Optimize memory allocation

A number of memory allocation optimizations have been implemented. Most
optimizations reduce contention caused by synchronization between
threads during allocation and deallocation of memory. Most notably:
* Synchronization of memory management in scheduler specific allocator
  instances has been rewritten to use lock-free synchronization.
* Synchronization of memory management in scheduler specific
  pre-allocators has been rewritten to use lock-free synchronization.
* The 'mseg_alloc' memory segment allocator now use scheduler specific
  instances instead of one instance. Apart from reducing contention
  this also ensures that memory allocators always create memory
  segments on the local NUMA node on a NUMA system.

1 files changed, 844 insertions, 173 deletions

diff --git a/erts/emulator/beam/erl_alloc_util.c b/erts/emulator/beam/erl_alloc_util.c
index d51ed0c36d..daf8822564 100644
--- a/erts/emulator/beam/erl_alloc_util.c
+++ b/erts/emulator/beam/erl_alloc_util.c
@@ -46,6 +46,7 @@
 #include "erl_alloc_util.h"
 #include "erl_mseg.h"
 #include "erl_threads.h"
+#include "erl_thr_progress.h"
 
 #ifdef ERTS_ENABLE_LOCK_COUNT
 #include "erl_lock_count.h"
@@ -61,6 +62,13 @@
 #warning "* * * * * * * * * *"
 #endif
 
+#define ERTS_ALCU_DD_OPS_LIM_HIGH 20
+#define ERTS_ALCU_DD_OPS_LIM_LOW 2
+
+/* Fix alloc limit */
+#define ERTS_ALCU_FIX_MAX_LIST_SZ 1000
+#define ERTS_ALC_FIX_MAX_SHRINK_OPS 30
+
 #define ALLOC_ZERO_EQ_NULL 0
 
 static int atoms_initialized = 0;
@@ -269,7 +277,6 @@ static void check_blk_carrier(Allctr_t *, Block_t *);
 #define HARD_CHECK_BLK_CARRIER(A, B)
 #endif
 
-
 /* Statistics updating ... */
 
 #ifdef DEBUG
@@ -465,26 +472,36 @@ do {									\
 
 #ifdef DEBUG
 #ifdef USE_THREADS
-#define ERTS_ALCU_DBG_CHK_THR_SPEC(A)					\
+#define ERTS_ALCU_DBG_CHK_THR_ACCESS(A)					\
 do {									\
     if (!(A)->thread_safe) {						\
-	if (!(A)->debug.saved_tid)					\
+	if (!(A)->debug.saved_tid) {					\
 	    (A)->debug.tid = erts_thr_self();				\
+	    (A)->debug.saved_tid = 1;					\
+	}								\
 	else {								\
-	    ASSERT(ethr_equal_tids((A)->debug.tid, erts_thr_self()));	\
+	    ERTS_SMP_LC_ASSERT(						\
+		ethr_equal_tids((A)->debug.tid, erts_thr_self())	\
+		|| erts_is_system_blocked(ERTS_BS_FLG_ALLOW_GC)		\
+		|| (ERTS_IS_CRASH_DUMPING				\
+		    && erts_is_system_blocked(ERTS_BS_FLG_ALLOW_GC)));	\
 	}								\
     }									\
 } while (0)
 #else
-#define ERTS_ALCU_DBG_CHK_THR_SPEC(A)
+#define ERTS_ALCU_DBG_CHK_THR_ACCESS(A)
 #endif
 #else
-#define ERTS_ALCU_DBG_CHK_THR_SPEC(A)
+#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);
+
 
 /* mseg ... */
 
@@ -651,6 +668,446 @@ 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 *);
 
