp, szp, &res,
-		     fix_type_atoms[ix],
-		     bld_unstable_uint(hpp, szp, alloced),
-		     bld_unstable_uint(hpp, szp, used));
+		if (hpp || szp) {
+		    add_3tup(hpp, szp, &res,
+			     fix_type_atoms[ix],
+			     bld_unstable_uint(hpp, szp, alloced),
+			     bld_unstable_uint(hpp, szp, used));
+		}
+	    }
 	}
     }
+    else {
 
+	for (ix = ERTS_ALC_NO_FIXED_SIZES-1; ix >= 0; ix--) {
+	    ErtsAlcFixList_t *fix = &allctr->fix[ix];
+	    UWord alloced = fix->type_size * fix->u.nocpool.allocated;
+	    UWord used = fix->type_size*fix->u.nocpool.used;
+
+	    if (print_to_p) {
+		int to = *print_to_p;
+		void *arg = print_to_arg;
+		erts_print(to,
+			   arg,
+			   "fix type: %s %bpu %bpu\n",
+			   (char *) ERTS_ALC_N2TD(ERTS_ALC_N_MIN_A_FIXED_SIZE
+						  + ix),
+			   alloced,
+			   used);
+	    }
+
+	    if (hpp || szp) {
+		add_3tup(hpp, szp, &res,
+			 fix_type_atoms[ix],
+			 bld_unstable_uint(hpp, szp, alloced),
+			 bld_unstable_uint(hpp, szp, used));
+	    }
+	}
+    }
     return res;
 }
 
@@ -2727,9 +3969,7 @@ sz_info_carriers(Allctr_t *allctr,
 		 Uint *szp)
 {
     Eterm res = THE_NON_VALUE;
-    Uint curr_size = (cs == &allctr->sbmbcs
-		      ? cs->curr.small_block.size
-		      : cs->curr.norm.mseg.size + cs->curr.norm.sys_alloc.size);
+    UWord curr_size = cs->curr.norm.mseg.size + cs->curr.norm.sys_alloc.size;
 
     if (print_to_p) {
 	int to = *print_to_p;
@@ -2743,7 +3983,7 @@ sz_info_carriers(Allctr_t *allctr,
 		   cs->blocks.max_ever.size);
 	erts_print(to,
 		   arg,
-		   "%scarriers size: %beu %bpu %bpu\n",
+		   "%scarriers size: %bpu %bpu %bpu\n",
 		   prefix,
 		   curr_size,
 		   cs->max.size,
@@ -2767,6 +4007,62 @@ sz_info_carriers(Allctr_t *allctr,
     return res;
 }
 
+#ifdef ERTS_SMP
+
+static Eterm
+info_cpool(Allctr_t *allctr,
+	   int sz_only,
+	   char *prefix,
+	   int *print_to_p,
+	   void *print_to_arg,
+	   Uint **hpp,
+	   Uint *szp)
+{
+    Eterm res = THE_NON_VALUE;
+    UWord noc, csz, nob, bsz;
+
+    noc = csz = nob = bsz = ~0;
+    if (print_to_p || hpp) {
+	if (sz_only)
+	    cpool_read_stat(allctr, NULL, &csz, NULL, &bsz);
+	else
+	    cpool_read_stat(allctr, &noc, &csz, &nob, &bsz);
+    }
+
+    if (print_to_p) {
+	int to = *print_to_p;
+	void *arg = print_to_arg;
+	if (!sz_only)
+	    erts_print(to, arg, "%sblocks: %bpu\n", prefix, nob);
+	erts_print(to, arg, "%sblocks size: %bpu\n", prefix, bsz);
+	if (!sz_only)
+	    erts_print(to, arg, "%scarriers: %bpu\n", prefix, noc);
+	erts_print(to, arg, "%scarriers size: %bpu\n", prefix, csz);
+    }
+
+    if (hpp || szp) {
+	res = NIL;
+	add_2tup(hpp, szp, &res,
+		 am.carriers_size,
+		 bld_unstable_uint(hpp, szp, csz));
+	if (!sz_only)
+	    add_2tup(hpp, szp, &res,
+		     am.carriers,
+		     bld_unstable_uint(hpp, szp, noc));
+	add_2tup(hpp, szp, &res,
+		 am.blocks_size,
+		 bld_unstable_uint(hpp, szp, bsz));
+	if (!sz_only)
+	    add_2tup(hpp, szp, &res,
+		     am.blocks,
+		     bld_unstable_uint(hpp, szp, nob));
+    }
+
+    return res;
+}
+
+#endif /* ERTS_SMP */
+
 static Eterm
 info_carriers(Allctr_t *allctr,
 	      CarriersStats_t *cs,
@@ -2777,17 +4073,10 @@ info_carriers(Allctr_t *allctr,
 	      Uint *szp)
 {
     Eterm res = THE_NON_VALUE;
-    Uint curr_no, curr_size;
-    int small_block = cs == &allctr->sbmbcs;
-
-    if (small_block) {
-	curr_no = cs->curr.small_block.no;
-	curr_size = cs->curr.small_block.size;
-    }
-    else {
-	curr_no = cs->curr.norm.mseg.no + cs->curr.norm.sys_alloc.no;
-	curr_size = cs->curr.norm.mseg.size + cs->curr.norm.sys_alloc.size;
-    }
+    UWord curr_no, curr_size;
+    
+    curr_no = cs->curr.norm.mseg.no + cs->curr.norm.sys_alloc.no;
+    curr_size = cs->curr.norm.mseg.size + cs->curr.norm.sys_alloc.size;
 
     if (print_to_p) {
 	int to = *print_to_p;
@@ -2808,75 +4097,67 @@ info_carriers(Allctr_t *allctr,
 		   cs->blocks.max_ever.size);
 	erts_print(to,
 		   arg,
-		   "%scarriers: %beu %bpu %bpu\n",
+		   "%scarriers: %bpu %bpu %bpu\n",
 		   prefix,
 		   curr_no,
 		   cs->max.no,
 		   cs->max_ever.no);
-	if (!small_block) {
 #if HAVE_ERTS_MSEG
-	    erts_print(to,
-		       arg,
-		       "%smseg carriers: %bpu\n",
-		       prefix,
-		       cs->curr.norm.mseg.no);
-#endif
-	    erts_print(to,
-		       arg,
-		       "%ssys_alloc carriers: %bpu\n",
-		       prefix,
-		       cs->curr.norm.sys_alloc.no);
-	}
 	erts_print(to,
 		   arg,
-		   "%scarriers size: %beu %bpu %bpu\n",
+		   "%smseg carriers: %bpu\n",
+		   prefix,
+		   cs->curr.norm.mseg.no);
+#endif
+	erts_print(to,
+		   arg,
+		   "%ssys_alloc carriers: %bpu\n",
+		   prefix,
+		   cs->curr.norm.sys_alloc.no);
+	erts_print(to,
+		   arg,
+		   "%scarriers size: %bpu %bpu %bpu\n",
 		   prefix,
 		   curr_size,
 		   cs->max.size,
 		   cs->max_ever.size);
-	if (!small_block) {
 #if HAVE_ERTS_MSEG
-	    erts_print(to,
-		       arg,
-		       "%smseg carriers size: %bpu\n",
-		       prefix,
-		       cs->curr.norm.mseg.size);
-#endif
-	    erts_print(to,
-		       arg,
-		       "%ssys_alloc carriers size: %bpu\n",
-		       prefix,
-		       cs->curr.norm.sys_alloc.size);
-	}
+	erts_print(to,
+		   arg,
+		   "%smseg carriers size: %bpu\n",
+		   prefix,
+		   cs->curr.norm.mseg.size);
+#endif
+	erts_print(to,
+		   arg,
+		   "%ssys_alloc carriers size: %bpu\n",
+		   prefix,
+		   cs->curr.norm.sys_alloc.size);
     }
 
