Changeset c2b3243 for libcfa/src/heap.cfa

Timestamp:

Oct 18, 2022, 9:13:33 PM (3 years ago)

Author:

JiadaL <j82liang@…>

Branches:

ADT, ast-experimental, master

Children:

9511841

Parents:

5408b59 (diff), ce7d197 (diff)
Note: this is a merge changeset, the changes displayed below correspond to the merge itself.
Use the (diff) links above to see all the changes relative to each parent.

Message:

Merge branch 'master' of plg.uwaterloo.ca:software/cfa/cfa-cc

File:

• libcfa/src/heap.cfa (modified) (55 diffs)

libcfa/src/heap.cfa

@@ -10 +10 @@
 // Created On       : Tue Dec 19 21:58:35 2017
 // Last Modified By : Peter A. Buhr
-// Last Modified On : Fri Apr 29 19:05:03 2022
-// Update Count     : 1167
+// Last Modified On : Thu Oct 13 22:21:52 2022
+// Update Count     : 1557
 //
 
+#include <stdio.h>
 #include <string.h>                                                                             // memset, memcpy
 #include <limits.h>                                                                             // ULONG_MAX
@@ -21 +22 @@
 #include <malloc.h>                                                                             // memalign, malloc_usable_size
 #include <sys/mman.h>                                                                   // mmap, munmap
+extern "C" {
 #include <sys/sysinfo.h>                                                                // get_nprocs
+} // extern "C"
 
 #include "bits/align.hfa"                                                               // libAlign
 #include "bits/defs.hfa"                                                                // likely, unlikely
-#include "bits/locks.hfa"                                                               // __spinlock_t
+#include "concurrency/kernel/fwd.hfa"                                   // __POLL_PREEMPTION
 #include "startup.hfa"                                                                  // STARTUP_PRIORITY_MEMORY
-#include "math.hfa"                                                                             // min
+#include "math.hfa"                                                                             // ceiling, min
 #include "bitmanip.hfa"                                                                 // is_pow2, ceiling2
 
-#define FASTLOOKUP
-#define __STATISTICS__
+// supported mallopt options
+#ifndef M_MMAP_THRESHOLD
+#define M_MMAP_THRESHOLD (-1)
+#endif // M_MMAP_THRESHOLD
+
+#ifndef M_TOP_PAD
+#define M_TOP_PAD (-2)
+#endif // M_TOP_PAD
+
+#define FASTLOOKUP                                                                              // use O(1) table lookup from allocation size to bucket size
+#define RETURNSPIN                                                                              // toggle spinlock / lockfree stack
+#define OWNERSHIP                                                                               // return freed memory to owner thread
+
+#define CACHE_ALIGN 64
+#define CALIGN __attribute__(( aligned(CACHE_ALIGN) ))
+
+#define TLSMODEL __attribute__(( tls_model("initial-exec") ))
+
+//#define __STATISTICS__
+
+enum {
+        // The default extension heap amount in units of bytes. When the current heap reaches the brk address, the brk
+        // address is extended by the extension amount.
+        __CFA_DEFAULT_HEAP_EXPANSION__ = 10 * 1024 * 1024,
+
+        // The mmap crossover point during allocation. Allocations less than this amount are allocated from buckets; values
+        // greater than or equal to this value are mmap from the operating system.
+        __CFA_DEFAULT_MMAP_START__ = 512 * 1024 + 1,
+
+        // The default unfreed storage amount in units of bytes. When the uC++ program ends it subtracts this amount from
+        // the malloc/free counter to adjust for storage the program does not free.
+        __CFA_DEFAULT_HEAP_UNFREED__ = 0
+}; // enum
+
+
+//####################### Heap Trace/Print ####################
 
 
@@ -55 +92 @@
 static bool prtFree = false;
 
-static bool prtFree() {
+bool prtFree() {
         return prtFree;
 } // prtFree
 
-static bool prtFreeOn() {
+bool prtFreeOn() {
         bool temp = prtFree;
         prtFree = true;
@@ -65 +102 @@
 } // prtFreeOn
 
-static bool prtFreeOff() {
+bool prtFreeOff() {
         bool temp = prtFree;
         prtFree = false;
@@ -72 +109 @@
 
 
-enum {
-        // The default extension heap amount in units of bytes. When the current heap reaches the brk address, the brk
-        // address is extended by the extension amount.
-        __CFA_DEFAULT_HEAP_EXPANSION__ = 10 * 1024 * 1024,
-
-        // The mmap crossover point during allocation. Allocations less than this amount are allocated from buckets; values
-        // greater than or equal to this value are mmap from the operating system.
-        __CFA_DEFAULT_MMAP_START__ = 512 * 1024 + 1,
-
-        // The default unfreed storage amount in units of bytes. When the uC++ program ends it subtracts this amount from
-        // the malloc/free counter to adjust for storage the program does not free.
-        __CFA_DEFAULT_HEAP_UNFREED__ = 0
-}; // enum
+//######################### Spin Lock #########################
+
+
+// pause to prevent excess processor bus usage
+#if defined( __i386 ) || defined( __x86_64 )
+        #define Pause() __asm__ __volatile__ ( "pause" : : : )
+#elif defined(__ARM_ARCH)
+        #define Pause() __asm__ __volatile__ ( "YIELD" : : : )
+#else
+        #error unsupported architecture
+#endif
+
+typedef volatile uintptr_t SpinLock_t CALIGN;                   // aligned addressable word-size
+
+static inline __attribute__((always_inline)) void lock( volatile SpinLock_t & slock ) {
+        enum { SPIN_START = 4, SPIN_END = 64 * 1024, };
+        unsigned int spin = SPIN_START;
+
+        for ( unsigned int i = 1;; i += 1 ) {
+          if ( slock == 0 && __atomic_test_and_set( &slock, __ATOMIC_SEQ_CST ) == 0 ) break; // Fence
+                for ( volatile unsigned int s = 0; s < spin; s += 1 ) Pause(); // exponential spin
+                spin += spin;                                                                   // powers of 2
+                //if ( i % 64 == 0 ) spin += spin;                              // slowly increase by powers of 2
+                if ( spin > SPIN_END ) spin = SPIN_END;                 // cap spinning
+        } // for
+} // spin_lock
+
+static inline __attribute__((always_inline)) void unlock( volatile SpinLock_t & slock ) {
+        __atomic_clear( &slock, __ATOMIC_SEQ_CST );                     // Fence
+} // spin_unlock
 
 
@@ -120 +174 @@
                 unsigned int free_calls, free_null_calls;
                 unsigned long long int free_storage_request, free_storage_alloc;
-                unsigned int away_pulls, away_pushes;
-                unsigned long long int away_storage_request, away_storage_alloc;
+                unsigned int return_pulls, return_pushes;
+                unsigned long long int return_storage_request, return_storage_alloc;
                 unsigned int mmap_calls, mmap_0_calls;                  // no zero calls
                 unsigned long long int mmap_storage_request, mmap_storage_alloc;
@@ -131 +185 @@
 
 static_assert( sizeof(HeapStatistics) == CntTriples * sizeof(StatsOverlay),
-                           "Heap statistics counter-triplets does not match with array size" );
+                           "Heap statistics counter-triplets does not match with array size" );
 
 static void HeapStatisticsCtor( HeapStatistics & stats ) {
@@ -203 +257 @@
         static_assert( libAlign() >= sizeof( Storage ), "minimum alignment < sizeof( Storage )" );
 
-        struct FreeHeader {
-                size_t blockSize __attribute__(( aligned (8) )); // size of allocations on this list
+        struct __attribute__(( aligned (8) )) FreeHeader {
+                size_t blockSize __attribute__(( aligned(8) )); // size of allocations on this list
                 #if BUCKETLOCK == SPINLOCK
-                __spinlock_t lock;
-                Storage * freeList;
+                #ifdef OWNERSHIP
+                #ifdef RETURNSPIN
+                SpinLock_t returnLock;
+                #endif // RETURNSPIN
+                Storage * returnList;                                                   // other thread return list
+                #endif // OWNERSHIP
+                Storage * freeList;                                                             // thread free list
                 #else
                 StackLF(Storage) freeList;
                 #endif // BUCKETLOCK
-        } __attribute__(( aligned (8) )); // FreeHeader
+                Heap * homeManager;                                                             // heap owner (free storage to bucket, from bucket to heap)
+        }; // FreeHeader
 
         FreeHeader freeLists[NoBucketSizes];                            // buckets for different allocation sizes
-
-        __spinlock_t extlock;                                                           // protects allocation-buffer extension
-        void * heapBegin;                                                                       // start of heap
-        void * heapEnd;                                                                         // logical end of heap
-        size_t heapRemaining;                                                           // amount of storage not allocated in the current chunk
+        void * heapBuffer;                                                                      // start of free storage in buffer
+        size_t heapReserve;                                                                     // amount of remaining free storage in buffer
+
+        #if defined( __STATISTICS__ ) || defined( __CFA_DEBUG__ )
+        Heap * nextHeapManager;                                                         // intrusive link of existing heaps; traversed to collect statistics or check unfreed storage
+        #endif // __STATISTICS__ || __CFA_DEBUG__
+        Heap * nextFreeHeapManager;                                                     // intrusive link of free heaps from terminated threads; reused by new threads
+
+        #ifdef __CFA_DEBUG__
+        int64_t allocUnfreed;                                                           // running total of allocations minus frees; can be negative
+        #endif // __CFA_DEBUG__
+
+        #ifdef __STATISTICS__
+        HeapStatistics stats;                                                           // local statistic table for this heap
+        #endif // __STATISTICS__
 }; // Heap
 
 #if BUCKETLOCK == LOCKFREE
-static inline {
+inline __attribute__((always_inline))
+static {
         Link(Heap.Storage) * ?`next( Heap.Storage * this ) { return &this->header.kind.real.next; }
         void ?{}( Heap.FreeHeader & ) {}
@@ -229 +300 @@
 #endif // LOCKFREE
 
-static inline size_t getKey( const Heap.FreeHeader & freeheader ) { return freeheader.blockSize; }
+
+struct HeapMaster {
+        SpinLock_t extLock;                                                                     // protects allocation-buffer extension
+        SpinLock_t mgrLock;                                                                     // protects freeHeapManagersList, heapManagersList, heapManagersStorage, heapManagersStorageEnd
+
+        void * heapBegin;                                                                       // start of heap
+        void * heapEnd;                                                                         // logical end of heap
+        size_t heapRemaining;                                                           // amount of storage not allocated in the current chunk
+        size_t pageSize;                                                                        // architecture pagesize
+        size_t heapExpand;                                                                      // sbrk advance
+        size_t mmapStart;                                                                       // cross over point for mmap
+        unsigned int maxBucketsUsed;                                            // maximum number of buckets in use
+
+        Heap * heapManagersList;                                                        // heap-list head
+        Heap * freeHeapManagersList;                                            // free-list head
+
+        // Heap superblocks are not linked; heaps in superblocks are linked via intrusive links.
+        Heap * heapManagersStorage;                                                     // next heap to use in heap superblock
+        Heap * heapManagersStorageEnd;                                          // logical heap outside of superblock's end
+
+        #ifdef __STATISTICS__
+        HeapStatistics stats;                                                           // global stats for thread-local heaps to add there counters when exiting
+        unsigned long int threads_started, threads_exited;      // counts threads that have started and exited
+        unsigned long int reused_heap, new_heap;                        // counts reusability of heaps
+        unsigned int sbrk_calls;
+        unsigned long long int sbrk_storage;
+        int stats_fd;
+        #endif // __STATISTICS__
+}; // HeapMaster
 