+#if 0
+#define ERTS_DBG_CHK_FIX_LIST(A, FIX, IX, B)			\
+    do { if ((FIX)) chk_fix_list((A), (FIX), (IX), (B)); } while (0)
+static void
+chk_fix_list(Allctr_t *allctr, ErtsAlcFixList_t *fix, int ix, int before)
+{
+    void *p;
+    int n;
+    for (n = 0, p = fix[ix].list; p; p = *((void **) p))
+	n++;
+    if (n != fix[ix].list_size) {
+	erts_fprintf(stderr, "FOUND IT ts=%d, sched=%d, ix=%d, n=%d, ls=%d %s!\n",
+		     allctr->thread_safe, allctr->ix, ix, n, fix[ix].list_size, before ? "before" : "after");
+	abort();
+    }
+}
+#else
+#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)
+{
+    int all_empty = 1;
+    erts_aint32_t res = 0;
+    int ix, o;
+    ErtsAlcFixList_t *fix = allctr->fix;
+    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++) {
+	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);
+	}
+	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)
+		break;
+	    if (fix[ix].list_size == 0)
+		break;
+	    ptr = fix[ix].list;
+	    fix[ix].list = *((void **) ptr);
+	    fix[ix].list_size--;	    
+
+	    blk = UMEM2BLK(ptr);
+
+	    if (IS_SBC_BLK(blk))
+		destroy_carrier(allctr, blk);
+	    else
+		mbc_free(allctr, ptr);
+
+	    fix[ix].allocated--;
+	}
+	if (fix[ix].list_size != 0) {
+	    if (fix[ix].limit < fix[ix].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);
+    }
+
+#ifdef USE_THREADS
+    if (allctr->thread_safe)
+	erts_mtx_unlock(&allctr->mutex);
+#endif
+
+    return res;
+}
+
+#ifdef ERTS_SMP
+
+#define ERTS_ALCU_DD_FIX_TYPE_OFFS \
+  ((sizeof(ErtsAllctrDDBlock_t)-1)/sizeof(UWord) + 1)
+
+#define ERTS_AU_PREF_ALLOC_IX_MASK \
+   ((((UWord) 1) << ERTS_AU_PREF_ALLOC_BITS) - 1)
+#define ERTS_AU_PREF_ALLOC_SIZE_MASK \
+   ((((UWord) 1) << (sizeof(UWord)*8 - ERTS_AU_PREF_ALLOC_BITS)) - 1)
+
+static ERTS_INLINE int
+get_pref_allctr(void *extra, Allctr_t **allctr)
+{
+    ErtsAllocatorThrSpec_t *tspec = (ErtsAllocatorThrSpec_t *) extra;
+    int pref_ix;
+
+    pref_ix = ERTS_ALC_GET_THR_IX();
+
+    ASSERT(sizeof(UWord) == sizeof(Allctr_t *));
+    ASSERT(0 <= pref_ix && pref_ix < tspec->size);
+
+    *allctr = tspec->allctr[pref_ix];
+    return pref_ix;
+}
+
+static ERTS_INLINE void *
+get_used_allctr(void *extra, void *p, Allctr_t **allctr, UWord *sizep)
+{
+    ErtsAllocatorThrSpec_t *tspec = (ErtsAllocatorThrSpec_t *) extra;
+    void *ptr = (void *) (((char *) p) - sizeof(UWord));
+    UWord ainfo = *((UWord *) ptr);
+    int aix = (int) (ainfo & ERTS_AU_PREF_ALLOC_IX_MASK);
+    *allctr = tspec->allctr[aix];
+    if (sizep)
+	*sizep = ((ainfo >> ERTS_AU_PREF_ALLOC_BITS)
+		  & ERTS_AU_PREF_ALLOC_SIZE_MASK);
+    return ptr;
+}
+
+static ERTS_INLINE void *
+put_used_allctr(void *p, int ix, UWord size)
+{
+    UWord ainfo = (size >= ERTS_AU_PREF_ALLOC_SIZE_MASK
+		   ? ERTS_AU_PREF_ALLOC_SIZE_MASK
+		   : size);
+    ainfo <<= ERTS_AU_PREF_ALLOC_BITS;
+    ainfo |= (UWord) ix;
+    *((UWord *) p) = ainfo;
+    return (void *) (((char *) p) + sizeof(UWord));
+}
+
+static void
+init_dd_queue(ErtsAllctrDDQueue_t *ddq)
+{
+    erts_atomic_init_nob(&ddq->tail.data.marker.atmc_next, ERTS_AINT_NULL);
+    erts_atomic_init_nob(&ddq->tail.data.last,
+			 (erts_aint_t) &ddq->tail.data.marker);
+    erts_atomic_init_nob(&ddq->tail.data.um_refc[0], 0);
+    erts_atomic_init_nob(&ddq->tail.data.um_refc[1], 0);
+    erts_atomic32_init_nob(&ddq->tail.data.um_refc_ix, 0);
+    ddq->head.first = &ddq->tail.data.marker;
+    ddq->head.unref_end = &ddq->tail.data.marker;
+    ddq->head.next.thr_progress = erts_thr_progress_current();
+    ddq->head.next.thr_progress_reached = 1;
+    ddq->head.next.um_refc_ix = 1;
+    ddq->head.next.unref_end = &ddq->tail.data.marker;
+    ddq->head.used_marker = 1;
+}
+
+static ERTS_INLINE erts_aint_t
+ddq_managed_thread_enqueue(ErtsAllctrDDQueue_t *ddq, void *ptr)
+{
+    erts_aint_t ilast, itmp;
+    ErtsAllctrDDBlock_t *this = ptr;
+
+    erts_atomic_init_nob(&this->atmc_next, ERTS_AINT_NULL);
+
+    /* Enqueue at end of list... */
+
+    ilast = erts_atomic_read_nob(&ddq->tail.data.last);
+    while (1) {
+	ErtsAllctrDDBlock_t *last = (ErtsAllctrDDBlock_t *) ilast;
+	itmp = erts_atomic_cmpxchg_mb(&last->atmc_next,
+				       (erts_aint_t) this,
+				       ERTS_AINT_NULL);
+	if (itmp == ERTS_AINT_NULL)
+	    break;
+	ilast = itmp;
+    }
+
+    /* Move last pointer forward... */
+    while (1) {
+	if (erts_atomic_read_rb(&this->atmc_next) != ERTS_AINT_NULL) {
+	    /* Someone else will move it forward */
+	    return erts_atomic_read_rb(&ddq->tail.data.last);
+	}
+	itmp = erts_atomic_cmpxchg_mb(&ddq->tail.data.last,
+				      (erts_aint_t) this,
+				      ilast);
+	if (ilast == itmp)
+	    return (erts_aint_t) this;
+	ilast = itmp;
+    }
+}
+
+static ERTS_INLINE int
+ddq_enqueue(ErtsAlcType_t type, ErtsAllctrDDQueue_t *ddq, void *ptr)
+{
+    erts_aint_t ilast;
+    int um_refc_ix = 0;
+    int managed_thread = erts_thr_progress_is_managed_thread();
+    if (!managed_thread) {
+	um_refc_ix = erts_atomic32_read_acqb(&ddq->tail.data.um_refc_ix);
+	while (1) {
+	    int tmp_um_refc_ix;