     if (hpp || szp) {
 	res = NIL;
-	if (!small_block) {
-	    add_2tup(hpp, szp, &res,
-		     am.sys_alloc_carriers_size,
-		     bld_unstable_uint(hpp, szp, cs->curr.norm.sys_alloc.size));
+	add_2tup(hpp, szp, &res,
+		 am.sys_alloc_carriers_size,
+		 bld_unstable_uint(hpp, szp, cs->curr.norm.sys_alloc.size));
 #if HAVE_ERTS_MSEG
-	    add_2tup(hpp, szp, &res,
-		     am.mseg_alloc_carriers_size,
-		     bld_unstable_uint(hpp, szp, cs->curr.norm.mseg.size));
+	add_2tup(hpp, szp, &res,
+		 am.mseg_alloc_carriers_size,
+		 bld_unstable_uint(hpp, szp, cs->curr.norm.mseg.size));
 #endif
-	}
 	add_4tup(hpp, szp, &res,
 		 am.carriers_size,
 		 bld_unstable_uint(hpp, szp, curr_size),
 		 bld_unstable_uint(hpp, szp, cs->max.size),
 		 bld_unstable_uint(hpp, szp, cs->max_ever.size));
-	if (!small_block) {
-	    add_2tup(hpp, szp, &res,
-		     am.sys_alloc_carriers,
-		     bld_unstable_uint(hpp, szp, cs->curr.norm.sys_alloc.no));
+	add_2tup(hpp, szp, &res,
+		 am.sys_alloc_carriers,
+		 bld_unstable_uint(hpp, szp, cs->curr.norm.sys_alloc.no));
 #if HAVE_ERTS_MSEG
-	    add_2tup(hpp, szp, &res,
-		     am.mseg_alloc_carriers,
-		     bld_unstable_uint(hpp, szp, cs->curr.norm.mseg.no));
+	add_2tup(hpp, szp, &res,
+		 am.mseg_alloc_carriers,
+		 bld_unstable_uint(hpp, szp, cs->curr.norm.mseg.no));
 #endif
-	}
 	add_4tup(hpp, szp, &res,
 		 am.carriers,
 		 bld_unstable_uint(hpp, szp, curr_no),
@@ -2935,16 +4216,10 @@ info_calls(Allctr_t *allctr,
     if (print_to_p) {
 
 #define PRINT_CC_4(TO, TOA, NAME, CC)					\
-    if ((CC).giga_no == 0)						\
-	erts_print(TO, TOA, "%s calls: %b32u\n", NAME, CC.no);		\
-    else								\
-	erts_print(TO, TOA, "%s calls: %b32u%09lu\n", NAME, CC.giga_no, CC.no)
+	erts_print(TO, TOA, "%s calls: %b64u\n", NAME, CC)
 
 #define PRINT_CC_5(TO, TOA, PRFX, NAME, CC)				\
-    if ((CC).giga_no == 0)						\
-	erts_print(TO, TOA, "%s%s calls: %b32u\n",PRFX,NAME,CC.no);	\
-    else								\
-	erts_print(TO, TOA, "%s%s calls: %b32u%09lu\n",PRFX,NAME,CC.giga_no,CC.no)
+	erts_print(TO, TOA, "%s%s calls: %b64u\n",PRFX,NAME,CC)
 
 	char *prefix = allctr->name_prefix;
 	int to = *print_to_p;
@@ -2954,9 +4229,6 @@ info_calls(Allctr_t *allctr,
 	PRINT_CC_5(to, arg, prefix, "free",         allctr->calls.this_free);
 	PRINT_CC_5(to, arg, prefix, "realloc",      allctr->calls.this_realloc);
 
-	PRINT_CC_4(to, arg,         "sbmbc_alloc",  allctr->calls.sbmbc_alloc);
-	PRINT_CC_4(to, arg,         "sbmbc_free",   allctr->calls.sbmbc_free);
-
 #if HAVE_ERTS_MSEG
 	PRINT_CC_4(to, arg,         "mseg_alloc",   allctr->calls.mseg_alloc);
 	PRINT_CC_4(to, arg,         "mseg_dealloc", allctr->calls.mseg_dealloc);
@@ -2983,50 +4255,42 @@ info_calls(Allctr_t *allctr,
 
 	add_3tup(hpp, szp, &res,
 		 am.sys_realloc,
-		 bld_unstable_uint(hpp, szp, allctr->calls.sys_realloc.giga_no),
-		 bld_unstable_uint(hpp, szp, allctr->calls.sys_realloc.no));
+		 bld_unstable_uint(hpp, szp, ERTS_ALC_CC_GIGA_VAL(allctr->calls.sys_realloc)),
+		 bld_unstable_uint(hpp, szp, ERTS_ALC_CC_VAL(allctr->calls.sys_realloc)));
 	add_3tup(hpp, szp, &res,
 		 am.sys_free,
-		 bld_unstable_uint(hpp, szp, allctr->calls.sys_free.giga_no),
-		 bld_unstable_uint(hpp, szp, allctr->calls.sys_free.no));
+		 bld_unstable_uint(hpp, szp, ERTS_ALC_CC_GIGA_VAL(allctr->calls.sys_free)),
+		 bld_unstable_uint(hpp, szp, ERTS_ALC_CC_VAL(allctr->calls.sys_free)));
 	add_3tup(hpp, szp, &res,
 		 am.sys_alloc,
-		 bld_unstable_uint(hpp, szp, allctr->calls.sys_alloc.giga_no),
-		 bld_unstable_uint(hpp, szp, allctr->calls.sys_alloc.no));
+		 bld_unstable_uint(hpp, szp, ERTS_ALC_CC_GIGA_VAL(allctr->calls.sys_alloc)),
+		 bld_unstable_uint(hpp, szp, ERTS_ALC_CC_VAL(allctr->calls.sys_alloc)));
 #if HAVE_ERTS_MSEG
 	add_3tup(hpp, szp, &res,
 		 am.mseg_realloc,
-		 bld_unstable_uint(hpp, szp, allctr->calls.mseg_realloc.giga_no),
-		 bld_unstable_uint(hpp, szp, allctr->calls.mseg_realloc.no));
+		 bld_unstable_uint(hpp, szp, ERTS_ALC_CC_GIGA_VAL(allctr->calls.mseg_realloc)),
+		 bld_unstable_uint(hpp, szp, ERTS_ALC_CC_VAL(allctr->calls.mseg_realloc)));
 	add_3tup(hpp, szp, &res,
 		 am.mseg_dealloc,
-		 bld_unstable_uint(hpp, szp, allctr->calls.mseg_dealloc.giga_no),
-		 bld_unstable_uint(hpp, szp, allctr->calls.mseg_dealloc.no));
+		 bld_unstable_uint(hpp, szp, ERTS_ALC_CC_GIGA_VAL(allctr->calls.mseg_dealloc)),
+		 bld_unstable_uint(hpp, szp, ERTS_ALC_CC_VAL(allctr->calls.mseg_dealloc)));
 	add_3tup(hpp, szp, &res,
 		 am.mseg_alloc,
-		 bld_unstable_uint(hpp, szp, allctr->calls.mseg_alloc.giga_no),
-		 bld_unstable_uint(hpp, szp, allctr->calls.mseg_alloc.no));
+		 bld_unstable_uint(hpp, szp, ERTS_ALC_CC_GIGA_VAL(allctr->calls.mseg_alloc)),
+		 bld_unstable_uint(hpp, szp, ERTS_ALC_CC_VAL(allctr->calls.mseg_alloc)));
 #endif
 	add_3tup(hpp, szp, &res,
-		 am.sbmbc_free,
-		 bld_unstable_uint(hpp, szp, allctr->calls.sbmbc_free.giga_no),
-		 bld_unstable_uint(hpp, szp, allctr->calls.sbmbc_free.no));
-	add_3tup(hpp, szp, &res,
-		 am.sbmbc_alloc,
-		 bld_unstable_uint(hpp, szp, allctr->calls.sbmbc_alloc.giga_no),
-		 bld_unstable_uint(hpp, szp, allctr->calls.sbmbc_alloc.no));
-	add_3tup(hpp, szp, &res,
 		 allctr->name.realloc,
-		 bld_unstable_uint(hpp, szp, allctr->calls.this_realloc.giga_no),
-		 bld_unstable_uint(hpp, szp, allctr->calls.this_realloc.no));
+		 bld_unstable_uint(hpp, szp, ERTS_ALC_CC_GIGA_VAL(allctr->calls.this_realloc)),
+		 bld_unstable_uint(hpp, szp, ERTS_ALC_CC_VAL(allctr->calls.this_realloc)));
 	add_3tup(hpp, szp, &res,
 		 allctr->name.free,
-		 bld_unstable_uint(hpp, szp, allctr->calls.this_free.giga_no),
-		 bld_unstable_uint(hpp, szp, allctr->calls.this_free.no));
+		 bld_unstable_uint(hpp, szp, ERTS_ALC_CC_GIGA_VAL(allctr->calls.this_free)),
+		 bld_unstable_uint(hpp, szp, ERTS_ALC_CC_VAL(allctr->calls.this_free)));
 	add_3tup(hpp, szp, &res,
 		 allctr->name.alloc,
-		 bld_unstable_uint(hpp, szp, allctr->calls.this_alloc.giga_no),
-		 bld_unstable_uint(hpp, szp, allctr->calls.this_alloc.no));
+		 bld_unstable_uint(hpp, szp, ERTS_ALC_CC_GIGA_VAL(allctr->calls.this_alloc)),
+		 bld_unstable_uint(hpp, szp, ERTS_ALC_CC_VAL(allctr->calls.this_alloc)));
     }
 