 
 #ifdef FASTLOOKUP
-enum { LookupSizes = 65_536 + sizeof(Heap.Storage) }; // number of fast lookup sizes
+enum { LookupSizes = 65_536 + sizeof(Heap.Storage) };   // number of fast lookup sizes
 static unsigned char lookup[LookupSizes];                               // O(1) lookup for small sizes
 #endif // FASTLOOKUP
 
-static const off_t mmapFd = -1;                                                 // fake or actual fd for anonymous file
-#ifdef __CFA_DEBUG__
-static bool heapBoot = 0;                                                               // detect recursion during boot
-#endif // __CFA_DEBUG__
+static volatile bool heapMasterBootFlag = false;                // trigger for first heap
+static HeapMaster heapMaster @= {};                                             // program global
+
+static void heapMasterCtor();
+static void heapMasterDtor();
+static Heap * getHeap();
 
 
@@ -268 +369 @@
 static_assert( NoBucketSizes == sizeof(bucketSizes) / sizeof(bucketSizes[0] ), "size of bucket array wrong" );
 
-// The constructor for heapManager is called explicitly in memory_startup.
-static Heap heapManager __attribute__(( aligned (128) )) @= {}; // size of cache line to prevent false sharing
+
+// extern visibility, used by runtime kernel
+libcfa_public size_t __page_size;                                               // architecture pagesize
+libcfa_public int __map_prot;                                                   // common mmap/mprotect protection
+
+
+// Thread-local storage is allocated lazily when the storage is accessed.
+static __thread size_t PAD1 CALIGN TLSMODEL __attribute__(( unused )); // protect false sharing
+static __thread Heap * volatile heapManager CALIGN TLSMODEL;
+static __thread size_t PAD2 CALIGN TLSMODEL __attribute__(( unused )); // protect further false sharing
+
+
+// declare helper functions for HeapMaster
+void noMemory();                                                                                // forward, called by "builtin_new" when malloc returns 0
+
+
+// generic Bsearchl does not inline, so substitute with hand-coded binary-search.
+inline __attribute__((always_inline))
+static size_t Bsearchl( unsigned int key, const unsigned int vals[], size_t dim ) {
+        size_t l = 0, m, h = dim;
+        while ( l < h ) {
+                m = (l + h) / 2;
+                if ( (unsigned int &)(vals[m]) < key ) {                // cast away const
+                        l = m + 1;
+                } else {
+                        h = m;
+                } // if
+        } // while
+        return l;
+} // Bsearchl
+
+
+void heapMasterCtor() with( heapMaster ) {
+        // Singleton pattern to initialize heap master
+
+        verify( bucketSizes[0] == (16 + sizeof(Heap.Storage)) );
+
+        __page_size = sysconf( _SC_PAGESIZE );
+        __map_prot = PROT_READ | PROT_WRITE | PROT_EXEC;
+
+        ?{}( extLock );
+        ?{}( mgrLock );
+
+        char * end = (char *)sbrk( 0 );
+        heapBegin = heapEnd = sbrk( (char *)ceiling2( (long unsigned int)end, libAlign() ) - end ); // move start of heap to multiple of alignment
+        heapRemaining = 0;
+        heapExpand = malloc_expansion();
+        mmapStart = malloc_mmap_start();
+
+        // find the closest bucket size less than or equal to the mmapStart size
+        maxBucketsUsed = Bsearchl( mmapStart, bucketSizes, NoBucketSizes ); // binary search
+
+        verify( (mmapStart >= pageSize) && (bucketSizes[NoBucketSizes - 1] >= mmapStart) );
+        verify( maxBucketsUsed < NoBucketSizes );                       // subscript failure ?
+        verify( mmapStart <= bucketSizes[maxBucketsUsed] ); // search failure ?
+
+        heapManagersList = 0p;
+        freeHeapManagersList = 0p;
+
+        heapManagersStorage = 0p;
+        heapManagersStorageEnd = 0p;
+
+        #ifdef __STATISTICS__
+        HeapStatisticsCtor( stats );                                            // clear statistic counters
+        threads_started = threads_exited = 0;
+        reused_heap = new_heap = 0;
+        sbrk_calls = sbrk_storage = 0;
+        stats_fd = STDERR_FILENO;
+        #endif // __STATISTICS__
+
+        #ifdef FASTLOOKUP
+        for ( unsigned int i = 0, idx = 0; i < LookupSizes; i += 1 ) {
+                if ( i > bucketSizes[idx] ) idx += 1;
+                lookup[i] = idx;
+                verify( i <= bucketSizes[idx] );
+                verify( (i <= 32 && idx == 0) || (i > bucketSizes[idx - 1]) );
+        } // for
+        #endif // FASTLOOKUP
+
+        heapMasterBootFlag = true;
+} // heapMasterCtor
+
+
+#define NO_MEMORY_MSG "**** Error **** insufficient heap memory available to allocate %zd new bytes."
+
+Heap * getHeap() with( heapMaster ) {
+        Heap * heap;
+        if ( freeHeapManagersList ) {                                           // free heap for reused ?
+                heap = freeHeapManagersList;
+                freeHeapManagersList = heap->nextFreeHeapManager;
+
+                #ifdef __STATISTICS__
+                reused_heap += 1;
+                #endif // __STATISTICS__
+        } else {                                                                                        // free heap not found, create new
+                // Heap size is about 12K, FreeHeader (128 bytes because of cache alignment) * NoBucketSizes (91) => 128 heaps *
+                // 12K ~= 120K byte superblock.  Where 128-heap superblock handles a medium sized multi-processor server.
+                size_t remaining = heapManagersStorageEnd - heapManagersStorage; // remaining free heaps in superblock
+                if ( ! heapManagersStorage || remaining != 0 ) {
+                        // Each block of heaps is a multiple of the number of cores on the computer.
+                        int HeapDim = get_nprocs();                                     // get_nprocs_conf does not work
+                        size_t size = HeapDim * sizeof( Heap );
+
+                        heapManagersStorage = (Heap *)mmap( 0, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0 );
+                        if ( unlikely( heapManagersStorage == (Heap *)MAP_FAILED ) ) { // failed ?
+                                if ( errno == ENOMEM ) abort( NO_MEMORY_MSG, size ); // no memory
+                                // Do not call strerror( errno ) as it may call malloc.
+                                abort( "**** Error **** attempt to allocate block of heaps of size %zu bytes and mmap failed with errno %d.", size, errno );
+                        } // if
+                        heapManagersStorageEnd = &heapManagersStorage[HeapDim]; // outside array
+                } // if
+
+                heap = heapManagersStorage;
+                heapManagersStorage = heapManagersStorage + 1; // bump next heap
+
+                #if defined( __STATISTICS__ ) || defined( __CFA_DEBUG__ )
+                heap->nextHeapManager = heapManagersList;
+                #endif // __STATISTICS__ || __CFA_DEBUG__
+                heapManagersList = heap;
+
+                #ifdef __STATISTICS__
+                new_heap += 1;
+                #endif // __STATISTICS__
+
+                with( *heap ) {
+                        for ( unsigned int j = 0; j < NoBucketSizes; j += 1 ) { // initialize free lists
+                                #ifdef OWNERSHIP
+                                #ifdef RETURNSPIN
+                                ?{}( freeLists[j].returnLock );
+                                #endif // RETURNSPIN
+                                freeLists[j].returnList = 0p;
+                                #endif // OWNERSHIP
+                                freeLists[j].freeList = 0p;
+                                freeLists[j].homeManager = heap;
+                                freeLists[j].blockSize = bucketSizes[j];
+                        } // for
+        
+                        heapBuffer = 0p;
+                        heapReserve = 0;
+                        nextFreeHeapManager = 0p;
+                        #ifdef __CFA_DEBUG__
+                        allocUnfreed = 0;
+                        #endif // __CFA_DEBUG__
+                } // with
+        } // if
+
+        return heap;
+} // getHeap
+
+
+void heapManagerCtor() libcfa_public {
+        if ( unlikely( ! heapMasterBootFlag ) ) heapMasterCtor();
+
+        lock( heapMaster.mgrLock );             // protect heapMaster counters
+
+        // get storage for heap manager
+
+        heapManager = getHeap();
+
+        #ifdef __STATISTICS__
+        HeapStatisticsCtor( heapManager->stats );                       // heap local
+        heapMaster.threads_started += 1;
+        #endif // __STATISTICS__
+
+        unlock( heapMaster.mgrLock );
+} // heapManagerCtor
+
+
+void heapManagerDtor() libcfa_public {
+        lock( heapMaster.mgrLock );
+
+        // place heap on list of free heaps for reusability
+        heapManager->nextFreeHeapManager = heapMaster.freeHeapManagersList;
+        heapMaster.freeHeapManagersList = heapManager;
+
+        #ifdef __STATISTICS__
+        heapMaster.threads_exited += 1;
+        #endif // __STATISTICS__
+
+        // Do not set heapManager to NULL because it is used after Cforall is shutdown but before the program shuts down.
+
+        unlock( heapMaster.mgrLock );
+} // heapManagerDtor
 
 
 //####################### Memory Allocation Routines Helpers ####################
 
-
-#ifdef __CFA_DEBUG__
-static size_t allocUnfreed;                                                             // running total of allocations minus frees
-
-static void prtUnfreed() {
-        if ( allocUnfreed != 0 ) {
-                // DO NOT USE STREAMS AS THEY MAY BE UNAVAILABLE AT THIS POINT.
-                char helpText[512];
-                __cfaabi_bits_print_buffer( STDERR_FILENO, helpText, sizeof(helpText),
-                                                                        "CFA warning (UNIX pid:%ld) : program terminating with %zu(0x%zx) bytes of storage allocated but not freed.\n"
-                                                                        "Possible cause is unfreed storage allocated by the program or system/library routines called from the program.\n",
-                                                                        (long int)getpid(), allocUnfreed, allocUnfreed ); // always print the UNIX pid
-        } // if
-} // prtUnfreed
 
 extern int cfa_main_returned;                                                   // from interpose.cfa
 extern "C" {
+        void memory_startup( void ) {
+                if ( ! heapMasterBootFlag ) heapManagerCtor();  // sanity check
+        } // memory_startup
+
+        void memory_shutdown( void ) {
+                heapManagerDtor();
+        } // memory_shutdown
+
         void heapAppStart() {                                                           // called by __cfaabi_appready_startup
-                allocUnfreed = 0;
+                verify( heapManager );
+                #ifdef __CFA_DEBUG__
+                heapManager->allocUnfreed = 0;                                  // clear prior allocation counts
+                #endif // __CFA_DEBUG__
+
+                #ifdef __STATISTICS__
+                HeapStatisticsCtor( heapManager->stats );               // clear prior statistic counters
+                #endif // __STATISTICS__
         } // heapAppStart
 
         void heapAppStop() {                                                            // called by __cfaabi_appready_startdown
-                fclose( stdin ); fclose( stdout );
-                if ( cfa_main_returned ) prtUnfreed();                  // do not check unfreed storage if exit called
+                fclose( stdin ); fclose( stdout );                              // free buffer storage
+          if ( ! cfa_main_returned ) return;                            // do not check unfreed storage if exit called
+
+                #ifdef __CFA_DEBUG__
+                // allocUnfreed is set to 0 when a heap is created and it accumulates any unfreed storage during its multiple thread
+                // usages.  At the end, add up each heap allocUnfreed value across all heaps to get the total unfreed storage.
+                int64_t allocUnfreed = 0;
+                for ( Heap * heap = heapMaster.heapManagersList; heap; heap = heap->nextHeapManager ) {
+                        allocUnfreed += heap->allocUnfreed;
+                } // for
+
+                allocUnfreed -= malloc_unfreed();                               // subtract any user specified unfreed storage
+                if ( allocUnfreed > 0 ) {
+                        // DO NOT USE STREAMS AS THEY MAY BE UNAVAILABLE AT THIS POINT.
+                        char helpText[512];
+                        __cfaabi_bits_print_buffer( STDERR_FILENO, helpText, sizeof(helpText),
+                                                                                "CFA warning (UNIX pid:%ld) : program terminating with %ju(0x%jx) bytes of storage allocated but not freed.\n"
+                                                                                "Possible cause is unfreed storage allocated by the program or system/library routines called from the program.\n",
+                                                                                (long int)getpid(), allocUnfreed, allocUnfreed ); // always print the UNIX pid
+                } // if
+                #endif // __CFA_DEBUG__
         } // heapAppStop
 } // extern "C"
-#endif // __CFA_DEBUG__
 