+	    erts_atomic_inc_acqb(&ddq->tail.data.um_refc[um_refc_ix]);
+	    tmp_um_refc_ix = erts_atomic32_read_acqb(&ddq->tail.data.um_refc_ix);
+	    if (tmp_um_refc_ix == um_refc_ix)
+		break;
+	    erts_atomic_dec_relb(&ddq->tail.data.um_refc[um_refc_ix]);
+	    um_refc_ix = tmp_um_refc_ix;
+	}
+    }
+
+    ilast = ddq_managed_thread_enqueue(ddq, ptr);
+
+    if (!managed_thread)
+	erts_atomic_dec_relb(&ddq->tail.data.um_refc[um_refc_ix]);
+    return ilast == (erts_aint_t) ptr;
+}
+
+static ERTS_INLINE void *
+ddq_dequeue(ErtsAllctrDDQueue_t *ddq)
+{
+    ErtsAllctrDDBlock_t *blk;
+
+    if (ddq->head.first == ddq->head.unref_end)
+	return NULL;
+
+    blk = ddq->head.first;
+    if (blk == &ddq->tail.data.marker) {
+	ASSERT(ddq->head.used_marker);
+	ddq->head.used_marker = 0;
+	blk = ((ErtsAllctrDDBlock_t *)
+	       erts_atomic_read_nob(&blk->atmc_next));
+	if (blk == ddq->head.unref_end) {
+	    ddq->head.first = blk;
+	    return NULL;
+	}
+    }
+
+    ddq->head.first = ((ErtsAllctrDDBlock_t *)
+		       erts_atomic_read_nob(&blk->atmc_next));
+
+    ASSERT(ddq->head.first);
+
+    return (void *) blk;
+}
+
+static int
+ddq_check_incoming(ErtsAllctrDDQueue_t *ddq)
+{
+    erts_aint_t ilast = erts_atomic_read_nob(&ddq->tail.data.last);
+    if (((ErtsAllctrDDBlock_t *) ilast) == &ddq->tail.data.marker
+	&& ddq->head.first == &ddq->tail.data.marker) {
+	/* Nothing more to do... */
+	return 0;
+    }
+
+    if (ddq->head.next.thr_progress_reached
+	|| erts_thr_progress_has_reached(ddq->head.next.thr_progress)) {
+	int um_refc_ix;
+	ddq->head.next.thr_progress_reached = 1;
+	um_refc_ix = ddq->head.next.um_refc_ix;
+	if (erts_atomic_read_acqb(&ddq->tail.data.um_refc[um_refc_ix]) == 0) {
+	    /* Move unreferenced end pointer forward... */
+
+	    ddq->head.unref_end = ddq->head.next.unref_end;
+
+	    if (!ddq->head.used_marker
+		&& ddq->head.unref_end == (ErtsAllctrDDBlock_t *) ilast) {
+		ddq->head.used_marker = 1;
+		ilast = ddq_managed_thread_enqueue(ddq, &ddq->tail.data.marker);
+	    }
+
+	    if (ddq->head.unref_end == (ErtsAllctrDDBlock_t *) ilast)
+		ERTS_THR_MEMORY_BARRIER;
+	    else {
+		ddq->head.next.unref_end = (ErtsAllctrDDBlock_t *) ilast;
+		ERTS_THR_MEMORY_BARRIER;
+		ddq->head.next.thr_progress = erts_thr_progress_later();
+		erts_atomic32_set_relb(&ddq->tail.data.um_refc_ix,
+				       um_refc_ix);
+		ddq->head.next.um_refc_ix = um_refc_ix == 0 ? 1 : 0;
+		ddq->head.next.thr_progress_reached = 0;
+	    }
+	}
+    }
+    return 1;
+}
+
+static ERTS_INLINE int
+handle_delayed_dealloc(Allctr_t *allctr,
+		       int allctr_locked,
+		       int use_limit,
+		       int ops_limit,
+		       int *need_thr_progress,
+		       int *need_more_work)
+{
+    int need_thr_prgr = 0;
+    int need_mr_wrk = 0;
+    int have_checked_incoming = 0;
+    int ops = 0;
+    ErtsAlcFixList_t *fix;
+    int res;
+    ErtsAllctrDDQueue_t *ddq;
+
+    if (allctr->thread_safe && !allctr_locked)
+	erts_mtx_lock(&allctr->mutex);
+
+    ERTS_ALCU_DBG_CHK_THR_ACCESS(allctr);
+
+    fix = allctr->fix;
+
+    ddq = &allctr->dd.q;
+
+    res = 0;
+
+    while (1) {
+	Block_t *blk;
+	void *ptr;
+	int ix;
+
+	if (use_limit && ++ops > ops_limit) {
+	    if (ddq->head.first != ddq->head.unref_end) {
+		need_mr_wrk = 1;
+		if (need_more_work)
+		    *need_more_work |= 1;
+	    }
+	    break;
+	}
+
+    dequeue:
+	ptr = ddq_dequeue(ddq);
+	if (!ptr) {
+	    if (have_checked_incoming)
+		break;
+	    need_thr_prgr = ddq_check_incoming(ddq);
+	    if (need_thr_progress)
+		*need_thr_progress |= need_thr_prgr;
+	    have_checked_incoming = 1;
+	    goto dequeue;
+	}
+
+	res = 1;
+
+	INC_CC(allctr->calls.this_free);
+
+	if (fix) {
+	    ErtsAlcType_t type;
+
+	    type = (ErtsAlcType_t) ((UWord *) ptr)[ERTS_ALCU_DD_FIX_TYPE_OFFS];
+	    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_SBC_BLK(blk))
+	    destroy_carrier(allctr, blk);
+	else
+	    mbc_free(allctr, ptr);
+	ERTS_DBG_CHK_FIX_LIST(allctr, fix, ix, 0);
+    }
+
+    if (need_thr_progress && !(need_thr_prgr | need_mr_wrk)) {
+	need_thr_prgr = ddq_check_incoming(ddq);
+	*need_thr_progress |= need_thr_prgr;
+    }
+
+    if (allctr->thread_safe && !allctr_locked)
+	erts_mtx_unlock(&allctr->mutex);
+   return res;
+}
+
+static ERTS_INLINE void
+enqueue_dealloc_other_instance(ErtsAlcType_t type, Allctr_t *allctr, void *ptr)
+{
+    if (allctr->fix)
+	((UWord *) ptr)[ERTS_ALCU_DD_FIX_TYPE_OFFS] = (UWord) type;
+
+    if (ddq_enqueue(type, &allctr->dd.q, ptr))
+	erts_alloc_notify_delayed_dealloc(allctr->ix);
+}
+
+#endif
+
+void
+erts_alcu_check_delayed_dealloc(Allctr_t *allctr,
+				int limit,
+				int *need_thr_progress,
+				int *more_work)
+{
+#ifdef ERTS_SMP
+    handle_delayed_dealloc(allctr,
+			   0,
+			   limit,
+			   ERTS_ALCU_DD_OPS_LIM_HIGH,
+			   need_thr_progress,
+			   more_work);
+#endif
+}
+
+#define ERTS_ALCU_HANDLE_DD_IN_OP(Allctr, Locked) \
+    handle_delayed_dealloc((Allctr), (Locked), 1, \
+			 ERTS_ALCU_DD_OPS_LIM_LOW, NULL, NULL)
+
 /* Multi block carrier alloc/realloc/free ... */
 