     return res;
@@ -3040,6 +4304,7 @@ info_options(Allctr_t *allctr,
 	     Uint *szp)
 {
     Eterm res = THE_NON_VALUE;
+    int acul;
 
     if (!allctr) {
 	if (print_to_p)
@@ -3051,6 +4316,12 @@ info_options(Allctr_t *allctr,
 	return res;
     }
 
+#ifdef ERTS_SMP
+    acul = allctr->cpool.util_limit;
+#else
+    acul = 0;
+#endif
+
     if (print_to_p) {
 	char topt[21]; /* Enough for any 64-bit integer */
 	if (allctr->t)
@@ -3079,9 +4350,8 @@ info_options(Allctr_t *allctr,
 #endif
 		   "option lmbcs: %beu\n"
 		   "option smbcs: %beu\n"
-		   "option mbcgs: %beu\n"
-		   "option sbmbcs: %beu\n"
-		   "option sbmbct: %beu\n",
+		   "option mbcgs: %beu\n",
+		   "option acul: %d\n",
 		   topt,
 		   allctr->ramv ? "true" : "false",
 #if HALFWORD_HEAP
@@ -3102,8 +4372,7 @@ info_options(Allctr_t *allctr,
 		   allctr->largest_mbc_size,
 		   allctr->smallest_mbc_size,
 		   allctr->mbc_growth_stages,
-		   allctr->sbmbc_size,
-		   allctr->sbmbc_threshold);
+		   acul);
     }
 
     res = (*allctr->info_options)(allctr, "option ", print_to_p, print_to_arg,
@@ -3111,11 +4380,8 @@ info_options(Allctr_t *allctr,
 
     if (hpp || szp) {
 	add_2tup(hpp, szp, &res,
-		 am.sbmbct,
-		 bld_uint(hpp, szp, allctr->sbmbc_threshold));
-	add_2tup(hpp, szp, &res,
-		 am.sbmbcs,
-		 bld_uint(hpp, szp, allctr->sbmbc_size));
+		 am.acul,
+		 bld_uint(hpp, szp, (UWord) acul));
 	add_2tup(hpp, szp, &res,
 		 am.mbcgs,
 		 bld_uint(hpp, szp, allctr->mbc_growth_stages));
@@ -3261,13 +4527,17 @@ erts_alcu_info_options(Allctr_t *allctr,
 
 Eterm
 erts_alcu_sz_info(Allctr_t *allctr,
+		  int internal,
 		  int begin_max_period,
 		  int *print_to_p,
 		  void *print_to_arg,
 		  Uint **hpp,
 		  Uint *szp)
 {
-    Eterm res, sbmbcs, mbcs, sbcs, fix = THE_NON_VALUE;
+    Eterm res, mbcs, sbcs, fix = THE_NON_VALUE;
+#ifdef ERTS_SMP
+    Eterm mbcs_pool;
+#endif
 
     res  = THE_NON_VALUE;
 
@@ -3296,30 +4566,35 @@ erts_alcu_sz_info(Allctr_t *allctr,
 	= allctr->sbcs.curr.norm.mseg.no + allctr->sbcs.curr.norm.sys_alloc.no;
     allctr->sbcs.blocks.max.no = allctr->sbcs.max.no;
 
-    update_max_ever_values(&allctr->sbmbcs);
     update_max_ever_values(&allctr->mbcs);
     update_max_ever_values(&allctr->sbcs);
 
     if (allctr->fix)
-	fix = sz_info_fix(allctr, print_to_p, print_to_arg, hpp, szp);
-    sbmbcs = sz_info_carriers(allctr, &allctr->sbmbcs, "sbmbcs ", print_to_p,
-			      print_to_arg, hpp, szp);
+	fix = sz_info_fix(allctr, internal, print_to_p, print_to_arg, hpp, szp);
     mbcs = sz_info_carriers(allctr, &allctr->mbcs, "mbcs ", print_to_p,
 			    print_to_arg, hpp, szp);
+#ifdef ERTS_SMP
+    if (ERTS_ALC_IS_CPOOL_ENABLED(allctr))
+	mbcs_pool = info_cpool(allctr, 1, "mbcs_pool ", print_to_p,
+			       print_to_arg, hpp, szp);
+    else
+	mbcs_pool = THE_NON_VALUE; /* shut up annoying warning... */
+#endif
     sbcs = sz_info_carriers(allctr, &allctr->sbcs, "sbcs ", print_to_p,
 			    print_to_arg, hpp, szp);
 
     if (hpp || szp) {
 	res = NIL;
 	add_2tup(hpp, szp, &res, am.sbcs, sbcs);
+#ifdef ERTS_SMP
+	if (ERTS_ALC_IS_CPOOL_ENABLED(allctr))
+	    add_2tup(hpp, szp, &res, am.mbcs_pool, mbcs_pool);
+#endif
 	add_2tup(hpp, szp, &res, am.mbcs, mbcs);
-	add_2tup(hpp, szp, &res, am.sbmbcs, sbmbcs);
-	if (allctr->fix)
-	    add_2tup(hpp, szp, &res, am.fix_types, fix);
+	add_fix_types(allctr, internal, hpp, szp, &res, fix);
     }
 
     if (begin_max_period) {
-	reset_max_values(&allctr->sbmbcs);
 	reset_max_values(&allctr->mbcs);
 	reset_max_values(&allctr->sbcs);
     }
@@ -3338,13 +4613,17 @@ erts_alcu_sz_info(Allctr_t *allctr,
 