 
 #ifdef __STATISTICS__
 static HeapStatistics stats;                                                    // zero filled
-static unsigned int sbrk_calls;
-static unsigned long long int sbrk_storage;
-// Statistics file descriptor (changed by malloc_stats_fd).
-static int stats_fd = STDERR_FILENO;                                    // default stderr
 
 #define prtFmt \
@@ -321 +618 @@
         "  realloc   >0 calls %'u; 0 calls %'u; storage %'llu / %'llu bytes\n" \
         "  free      !null calls %'u; null calls %'u; storage %'llu / %'llu bytes\n" \
-        "  sbrk      calls %'u; storage %'llu bytes\n"                                          \
-        "  mmap      calls %'u; storage %'llu / %'llu bytes\n"                          \
-        "  munmap    calls %'u; storage %'llu / %'llu bytes\n"                          \
+        "  return    pulls %'u; pushes %'u; storage %'llu / %'llu bytes\n" \
+        "  sbrk      calls %'u; storage %'llu bytes\n" \
+        "  mmap      calls %'u; storage %'llu / %'llu bytes\n" \
+        "  munmap    calls %'u; storage %'llu / %'llu bytes\n" \
+        "  threads   started %'lu; exited %'lu\n" \
+        "  heaps     new %'lu; reused %'lu\n"
 
 // Use "write" because streams may be shutdown when calls are made.
-static int printStats() {                                                               // see malloc_stats
+static int printStats( HeapStatistics & stats ) with( heapMaster, stats ) {     // see malloc_stats
         char helpText[sizeof(prtFmt) + 1024];                           // space for message and values
-        return __cfaabi_bits_print_buffer( STDERR_FILENO, helpText, sizeof(helpText), prtFmt,
-                        stats.malloc_calls, stats.malloc_0_calls, stats.malloc_storage_request, stats.malloc_storage_alloc,
-                        stats.aalloc_calls, stats.aalloc_0_calls, stats.aalloc_storage_request, stats.aalloc_storage_alloc,
-                        stats.calloc_calls, stats.calloc_0_calls, stats.calloc_storage_request, stats.calloc_storage_alloc,
-                        stats.memalign_calls, stats.memalign_0_calls, stats.memalign_storage_request, stats.memalign_storage_alloc,
-                        stats.amemalign_calls, stats.amemalign_0_calls, stats.amemalign_storage_request, stats.amemalign_storage_alloc,
-                        stats.cmemalign_calls, stats.cmemalign_0_calls, stats.cmemalign_storage_request, stats.cmemalign_storage_alloc,
-                        stats.resize_calls, stats.resize_0_calls, stats.resize_storage_request, stats.resize_storage_alloc,
-                        stats.realloc_calls, stats.realloc_0_calls, stats.realloc_storage_request, stats.realloc_storage_alloc,
-                        stats.free_calls, stats.free_null_calls, stats.free_storage_request, stats.free_storage_alloc,
+        return __cfaabi_bits_print_buffer( stats_fd, helpText, sizeof(helpText), prtFmt,
+                        malloc_calls, malloc_0_calls, malloc_storage_request, malloc_storage_alloc,
+                        aalloc_calls, aalloc_0_calls, aalloc_storage_request, aalloc_storage_alloc,
+                        calloc_calls, calloc_0_calls, calloc_storage_request, calloc_storage_alloc,
+                        memalign_calls, memalign_0_calls, memalign_storage_request, memalign_storage_alloc,
+                        amemalign_calls, amemalign_0_calls, amemalign_storage_request, amemalign_storage_alloc,
+                        cmemalign_calls, cmemalign_0_calls, cmemalign_storage_request, cmemalign_storage_alloc,
+                        resize_calls, resize_0_calls, resize_storage_request, resize_storage_alloc,
+                        realloc_calls, realloc_0_calls, realloc_storage_request, realloc_storage_alloc,
+                        free_calls, free_null_calls, free_storage_request, free_storage_alloc,
+                        return_pulls, return_pushes, return_storage_request, return_storage_alloc,
                         sbrk_calls, sbrk_storage,
-                        stats.mmap_calls, stats.mmap_storage_request, stats.mmap_storage_alloc,
-                        stats.munmap_calls, stats.munmap_storage_request, stats.munmap_storage_alloc
+                        mmap_calls, mmap_storage_request, mmap_storage_alloc,
+                        munmap_calls, munmap_storage_request, munmap_storage_alloc,
+                        threads_started, threads_exited,
+                        new_heap, reused_heap
                 );
 } // printStats
@@ -358 +661 @@
         "<total type=\"realloc\" >0 count=\"%'u;\" 0 count=\"%'u;\" size=\"%'llu / %'llu\"/> bytes\n" \
         "<total type=\"free\" !null=\"%'u;\" 0 null=\"%'u;\" size=\"%'llu / %'llu\"/> bytes\n" \
+        "<total type=\"return\" pulls=\"%'u;\" 0 pushes=\"%'u;\" size=\"%'llu / %'llu\"/> bytes\n" \
         "<total type=\"sbrk\" count=\"%'u;\" size=\"%'llu\"/> bytes\n" \
         "<total type=\"mmap\" count=\"%'u;\" size=\"%'llu / %'llu\" / > bytes\n" \
         "<total type=\"munmap\" count=\"%'u;\" size=\"%'llu / %'llu\"/> bytes\n" \
+        "<total type=\"threads\" started=\"%'lu;\" exited=\"%'lu\"/>\n" \
+        "<total type=\"heaps\" new=\"%'lu;\" reused=\"%'lu\"/>\n" \
         "</malloc>"
 
-static int printStatsXML( FILE * stream ) {                             // see malloc_info
+static int printStatsXML( HeapStatistics & stats, FILE * stream ) with( heapMaster, stats ) { // see malloc_info
         char helpText[sizeof(prtFmtXML) + 1024];                        // space for message and values
         return __cfaabi_bits_print_buffer( fileno( stream ), helpText, sizeof(helpText), prtFmtXML,
-                        stats.malloc_calls, stats.malloc_0_calls, stats.malloc_storage_request, stats.malloc_storage_alloc,
-                        stats.aalloc_calls, stats.aalloc_0_calls, stats.aalloc_storage_request, stats.aalloc_storage_alloc,
-                        stats.calloc_calls, stats.calloc_0_calls, stats.calloc_storage_request, stats.calloc_storage_alloc,
-                        stats.memalign_calls, stats.memalign_0_calls, stats.memalign_storage_request, stats.memalign_storage_alloc,
-                        stats.amemalign_calls, stats.amemalign_0_calls, stats.amemalign_storage_request, stats.amemalign_storage_alloc,
-                        stats.cmemalign_calls, stats.cmemalign_0_calls, stats.cmemalign_storage_request, stats.cmemalign_storage_alloc,
-                        stats.resize_calls, stats.resize_0_calls, stats.resize_storage_request, stats.resize_storage_alloc,
-                        stats.realloc_calls, stats.realloc_0_calls, stats.realloc_storage_request, stats.realloc_storage_alloc,
-                        stats.free_calls, stats.free_null_calls, stats.free_storage_request, stats.free_storage_alloc,
+                        malloc_calls, malloc_0_calls, malloc_storage_request, malloc_storage_alloc,
+                        aalloc_calls, aalloc_0_calls, aalloc_storage_request, aalloc_storage_alloc,
+                        calloc_calls, calloc_0_calls, calloc_storage_request, calloc_storage_alloc,
+                        memalign_calls, memalign_0_calls, memalign_storage_request, memalign_storage_alloc,
+                        amemalign_calls, amemalign_0_calls, amemalign_storage_request, amemalign_storage_alloc,
+                        cmemalign_calls, cmemalign_0_calls, cmemalign_storage_request, cmemalign_storage_alloc,
+                        resize_calls, resize_0_calls, resize_storage_request, resize_storage_alloc,
+                        realloc_calls, realloc_0_calls, realloc_storage_request, realloc_storage_alloc,
+                        free_calls, free_null_calls, free_storage_request, free_storage_alloc,
+                        return_pulls, return_pushes, return_storage_request, return_storage_alloc,
                         sbrk_calls, sbrk_storage,
-                        stats.mmap_calls, stats.mmap_storage_request, stats.mmap_storage_alloc,
-                        stats.munmap_calls, stats.munmap_storage_request, stats.munmap_storage_alloc
+                        mmap_calls, mmap_storage_request, mmap_storage_alloc,
+                    munmap_calls, munmap_storage_request, munmap_storage_alloc,
+                        threads_started, threads_exited,
+                        new_heap, reused_heap
                 );
 } // printStatsXML
+
+static HeapStatistics & collectStats( HeapStatistics & stats ) with( heapMaster ) {
+        lock( mgrLock );
+
+        stats += heapMaster.stats;
+        for ( Heap * heap = heapManagersList; heap; heap = heap->nextHeapManager ) {
+                stats += heap->stats;
+        } // for
+
+        unlock( mgrLock );
+        return stats;
+} // collectStats
 #endif // __STATISTICS__
 
 
-// statically allocated variables => zero filled.
-static size_t heapExpand;                                                               // sbrk advance
-static size_t mmapStart;                                                                // cross over point for mmap
-static unsigned int maxBucketsUsed;                                             // maximum number of buckets in use
-// extern visibility, used by runtime kernel
-// would be cool to remove libcfa_public but it's needed for libcfathread
-libcfa_public size_t __page_size;                                                       // architecture pagesize
-libcfa_public int __map_prot;                                                           // common mmap/mprotect protection
-
-
-// thunk problem
-size_t Bsearchl( unsigned int key, const unsigned int * vals, size_t dim ) {
-        size_t l = 0, m, h = dim;
-        while ( l < h ) {
-                m = (l + h) / 2;
-                if ( (unsigned int &)(vals[m]) < key ) {                // cast away const
-                        l = m + 1;
-                } else {
-                        h = m;
-                } // if
-        } // while
-        return l;
-} // Bsearchl
-
-
-static inline bool setMmapStart( size_t value ) {               // true => mmapped, false => sbrk
+static bool setMmapStart( size_t value ) with( heapMaster ) { // true => mmapped, false => sbrk
   if ( value < __page_size || bucketSizes[NoBucketSizes - 1] < value ) return false;
         mmapStart = value;                                                                      // set global
 