 /* NOTE! mbc_alloc() may in case of memory shortage place the requested
@@ -680,8 +1137,21 @@ mbc_alloc_block(Allctr_t *allctr, Uint size, Uint *blk_szp, Uint32 *alcu_flgsp)
 	}
     }
 
+#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
+
     if (!blk) {
 	if ((*alcu_flgsp) & ERTS_ALCU_FLG_SBMBC) 
 	    blk = create_sbmbc(allctr, get_blk_sz);
@@ -939,6 +1409,11 @@ 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);
@@ -1005,7 +1480,6 @@ mbc_realloc(Allctr_t *allctr, void *p, Uint size, Uint32 alcu_flgs)
 						cand_blk,
 						cand_blk_sz,
 						alcu_flgs);
-
 	    if (new_blk || cand_blk != blk)
 		goto move_into_new_blk;
 	}
@@ -1441,7 +1915,7 @@ create_carrier(Allctr_t *allctr, Uint umem_sz, UWord flags)
 	goto try_sys_alloc;
     if (flags & CFLG_FORCE_MSEG)
 	goto try_mseg;
-    if (erts_mseg_no() >= max_mseg_carriers)
+    if (erts_mseg_no(&allctr->mseg_opt) >= max_mseg_carriers)
 	goto try_sys_alloc;
     if (flags & CFLG_SBC) {
 	if (allctr->sbcs.curr.norm.mseg.no >= allctr->max_mseg_sbcs)
@@ -1840,8 +2314,12 @@ static struct {
     Eterm ycs;
 
     /* Eterm sbmbcs; */
+
+    Eterm fix_types;
+
     Eterm mbcs;
     Eterm sbcs;
+
     Eterm sys_alloc_carriers_size;
 #if HAVE_ERTS_MSEG
     Eterm mseg_alloc_carriers_size;
@@ -1871,6 +2349,8 @@ static struct {
 #endif
 } am;
 
+static Eterm fix_type_atoms[ERTS_ALC_NO_FIXED_SIZES];
+
 static ERTS_INLINE void atom_init(Eterm *atom, char *name)
 {
     *atom = am_atom_put(name, strlen(name));
@@ -1891,6 +2371,7 @@ init_atoms(Allctr_t *allctr)
     erts_mtx_lock(&init_atoms_mtx);
 
     if (!atoms_initialized) {
+	int ix;
 #ifdef DEBUG
 	Eterm *atom;
 
@@ -1933,8 +2414,12 @@ init_atoms(Allctr_t *allctr)
 	AM_INIT(ycs);
 
 	/*AM_INIT(sbmbcs);*/
+
+	AM_INIT(fix_types);
+
 	AM_INIT(mbcs);
 	AM_INIT(sbcs);
+
 	AM_INIT(sys_alloc_carriers_size);
 #if HAVE_ERTS_MSEG
 	AM_INIT(mseg_alloc_carriers_size);
@@ -1965,6 +2450,13 @@ init_atoms(Allctr_t *allctr)
 	    ASSERT(*atom != THE_NON_VALUE);
 	}
 #endif
+
+	for (ix = 0; ix < ERTS_ALC_NO_FIXED_SIZES; ix++) {
+	    ErtsAlcType_t n = ERTS_ALC_N_MIN_A_FIXED_SIZE + ix;
+	    char *name = (char *) ERTS_ALC_N2TD(n);
+	    size_t len = strlen(name);
+	    fix_type_atoms[ix] = am_atom_put(name, len);
+	}
     }
 
     
@@ -2043,6 +2535,48 @@ add_4tup(Uint **hpp, Uint *szp, Eterm *lp,
 }
 
 static Eterm
+sz_info_fix(Allctr_t *allctr,
+	    int *print_to_p,
+	    void *print_to_arg,
+	    Uint **hpp,
+	    Uint *szp)
+{
+    Eterm res;
+    int ix;
+    ErtsAlcFixList_t *fix = allctr->fix;
+
+    ASSERT(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 (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;
+}
+
+static Eterm
 sz_info_carriers(Allctr_t *allctr,
 		 CarriersStats_t *cs,
 		 char *prefix,
@@ -2590,7 +3124,7 @@ erts_alcu_sz_info(Allctr_t *allctr,
 		  Uint **hpp,
 		  Uint *szp)
 {
-    Eterm res, sbmbcs, mbcs, sbcs;
+    Eterm res, sbmbcs, mbcs, sbcs, fix = THE_NON_VALUE;
 
     res  = THE_NON_VALUE;
 
@@ -2607,6 +3141,8 @@ erts_alcu_sz_info(Allctr_t *allctr,
 	erts_mtx_lock(&allctr->mutex);
 #endif
 
+    ERTS_ALCU_DBG_CHK_THR_ACCESS(allctr);
+
     if (hpp || szp)
 	ensure_atoms_initialized(allctr);
 
@@ -2619,6 +3155,8 @@ erts_alcu_sz_info(Allctr_t *allctr,
     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);
     mbcs = sz_info_carriers(allctr, &allctr->mbcs, "mbcs ", print_to_p,
@@ -2631,6 +3169,8 @@ erts_alcu_sz_info(Allctr_t *allctr,
 	add_2tup(hpp, szp, &res, am.sbcs, sbcs);
 	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);
     }
 
     if (begin_max_period) {
@@ -2656,7 +3196,7 @@ erts_alcu_info(Allctr_t *allctr,
 	       Uint **hpp,
 	       Uint *szp)
 {
-    Eterm res, sett, sbmbcs, mbcs, sbcs, calls;
+    Eterm res, sett, sbmbcs, mbcs, sbcs, calls, fix = THE_NON_VALUE;
 
     res  = THE_NON_VALUE;
 