 Eterm
 erts_alcu_info(Allctr_t *allctr,
+	       int internal,
 	       int begin_max_period,
 	       int *print_to_p,
 	       void *print_to_arg,
 	       Uint **hpp,
 	       Uint *szp)
 {
-    Eterm res, sett, sbmbcs, mbcs, sbcs, calls, fix = THE_NON_VALUE;
+    Eterm res, sett, mbcs, sbcs, calls, fix = THE_NON_VALUE;
+#ifdef ERTS_SMP
+    Eterm mbcs_pool;
+#endif
 
     res  = THE_NON_VALUE;
 
@@ -3373,7 +4652,6 @@ erts_alcu_info(Allctr_t *allctr,
 	= allctr->sbcs.curr.norm.mseg.no + allctr->sbcs.curr.norm.sys_alloc.no;
     allctr->sbcs.blocks.max.no = allctr->sbcs.max.no;
 
-    update_max_ever_values(&allctr->sbmbcs);
     update_max_ever_values(&allctr->mbcs);
     update_max_ever_values(&allctr->sbcs);
 
@@ -3387,11 +4665,16 @@ erts_alcu_info(Allctr_t *allctr,
 
     sett = info_options(allctr, print_to_p, print_to_arg, hpp, szp);
     if (allctr->fix)
-	fix = sz_info_fix(allctr, print_to_p, print_to_arg, hpp, szp);
-    sbmbcs = info_carriers(allctr, &allctr->sbmbcs, "sbmbcs ", print_to_p,
-			   print_to_arg, hpp, szp);
+	fix = sz_info_fix(allctr, internal, print_to_p, print_to_arg, hpp, szp);
     mbcs = info_carriers(allctr, &allctr->mbcs, "mbcs ", print_to_p,
 			 print_to_arg, hpp, szp);
+#ifdef ERTS_SMP
+    if (ERTS_ALC_IS_CPOOL_ENABLED(allctr))
+	mbcs_pool = info_cpool(allctr, 0, "mbcs_pool ", print_to_p,
+			       print_to_arg, hpp, szp);
+    else
+	mbcs_pool = THE_NON_VALUE; /* shut up annoying warning... */
+#endif
     sbcs = info_carriers(allctr, &allctr->sbcs, "sbcs ", print_to_p,
 			 print_to_arg, hpp, szp);
     calls = info_calls(allctr, print_to_p, print_to_arg, hpp, szp);
@@ -3401,10 +4684,12 @@ erts_alcu_info(Allctr_t *allctr,
 
 	add_2tup(hpp, szp, &res, am.calls, calls);
 	add_2tup(hpp, szp, &res, am.sbcs, sbcs);
+#ifdef ERTS_SMP
+	if (ERTS_ALC_IS_CPOOL_ENABLED(allctr))
+	    add_2tup(hpp, szp, &res, am.mbcs_pool, mbcs_pool);
+#endif
 	add_2tup(hpp, szp, &res, am.mbcs, mbcs);
-	add_2tup(hpp, szp, &res, am.sbmbcs, sbmbcs);
-	if (allctr->fix)
-	    add_2tup(hpp, szp, &res, am.fix_types, fix);
+	add_fix_types(allctr, internal, hpp, szp, &res, fix);
 	add_2tup(hpp, szp, &res, am.options, sett);
 	add_3tup(hpp, szp, &res,
 		 am.versions,
@@ -3413,7 +4698,6 @@ erts_alcu_info(Allctr_t *allctr,
     }
 
     if (begin_max_period) {
-	reset_max_values(&allctr->sbmbcs);
 	reset_max_values(&allctr->mbcs);
 	reset_max_values(&allctr->sbcs);
     }
@@ -3441,22 +4725,37 @@ erts_alcu_current_size(Allctr_t *allctr, AllctrSize_t *size, ErtsAlcUFixInfo_t *
 
     size->carriers = allctr->mbcs.curr.norm.mseg.size;
     size->carriers += allctr->mbcs.curr.norm.sys_alloc.size;
-    size->carriers += allctr->sbmbcs.curr.small_block.size;
     size->carriers += allctr->sbcs.curr.norm.mseg.size;
     size->carriers += allctr->sbcs.curr.norm.sys_alloc.size;
 
     size->blocks = allctr->mbcs.blocks.curr.size;
-    size->blocks += allctr->sbmbcs.blocks.curr.size;
     size->blocks += allctr->sbcs.blocks.curr.size;
 
+#ifdef ERTS_SMP
+    if (ERTS_ALC_IS_CPOOL_ENABLED(allctr)) {
+	UWord csz, bsz;
+	cpool_read_stat(allctr, NULL, &csz, NULL, &bsz);
+	size->blocks += bsz;
+	size->carriers += csz;
+    }
+#endif
+
     if (fi) {
 	int ix;
 	for (ix = 0; ix < fisz; ix++) {
 	    if (allctr->fix) {
-		fi[ix].allocated += (allctr->fix[ix].type_size
-				     * allctr->fix[ix].allocated);
-		fi[ix].used += (allctr->fix[ix].type_size
-				* allctr->fix[ix].used);
+		if (ERTS_ALC_IS_CPOOL_ENABLED(allctr)) {
+		    fi[ix].allocated += (allctr->fix[ix].type_size
+					 * allctr->fix[ix].u.cpool.allocated);
+		    fi[ix].used += (allctr->fix[ix].type_size
+				    * allctr->fix[ix].u.cpool.used);
+		}
+		else {
+		    fi[ix].allocated += (allctr->fix[ix].type_size
+					 * allctr->fix[ix].u.nocpool.allocated);
+		    fi[ix].used += (allctr->fix[ix].type_size
+				    * allctr->fix[ix].u.nocpool.used);
+		}
 	    }
 	}
     }
@@ -3474,7 +4773,6 @@ do_erts_alcu_alloc(ErtsAlcType_t type, void *extra, Uint size)
 {
     Allctr_t *allctr = (Allctr_t *) extra; 
     void *res;
-    ErtsAlcFixList_t *fix;
 
     ASSERT(initialized);
 
@@ -3492,57 +4790,21 @@ do_erts_alcu_alloc(ErtsAlcType_t type, void *extra, Uint size)
 
     INC_CC(allctr->calls.this_alloc);
 
-    fix = allctr->fix;
-    if (fix) {
-	int ix = type - ERTS_ALC_N_MIN_A_FIXED_SIZE;
-	ASSERT((unsigned)ix < ERTS_ALC_NO_FIXED_SIZES);
-	ERTS_DBG_CHK_FIX_LIST(allctr, fix, ix, 1);
-	ASSERT(size <= fix[ix].type_size);
-	fix[ix].used++;
-	res = fix[ix].list;
-	if (res) {
-	    fix[ix].list_size--;
-	    fix[ix].list = *((void **) res);
-	    if (fix[ix].list && fix[ix].allocated > fix[ix].limit) {
-		void *p = fix[ix].list;
-		Block_t *blk;
-		fix[ix].list = *((void **) p);
-		fix[ix].list_size--;
-		blk = UMEM2BLK(p);
-		if (IS_SBC_BLK(blk))
-		    destroy_carrier(allctr, blk);
-		else
-		    mbc_free(allctr, p);
-		fix[ix].allocated--;
-	    }
-	    ERTS_DBG_CHK_FIX_LIST(allctr, fix, ix, 0);
-	    return res;
-	}
-	size = fix[ix].type_size;
-	if (fix[ix].limit < fix[ix].used)
-	    fix[ix].limit = fix[ix].used;
-	if (fix[ix].max_used < fix[ix].used)
-	    fix[ix].max_used = fix[ix].used;
-	fix[ix].allocated++;
+    if (allctr->fix) {
+	if (ERTS_ALC_IS_CPOOL_ENABLED(allctr))
+	    return fix_cpool_alloc(allctr, type, size);
+	else
+	    return fix_nocpool_alloc(allctr, type, size);
     }
 
     if (size >= allctr->sbc_threshold) {
 	Block_t *blk;
-#ifdef ERTS_SMP
-	if (allctr->dd.use)
-	    ERTS_ALCU_HANDLE_DD_IN_OP(allctr, 1);
-#endif
 	blk = create_carrier(allctr, size, CFLG_SBC);
 	res = blk ? BLK2UMEM(blk) : NULL;
     }
     else
 	res = mbc_alloc(allctr, size);
 