         // find the closest bucket size less than or equal to the mmapStart size
-        maxBucketsUsed = Bsearchl( (unsigned int)mmapStart, bucketSizes, NoBucketSizes ); // binary search
-        assert( maxBucketsUsed < NoBucketSizes );                       // subscript failure ?
-        assert( mmapStart <= bucketSizes[maxBucketsUsed] ); // search failure ?
+        maxBucketsUsed = Bsearchl( mmapStart, bucketSizes, NoBucketSizes ); // binary search
+        verify( maxBucketsUsed < NoBucketSizes );                       // subscript failure ?
+        verify( mmapStart <= bucketSizes[maxBucketsUsed] ); // search failure ?
         return true;
 } // setMmapStart
@@ -438 +734 @@
 
 
-static inline void checkAlign( size_t alignment ) {
+inline __attribute__((always_inline))
+static void checkAlign( size_t alignment ) {
         if ( unlikely( alignment < libAlign() || ! is_pow2( alignment ) ) ) {
                 abort( "**** Error **** alignment %zu for memory allocation is less than %d and/or not a power of 2.", alignment, libAlign() );
@@ -445 +742 @@
 
 
-static inline void checkHeader( bool check, const char name[], void * addr ) {
+inline __attribute__((always_inline))
+static void checkHeader( bool check, const char name[], void * addr ) {
         if ( unlikely( check ) ) {                                                      // bad address ?
                 abort( "**** Error **** attempt to %s storage %p with address outside the heap.\n"
@@ -470 +768 @@
 
 
-static inline void fakeHeader( Heap.Storage.Header *& header, size_t & alignment ) {
+inline __attribute__((always_inline))
+static void fakeHeader( Heap.Storage.Header *& header, size_t & alignment ) {
         if ( unlikely( AlignmentBit( header ) ) ) {                     // fake header ?
                 alignment = ClearAlignmentBit( header );                // clear flag from value
@@ -483 +782 @@
 
 
-static inline bool headers( const char name[] __attribute__(( unused )), void * addr, Heap.Storage.Header *& header,
-                                                        Heap.FreeHeader *& freeHead, size_t & size, size_t & alignment ) with( heapManager ) {
+inline __attribute__((always_inline))
+static bool headers( const char name[] __attribute__(( unused )), void * addr, Heap.Storage.Header *& header,
+                                                        Heap.FreeHeader *& freeHead, size_t & size, size_t & alignment ) with( heapMaster, *heapManager ) {
         header = HeaderAddr( addr );
 
@@ -509 +809 @@
         checkHeader( header < (Heap.Storage.Header *)heapBegin || (Heap.Storage.Header *)heapEnd < header, name, addr ); // bad address ? (offset could be + or -)
 
+        Heap * homeManager;
         if ( unlikely( freeHead == 0p || // freed and only free-list node => null link
                                    // freed and link points at another free block not to a bucket in the bucket array.
-                                   freeHead < &freeLists[0] || &freeLists[NoBucketSizes] <= freeHead ) ) {
+                                   (homeManager = freeHead->homeManager, freeHead < &homeManager->freeLists[0] ||
+                                        &homeManager->freeLists[NoBucketSizes] <= freeHead ) ) ) {
                 abort( "**** Error **** attempt to %s storage %p with corrupted header.\n"
                            "Possible cause is duplicate free on same block or overwriting of header information.",
@@ -521 +823 @@
 } // headers
 
-// #ifdef __CFA_DEBUG__
-// #if __SIZEOF_POINTER__ == 4
-// #define MASK 0xdeadbeef
-// #else
-// #define MASK 0xdeadbeefdeadbeef
-// #endif
-// #define STRIDE size_t
-
-// static void * Memset( void * addr, STRIDE size ) {           // debug only
-//      if ( size % sizeof(STRIDE) != 0 ) abort( "Memset() : internal error, size %zd not multiple of %zd.", size, sizeof(STRIDE) );
-//      if ( (STRIDE)addr % sizeof(STRIDE) != 0 ) abort( "Memset() : internal error, addr %p not multiple of %zd.", addr, sizeof(STRIDE) );
-
-//      STRIDE * end = (STRIDE *)addr + size / sizeof(STRIDE);
-//      for ( STRIDE * p = (STRIDE *)addr; p < end; p += 1 ) *p = MASK;
-//      return addr;
-// } // Memset
-// #endif // __CFA_DEBUG__
-
-
-#define NO_MEMORY_MSG "insufficient heap memory available for allocating %zd new bytes."
-
-static inline void * extend( size_t size ) with( heapManager ) {
-        lock( extlock __cfaabi_dbg_ctx2 );
+
+static void * master_extend( size_t size ) with( heapMaster ) {
+        lock( extLock );
 
         ptrdiff_t rem = heapRemaining - size;
@@ -549 +831 @@
                 // If the size requested is bigger than the current remaining storage, increase the size of the heap.
 
-                size_t increase = ceiling2( size > heapExpand ? size : heapExpand, __page_size );
+                size_t increase = ceiling2( size > heapExpand ? size : heapExpand, libAlign() );
                 // Do not call abort or strerror( errno ) as they may call malloc.
-                if ( sbrk( increase ) == (void *)-1 ) {                 // failed, no memory ?
-                        unlock( extlock );
-                        __cfaabi_bits_print_nolock( STDERR_FILENO, NO_MEMORY_MSG, size );
-                        _exit( EXIT_FAILURE );                                          // give up
+                if ( unlikely( sbrk( increase ) == (void *)-1 ) ) {     // failed, no memory ?
+                        unlock( extLock );
+                        abort( NO_MEMORY_MSG, size );                           // no memory
                 } // if
 
                 // Make storage executable for thunks.
                 if ( mprotect( (char *)heapEnd + heapRemaining, increase, __map_prot ) ) {
-                        unlock( extlock );
-                        __cfaabi_bits_print_nolock( STDERR_FILENO, "extend() : internal error, mprotect failure, heapEnd:%p size:%zd, errno:%d.\n", heapEnd, increase, errno );
-                        _exit( EXIT_FAILURE );
-                } // if
+                        unlock( extLock );
+                        abort( "**** Error **** attempt to make heap storage executable for thunks and mprotect failed with errno %d.", errno );
+                } // if
+
+                rem = heapRemaining + increase - size;
 
                 #ifdef __STATISTICS__
@@ -568 +850 @@
                 sbrk_storage += increase;
                 #endif // __STATISTICS__
-
-                #ifdef __CFA_DEBUG__
-                // Set new memory to garbage so subsequent uninitialized usages might fail.
-                memset( (char *)heapEnd + heapRemaining, '\xde', increase );
-                //Memset( (char *)heapEnd + heapRemaining, increase );
-                #endif // __CFA_DEBUG__
-
-                rem = heapRemaining + increase - size;
         } // if
 
@@ -581 +855 @@
         heapRemaining = rem;
         heapEnd = (char *)heapEnd + size;
-        unlock( extlock );
+
+        unlock( extLock );
         return block;
-} // extend
-
-
-static inline void * doMalloc( size_t size ) with( heapManager ) {
-        Heap.Storage * block;                                           // pointer to new block of storage
+} // master_extend
+
+
+__attribute__(( noinline ))
+static void * manager_extend( size_t size ) with( *heapManager ) {
+        ptrdiff_t rem = heapReserve - size;
+
+        if ( unlikely( rem < 0 ) ) {                                            // negative
+                // If the size requested is bigger than the current remaining reserve, use the current reserve to populate
+                // smaller freeLists, and increase the reserve.
+
+                rem = heapReserve;                                                              // positive
+
+                if ( rem >= bucketSizes[0] ) {                                  // minimal size ? otherwise ignore
+                        size_t bucket;
+                        #ifdef FASTLOOKUP
+                        if ( likely( rem < LookupSizes ) ) bucket = lookup[rem];
+                        #endif // FASTLOOKUP
+                                bucket = Bsearchl( rem, bucketSizes, heapMaster.maxBucketsUsed );
+                        verify( 0 <= bucket && bucket <= heapMaster.maxBucketsUsed );
+                        Heap.FreeHeader * freeHead = &(freeLists[bucket]);
+
+                        // The remaining storage many not be bucket size, whereas all other allocations are. Round down to previous
+                        // bucket size in this case.
+                        if ( unlikely( freeHead->blockSize > (size_t)rem ) ) freeHead -= 1;
+                        Heap.Storage * block = (Heap.Storage *)heapBuffer;
+
+                        block->header.kind.real.next = freeHead->freeList; // push on stack
+                        freeHead->freeList = block;
+                } // if
+
+                size_t increase = ceiling( size > ( heapMaster.heapExpand / 10 ) ? size : ( heapMaster.heapExpand / 10 ), libAlign() );
+                heapBuffer = master_extend( increase );
+                rem = increase - size;
+        } // if
+
+        Heap.Storage * block = (Heap.Storage *)heapBuffer;
+        heapReserve = rem;
+        heapBuffer = (char *)heapBuffer + size;
+
+        return block;
+} // manager_extend
+
+
+#define BOOT_HEAP_MANAGER \
+        if ( unlikely( ! heapMasterBootFlag ) ) { \
+                heapManagerCtor(); /* trigger for first heap */ \
+        } /* if */
+
+#ifdef __STATISTICS__
+#define STAT_NAME __counter
+#define STAT_PARM , unsigned int STAT_NAME
+#define STAT_ARG( name ) , name
+#define STAT_0_CNT( counter ) stats.counters[counter].calls_0 += 1
+#else
+#define STAT_NAME
+#define STAT_PARM
+#define STAT_ARG( name )
+#define STAT_0_CNT( counter )
+#endif // __STATISTICS__
+
+#define PROLOG( counter, ... ) \
+        BOOT_HEAP_MANAGER; \
+        if ( unlikely( size == 0 ) ||                                           /* 0 BYTE ALLOCATION RETURNS NULL POINTER */ \
+                unlikely( size > ULONG_MAX - sizeof(Heap.Storage) ) ) { /* error check */ \
+                STAT_0_CNT( counter ); \
+                __VA_ARGS__; \
+                return 0p; \
+        } /* if */
+
+
+#define SCRUB_SIZE 1024lu
+// Do not use '\xfe' for scrubbing because dereferencing an address composed of it causes a SIGSEGV *without* a valid IP
+// pointer in the interrupt frame.
+#define SCRUB '\xff'
+
+static void * doMalloc( size_t size STAT_PARM ) libcfa_nopreempt with( *heapManager ) {
+        PROLOG( STAT_NAME );
+
+        verify( heapManager );
+        Heap.Storage * block;                                                           // pointer to new block of storage
 
         // Look up size in the size list.  Make sure the user request includes space for the header that must be allocated
         // along with the block and is a multiple of the alignment size.
-
         size_t tsize = size + sizeof(Heap.Storage);
 
-        if ( likely( tsize < mmapStart ) ) {                            // small size => sbrk
-                size_t posn;
+        #ifdef __STATISTICS__
+        stats.counters[STAT_NAME].calls += 1;
+        stats.counters[STAT_NAME].request += size;
+        #endif // __STATISTICS__
+
+        #ifdef __CFA_DEBUG__
+        allocUnfreed += size;
+        #endif // __CFA_DEBUG__
+
+        if ( likely( tsize < heapMaster.mmapStart ) ) {         // small size => sbrk
+                size_t bucket;
                 #ifdef FASTLOOKUP
-                if ( tsize < LookupSizes ) posn = lookup[tsize];
+                if ( likely( tsize < LookupSizes ) ) bucket = lookup[tsize];
                 else
                 #endif // FASTLOOKUP
-                        posn = Bsearchl( (unsigned int)tsize, bucketSizes, (size_t)maxBucketsUsed );
-                Heap.FreeHeader * freeElem = &freeLists[posn];
-                verify( freeElem <= &freeLists[maxBucketsUsed] ); // subscripting error ?
-                verify( tsize <= freeElem->blockSize );                 // search failure ?
-                tsize = freeElem->blockSize;                                    // total space needed for request
+                        bucket = Bsearchl( tsize, bucketSizes, heapMaster.maxBucketsUsed );
+                verify( 0 <= bucket && bucket <= heapMaster.maxBucketsUsed );
+                Heap.FreeHeader * freeHead = &freeLists[bucket];
+
+                verify( freeHead <= &freeLists[heapMaster.maxBucketsUsed] ); // subscripting error ?
+                verify( tsize <= freeHead->blockSize );                 // search failure ?
+
+                tsize = freeHead->blockSize;                                    // total space needed for request
+                #ifdef __STATISTICS__
+                stats.counters[STAT_NAME].alloc += tsize;
+                #endif // __STATISTICS__
 
                 // Spin until the lock is acquired for this particular size of block.
 