@@ -2673,6 +3213,8 @@ erts_alcu_info(Allctr_t *allctr,
 	erts_mtx_lock(&allctr->mutex);
 #endif
 
+    ERTS_ALCU_DBG_CHK_THR_ACCESS(allctr);
+
     if (hpp || szp)
 	ensure_atoms_initialized(allctr);
 
@@ -2694,6 +3236,8 @@ 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);
     mbcs = info_carriers(allctr, &allctr->mbcs, "mbcs ", print_to_p,
@@ -2709,6 +3253,8 @@ erts_alcu_info(Allctr_t *allctr,
 	add_2tup(hpp, szp, &res, am.sbcs, sbcs);
 	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_2tup(hpp, szp, &res, am.options, sett);
 	add_3tup(hpp, szp, &res,
 		 am.versions,
@@ -2733,7 +3279,7 @@ erts_alcu_info(Allctr_t *allctr,
 
 
 void
-erts_alcu_current_size(Allctr_t *allctr, AllctrSize_t *size)
+erts_alcu_current_size(Allctr_t *allctr, AllctrSize_t *size, ErtsAlcUFixInfo_t *fi, int fisz)
 {
 
 #ifdef USE_THREADS
@@ -2751,6 +3297,18 @@ erts_alcu_current_size(Allctr_t *allctr, AllctrSize_t *size)
     size->blocks += allctr->sbmbcs.blocks.curr.size;
     size->blocks += allctr->sbcs.blocks.curr.size;
 
+    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);
+	    }
+	}
+    }
+
 #ifdef USE_THREADS
     if (allctr->thread_safe)
 	erts_mtx_unlock(&allctr->mutex);
@@ -2764,12 +3322,16 @@ do_erts_alcu_alloc(ErtsAlcType_t type, void *extra, Uint size)
 {
     Allctr_t *allctr = (Allctr_t *) extra; 
     void *res;
+    ErtsAlcFixList_t *fix;
 
     ASSERT(initialized);
 
     ASSERT(allctr);
 
-    ERTS_ALCU_DBG_CHK_THR_SPEC(allctr);
+    ERTS_SMP_LC_ASSERT(!allctr->thread_safe
+		       || erts_lc_mtx_is_locked(&allctr->mutex));
+
+    ERTS_ALCU_DBG_CHK_THR_ACCESS(allctr);
 
 #if ALLOC_ZERO_EQ_NULL
     if (!size)
@@ -2778,18 +3340,61 @@ 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;
+	ERTS_DBG_CHK_FIX_LIST(allctr, fix, ix, 1);
+	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;
+	}
+	if (size < 2*sizeof(UWord))
+	    size += sizeof(UWord);
+	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 (size >= allctr->sbc_threshold) {
+	Block_t *blk;
+#ifdef ERTS_SMP
+	if (allctr->dd.use)
+	    ERTS_ALCU_HANDLE_DD_IN_OP(allctr, 1);
+#endif
 #if HALFWORD_HEAP
-	Block_t *blk = create_carrier(allctr, size,
-				      CFLG_SBC | CFLG_FORCE_MSEG);
+	blk = create_carrier(allctr, size,
+			     CFLG_SBC | CFLG_FORCE_MSEG);
 #else
-	Block_t *blk = create_carrier(allctr, size, CFLG_SBC);
+	blk = create_carrier(allctr, size, CFLG_SBC);
 #endif
 	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;
 }
 
@@ -2818,29 +3423,28 @@ erts_alcu_alloc_ts(ErtsAlcType_t type, void *extra, Uint size)
     return res;
 }
 
+#ifdef ERTS_SMP
+
 void *
 erts_alcu_alloc_thr_spec(ErtsAlcType_t type, void *extra, Uint size)
 {
     ErtsAllocatorThrSpec_t *tspec = (ErtsAllocatorThrSpec_t *) extra;
-    int ix = erts_alc_get_thr_ix();
+    int ix;
     Allctr_t *allctr;
-    int unlock;
     void *res;
 
-    ASSERT(ix > 0);
-    if (ix < tspec->size) {
-	allctr = tspec->allctr[ix];
-	unlock = 0;
-    }
-    else {
-	allctr = tspec->allctr[0];
-	unlock = 1;
+    ix = ERTS_ALC_GET_THR_IX();
+
+    ASSERT(0 <= ix && ix < tspec->size);
+
+    allctr = tspec->allctr[ix];
+
+    if (allctr->thread_safe)
 	erts_mtx_lock(&allctr->mutex);
-    }
 
     res = do_erts_alcu_alloc(type, allctr, size);
 
-    if (unlock)
+    if (allctr->thread_safe)
 	erts_mtx_unlock(&allctr->mutex);
 
     DEBUG_CHECK_ALIGNMENT(res);
@@ -2851,51 +3455,96 @@ erts_alcu_alloc_thr_spec(ErtsAlcType_t type, void *extra, Uint size)
 void *
 erts_alcu_alloc_thr_pref(ErtsAlcType_t type, void *extra, Uint size)
 {
-    ErtsAllocatorThrSpec_t *tspec = (ErtsAllocatorThrSpec_t *) extra;
-    int ix = erts_alc_get_thr_ix();
-    Allctr_t *allctr;
+    int pref_ix;
+    Allctr_t *pref_allctr;
     void *res;
 