-    if (!res && fix) {
-	int ix = type - ERTS_ALC_N_MIN_A_FIXED_SIZE;
-	fix[ix].allocated--;
-	fix[ix].used--;
-    }
     return res;
 }
 
@@ -3611,9 +4873,22 @@ erts_alcu_alloc_thr_pref(ErtsAlcType_t type, void *extra, Uint size)
     if (pref_allctr->thread_safe)
 	erts_mtx_lock(&pref_allctr->mutex);
 
+#ifdef ERTS_SMP
+    ASSERT(pref_allctr->dd.use);
+    ERTS_ALCU_HANDLE_DD_IN_OP(pref_allctr, 1);
+#endif
+
     ERTS_ALCU_DBG_CHK_THR_ACCESS(pref_allctr);
 
     res = do_erts_alcu_alloc(type, pref_allctr, size);
+
+#ifdef ERTS_SMP
+    if (!res && ERTS_ALCU_HANDLE_DD_IN_OP(pref_allctr, 1)) {
+	/* Cleaned up a bit more; try one more time... */
+	res = do_erts_alcu_alloc(type, pref_allctr, size);
+    }
+#endif
+
     if (pref_allctr->thread_safe)
 	erts_mtx_unlock(&pref_allctr->mutex);
 
@@ -3630,9 +4905,9 @@ erts_alcu_alloc_thr_pref(ErtsAlcType_t type, void *extra, Uint size)
 /* ------------------------------------------------------------------------- */
 
 static ERTS_INLINE void
-do_erts_alcu_free(ErtsAlcType_t type, void *extra, void *p)
+do_erts_alcu_free(ErtsAlcType_t type, void *extra, void *p,
+		  Carrier_t **busy_pcrr_pp)
 {
-    int ix;
     Allctr_t *allctr = (Allctr_t *) extra; 
     ASSERT(initialized);
 
@@ -3644,57 +4919,28 @@ do_erts_alcu_free(ErtsAlcType_t type, void *extra, void *p)
     ERTS_ALCU_DBG_CHK_THR_ACCESS(allctr);
 
     if (p) {
-	ErtsAlcFixList_t *fix = allctr->fix;
-	Block_t *blk;
 
 	INC_CC(allctr->calls.this_free);
 
-	if (fix) {
-	    ix = type - ERTS_ALC_N_MIN_A_FIXED_SIZE;
-	    ERTS_DBG_CHK_FIX_LIST(allctr, fix, ix, 1);
-	    fix[ix].used--;
-	    if (fix[ix].allocated < fix[ix].limit
-		&& fix[ix].list_size < ERTS_ALCU_FIX_MAX_LIST_SZ) {
-		*((void **) p) = fix[ix].list;
-		fix[ix].list = p;
-		fix[ix].list_size++;
-		if (!allctr->fix_shrink_scheduled) {
-		    allctr->fix_shrink_scheduled = 1;
-		    erts_set_aux_work_timeout(
-			allctr->ix,
-			(ERTS_SSI_AUX_WORK_FIX_ALLOC_LOWER_LIM
-			 | ERTS_SSI_AUX_WORK_FIX_ALLOC_DEALLOC),
-			1);
-		}
-		ERTS_DBG_CHK_FIX_LIST(allctr, fix, ix, 0);
-		return;
-	    }
-	    fix[ix].allocated--;
-	    if (fix[ix].list && fix[ix].allocated > fix[ix].limit) {
-		blk = UMEM2BLK(p);
-		if (IS_SBC_BLK(blk))
-		    destroy_carrier(allctr, blk);
-		else
-		    mbc_free(allctr, p);
-		p = fix[ix].list;
-		fix[ix].list = *((void **) p);
-		fix[ix].list_size--;
-		fix[ix].allocated--;
-	    }
+	if (allctr->fix) {
+	    if (ERTS_ALC_IS_CPOOL_ENABLED(allctr))
+		fix_cpool_free(allctr, type, p, busy_pcrr_pp);
+	    else
+		fix_nocpool_free(allctr, type, p);
+	}
+	else {
+	    Block_t *blk = UMEM2BLK(p);
+	    if (IS_SBC_BLK(blk))
+		destroy_carrier(allctr, blk, NULL);
+	    else
+		mbc_free(allctr, p, busy_pcrr_pp);
 	}
-
-	blk = UMEM2BLK(p);
-	if (IS_SBC_BLK(blk))
-	    destroy_carrier(allctr, blk);
-	else
-	    mbc_free(allctr, p);
-	ERTS_DBG_CHK_FIX_LIST(allctr, fix, ix, 0);
     }
 }
 
 void erts_alcu_free(ErtsAlcType_t type, void *extra, void *p)
 {
-    do_erts_alcu_free(type, extra, p);
+    do_erts_alcu_free(type, extra, p, NULL);
 }
 
 #ifdef USE_THREADS
@@ -3704,7 +4950,7 @@ erts_alcu_free_ts(ErtsAlcType_t type, void *extra, void *p)
 {
     Allctr_t *allctr = (Allctr_t *) extra;
     erts_mtx_lock(&allctr->mutex);
-    do_erts_alcu_free(type, extra, p);
+    do_erts_alcu_free(type, extra, p, NULL);
     erts_mtx_unlock(&allctr->mutex);
 }
 
@@ -3726,7 +4972,7 @@ erts_alcu_free_thr_spec(ErtsAlcType_t type, void *extra, void *p)
     if (allctr->thread_safe)
 	erts_mtx_lock(&allctr->mutex);
 
-    do_erts_alcu_free(type, allctr, p);
+    do_erts_alcu_free(type, allctr, p, NULL);
 
     if (allctr->thread_safe)
 	erts_mtx_unlock(&allctr->mutex);
@@ -3736,10 +4982,12 @@ void
 erts_alcu_free_thr_pref(ErtsAlcType_t type, void *extra, void *p)
 {
     if (p) {
+	Carrier_t *busy_pcrr_p;
 	Allctr_t *pref_allctr, *used_allctr;
 