                 #if BUCKETLOCK == SPINLOCK
-                lock( freeElem->lock __cfaabi_dbg_ctx2 );
-                block = freeElem->freeList;                                             // remove node from stack
+                block = freeHead->freeList;                                             // remove node from stack
                 #else
-                block = pop( freeElem->freeList );
+                block = pop( freeHead->freeList );
                 #endif // BUCKETLOCK
                 if ( unlikely( block == 0p ) ) {                                // no free block ?
+                        #ifdef OWNERSHIP
+                        // Freelist for that size is empty, so carve it out of the heap, if there is enough left, or get some more
+                        // and then carve it off.
+                        #ifdef RETURNSPIN
                         #if BUCKETLOCK == SPINLOCK
-                        unlock( freeElem->lock );
+                        lock( freeHead->returnLock );
+                        block = freeHead->returnList;
+                        freeHead->returnList = 0p;
+                        unlock( freeHead->returnLock );
+                        #else
+                        block = __atomic_exchange_n( &freeHead->returnList, nullptr, __ATOMIC_SEQ_CST );
+                        #endif // RETURNSPIN
+
+                        if ( likely( block == 0p ) ) {                  // return list also empty?
+                        #endif // OWNERSHIP
+                                // Do not leave kernel thread as manager_extend accesses heapManager.
+                                disable_interrupts();
+                                block = (Heap.Storage *)manager_extend( tsize ); // mutual exclusion on call
+                                enable_interrupts( false );
+
+                                // OK TO BE PREEMPTED HERE AS heapManager IS NO LONGER ACCESSED.
+
+                                #ifdef __CFA_DEBUG__
+                                // Scrub new memory so subsequent uninitialized usages might fail. Only scrub the first 1024 bytes.
+                                memset( block->data, SCRUB, min( SCRUB_SIZE, tsize - sizeof(Heap.Storage) ) );
+                                #endif // __CFA_DEBUG__
                         #endif // BUCKETLOCK
-
-                        // Freelist for that size was empty, so carve it out of the heap if there's enough left, or get some more
-                        // and then carve it off.
-
-                        block = (Heap.Storage *)extend( tsize );        // mutual exclusion on call
-                #if BUCKETLOCK == SPINLOCK
+                        #ifdef OWNERSHIP
+                        } else {                                                                        // merge returnList into freeHead
+                                #ifdef __STATISTICS__
+                                stats.return_pulls += 1;
+                                #endif // __STATISTICS__
+
+                                // OK TO BE PREEMPTED HERE AS heapManager IS NO LONGER ACCESSED.
+
+                                freeHead->freeList = block->header.kind.real.next;
+                        } // if
+                        #endif // OWNERSHIP
                 } else {
-                        freeElem->freeList = block->header.kind.real.next;
-                        unlock( freeElem->lock );
-                #endif // BUCKETLOCK
-                } // if
-
-                block->header.kind.real.home = freeElem;                // pointer back to free list of apropriate size
+                        // Memory is scrubbed in doFree.
+                        freeHead->freeList = block->header.kind.real.next;
+                } // if
+
+                block->header.kind.real.home = freeHead;                // pointer back to free list of apropriate size
         } else {                                                                                        // large size => mmap
   if ( unlikely( size > ULONG_MAX - __page_size ) ) return 0p;
                 tsize = ceiling2( tsize, __page_size );                 // must be multiple of page size
                 #ifdef __STATISTICS__
-                __atomic_add_fetch( &stats.mmap_calls, 1, __ATOMIC_SEQ_CST );
-                __atomic_add_fetch( &stats.mmap_storage_request, size, __ATOMIC_SEQ_CST );
-                __atomic_add_fetch( &stats.mmap_storage_alloc, tsize, __ATOMIC_SEQ_CST );
+                stats.counters[STAT_NAME].alloc += tsize;
+                stats.mmap_calls += 1;
+                stats.mmap_storage_request += size;
+                stats.mmap_storage_alloc += tsize;
                 #endif // __STATISTICS__
 
-                block = (Heap.Storage *)mmap( 0, tsize, __map_prot, MAP_PRIVATE | MAP_ANONYMOUS, mmapFd, 0 );
-                if ( block == (Heap.Storage *)MAP_FAILED ) { // failed ?
+                disable_interrupts();
+                block = (Heap.Storage *)mmap( 0, tsize, __map_prot, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0 );
+                enable_interrupts( false );
+
+                // OK TO BE PREEMPTED HERE AS heapManager IS NO LONGER ACCESSED.
+
+                if ( unlikely( block == (Heap.Storage *)MAP_FAILED ) ) { // failed ?
                         if ( errno == ENOMEM ) abort( NO_MEMORY_MSG, tsize ); // no memory
                         // Do not call strerror( errno ) as it may call malloc.
-                        abort( "(Heap &)0x%p.doMalloc() : internal error, mmap failure, size:%zu errno:%d.", &heapManager, tsize, errno );
-                } //if
+                        abort( "**** Error **** attempt to allocate large object (> %zu) of size %zu bytes and mmap failed with errno %d.", size, heapMaster.mmapStart, errno );
+                } // if
+                block->header.kind.real.blockSize = MarkMmappedBit( tsize ); // storage size for munmap
+
                 #ifdef __CFA_DEBUG__
-                // Set new memory to garbage so subsequent uninitialized usages might fail.
-                memset( block, '\xde', tsize );
-                //Memset( block, tsize );
+                // Scrub new memory so subsequent uninitialized usages might fail. Only scrub the first 1024 bytes.  The rest of
+                // the storage set to 0 by mmap.
+                memset( block->data, SCRUB, min( SCRUB_SIZE, tsize - sizeof(Heap.Storage) ) );
                 #endif // __CFA_DEBUG__
-                block->header.kind.real.blockSize = MarkMmappedBit( tsize ); // storage size for munmap
         } // if
 
@@ -659 +1058 @@
 
         #ifdef __CFA_DEBUG__
-        __atomic_add_fetch( &allocUnfreed, tsize, __ATOMIC_SEQ_CST );
         if ( traceHeap() ) {
                 char helpText[64];
@@ -667 +1065 @@
         #endif // __CFA_DEBUG__
 
+//      poll_interrupts();                                                                      // call rollforward
+
         return addr;
 } // doMalloc
 
 
-static inline void doFree( void * addr ) with( heapManager ) {
+static void doFree( void * addr ) libcfa_nopreempt with( *heapManager ) {
+        verify( addr );
+
+        // detect free after thread-local storage destruction and use global stats in that case
+
+        Heap.Storage.Header * header;
+        Heap.FreeHeader * freeHead;
+        size_t size, alignment;
+
+        bool mapped = headers( "free", addr, header, freeHead, size, alignment );
+        #if defined( __STATISTICS__ ) || defined( __CFA_DEBUG__ )
+        size_t rsize = header->kind.real.size;                          // optimization
+        #endif // __STATISTICS__ || __CFA_DEBUG__
+
+        #ifdef __STATISTICS__
+        stats.free_storage_request += rsize;
+        stats.free_storage_alloc += size;
+        #endif // __STATISTICS__
+
         #ifdef __CFA_DEBUG__
-        if ( unlikely( heapManager.heapBegin == 0p ) ) {
-                abort( "doFree( %p ) : internal error, called before heap is initialized.", addr );
-        } // if
+        allocUnfreed -= rsize;
         #endif // __CFA_DEBUG__
 
-        Heap.Storage.Header * header;
-        Heap.FreeHeader * freeElem;
-        size_t size, alignment;                                                         // not used (see realloc)
-
-        if ( headers( "free", addr, header, freeElem, size, alignment ) ) { // mmapped ?
+        if ( unlikely( mapped ) ) {                                                     // mmapped ?
                 #ifdef __STATISTICS__
-                __atomic_add_fetch( &stats.munmap_calls, 1, __ATOMIC_SEQ_CST );
-                __atomic_add_fetch( &stats.munmap_storage_request, header->kind.real.size, __ATOMIC_SEQ_CST );
-                __atomic_add_fetch( &stats.munmap_storage_alloc, size, __ATOMIC_SEQ_CST );
+                stats.munmap_calls += 1;
+                stats.munmap_storage_request += rsize;
+                stats.munmap_storage_alloc += size;
                 #endif // __STATISTICS__
-                if ( munmap( header, size ) == -1 ) {
-                        abort( "Attempt to deallocate storage %p not allocated or with corrupt header.\n"
-                                   "Possible cause is invalid pointer.",
-                                   addr );
+
+                // OK TO BE PREEMPTED HERE AS heapManager IS NO LONGER ACCESSED.
+
+                // Does not matter where this storage is freed.
+                if ( unlikely( munmap( header, size ) == -1 ) ) {
+                        // Do not call strerror( errno ) as it may call malloc.
+                        abort( "**** Error **** attempt to deallocate large object %p and munmap failed with errno %d.\n"
+                                   "Possible cause is invalid delete pointer: either not allocated or with corrupt header.",
+                                   addr, errno );
                 } // if
         } else {
                 #ifdef __CFA_DEBUG__
-                // Set free memory to garbage so subsequent usages might fail.
-                memset( ((Heap.Storage *)header)->data, '\xde', freeElem->blockSize - sizeof( Heap.Storage ) );
-                //Memset( ((Heap.Storage *)header)->data, freeElem->blockSize - sizeof( Heap.Storage ) );
+                // memset is NOT always inlined!
+                disable_interrupts();
+                // Scrub old memory so subsequent usages might fail. Only scrub the first/last SCRUB_SIZE bytes.
+                char * data = ((Heap.Storage *)header)->data;   // data address
+                size_t dsize = size - sizeof(Heap.Storage);             // data size
+                if ( dsize <= SCRUB_SIZE * 2 ) {
+                        memset( data, SCRUB, dsize );                           // scrub all
+                } else {
+                        memset( data, SCRUB, SCRUB_SIZE );                      // scrub front
+                        memset( data + dsize - SCRUB_SIZE, SCRUB, SCRUB_SIZE ); // scrub back
+                } // if
+                enable_interrupts( false );
                 #endif // __CFA_DEBUG__
 