-    ASSERT(sizeof(UWord) == sizeof(Allctr_t *));
-    ASSERT(ix > 0);
-    if (ix >= tspec->size)
-	ix = (ix % (tspec->size - 1)) + 1;
-    allctr = tspec->allctr[ix];
-    erts_mtx_lock(&allctr->mutex);
-    res = do_erts_alcu_alloc(type, allctr, size + sizeof(UWord));
-    if (res) {
-	*((Allctr_t **) res) = allctr;
-	res = (void *) (((char *) res) + sizeof(UWord));
-    }
-    erts_mtx_unlock(&allctr->mutex);
+    pref_ix = get_pref_allctr(extra, &pref_allctr);
+
+    if (pref_allctr->thread_safe)
+	erts_mtx_lock(&pref_allctr->mutex);
+
+    ERTS_ALCU_DBG_CHK_THR_ACCESS(pref_allctr);
+
+    res = do_erts_alcu_alloc(type, pref_allctr, size + sizeof(UWord));
+    if (pref_allctr->thread_safe)
+	erts_mtx_unlock(&pref_allctr->mutex);
+
+    if (res)
+	res = put_used_allctr(res, pref_ix, size);
+
     DEBUG_CHECK_ALIGNMENT(res);
+
+
     return res;
 }
 
 #endif
 
+#endif
+
 /* ------------------------------------------------------------------------- */
 
 static ERTS_INLINE void
 do_erts_alcu_free(ErtsAlcType_t type, void *extra, void *p)
 {
+    int ix;
     Allctr_t *allctr = (Allctr_t *) extra; 
     ASSERT(initialized);
 
     ASSERT(allctr);
 
-    ERTS_ALCU_DBG_CHK_THR_SPEC(allctr);
+    ERTS_SMP_LC_ASSERT(!allctr->thread_safe
+		       || erts_lc_mtx_is_locked(&allctr->mutex));
+
+    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--;
+	    }
+	}
+
 	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);
     }
 }
 
@@ -2915,44 +3564,56 @@ erts_alcu_free_ts(ErtsAlcType_t type, void *extra, void *p)
     erts_mtx_unlock(&allctr->mutex);
 }
 
+#ifdef ERTS_SMP
+
 void
 erts_alcu_free_thr_spec(ErtsAlcType_t type, void *extra, void *p)
 {
     ErtsAllocatorThrSpec_t *tspec = (ErtsAllocatorThrSpec_t *) extra;
-    int ix = erts_alc_get_thr_ix();
-    int unlock;
+    int ix;
     Allctr_t *allctr;
 
-    ASSERT(ix > 0);
-    if (ix < tspec->size) {
-	allctr = tspec->allctr[ix];
-	unlock = 0;
-    }
-    else {
-	allctr = tspec->allctr[0];
-	unlock = 1;
+    ix = ERTS_ALC_GET_THR_IX();
+
+    ASSERT(0 <= ix && ix < tspec->size);
+
+    allctr = tspec->allctr[ix];
+
+    if (allctr->thread_safe)
 	erts_mtx_lock(&allctr->mutex);
-    }
 
     do_erts_alcu_free(type, allctr, p);
-    if (unlock)
+
+    if (allctr->thread_safe)
 	erts_mtx_unlock(&allctr->mutex);
 }
 
 void
-erts_alcu_free_thr_pref(ErtsAlcType_t type, void *unused, void *p)
+erts_alcu_free_thr_pref(ErtsAlcType_t type, void *extra, void *p)
 {
     if (p) {
-	void *ptr = (void *) (((char *) p) - sizeof(UWord));
-	Allctr_t *allctr = *((Allctr_t **) ptr);
-	erts_mtx_lock(&allctr->mutex);
-	do_erts_alcu_free(type, allctr, ptr);
-	erts_mtx_unlock(&allctr->mutex);
+	Allctr_t *pref_allctr, *used_allctr;
+	void *ptr;
+
+	get_pref_allctr(extra, &pref_allctr);
+	ptr = get_used_allctr(extra, p, &used_allctr, NULL);
+	if (pref_allctr != used_allctr)
+	    enqueue_dealloc_other_instance(type, used_allctr, ptr);
+	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, ptr);
+	    if (used_allctr->thread_safe)
+		erts_mtx_unlock(&used_allctr->mutex);
+	}
     }
 }
 
 #endif
 
+#endif
+
 /* ------------------------------------------------------------------------- */
 
 static ERTS_INLINE void *
@@ -2970,7 +3631,10 @@ do_erts_alcu_realloc(ErtsAlcType_t type,
 
     ASSERT(allctr);
 
-    ERTS_ALCU_DBG_CHK_THR_SPEC(allctr);
+    ERTS_SMP_LC_ASSERT(!allctr->thread_safe
+		       || erts_lc_mtx_is_locked(&allctr->mutex));
+
+    ERTS_ALCU_DBG_CHK_THR_ACCESS(allctr);
 
     if (!p) {
 	res = do_erts_alcu_alloc(type, extra, size);
@@ -3063,6 +3727,10 @@ do_erts_alcu_realloc(ErtsAlcType_t type,
     }
     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
@@ -3166,30 +3834,29 @@ erts_alcu_realloc_mv_ts(ErtsAlcType_t type, void *extra, void *p, Uint size)
     return res;
 }
 
+#ifdef ERTS_SMP
+
 void *
 erts_alcu_realloc_thr_spec(ErtsAlcType_t type, void *extra,
 			   void *ptr, Uint size)
 {
     ErtsAllocatorThrSpec_t *tspec = (ErtsAllocatorThrSpec_t *) extra;
-    int ix = erts_alc_get_thr_ix();
+    int ix;
     Allctr_t *allctr;
-    int unlock;
     void *res;
 
-    ASSERT(ix > 0);
-    if (ix < tspec->size) {
-	allctr = tspec->allctr[ix];
-	unlock = 0;
-    }
-    else {
-	allctr = tspec->allctr[0];
-	unlock = 1;
+    ix = ERTS_ALC_GET_THR_IX();
+
+    ASSERT(0 <= ix && ix < tspec->size);
+
+    allctr = tspec->allctr[ix];
+
+    if (allctr->thread_safe)
 	erts_mtx_lock(&allctr->mutex);
-    }
 
     res = do_erts_alcu_realloc(type, allctr, ptr, size, 0);
 
-    if (unlock)
+    if (allctr->thread_safe)
 	erts_mtx_unlock(&allctr->mutex);
 