 	pref_allctr = get_pref_allctr(extra);
-	used_allctr = get_used_allctr(extra, p, NULL);
+	used_allctr = get_used_allctr(pref_allctr, ERTS_ALC_TS_PREF_LOCK_IF_USED,
+				      p, NULL, &busy_pcrr_p);
 	if (pref_allctr != used_allctr)
 	    enqueue_dealloc_other_instance(type,
 					   used_allctr,
@@ -3747,12 +4995,11 @@ erts_alcu_free_thr_pref(ErtsAlcType_t type, void *extra, void *p)
 					   (used_allctr->dd.ix
 					    - pref_allctr->dd.ix));
 	else {
-	    if (used_allctr->thread_safe)
-		erts_mtx_lock(&used_allctr->mutex);
 	    ERTS_ALCU_DBG_CHK_THR_ACCESS(used_allctr);
-	    do_erts_alcu_free(type, used_allctr, p);
-	    if (used_allctr->thread_safe)
-		erts_mtx_unlock(&used_allctr->mutex);
+	    do_erts_alcu_free(type, used_allctr, p, &busy_pcrr_p);
+	    clear_busy_pool_carrier(used_allctr, busy_pcrr_p);
+	    if (pref_allctr->thread_safe)
+		erts_mtx_unlock(&pref_allctr->mutex);
 	}
     }
 }
@@ -3768,7 +5015,8 @@ do_erts_alcu_realloc(ErtsAlcType_t type,
 		     void *extra,
 		     void *p,
 		     Uint size,
-		     Uint32 alcu_flgs)
+		     Uint32 alcu_flgs,
+		     Carrier_t **busy_pcrr_pp)
 {
     Allctr_t *allctr = (Allctr_t *) extra; 
     Block_t *blk;
@@ -3793,7 +5041,7 @@ do_erts_alcu_realloc(ErtsAlcType_t type,
 #if ALLOC_ZERO_EQ_NULL
     if (!size) {
 	ASSERT(p);
-	do_erts_alcu_free(type, extra, p);
+	do_erts_alcu_free(type, extra, p, busy_pcrr_pp);
 	INC_CC(allctr->calls.this_realloc);
 	DEC_CC(allctr->calls.this_free);
 	return NULL;
@@ -3804,32 +5052,9 @@ do_erts_alcu_realloc(ErtsAlcType_t type,
     
     blk = UMEM2BLK(p);
 
-    if (allctr->sbmbc_threshold > 0) {
-	Uint old_sz, new_sz, lim;
-	lim = allctr->sbmbc_threshold;
-	old_sz = BLK_SZ(blk);
-	new_sz = UMEMSZ2BLKSZ(allctr, size);
-	if ((old_sz < lim && lim <= new_sz)
-	    || (new_sz < lim && lim <= old_sz)) {
-	    /* *Need* to move it... */
-
-	    INC_CC(allctr->calls.this_realloc);
-	    res = do_erts_alcu_alloc(type, extra, size);
-	    DEC_CC(allctr->calls.this_alloc);
-
-	    sys_memcpy(res, p, MIN(size, old_sz - ABLK_HDR_SZ));
-
-	    do_erts_alcu_free(type, extra, p);
-	    DEC_CC(allctr->calls.this_free);
-	    return res;
-	}
-	if (old_sz < lim)
-	    alcu_flgs |= ERTS_ALCU_FLG_SBMBC;
-    }
-
     if (size < allctr->sbc_threshold) {
 	if (IS_MBC_BLK(blk))
-	    res = mbc_realloc(allctr, p, size, alcu_flgs);
+	    res = mbc_realloc(allctr, p, size, alcu_flgs, busy_pcrr_pp);
 	else {
 	    Uint used_sz = SBC_HEADER_SIZE + ABLK_HDR_SZ + size;
 	    Uint crr_sz;
@@ -3868,16 +5093,12 @@ do_erts_alcu_realloc(ErtsAlcType_t type,
 		sys_memcpy((void*) res,
 			   (void*) p,
 			   MIN(SBC_BLK_SZ(blk) - ABLK_HDR_SZ, size));
-		destroy_carrier(allctr, blk);
+		destroy_carrier(allctr, blk, NULL);
 	    }
 	}
     }
     else {
 	Block_t *new_blk;
-#ifdef ERTS_SMP
-	if (allctr->dd.use)
-	    ERTS_ALCU_HANDLE_DD_IN_OP(allctr, 1);
-#endif
 	if(IS_SBC_BLK(blk)) {
 	do_carrier_resize:
 #if HALFWORD_HEAP
@@ -3896,7 +5117,7 @@ do_erts_alcu_realloc(ErtsAlcType_t type,
 		sys_memcpy((void *) res,
 			   (void *) p,
 			   MIN(MBC_ABLK_SZ(blk) - ABLK_HDR_SZ, size));
-		mbc_free(allctr, p);
+		mbc_free(allctr, p, busy_pcrr_pp);
 	    }
 	    else
 		res = NULL;
@@ -3910,7 +5131,7 @@ void *
 erts_alcu_realloc(ErtsAlcType_t type, void *extra, void *p, Uint size)
 {
     void *res;
-    res = do_erts_alcu_realloc(type, extra, p, size, 0);
+    res = do_erts_alcu_realloc(type, extra, p, size, 0, NULL);
     DEBUG_CHECK_ALIGNMENT(res);
     return res;
 }
@@ -3931,7 +5152,7 @@ erts_alcu_realloc_mv(ErtsAlcType_t type, void *extra, void *p, Uint size)
 	if (cpy_size > size)
 	    cpy_size = size;
 	sys_memcpy(res, p, cpy_size);
-	do_erts_alcu_free(type, extra, p);
+	do_erts_alcu_free(type, extra, p, NULL);
     }
     DEBUG_CHECK_ALIGNMENT(res);
     return res;
@@ -3946,7 +5167,7 @@ erts_alcu_realloc_ts(ErtsAlcType_t type, void *extra, void *ptr, Uint size)
     Allctr_t *allctr = (Allctr_t *) extra;
     void *res;
     erts_mtx_lock(&allctr->mutex);
-    res = do_erts_alcu_realloc(type, extra, ptr, size, 0);
+    res = do_erts_alcu_realloc(type, extra, ptr, size, 0, NULL);
     erts_mtx_unlock(&allctr->mutex);
     DEBUG_CHECK_ALIGNMENT(res);
     return res;
@@ -3970,7 +5191,7 @@ erts_alcu_realloc_mv_ts(ErtsAlcType_t type, void *extra, void *p, Uint size)
 	if (cpy_size > size)
 	    cpy_size = size;
 	sys_memcpy(res, p, cpy_size);
-	do_erts_alcu_free(type, extra, p);
+	do_erts_alcu_free(type, extra, p, NULL);
     }
     erts_mtx_unlock(&allctr->mutex);
     DEBUG_CHECK_ALIGNMENT(res);
@@ -3997,7 +5218,7 @@ erts_alcu_realloc_thr_spec(ErtsAlcType_t type, void *extra,
     if (allctr->thread_safe)
 	erts_mtx_lock(&allctr->mutex);
 
-    res = do_erts_alcu_realloc(type, allctr, ptr, size, 0);
+    res = do_erts_alcu_realloc(type, allctr, ptr, size, 0, NULL);
 
     if (allctr->thread_safe)
 	erts_mtx_unlock(&allctr->mutex);
@@ -4040,7 +5261,7 @@ erts_alcu_realloc_mv_thr_spec(ErtsAlcType_t type, void *extra,
 	if (cpy_size > size)
 	    cpy_size = size;
 	sys_memcpy(res, ptr, cpy_size);
-	do_erts_alcu_free(type, allctr, ptr);
+	do_erts_alcu_free(type, allctr, ptr, NULL);
 	if (allctr->thread_safe)
 	    erts_mtx_unlock(&allctr->mutex);
     }
@@ -4057,40 +5278,64 @@ realloc_thr_pref(ErtsAlcType_t type, void *extra, void *p, Uint size,
     void *res;
     Allctr_t *pref_allctr, *used_allctr;
     UWord old_user_size;
+    Carrier_t *busy_pcrr_p;
+#ifdef ERTS_SMP
+    int retried;
+#endif
 
     if (!p)
 	return erts_alcu_alloc_thr_pref(type, extra, size);
 
     pref_allctr = get_pref_allctr(extra);
-    used_allctr = get_used_allctr(extra, p, &old_user_size);
+
+    if (pref_allctr->thread_safe)
+	erts_mtx_lock(&pref_allctr->mutex);
+
+#ifdef ERTS_SMP
+    ASSERT(pref_allctr->dd.use);
+    ERTS_ALCU_HANDLE_DD_IN_OP(pref_allctr, 1);
+    retried = 0;
+restart:
+#endif
+
+    used_allctr = get_used_allctr(pref_allctr, ERTS_ALC_TS_PREF_LOCK_NO,
+				  p, &old_user_size, &busy_pcrr_p);
 
     ASSERT(used_allctr && pref_allctr);
 
     if (!force_move && used_allctr == pref_allctr) {
-	if (used_allctr->thread_safe)
-	    erts_mtx_lock(&used_allctr->mutex);
 	ERTS_ALCU_DBG_CHK_THR_ACCESS(used_allctr);
 	res = do_erts_alcu_realloc(type,
 				   used_allctr,
 				   p,
 				   size,
-				   0);
-	if (used_allctr->thread_safe)
-	    erts_mtx_unlock(&used_allctr->mutex);
+				   0,
+				   &busy_pcrr_p);
+	clear_busy_pool_carrier(used_allctr, busy_pcrr_p);
+#ifdef ERTS_SMP
+	if (!res && !retried && ERTS_ALCU_HANDLE_DD_IN_OP(pref_allctr, 1)) {
+	    /* Cleaned up a bit more; try one more time... */
+	    retried = 1;
+	    goto restart;
+	}
+#endif	    
+	if (pref_allctr->thread_safe)
+	    erts_mtx_unlock(&pref_allctr->mutex);
     }
     else {
-	if (pref_allctr->thread_safe)
-	    erts_mtx_lock(&pref_allctr->mutex);
 	res = do_erts_alcu_alloc(type, pref_allctr, size);
-	if (pref_allctr->thread_safe && used_allctr != pref_allctr) {
-	    erts_mtx_unlock(&pref_allctr->mutex);
-	}
-	if (res) {
-	    DEBUG_CHECK_ALIGNMENT(res);
+	if (!res)
+	    goto unlock_ts_return;
+	else {
 
-	    sys_memcpy(res, p, MIN(size,old_user_size));
+	    DEBUG_CHECK_ALIGNMENT(res);
 
 	    if (used_allctr != pref_allctr) {
+		if (pref_allctr->thread_safe)
+		    erts_mtx_unlock(&pref_allctr->mutex);
+
+		sys_memcpy(res, p, MIN(size, old_user_size));
+
 		enqueue_dealloc_other_instance(type,
 					       used_allctr,
 					       p,
@@ -4098,8 +5343,14 @@ realloc_thr_pref(ErtsAlcType_t type, void *extra, void *p, Uint size,
 						- pref_allctr->dd.ix));
 	    }
 	    else {
-		do_erts_alcu_free(type, used_allctr, p);
+
+		sys_memcpy(res, p, MIN(size, old_user_size));
+
+		do_erts_alcu_free(type, used_allctr, p, &busy_pcrr_p);
 		ASSERT(pref_allctr == used_allctr);
+		clear_busy_pool_carrier(used_allctr, busy_pcrr_p);
+
+	    unlock_ts_return:
 		if (pref_allctr->thread_safe)
 		    erts_mtx_unlock(&pref_allctr->mutex);
 	    }
@@ -4213,6 +5464,17 @@ erts_alcu_start(Allctr_t *allctr, AllctrInit_t *init)
 	if (sz > allctr->min_block_size)
 	    allctr->min_block_size = sz;
     }
+
+    allctr->cpool.dc_list.first = NULL;
+    allctr->cpool.dc_list.last = NULL;
+    allctr->cpool.abandon_limit = 0;
+    allctr->cpool.disable_abandon = 0;
+    erts_atomic_init_nob(&allctr->cpool.stat.blocks_size, 0);
+    erts_atomic_init_nob(&allctr->cpool.stat.no_blocks, 0);
+    erts_atomic_init_nob(&allctr->cpool.stat.carriers_size, 0);
+    erts_atomic_init_nob(&allctr->cpool.stat.no_carriers, 0);
+    allctr->cpool.check_limit_count = ERTS_ALC_CPOOL_CHECK_LIMIT_COUNT;
+    allctr->cpool.util_limit = init->acul;
 #endif
 
     allctr->sbc_threshold		= init->sbct;
@@ -4232,27 +5494,6 @@ erts_alcu_start(Allctr_t *allctr, AllctrInit_t *init)
     }
 #endif
 
-
-
-    allctr->sbmbc_threshold		= init->sbmbct;
-
-    if (!erts_have_sbmbc_alloc
-	|| ERTS_IS_SBMBC_ALLOCATOR_NO__(allctr->alloc_no))
-	allctr->sbmbc_threshold = 0;
-
-    if (!allctr->sbmbc_threshold)
-	allctr->sbmbc_size = 0;
-    else {
-	Uint min_size;
-	allctr->sbmbc_size = init->sbmbcs;
-	min_size = allctr->sbmbc_threshold;
-	min_size += allctr->min_block_size;
-	min_size += MBC_HEADER_SIZE(allctr);
-	if (allctr->sbmbc_size < min_size)
-	    allctr->sbmbc_size = min_size;
-    }
-
-
 #if HAVE_ERTS_MSEG
     if (allctr->mseg_opt.abs_shrink_th > ~((UWord) 0) / 100)
 	allctr->mseg_opt.abs_shrink_th = ~((UWord) 0) / 100;
@@ -4264,16 +5505,12 @@ erts_alcu_start(Allctr_t *allctr, AllctrInit_t *init)
 	
 #ifdef ERTS_ENABLE_LOCK_COUNT
 	erts_mtx_init_x_opt(&allctr->mutex,
-			    ERTS_IS_SBMBC_ALLOCATOR_NO__(allctr->alloc_no)
-			    ? "sbmbc_alloc"
-			    : "alcu_allocator",
+			    "alcu_allocator",
 			    make_small(allctr->alloc_no),
 			    ERTS_LCNT_LT_ALLOC);
 #else
 	erts_mtx_init_x(&allctr->mutex,
-			ERTS_IS_SBMBC_ALLOCATOR_NO__(allctr->alloc_no)
-			? "sbmbc_alloc"
-			: "alcu_allocator",
+			"alcu_allocator",
 			make_small(allctr->alloc_no));
 #endif /*ERTS_ENABLE_LOCK_COUNT*/
 	
@@ -4292,6 +5529,8 @@ erts_alcu_start(Allctr_t *allctr, AllctrInit_t *init)
     if (!allctr->get_next_mbc_size)
 	allctr->get_next_mbc_size = get_next_mbc_size;
 
+    if (allctr->mbc_header_size < sizeof(Carrier_t))
+	goto error;
 #ifdef ERTS_SMP
     allctr->dd.use = 0;
     if (init->tpref) {
@@ -4300,6 +5539,9 @@ erts_alcu_start(Allctr_t *allctr, AllctrInit_t *init)
 	allctr->dd.ix = init->ix;
     }
 #endif
+    allctr->mbc_header_size = (UNIT_CEILING(allctr->mbc_header_size
+					    + ABLK_HDR_SZ)
+			       - ABLK_HDR_SZ);
 
     if (allctr->main_carrier_size) {
 	Block_t *blk;
@@ -4308,6 +5550,7 @@ erts_alcu_start(Allctr_t *allctr, AllctrInit_t *init)
 			     allctr->main_carrier_size,
 			     CFLG_MBC
 			     | CFLG_FORCE_SIZE
+			     | CFLG_NO_CPOOL
 #if !HALFWORD_HEAP && !HAVE_SUPER_ALIGNED_MB_CARRIERS
 			     | CFLG_FORCE_SYS_ALLOC
 #endif
@@ -4315,7 +5558,7 @@ erts_alcu_start(Allctr_t *allctr, AllctrInit_t *init)
 	if (!blk)
 	    goto error;
 