-                #ifdef __STATISTICS__
-                __atomic_add_fetch( &stats.free_calls, 1, __ATOMIC_SEQ_CST );
-                __atomic_add_fetch( &stats.free_storage_request, header->kind.real.size, __ATOMIC_SEQ_CST );
-                __atomic_add_fetch( &stats.free_storage_alloc, size, __ATOMIC_SEQ_CST );
-                #endif // __STATISTICS__
-
-                #if BUCKETLOCK == SPINLOCK
-                lock( freeElem->lock __cfaabi_dbg_ctx2 );               // acquire spin lock
-                header->kind.real.next = freeElem->freeList;    // push on stack
-                freeElem->freeList = (Heap.Storage *)header;
-                unlock( freeElem->lock );                                               // release spin lock
-                #else
-                push( freeElem->freeList, *(Heap.Storage *)header );
-                #endif // BUCKETLOCK
+                if ( likely( heapManager == freeHead->homeManager ) ) { // belongs to this thread
+                        header->kind.real.next = freeHead->freeList; // push on stack
+                        freeHead->freeList = (Heap.Storage *)header;
+                } else {                                                                                // return to thread owner
+                        verify( heapManager );
+
+                        #ifdef OWNERSHIP
+                        #ifdef RETURNSPIN
+                        lock( freeHead->returnLock );
+                        header->kind.real.next = freeHead->returnList; // push to bucket return list
+                        freeHead->returnList = (Heap.Storage *)header;
+                        unlock( freeHead->returnLock );
+                        #else                                                                           // lock free
+                        header->kind.real.next = freeHead->returnList; // link new node to top node
+                        // CAS resets header->kind.real.next = freeHead->returnList on failure
+                        while ( ! __atomic_compare_exchange_n( &freeHead->returnList, &header->kind.real.next, header,
+                                                                                                   false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST ) );
+                        #endif // RETURNSPIN
+
+                        #else                                                                           // no OWNERSHIP
+
+                        freeHead = &heap->freeLists[ClearStickyBits( header->kind.real.home ) - &freeHead->homeManager->freeLists[0]];
+                        header->kind.real.next = freeHead->freeList; // push on stack
+                        freeHead->freeList = (Heap.Storage *)header;
+                        #endif // ! OWNERSHIP
+
+                        #ifdef __U_STATISTICS__
+                        stats.return_pushes += 1;
+                        stats.return_storage_request += rsize;
+                        stats.return_storage_alloc += size;
+                        #endif // __U_STATISTICS__
+
+                        // OK TO BE PREEMPTED HERE AS heapManager IS NO LONGER ACCESSED.
+                } // if
         } // if
 
         #ifdef __CFA_DEBUG__
-        __atomic_add_fetch( &allocUnfreed, -size, __ATOMIC_SEQ_CST );
         if ( traceHeap() ) {
                 char helpText[64];
@@ -724 +1169 @@
         } // if
         #endif // __CFA_DEBUG__
+
+//      poll_interrupts();                                                                      // call rollforward
 } // doFree
 
 
-static size_t prtFree( Heap & manager ) with( manager ) {
+size_t prtFree( Heap & manager ) with( manager ) {
         size_t total = 0;
         #ifdef __STATISTICS__
@@ -733 +1180 @@
         __cfaabi_bits_print_nolock( STDERR_FILENO, "\nBin lists (bin size : free blocks on list)\n" );
         #endif // __STATISTICS__
-        for ( unsigned int i = 0; i < maxBucketsUsed; i += 1 ) {
+        for ( unsigned int i = 0; i < heapMaster.maxBucketsUsed; i += 1 ) {
                 size_t size = freeLists[i].blockSize;
                 #ifdef __STATISTICS__
@@ -764 +1211 @@
         __cfaabi_bits_release();
         #endif // __STATISTICS__
-        return (char *)heapEnd - (char *)heapBegin - total;
+        return (char *)heapMaster.heapEnd - (char *)heapMaster.heapBegin - total;
 } // prtFree
 
 
-static void ?{}( Heap & manager ) with( manager ) {
-        __page_size = sysconf( _SC_PAGESIZE );
-        __map_prot = PROT_READ | PROT_WRITE | PROT_EXEC;
-
-        for ( unsigned int i = 0; i < NoBucketSizes; i += 1 ) { // initialize the free lists
-                freeLists[i].blockSize = bucketSizes[i];
-        } // for
-
-        #ifdef FASTLOOKUP
-        unsigned int idx = 0;
-        for ( unsigned int i = 0; i < LookupSizes; i += 1 ) {
-                if ( i > bucketSizes[idx] ) idx += 1;
-                lookup[i] = idx;
-        } // for
-        #endif // FASTLOOKUP
-
-        if ( ! setMmapStart( malloc_mmap_start() ) ) {
-                abort( "Heap : internal error, mmap start initialization failure." );
-        } // if
-        heapExpand = malloc_expansion();
-
-        char * end = (char *)sbrk( 0 );
-        heapBegin = heapEnd = sbrk( (char *)ceiling2( (long unsigned int)end, __page_size ) - end ); // move start of heap to multiple of alignment
-} // Heap
-
-
-static void ^?{}( Heap & ) {
-        #ifdef __STATISTICS__
-        if ( traceHeapTerm() ) {
-                printStats();
-                // prtUnfreed() called in heapAppStop()
-        } // if
-        #endif // __STATISTICS__
-} // ~Heap
-
-
-static void memory_startup( void ) __attribute__(( constructor( STARTUP_PRIORITY_MEMORY ) ));
-void memory_startup( void ) {
-        #ifdef __CFA_DEBUG__
-        if ( heapBoot ) {                                                                       // check for recursion during system boot
-                abort( "boot() : internal error, recursively invoked during system boot." );
-        } // if
-        heapBoot = true;
-        #endif // __CFA_DEBUG__
-
-        //verify( heapManager.heapBegin != 0 );
-        //heapManager{};
-        if ( heapManager.heapBegin == 0p ) heapManager{};       // sanity check
-} // memory_startup
-
-static void memory_shutdown( void ) __attribute__(( destructor( STARTUP_PRIORITY_MEMORY ) ));
-void memory_shutdown( void ) {
-        ^heapManager{};
-} // memory_shutdown
-
-
-static inline void * mallocNoStats( size_t size ) {             // necessary for malloc statistics
-        verify( heapManager.heapBegin != 0p );                          // called before memory_startup ?
-  if ( unlikely( size ) == 0 ) return 0p;                               // 0 BYTE ALLOCATION RETURNS NULL POINTER
-
-#if __SIZEOF_POINTER__ == 8
-        verify( size < ((typeof(size_t))1 << 48) );
-#endif // __SIZEOF_POINTER__ == 8
-        return doMalloc( size );
-} // mallocNoStats
-
-
-static inline void * memalignNoStats( size_t alignment, size_t size ) {
-  if ( unlikely( size ) == 0 ) return 0p;                               // 0 BYTE ALLOCATION RETURNS NULL POINTER
-
-        #ifdef __CFA_DEBUG__
+#ifdef __STATISTICS__
+static void incCalls( intptr_t statName ) libcfa_nopreempt {
+        heapManager->stats.counters[statName].calls += 1;
+} // incCalls
+
+static void incZeroCalls( intptr_t statName ) libcfa_nopreempt {
+        heapManager->stats.counters[statName].calls_0 += 1;
+} // incZeroCalls
+#endif // __STATISTICS__
+
+#ifdef __CFA_DEBUG__
+static void incUnfreed( intptr_t offset ) libcfa_nopreempt {
+        heapManager->allocUnfreed += offset;
+} // incUnfreed
+#endif // __CFA_DEBUG__
+
+
+static void * memalignNoStats( size_t alignment, size_t size STAT_PARM ) {
         checkAlign( alignment );                                                        // check alignment
-        #endif // __CFA_DEBUG__
-
-        // if alignment <= default alignment, do normal malloc as two headers are unnecessary
-  if ( unlikely( alignment <= libAlign() ) ) return mallocNoStats( size );
+
+        // if alignment <= default alignment or size == 0, do normal malloc as two headers are unnecessary
+  if ( unlikely( alignment <= libAlign() || size == 0 ) ) return doMalloc( size STAT_ARG( STAT_NAME ) );
 
         // Allocate enough storage to guarantee an address on the alignment boundary, and sufficient space before it for
@@ -854 +1247 @@
         // subtract libAlign() because it is already the minimum alignment
         // add sizeof(Storage) for fake header
-        char * addr = (char *)mallocNoStats( size + alignment - libAlign() + sizeof(Heap.Storage) );
+        size_t offset = alignment - libAlign() + sizeof(Heap.Storage);
+        char * addr = (char *)doMalloc( size + offset STAT_ARG( STAT_NAME ) );
 
         // address in the block of the "next" alignment address
@@ -860 +1254 @@
 
         // address of header from malloc
-        Heap.Storage.Header * RealHeader = HeaderAddr( addr );
-        RealHeader->kind.real.size = size;                                      // correct size to eliminate above alignment offset
-        // address of fake header * before* the alignment location
+        Heap.Storage.Header * realHeader = HeaderAddr( addr );
+        realHeader->kind.real.size = size;                                      // correct size to eliminate above alignment offset
+        #ifdef __CFA_DEBUG__
+        incUnfreed( -offset );                                                          // adjustment off the offset from call to doMalloc
+        #endif // __CFA_DEBUG__
+
+        // address of fake header *before* the alignment location
         Heap.Storage.Header * fakeHeader = HeaderAddr( user );
+
         // SKULLDUGGERY: insert the offset to the start of the actual storage block and remember alignment
-        fakeHeader->kind.fake.offset = (char *)fakeHeader - (char *)RealHeader;
+        fakeHeader->kind.fake.offset = (char *)fakeHeader - (char *)realHeader;
         // SKULLDUGGERY: odd alignment implies fake header
         fakeHeader->kind.fake.alignment = MarkAlignmentBit( alignment );
@@ -880 +1279 @@
         // then malloc() returns a unique pointer value that can later be successfully passed to free().
         void * malloc( size_t size ) libcfa_public {
-                #ifdef __STATISTICS__
-                if ( likely( size > 0 ) ) {
-                        __atomic_add_fetch( &stats.malloc_calls, 1, __ATOMIC_SEQ_CST );
-                        __atomic_add_fetch( &stats.malloc_storage_request, size, __ATOMIC_SEQ_CST );
-                } else {
-                        __atomic_add_fetch( &stats.malloc_0_calls, 1, __ATOMIC_SEQ_CST );
-                } // if
-                #endif // __STATISTICS__
-
-                return mallocNoStats( size );
+                return doMalloc( size STAT_ARG( MALLOC ) );
         } // malloc
 
@@ -895 +1285 @@
         // Same as malloc() except size bytes is an array of dim elements each of elemSize bytes.
         void * aalloc( size_t dim, size_t elemSize ) libcfa_public {
-                size_t size = dim * elemSize;
-                #ifdef __STATISTICS__
-                if ( likely( size > 0 ) ) {
-                        __atomic_add_fetch( &stats.aalloc_calls, 1, __ATOMIC_SEQ_CST );
-                        __atomic_add_fetch( &stats.aalloc_storage_request, size, __ATOMIC_SEQ_CST );
-                } else {
-                        __atomic_add_fetch( &stats.aalloc_0_calls, 1, __ATOMIC_SEQ_CST );
-                } // if
-                #endif // __STATISTICS__
-
-                return mallocNoStats( size );
+                return doMalloc( dim * elemSize STAT_ARG( AALLOC ) );
         } // aalloc
 