     DEBUG_CHECK_ALIGNMENT(res);
@@ -3202,26 +3869,22 @@ erts_alcu_realloc_mv_thr_spec(ErtsAlcType_t type, void *extra,
 			      void *ptr, Uint size)
 {
     ErtsAllocatorThrSpec_t *tspec = (ErtsAllocatorThrSpec_t *) extra;
-    int ix = erts_alc_get_thr_ix();
+    int ix;
     Allctr_t *allctr;
-    int unlock;
     void *res;
 
-    ASSERT(ix > 0);
-    if (ix < tspec->size) {
-	allctr = tspec->allctr[ix];
-	unlock = 0;
-    }
-    else {
-	allctr = tspec->allctr[0];
-	unlock = 1;
-	erts_mtx_lock(&allctr->mutex);
-    }
+    ix = ERTS_ALC_GET_THR_IX();
 
+    ASSERT(0 <= ix && ix < tspec->size);
+
+    allctr = tspec->allctr[ix];
+
+    if (allctr->thread_safe)
+	erts_mtx_lock(&allctr->mutex);
 
     res = do_erts_alcu_alloc(type, allctr, size);
     if (!res) {
-	if (unlock)
+	if (allctr->thread_safe)
 	    erts_mtx_unlock(&allctr->mutex);
 	res = erts_alcu_realloc_thr_spec(type, allctr, ptr, size);
     }
@@ -3235,7 +3898,7 @@ erts_alcu_realloc_mv_thr_spec(ErtsAlcType_t type, void *extra,
 	    cpy_size = size;
 	sys_memcpy(res, ptr, cpy_size);
 	do_erts_alcu_free(type, allctr, ptr);
-	if (unlock)
+	if (allctr->thread_safe)
 	    erts_mtx_unlock(&allctr->mutex);
     }
 
@@ -3244,129 +3907,101 @@ erts_alcu_realloc_mv_thr_spec(ErtsAlcType_t type, void *extra,
     return res;
 }
 
-void *
-erts_alcu_realloc_thr_pref(ErtsAlcType_t type, void *extra, void *p, Uint size)
+static ERTS_INLINE void *
+realloc_thr_pref(ErtsAlcType_t type, void *extra, void *p, Uint size,
+		 int force_move)
 {
-    ErtsAllocatorThrSpec_t *tspec = (ErtsAllocatorThrSpec_t *) extra;
-    int ix;
+    int pref_ix;
     void *ptr, *res;
     Allctr_t *pref_allctr, *used_allctr;
+    UWord old_user_size;
 
     if (!p)
 	return erts_alcu_alloc_thr_pref(type, extra, size);
 
-    ptr = (void *) (((char *) p) - sizeof(UWord));
-    used_allctr = *((Allctr_t **) ptr);
+    pref_ix = get_pref_allctr(extra, &pref_allctr);
+    ptr = get_used_allctr(extra, p, &used_allctr, &old_user_size);
 
-    ix = erts_alc_get_thr_ix();
-    ASSERT(ix > 0);
-    if (ix >= tspec->size)
-	ix = (ix % (tspec->size - 1)) + 1;
-    pref_allctr = tspec->allctr[ix];
     ASSERT(used_allctr && pref_allctr);
 
-    erts_mtx_lock(&used_allctr->mutex);
-    res = do_erts_alcu_realloc(type,
-			       used_allctr,
-			       ptr,
-			       size + sizeof(UWord),
-			       (pref_allctr != used_allctr
-				? ERTS_ALCU_FLG_FAIL_REALLOC_MOVE
-				: 0));
-    erts_mtx_unlock(&used_allctr->mutex);
-    if (res) {
-	ASSERT(used_allctr == *((Allctr_t **) res));
-	res = (void *) (((char *) res) + sizeof(UWord));
-	DEBUG_CHECK_ALIGNMENT(res);
+    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,
+				   ptr,
+				   size + sizeof(UWord),
+				   0);
+	if (used_allctr->thread_safe)
+	    erts_mtx_unlock(&used_allctr->mutex);
+	if (res)
+	    res = put_used_allctr(res, pref_ix, size);
     }
     else {
-	erts_mtx_lock(&pref_allctr->mutex);
+	if (pref_allctr->thread_safe)
+	    erts_mtx_lock(&pref_allctr->mutex);
 	res = do_erts_alcu_alloc(type, pref_allctr, size + sizeof(UWord));
-	erts_mtx_unlock(&pref_allctr->mutex);
+	if (pref_allctr->thread_safe && (!force_move
+					 || used_allctr != pref_allctr))
+	    erts_mtx_unlock(&pref_allctr->mutex);
 	if (res) {
 	    Block_t *blk;
 	    size_t cpy_size;
 
-	    *((Allctr_t **) res) = pref_allctr;
-	    res = (void *) (((char *) res) + sizeof(UWord));
+	    res = put_used_allctr(res, pref_ix, size);
 
 	    DEBUG_CHECK_ALIGNMENT(res);
 
-	    erts_mtx_lock(&used_allctr->mutex);
 	    blk = UMEM2BLK(ptr);
-	    cpy_size = BLK_SZ(blk) - ABLK_HDR_SZ - sizeof(UWord);
+	    if (old_user_size != ERTS_AU_PREF_ALLOC_SIZE_MASK)
+		cpy_size = old_user_size;
+	    else {
+		if (used_allctr->thread_safe && (!force_move
+						 || used_allctr != pref_allctr))
+		    erts_mtx_lock(&used_allctr->mutex);
+		ERTS_SMP_LC_ASSERT(erts_lc_mtx_is_locked(&used_allctr->mutex));
+		cpy_size = BLK_SZ(blk);
+		if (used_allctr->thread_safe && (!force_move
+						 || used_allctr != pref_allctr))
+		    erts_mtx_unlock(&used_allctr->mutex);
+		cpy_size -= ABLK_HDR_SZ + sizeof(UWord);
+	    }
 	    if (cpy_size > size)
 		cpy_size = size;
 	    sys_memcpy(res, p, cpy_size);
-	    do_erts_alcu_free(type, used_allctr, ptr);
-	    erts_mtx_unlock(&used_allctr->mutex);
+
+	    if (!force_move || used_allctr != pref_allctr)
+		enqueue_dealloc_other_instance(type, used_allctr, ptr);
+	    else {
+		do_erts_alcu_free(type, used_allctr, ptr);
+		ASSERT(pref_allctr == used_allctr);
+		if (pref_allctr->thread_safe)
+		    erts_mtx_unlock(&pref_allctr->mutex);
+	    }
 	}
     }
 