-	(*allctr->link_free_block)(allctr, blk, 0);
+	(*allctr->link_free_block)(allctr, blk);
 
 	HARD_CHECK_BLK_CARRIER(allctr, blk);
 
@@ -4326,16 +5569,24 @@ erts_alcu_start(Allctr_t *allctr, AllctrInit_t *init)
 	allctr->fix = init->fix;
 	allctr->fix_shrink_scheduled = 0;
 	for (i = 0; i < ERTS_ALC_NO_FIXED_SIZES; i++) {
-	    allctr->fix[i].max_used = 0;
-	    allctr->fix[i].limit = 0;
 	    allctr->fix[i].type_size = init->fix_type_size[i];
 	    allctr->fix[i].list_size = 0;
 	    allctr->fix[i].list = NULL;
-	    allctr->fix[i].allocated = 0;
-	    allctr->fix[i].used = 0;
 #ifdef ERTS_SMP
 	    ASSERT(allctr->fix[i].type_size >= sizeof(ErtsAllctrFixDDBlock_t));
 #endif
+	    if (ERTS_ALC_IS_CPOOL_ENABLED(allctr)) {
+		allctr->fix[i].u.cpool.min_list_size = 0;
+		allctr->fix[i].u.cpool.shrink_list = 0;
+		allctr->fix[i].u.cpool.allocated = 0;
+		allctr->fix[i].u.cpool.used = 0;
+	    }
+	    else {
+		allctr->fix[i].u.nocpool.max_used = 0;
+		allctr->fix[i].u.nocpool.limit = 0;
+		allctr->fix[i].u.nocpool.allocated = 0;
+		allctr->fix[i].u.nocpool.used = 0;
+	    }
 	}
     }
 
@@ -4360,11 +5611,9 @@ erts_alcu_stop(Allctr_t *allctr)
     allctr->stopped = 1;
 
     while (allctr->sbc_list.first)
-	destroy_carrier(allctr, SBC2BLK(allctr, allctr->sbc_list.first));
+	destroy_carrier(allctr, SBC2BLK(allctr, allctr->sbc_list.first), NULL);
     while (allctr->mbc_list.first)
-	destroy_carrier(allctr, MBC_TO_FIRST_BLK(allctr, allctr->mbc_list.first));
-    while (allctr->sbmbc_list.first)
-	destroy_sbmbc(allctr, MBC_TO_FIRST_BLK(allctr, allctr->sbmbc_list.first));
+	destroy_carrier(allctr, MBC_TO_FIRST_BLK(allctr, allctr->mbc_list.first), NULL);
 
 #ifdef USE_THREADS
     if (allctr->thread_safe)
@@ -4378,6 +5627,14 @@ erts_alcu_stop(Allctr_t *allctr)
 void
 erts_alcu_init(AlcUInit_t *init)
 {
+#ifdef ERTS_SMP
+    int i;
+    for (i = 0; i <= ERTS_ALC_A_MAX; i++) {
+	ErtsAlcCPoolData_t *sentinel = &carrier_pool[i].sentinel;
+	erts_atomic_init_nob(&sentinel->next, (erts_aint_t) sentinel);
+	erts_atomic_init_nob(&sentinel->prev, (erts_aint_t) sentinel);
+    }
+#endif
     ASSERT(SBC_BLK_SZ_MASK == MBC_FBLK_SZ_MASK); /* see BLK_SZ */
 #if HAVE_ERTS_MSEG
     ASSERT(erts_mseg_unit_size() == MSEG_UNIT_SZ);
@@ -4440,8 +5697,35 @@ erts_alcu_test(UWord op, UWord a1, UWord a2)
     case 0x019:	return (UWord) PREV_BLK((Block_t *) a1);
     case 0x01a: return (UWord) IS_MBC_FIRST_BLK((Allctr_t*)a1, (Block_t *) a2);
     case 0x01b: return (UWord) sizeof(Unit_t);
+    case 0x01c: return (unsigned long) BLK_TO_MBC((Block_t*) a1);
+    case 0x01d: ((Allctr_t*) a1)->add_mbc((Allctr_t*)a1, (Carrier_t*)a2); break;
+    case 0x01e: ((Allctr_t*) a1)->remove_mbc((Allctr_t*)a1, (Carrier_t*)a2); break;
+#ifdef ERTS_SMP
+    case 0x01f: return (UWord) sizeof(ErtsAlcCrrPool_t);
+    case 0x020:
+	SET_CARRIER_HDR((Carrier_t *) a2, 0, SCH_SYS_ALLOC|SCH_MBC, (Allctr_t *) a1);
+	cpool_init_carrier_data((Allctr_t *) a1, (Carrier_t *) a2);
+	return (UWord) a2;
+    case 0x021:
+	cpool_insert((Allctr_t *) a1, (Carrier_t *) a2);
+	return (UWord) a2;
+    case 0x022:
+	cpool_delete((Allctr_t *) a1, (Allctr_t *) a1, (Carrier_t *) a2);
+	return (UWord) a2;
+    case 0x023: return (UWord) cpool_is_empty((Allctr_t *) a1);
+    case 0x024: return (UWord) cpool_dbg_is_in_pool((Allctr_t *) a1, (Carrier_t *) a2);
+#else
+    case 0x01f: return (UWord) 0;
+    case 0x020: return (UWord) 0;
+    case 0x021: return (UWord) 0;
+    case 0x022: return (UWord) 0;
+    case 0x023: return (UWord) 0;
+    case 0x024: return (UWord) 0;
+#endif
+
     default:	ASSERT(0); return ~((UWord) 0);
     }
+    return 0;
 }
 
 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *\
@@ -4449,6 +5733,20 @@ erts_alcu_test(UWord op, UWord a1, UWord a2)
 \*                                                                           */
 
 void
+erts_alcu_assert_failed(char* expr, char* file, int line, char *func)
+{
+    fflush(stdout);
+    fprintf(stderr, "%s:%d:%s(): Assertion failed: %s\n",
+	    file, line, func, expr);
+    fflush(stderr);
+#if defined(__WIN__) || defined(__WIN32__)
+    DebugBreak();
+#else
+    abort();
+#endif
+}
+
+void
 erts_alcu_verify_unused(Allctr_t *allctr)
 {
     UWord no;
@@ -4456,12 +5754,10 @@ erts_alcu_verify_unused(Allctr_t *allctr)
     no = allctr->sbcs.curr.norm.mseg.no;
     no += allctr->sbcs.curr.norm.sys_alloc.no;
     no += allctr->mbcs.blocks.curr.no;
-    no += allctr->sbmbcs.blocks.curr.no;
 
     if (no) {
 	UWord sz = allctr->sbcs.blocks.curr.size;
 	sz += allctr->mbcs.blocks.curr.size;
-	sz += allctr->sbmbcs.blocks.curr.size;
 	erl_exit(ERTS_ABORT_EXIT,
 		 "%salloc() used when expected to be unused!\n"
 		 "Total amount of blocks allocated: %bpu\n"
@@ -4595,7 +5891,7 @@ check_blk_carrier(Allctr_t *allctr, Block_t *iblk)
 	cl = &allctr->mbc_list;
     }
 
-#if 0 /* FIXIT sbmbc */
+#ifdef DEBUG
     if (cl->first == crr) {
 	ASSERT(!crr->prev);
     }