@@ -912 +1292 @@
         void * calloc( size_t dim, size_t elemSize ) libcfa_public {
                 size_t size = dim * elemSize;
-          if ( unlikely( size ) == 0 ) {                        // 0 BYTE ALLOCATION RETURNS NULL POINTER
-                        #ifdef __STATISTICS__
-                        __atomic_add_fetch( &stats.calloc_0_calls, 1, __ATOMIC_SEQ_CST );
-                        #endif // __STATISTICS__
-                        return 0p;
-                } // if
-                #ifdef __STATISTICS__
-                __atomic_add_fetch( &stats.calloc_calls, 1, __ATOMIC_SEQ_CST );
-                __atomic_add_fetch( &stats.calloc_storage_request, dim * elemSize, __ATOMIC_SEQ_CST );
-                #endif // __STATISTICS__
-
-                char * addr = (char *)mallocNoStats( size );
+                char * addr = (char *)doMalloc( size STAT_ARG( CALLOC ) );
+
+          if ( unlikely( addr == NULL ) ) return NULL;          // stop further processing if 0p is returned
 
                 Heap.Storage.Header * header;
-                Heap.FreeHeader * freeElem;
+                Heap.FreeHeader * freeHead;
                 size_t bsize, alignment;
 
@@ -932 +1303 @@
                 bool mapped =
                         #endif // __CFA_DEBUG__
-                        headers( "calloc", addr, header, freeElem, bsize, alignment );
+                        headers( "calloc", addr, header, freeHead, bsize, alignment );
 
                 #ifndef __CFA_DEBUG__
                 // Mapped storage is zero filled, but in debug mode mapped memory is scrubbed in doMalloc, so it has to be reset to zero.
-                if ( ! mapped )
+                if ( likely( ! mapped ) )
                 #endif // __CFA_DEBUG__
                         // <-------0000000000000000000000000000UUUUUUUUUUUUUUUUUUUUUUUUU> bsize (bucket size) U => undefined
@@ -952 +1323 @@
         // call to malloc(), alloc(), calloc() or realloc(). If the area pointed to was moved, a free(oaddr) is done.
         void * resize( void * oaddr, size_t size ) libcfa_public {
-                // If size is equal to 0, either NULL or a pointer suitable to be passed to free() is returned.
-          if ( unlikely( size == 0 ) ) {                                        // special cases
-                        #ifdef __STATISTICS__
-                        __atomic_add_fetch( &stats.resize_0_calls, 1, __ATOMIC_SEQ_CST );
-                        #endif // __STATISTICS__
-                        free( oaddr );
-                        return 0p;
-                } // if
-                #ifdef __STATISTICS__
-                __atomic_add_fetch( &stats.resize_calls, 1, __ATOMIC_SEQ_CST );
-                #endif // __STATISTICS__
-
-          if ( unlikely( oaddr == 0p ) ) {
-                        #ifdef __STATISTICS__
-                        __atomic_add_fetch( &stats.resize_storage_request, size, __ATOMIC_SEQ_CST );
-                        #endif // __STATISTICS__
-                        return mallocNoStats( size );
-                } // if
+          if ( unlikely( oaddr == 0p ) ) {                              // => malloc( size )
+                        return doMalloc( size STAT_ARG( RESIZE ) );
+                } // if
+
+                PROLOG( RESIZE, doFree( oaddr ) );                              // => free( oaddr )
 
                 Heap.Storage.Header * header;
-                Heap.FreeHeader * freeElem;
+                Heap.FreeHeader * freeHead;
                 size_t bsize, oalign;
-                headers( "resize", oaddr, header, freeElem, bsize, oalign );
+                headers( "resize", oaddr, header, freeHead, bsize, oalign );
 
                 size_t odsize = DataStorage( bsize, oaddr, header ); // data storage available in bucket
@@ -980 +1338 @@
                 if ( oalign == libAlign() && size <= odsize && odsize <= size * 2 ) { // allow 50% wasted storage for smaller size
                         ClearZeroFillBit( header );                                     // no alignment and turn off 0 fill
+                        #ifdef __CFA_DEBUG__
+                        incUnfreed( size - header->kind.real.size ); // adjustment off the size difference
+                        #endif // __CFA_DEBUG__
                         header->kind.real.size = size;                          // reset allocation size
+                        #ifdef __STATISTICS__
+                        incCalls( RESIZE );
+                        #endif // __STATISTICS__
                         return oaddr;
                 } // if
 
-                #ifdef __STATISTICS__
-                __atomic_add_fetch( &stats.resize_storage_request, size, __ATOMIC_SEQ_CST );
-                #endif // __STATISTICS__
-
                 // change size, DO NOT preserve STICKY PROPERTIES.
-                free( oaddr );
-                return mallocNoStats( size );                                   // create new area
+                doFree( oaddr );                                                                // free previous storage
+
+                return doMalloc( size STAT_ARG( RESIZE ) );             // create new area
         } // resize
 
@@ -997 +1358 @@
         // the old and new sizes.
         void * realloc( void * oaddr, size_t size ) libcfa_public {
-                // If size is equal to 0, either NULL or a pointer suitable to be passed to free() is returned.
-          if ( unlikely( size == 0 ) ) {                                        // special cases
-                        #ifdef __STATISTICS__
-                        __atomic_add_fetch( &stats.realloc_0_calls, 1, __ATOMIC_SEQ_CST );
-                        #endif // __STATISTICS__
-                        free( oaddr );
-                        return 0p;
-                } // if
-                #ifdef __STATISTICS__
-                __atomic_add_fetch( &stats.realloc_calls, 1, __ATOMIC_SEQ_CST );
-                #endif // __STATISTICS__
-
-          if ( unlikely( oaddr == 0p ) ) {
-                        #ifdef __STATISTICS__
-                        __atomic_add_fetch( &stats.realloc_storage_request, size, __ATOMIC_SEQ_CST );
-                        #endif // __STATISTICS__
-                        return mallocNoStats( size );
-                } // if
+          if ( unlikely( oaddr == 0p ) ) {                                      // => malloc( size )
+                  return doMalloc( size STAT_ARG( REALLOC ) );
+                } // if
+
+                PROLOG( REALLOC, doFree( oaddr ) );                             // => free( oaddr )
 
                 Heap.Storage.Header * header;
-                Heap.FreeHeader * freeElem;
+                Heap.FreeHeader * freeHead;
                 size_t bsize, oalign;
-                headers( "realloc", oaddr, header, freeElem, bsize, oalign );
+                headers( "realloc", oaddr, header, freeHead, bsize, oalign );
 
                 size_t odsize = DataStorage( bsize, oaddr, header ); // data storage available in bucket
@@ -1025 +1373 @@
                 bool ozfill = ZeroFillBit( header );                    // old allocation zero filled
           if ( unlikely( size <= odsize ) && odsize <= size * 2 ) { // allow up to 50% wasted storage
-                        header->kind.real.size = size;                          // reset allocation size
+                        #ifdef __CFA_DEBUG__
+                        incUnfreed( size - header->kind.real.size ); // adjustment off the size difference
+                        #endif // __CFA_DEBUG__
+                        header->kind.real.size = size;                          // reset allocation size
                         if ( unlikely( ozfill ) && size > osize ) {     // previous request zero fill and larger ?
                                 memset( (char *)oaddr + osize, '\0', size - osize ); // initialize added storage
                         } // if
+                        #ifdef __STATISTICS__
+                        incCalls( REALLOC );
+                        #endif // __STATISTICS__
                         return oaddr;
                 } // if
 
-                #ifdef __STATISTICS__
-                __atomic_add_fetch( &stats.realloc_storage_request, size, __ATOMIC_SEQ_CST );
-                #endif // __STATISTICS__
-
                 // change size and copy old content to new storage
 
                 void * naddr;
-                if ( likely( oalign == libAlign() ) ) {                 // previous request not aligned ?
-                        naddr = mallocNoStats( size );                          // create new area
+                if ( likely( oalign <= libAlign() ) ) {                 // previous request not aligned ?
+                        naddr = doMalloc( size STAT_ARG( REALLOC ) ); // create new area
                 } else {
-                        naddr = memalignNoStats( oalign, size );        // create new aligned area
-                } // if
-
-                headers( "realloc", naddr, header, freeElem, bsize, oalign );
+                        naddr = memalignNoStats( oalign, size STAT_ARG( REALLOC ) ); // create new aligned area
+                } // if
+
+                headers( "realloc", naddr, header, freeHead, bsize, oalign );
+                // To preserve prior fill, the entire bucket must be copied versus the size.
                 memcpy( naddr, oaddr, min( osize, size ) );             // copy bytes
-                free( oaddr );
+                doFree( oaddr );                                                                // free previous storage
 
                 if ( unlikely( ozfill ) ) {                                             // previous request zero fill ?
@@ -1067 +1418 @@
         // Same as malloc() except the memory address is a multiple of alignment, which must be a power of two. (obsolete)
         void * memalign( size_t alignment, size_t size ) libcfa_public {
-                #ifdef __STATISTICS__
-                if ( likely( size > 0 ) ) {
-                        __atomic_add_fetch( &stats.memalign_calls, 1, __ATOMIC_SEQ_CST );
-                        __atomic_add_fetch( &stats.memalign_storage_request, size, __ATOMIC_SEQ_CST );
-                } else {
-                        __atomic_add_fetch( &stats.memalign_0_calls, 1, __ATOMIC_SEQ_CST );
-                } // if
-                #endif // __STATISTICS__
-
-                return memalignNoStats( alignment, size );
+                return memalignNoStats( alignment, size STAT_ARG( MEMALIGN ) );
         } // memalign
 
@@ -1082 +1424 @@
         // Same as aalloc() with memory alignment.
         void * amemalign( size_t alignment, size_t dim, size_t elemSize ) libcfa_public {
-                size_t size = dim * elemSize;
-                #ifdef __STATISTICS__
-                if ( likely( size > 0 ) ) {
-                        __atomic_add_fetch( &stats.cmemalign_calls, 1, __ATOMIC_SEQ_CST );
-                        __atomic_add_fetch( &stats.cmemalign_storage_request, size, __ATOMIC_SEQ_CST );
-                } else {
-                        __atomic_add_fetch( &stats.cmemalign_0_calls, 1, __ATOMIC_SEQ_CST );
-                } // if
-                #endif // __STATISTICS__
-
-                return memalignNoStats( alignment, size );
+                return memalignNoStats( alignment, dim * elemSize STAT_ARG( AMEMALIGN ) );
         } // amemalign
 
@@ -1099 +1431 @@
         void * cmemalign( size_t alignment, size_t dim, size_t elemSize ) libcfa_public {
                 size_t size = dim * elemSize;
-          if ( unlikely( size ) == 0 ) {                                        // 0 BYTE ALLOCATION RETURNS NULL POINTER
-                        #ifdef __STATISTICS__
-                        __atomic_add_fetch( &stats.cmemalign_0_calls, 1, __ATOMIC_SEQ_CST );
-                        #endif // __STATISTICS__
-                        return 0p;
-                } // if
-                #ifdef __STATISTICS__
-                __atomic_add_fetch( &stats.cmemalign_calls, 1, __ATOMIC_SEQ_CST );
-                __atomic_add_fetch( &stats.cmemalign_storage_request, dim * elemSize, __ATOMIC_SEQ_CST );
-                #endif // __STATISTICS__
-
-                char * addr = (char *)memalignNoStats( alignment, size );
+                char * addr = (char *)memalignNoStats( alignment, size STAT_ARG( CMEMALIGN ) );
+
+          if ( unlikely( addr == NULL ) ) return NULL;          // stop further processing if 0p is returned
 
                 Heap.Storage.Header * header;
-                Heap.FreeHeader * freeElem;
+                Heap.FreeHeader * freeHead;
                 size_t bsize;
 
@@ -1119 +1442 @@
                 bool mapped =
                         #endif // __CFA_DEBUG__
-                        headers( "cmemalign", addr, header, freeElem, bsize, alignment );
+                        headers( "cmemalign", addr, header, freeHead, bsize, alignment );
 
                 // Mapped storage is zero filled, but in debug mode mapped memory is scrubbed in doMalloc, so it has to be reset to zero.
@@ -1169 +1492 @@
         // 0p, no operation is performed.
         void free( void * addr ) libcfa_public {
+//              verify( heapManager );
+
           if ( unlikely( addr == 0p ) ) {                                       // special case
                         #ifdef __STATISTICS__
-                        __atomic_add_fetch( &stats.free_null_calls, 1, __ATOMIC_SEQ_CST );
+                  if ( heapManager )
+                        incZeroCalls( FREE );
                         #endif // __STATISTICS__
-
-                        // #ifdef __CFA_DEBUG__
-                        // if ( traceHeap() ) {
-                        //      #define nullmsg "Free( 0x0 ) size:0\n"
-                        //      // Do not debug print free( 0p ), as it can cause recursive entry from sprintf.
-                        //      __cfaabi_dbg_write( nullmsg, sizeof(nullmsg) - 1 );
-                        // } // if
-                        // #endif // __CFA_DEBUG__
                         return;
-                } // exit
-
-                doFree( addr );
+                } // if
+
+                #ifdef __STATISTICS__
+                incCalls( FREE );
+                #endif // __STATISTICS__
+
+                doFree( addr );                                                                 // handles heapManager == nullptr
         } // free
 
@@ -1227 +1549 @@
           if ( unlikely( addr == 0p ) ) return 0;                       // null allocation has 0 size
                 Heap.Storage.Header * header;
-                Heap.FreeHeader * freeElem;
+                Heap.FreeHeader * freeHead;
                 size_t bsize, alignment;
 
-                headers( "malloc_usable_size", addr, header, freeElem, bsize, alignment );
+                headers( "malloc_usable_size", addr, header, freeHead, bsize, alignment );
                 return DataStorage( bsize, addr, header );              // data storage in bucket
         } // malloc_usable_size
@@ -1238 +1560 @@
         void malloc_stats( void ) libcfa_public {
                 #ifdef __STATISTICS__
-                printStats();
-                if ( prtFree() ) prtFree( heapManager );
+                HeapStatistics stats;
+                HeapStatisticsCtor( stats );
+                if ( printStats( collectStats( stats ) ) == -1 ) {
+                #else
+                #define MALLOC_STATS_MSG "malloc_stats statistics disabled.\n"
+                if ( write( STDERR_FILENO, MALLOC_STATS_MSG, sizeof( MALLOC_STATS_MSG ) - 1 /* size includes '\0' */ ) == -1 ) {
                 #endif // __STATISTICS__
+                        abort( "**** Error **** write failed in malloc_stats" );
+                } // if
         } // malloc_stats
 
@@ -1247 +1575 @@
         int malloc_stats_fd( int fd __attribute__(( unused )) ) libcfa_public {
                 #ifdef __STATISTICS__
-                int temp = stats_fd;
-                stats_fd = fd;
+                int temp = heapMaster.stats_fd;
+                heapMaster.stats_fd = fd;
                 return temp;
                 #else
@@ -1262 +1590 @@
           if ( options != 0 ) { errno = EINVAL; return -1; }
                 #ifdef __STATISTICS__
-                return printStatsXML( stream );
+                HeapStatistics stats;
+                HeapStatisticsCtor( stats );
+                return printStatsXML( collectStats( stats ), stream ); // returns bytes written or -1
                 #else
                 return 0;                                                                               // unsupported
@@ -1275 +1605 @@
                 choose( option ) {
                   case M_TOP_PAD:
-                        heapExpand = ceiling2( value, __page_size );
+                        heapMaster.heapExpand = ceiling2( value, __page_size );
                         return 1;
                   case M_MMAP_THRESHOLD:
@@ -1319 +1649 @@
 // Must have CFA linkage to overload with C linkage realloc.
 void * resize( void * oaddr, size_t nalign, size_t size ) libcfa_public {
-        // If size is equal to 0, either NULL or a pointer suitable to be passed to free() is returned.
-  if ( unlikely( size == 0 ) ) {                                                // special cases
-                #ifdef __STATISTICS__
-                __atomic_add_fetch( &stats.resize_0_calls, 1, __ATOMIC_SEQ_CST );
-                #endif // __STATISTICS__
-                free( oaddr );
-                return 0p;
+  if ( unlikely( oaddr == 0p ) ) {                                              // => malloc( size )
+                return memalignNoStats( nalign, size STAT_ARG( RESIZE ) );
         } // if
 
-        if ( unlikely( nalign < libAlign() ) ) nalign = libAlign(); // reset alignment to minimum
-        #ifdef __CFA_DEBUG__
-        else checkAlign( nalign );                                                      // check alignment
-        #endif // __CFA_DEBUG__
-
-  if ( unlikely( oaddr == 0p ) ) {
-                #ifdef __STATISTICS__
-                __atomic_add_fetch( &stats.resize_calls, 1, __ATOMIC_SEQ_CST );
-                __atomic_add_fetch( &stats.resize_storage_request, size, __ATOMIC_SEQ_CST );
-                #endif // __STATISTICS__
-                return memalignNoStats( nalign, size );
-        } // if
+        PROLOG( RESIZE, doFree( oaddr ) );                                      // => free( oaddr )
 
         // Attempt to reuse existing alignment.
@@ -1347 +1661 @@
 
         if ( unlikely( isFakeHeader ) ) {
+                checkAlign( nalign );                                                   // check alignment
                 oalign = ClearAlignmentBit( header );                   // old alignment
                 if ( unlikely( (uintptr_t)oaddr % nalign == 0   // lucky match ?
@@ -1353 +1668 @@
                         ) ) {
                         HeaderAddr( oaddr )->kind.fake.alignment = MarkAlignmentBit( nalign ); // update alignment (could be the same)
-                        Heap.FreeHeader * freeElem;
+                        Heap.FreeHeader * freeHead;
                         size_t bsize, oalign;
-                        headers( "resize", oaddr, header, freeElem, bsize, oalign );
+                        headers( "resize", oaddr, header, freeHead, bsize, oalign );
                         size_t odsize = DataStorage( bsize, oaddr, header ); // data storage available in bucket
 
@@ -1361 +1676 @@
                                 HeaderAddr( oaddr )->kind.fake.alignment = MarkAlignmentBit( nalign ); // update alignment (could be the same)
                                 ClearZeroFillBit( header );                             // turn off 0 fill
+                                #ifdef __CFA_DEBUG__
+                                incUnfreed( size - header->kind.real.size ); // adjustment off the size difference
+                                #endif // __CFA_DEBUG__
                                 header->kind.real.size = size;                  // reset allocation size
+                                #ifdef __STATISTICS__
+                                incCalls( RESIZE );
+                                #endif // __STATISTICS__
                                 return oaddr;
                         } // if
@@ -1370 +1691 @@
         } // if
 
-        #ifdef __STATISTICS__
-        __atomic_add_fetch( &stats.resize_storage_request, size, __ATOMIC_SEQ_CST );
-        #endif // __STATISTICS__
-
         // change size, DO NOT preserve STICKY PROPERTIES.
-        free( oaddr );
-        return memalignNoStats( nalign, size );                         // create new aligned area
+        doFree( oaddr );                                                                        // free previous storage
+        return memalignNoStats( nalign, size STAT_ARG( RESIZE ) ); // create new aligned area
 } // resize
 
 
 void * realloc( void * oaddr, size_t nalign, size_t size ) libcfa_public {
-        // If size is equal to 0, either NULL or a pointer suitable to be passed to free() is returned.
-  if ( unlikely( size == 0 ) ) {                                                // special cases
-                #ifdef __STATISTICS__
-                __atomic_add_fetch( &stats.realloc_0_calls, 1, __ATOMIC_SEQ_CST );
-                #endif // __STATISTICS__
-                free( oaddr );
-                return 0p;
+  if ( unlikely( oaddr == 0p ) ) {                                              // => malloc( size )
+                return memalignNoStats( nalign, size STAT_ARG( REALLOC ) );
         } // if
 
-        if ( unlikely( nalign < libAlign() ) ) nalign = libAlign(); // reset alignment to minimum
-        #ifdef __CFA_DEBUG__
-        else checkAlign( nalign );                                                      // check alignment
-        #endif // __CFA_DEBUG__
-
-  if ( unlikely( oaddr == 0p ) ) {
-                #ifdef __STATISTICS__
-                __atomic_add_fetch( &stats.realloc_calls, 1, __ATOMIC_SEQ_CST );
-                __atomic_add_fetch( &stats.realloc_storage_request, size, __ATOMIC_SEQ_CST );
-                #endif // __STATISTICS__
-                return memalignNoStats( nalign, size );
-        } // if
+        PROLOG( REALLOC, doFree( oaddr ) );                                     // => free( oaddr )
 
         // Attempt to reuse existing alignment.
@@ -1408 +1709 @@
         size_t oalign;
         if ( unlikely( isFakeHeader ) ) {
+                checkAlign( nalign );                                                   // check alignment
                 oalign = ClearAlignmentBit( header );                   // old alignment
                 if ( unlikely( (uintptr_t)oaddr % nalign == 0   // lucky match ?
@@ -1421 +1723 @@
         } // if
 
-        #ifdef __STATISTICS__
-        __atomic_add_fetch( &stats.realloc_calls, 1, __ATOMIC_SEQ_CST );
-        __atomic_add_fetch( &stats.realloc_storage_request, size, __ATOMIC_SEQ_CST );
-        #endif // __STATISTICS__
-
-        Heap.FreeHeader * freeElem;
+        Heap.FreeHeader * freeHead;
         size_t bsize;
-        headers( "realloc", oaddr, header, freeElem, bsize, oalign );
+        headers( "realloc", oaddr, header, freeHead, bsize, oalign );
 
         // change size and copy old content to new storage
@@ -1435 +1732 @@
         bool ozfill = ZeroFillBit( header );                            // old allocation zero filled
 
-        void * naddr = memalignNoStats( nalign, size );         // create new aligned area
-
-        headers( "realloc", naddr, header, freeElem, bsize, oalign );
+        void * naddr = memalignNoStats( nalign, size STAT_ARG( REALLOC ) ); // create new aligned area
+
+        headers( "realloc", naddr, header, freeHead, bsize, oalign );
         memcpy( naddr, oaddr, min( osize, size ) );                     // copy bytes
-        free( oaddr );
+        doFree( oaddr );                                                                        // free previous storage
 
         if ( unlikely( ozfill ) ) {                                                     // previous request zero fill ?
@@ -1451 +1748 @@
 
 
+void * reallocarray( void * oaddr, size_t nalign, size_t dim, size_t elemSize ) __THROW {
+        return realloc( oaddr, nalign, dim * elemSize );
+} // reallocarray
+
+
 // Local Variables: //
 // tab-width: 4 //