     return res;
 }
 
+void *
+erts_alcu_realloc_thr_pref(ErtsAlcType_t type, void *extra, void *p, Uint size)
+{
+    return realloc_thr_pref(type, extra, p, size, 0);
+}
 
 void *
 erts_alcu_realloc_mv_thr_pref(ErtsAlcType_t type, void *extra,
 			      void *p, Uint size)
 {
-    ErtsAllocatorThrSpec_t *tspec = (ErtsAllocatorThrSpec_t *) extra;
-    int ix;
-    void *ptr, *res;
-    Allctr_t *pref_allctr, *used_allctr;
-
-    if (!p)
-	return erts_alcu_alloc_thr_pref(type, extra, size);
-
-    ptr = (void *) (((char *) p) - sizeof(UWord));
-    used_allctr = *((Allctr_t **) ptr);
-
-    ix = erts_alc_get_thr_ix();
-    ASSERT(ix > 0);
-    if (ix >= tspec->size)
-	ix = (ix % (tspec->size - 1)) + 1;
-    pref_allctr = tspec->allctr[ix];
-    ASSERT(used_allctr && pref_allctr);
-
-    erts_mtx_lock(&pref_allctr->mutex);
-    res = do_erts_alcu_alloc(type, pref_allctr, size + sizeof(UWord));
-    if (!res) {
-	erts_mtx_unlock(&pref_allctr->mutex);
-	res = erts_alcu_realloc_thr_pref(type, extra, p, size);
-    }
-    else {
-	Block_t *blk;
-	size_t cpy_size;
-	Allctr_t *allctr;
-
-	*((Allctr_t **) res) = pref_allctr;
-	res = (void *) (((char *) res) + sizeof(UWord));
-
-	DEBUG_CHECK_ALIGNMENT(res);
-
-	if (used_allctr == pref_allctr)
-	    allctr = pref_allctr;
-	else {
-	    erts_mtx_unlock(&pref_allctr->mutex);
-	    allctr = used_allctr;
-	    erts_mtx_lock(&allctr->mutex);
-	}
-
-	blk = UMEM2BLK(ptr);
-	cpy_size = BLK_SZ(blk) - ABLK_HDR_SZ - sizeof(UWord);
-	if (cpy_size > size)
-	    cpy_size = size;
-	sys_memcpy(res, p, cpy_size);
-	do_erts_alcu_free(type, allctr, ptr);
-	erts_mtx_unlock(&allctr->mutex);
-    }
-
-    return res;
+    return realloc_thr_pref(type, extra, p, size, 1);
 }
 
 #endif
 
+#endif
+
 /* ------------------------------------------------------------------------- */
 
 int
@@ -3381,6 +4016,10 @@ erts_alcu_start(Allctr_t *allctr, AllctrInit_t *init)
     sys_memcpy((void *) &allctr->mseg_opt,
 	       (void *) &erts_mseg_default_opt,
 	       sizeof(ErtsMsegOpt_t));
+#ifdef ERTS_SMP
+    if (init->tspec || init->tpref)
+	allctr->mseg_opt.sched_spec = 1;
+#endif
 # if HALFWORD_HEAP
     allctr->mseg_opt.low_mem = init->low_mem;
 # endif
@@ -3390,6 +4029,7 @@ erts_alcu_start(Allctr_t *allctr, AllctrInit_t *init)
     if (!allctr->name_prefix)
 	goto error;
 
+    allctr->ix				= init->ix;
     allctr->alloc_no			= init->alloc_no;
     if (allctr->alloc_no < ERTS_ALC_A_MIN
 	|| ERTS_ALC_A_MAX < allctr->alloc_no)
@@ -3431,6 +4071,18 @@ erts_alcu_start(Allctr_t *allctr, AllctrInit_t *init)
 	goto error;
     allctr->min_block_size		= UNIT_CEILING(allctr->min_block_size
 						       + sizeof(UWord));
+#if ERTS_SMP
+    if (init->tpref) {
+	Uint sz = sizeof(Block_t);
+	sz += ERTS_ALCU_DD_FIX_TYPE_OFFS*sizeof(UWord);
+	if (init->fix)
+	    sz += sizeof(UWord);
+	sz = UNIT_CEILING(sz);
+	if (sz > allctr->min_block_size)
+	    allctr->min_block_size = sz;
+    }
+#endif
+
 
 
     allctr->sbmbc_threshold		= init->sbmbct;
@@ -3493,7 +4145,8 @@ erts_alcu_start(Allctr_t *allctr, AllctrInit_t *init)
 
     if (allctr->mbc_header_size < sizeof(Carrier_t))
 	goto error;
-#ifdef USE_THREADS
+#ifdef ERTS_SMP
+    allctr->dd.use = 0;
     if (init->tpref) {
 	allctr->mbc_header_size = (UNIT_CEILING(allctr->mbc_header_size
 						+ FBLK_FTR_SZ
@@ -3507,6 +4160,9 @@ erts_alcu_start(Allctr_t *allctr, AllctrInit_t *init)
 						+ sizeof(UWord))
 				   - ABLK_HDR_SZ
 				   - sizeof(UWord));
+
+	allctr->dd.use = 1;
+	init_dd_queue(&allctr->dd.q);
     }
     else
 #endif
@@ -3548,6 +4204,21 @@ erts_alcu_start(Allctr_t *allctr, AllctrInit_t *init)
 
     }
 
+    if (init->fix) {
+	int i;
+	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;
+	}
+    }
+
     return 1;
 
  error: