AtomicGameEngine/Source/ThirdParty/embree/kernels/common/alloc.h

// ======================================================================== //
// Copyright 2009-2017 Intel Corporation                                    //
//                                                                          //
// Licensed under the Apache License, Version 2.0 (the "License");          //
// you may not use this file except in compliance with the License.         //
// You may obtain a copy of the License at                                  //
//                                                                          //
//     http://www.apache.org/licenses/LICENSE-2.0                           //
//                                                                          //
// Unless required by applicable law or agreed to in writing, software      //
// distributed under the License is distributed on an "AS IS" BASIS,        //
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. //
// See the License for the specific language governing permissions and      //
// limitations under the License.                                           //
// ======================================================================== //

#pragma once

#include "default.h"
#include "device.h"

namespace embree
{
  class FastAllocator 
  {
    /*! maximal supported alignment */
    static const size_t maxAlignment = 64;

    /*! maximal allocation size */

    /* default settings */
    //static const size_t defaultBlockSize = 4096;
#define maxAllocationSize size_t(4*1024*1024-maxAlignment)
    static const size_t MAX_THREAD_USED_BLOCK_SLOTS = 8;
    
  public:

    enum AllocationType { ALIGNED_MALLOC, OS_MALLOC, SHARED };

    /*! Per thread structure holding the current memory block. */
    struct __aligned(64) ThreadLocal 
    {
      ALIGNED_CLASS_(64);
    public:

      __forceinline ThreadLocal() {}

      /*! Constructor for usage with ThreadLocalData */
      __forceinline ThreadLocal (FastAllocator* alloc) 
	: alloc(alloc), ptr(nullptr), cur(0), end(0), allocBlockSize(((FastAllocator*)alloc)->defaultBlockSize), bytesUsed(0), bytesWasted(0) {}

      /*! resets the allocator */
      __forceinline void reset() 
      {
	ptr = nullptr;
	cur = end = 0;
	bytesWasted = bytesUsed = 0;
      }

      /* Allocate aligned memory from the threads memory block. */
      __forceinline void* operator() (size_t bytes, size_t align = 16) {
        return malloc(bytes,align);
      }

      /* Allocate aligned memory from the threads memory block. */
      __forceinline void* malloc(size_t bytes, size_t align = 16) 
      {
        assert(align <= maxAlignment);
	bytesUsed += bytes;
	
        /* try to allocate in local block */
	size_t ofs = (align - cur) & (align-1); 
        cur += bytes + ofs;
        if (likely(cur <= end)) { bytesWasted += ofs; return &ptr[cur - bytes]; }
	cur -= bytes + ofs;

        /* if allocation is too large allocate with parent allocator */
        if (4*bytes > allocBlockSize) {
          return alloc->malloc(bytes,maxAlignment,false);
	}

        /* get new partial block if allocation failed */
        size_t blockSize = allocBlockSize;
        ptr = (char*) alloc->malloc(blockSize,maxAlignment,true);
 	bytesWasted += end-cur;
	cur = 0; end = blockSize;
	
        /* retry allocation */
	ofs = (align - cur) & (align-1); 
        cur += bytes + ofs;
        if (likely(cur <= end)) { bytesWasted += ofs; return &ptr[cur - bytes]; }
	cur -= bytes + ofs;

        /* get new full block if allocation failed */
        blockSize = allocBlockSize;
        ptr = (char*) alloc->malloc(blockSize,maxAlignment,false);
	bytesWasted += end-cur;
	cur = 0; end = blockSize;
	
        /* retry allocation */
	ofs = (align - cur) & (align-1); 
        cur += bytes + ofs;
        if (likely(cur <= end)) { bytesWasted += ofs; return &ptr[cur - bytes]; }
	cur -= bytes + ofs;
	
        /* should never happen as large allocations get handled specially above */
        assert(false);
        return nullptr;
      }

      /*! returns amount of used bytes */
      size_t getUsedBytes() const { return bytesUsed; }
      
      /*! returns amount of wasted bytes */
      size_t getWastedBytes() const { return bytesWasted + (end-cur); }

    public:
      FastAllocator* alloc;  //!< parent allocator
      char*  ptr;            //!< pointer to memory block
      size_t cur;            //!< current location of the allocator
      size_t end;            //!< end of the memory block
      size_t allocBlockSize; //!< block size for allocations
    private:
      size_t bytesUsed;      //!< number of total bytes allocated
      size_t bytesWasted;    //!< number of bytes wasted
    };

    /*! Two thread local structures. */
    struct __aligned(64) ThreadLocal2
    {
      ALIGNED_STRUCT;

      /*! Constructor for usage with ThreadLocalData */
      __forceinline ThreadLocal2 (FastAllocator* alloc) 
      {
        allocators[0] = ThreadLocal(alloc); alloc0 = &allocators[0];
        allocators[1] = ThreadLocal(alloc); alloc1 = &allocators[1];
        if (alloc->use_single_mode) alloc1 = &allocators[0];
      }
      
      /*! resets the allocator */
      __forceinline void reset() {
        allocators[0].reset();
        allocators[1].reset();
      }

      /*! returns amount of used bytes */
      size_t getUsedBytes() const { return allocators[0].getUsedBytes() + allocators[1].getUsedBytes(); }
      
      /*! returns amount of wasted bytes */
      size_t getWastedBytes() const { return allocators[0].getWastedBytes() + allocators[1].getWastedBytes(); }
    
    public:  
      ThreadLocal* alloc0;
      ThreadLocal* alloc1;

    private:
      ThreadLocal allocators[2];
    };

    /*! Builder interface to create thread local allocator */
    struct CreateAlloc2
    {
    public:
      __forceinline CreateAlloc2 (FastAllocator* allocator) : allocator(allocator) {}
      __forceinline ThreadLocal2* operator() () const { return allocator->threadLocal2();  }

    private:
      FastAllocator* allocator;
    };

    FastAllocator (Device* device, bool osAllocation) 
      : device(device), slotMask(0), usedBlocks(nullptr), freeBlocks(nullptr), use_single_mode(false), defaultBlockSize(PAGE_SIZE), 
        growSize(PAGE_SIZE), log2_grow_size_scale(0), bytesUsed(0), bytesWasted(0), thread_local_allocators2(this), atype(osAllocation ? OS_MALLOC : ALIGNED_MALLOC)
    {
      for (size_t i=0; i<MAX_THREAD_USED_BLOCK_SLOTS; i++)
      {
        threadUsedBlocks[i] = nullptr;
        threadBlocks[i] = nullptr;
        assert(!slotMutex[i].isLocked());
      }
    } 

    ~FastAllocator () { 
      clear();
    }

    /*! returns the device attached to this allocator */
    Device* getDevice() {
      return device;
    }

    /*! returns first fast thread local allocator */
    __forceinline ThreadLocal* threadLocal() {
      return thread_local_allocators2.get()->alloc0;
    }

    /*! returns both fast thread local allocators */
    __forceinline ThreadLocal2* threadLocal2() {
      return thread_local_allocators2.get();
    }

   /*! initializes the grow size */
    __forceinline void initGrowSizeAndNumSlots(size_t bytesAllocate, size_t bytesReserve = 0) 
    {
      if (bytesReserve == 0) bytesReserve = bytesAllocate;

      bytesReserve  = ((bytesReserve +PAGE_SIZE-1) & ~(PAGE_SIZE-1)); // always consume full pages
      
      growSize = clamp(bytesReserve,size_t(PAGE_SIZE),maxAllocationSize); // PAGE_SIZE -maxAlignment ?
      log2_grow_size_scale = 0;
      slotMask = 0x0;
      if (MAX_THREAD_USED_BLOCK_SLOTS >= 2 && bytesAllocate >  4*maxAllocationSize) slotMask = 0x1;
      if (MAX_THREAD_USED_BLOCK_SLOTS >= 4 && bytesAllocate >  8*maxAllocationSize) slotMask = 0x3;
      if (MAX_THREAD_USED_BLOCK_SLOTS >= 8 && bytesAllocate > 16*maxAllocationSize) slotMask = 0x7;
    }

    void internal_fix_used_blocks()
    {
      /* move thread local blocks to global block list */
      for (size_t i = 0; i < MAX_THREAD_USED_BLOCK_SLOTS; i++)
      {
        while (threadBlocks[i].load() != nullptr) {
          Block* nextUsedBlock = threadBlocks[i].load()->next;
          threadBlocks[i].load()->next = usedBlocks.load();
          usedBlocks = threadBlocks[i].load();
          threadBlocks[i] = nextUsedBlock;
        }
        threadBlocks[i] = nullptr;
      }
    }

    /*! initializes the allocator */
    void init(size_t bytesAllocate, size_t bytesReserve = 0) 
    {     
      internal_fix_used_blocks();
      /* distribute the allocation to multiple thread block slots */
      slotMask = MAX_THREAD_USED_BLOCK_SLOTS-1;      
      if (usedBlocks.load() || freeBlocks.load()) { reset(); return; }
      if (bytesReserve == 0) bytesReserve = bytesAllocate;
      freeBlocks = Block::create(device,bytesAllocate,bytesReserve,nullptr,atype);
      defaultBlockSize = clamp(bytesAllocate/4,size_t(128),size_t(PAGE_SIZE+maxAlignment)); 
      initGrowSizeAndNumSlots(bytesAllocate,bytesReserve);
    }

    /*! initializes the allocator */
    void init_estimate(size_t bytesAllocate, const bool single_mode = false) 
    {      
      internal_fix_used_blocks();
      if (usedBlocks.load() || freeBlocks.load()) { reset(); return; }
      /* single allocator mode ? */
      use_single_mode = single_mode; 
      defaultBlockSize = clamp(bytesAllocate/4,size_t(128),size_t(PAGE_SIZE+maxAlignment)); 
      /* if in memory conservative single_mode, reduce bytesAllocate/growSize by 2 */
      initGrowSizeAndNumSlots(single_mode == false ? bytesAllocate : bytesAllocate/2);
    }

    /*! frees state not required after build */
    __forceinline void cleanup() 
    {
      internal_fix_used_blocks();
      
      for (size_t t=0; t<thread_local_allocators2.threads.size(); t++) {
	bytesUsed += thread_local_allocators2.threads[t]->getUsedBytes();
        bytesWasted += thread_local_allocators2.threads[t]->getWastedBytes();
      }

      thread_local_allocators2.clear();
    }

    /*! shrinks all memory blocks to the actually used size */
    void shrink () 
    {
      for (size_t i=0; i<MAX_THREAD_USED_BLOCK_SLOTS; i++)
        if (threadUsedBlocks[i].load() != nullptr) threadUsedBlocks[i].load()->shrink_list(device);
      if (usedBlocks.load() != nullptr) usedBlocks.load()->shrink_list(device);
      if (freeBlocks.load() != nullptr) freeBlocks.load()->clear_list(device); freeBlocks = nullptr;
    }

    /*! resets the allocator, memory blocks get reused */
    void reset () 
    {
      internal_fix_used_blocks();

      bytesUsed = 0;
      bytesWasted = 0;

      /* first reset all used blocks */
      if (usedBlocks.load() != nullptr) usedBlocks.load()->reset_list();
      
      /* move all used blocks to begin of free block list */
      while (usedBlocks.load() != nullptr) {
        Block* nextUsedBlock = usedBlocks.load()->next;
        usedBlocks.load()->next = freeBlocks.load();
        freeBlocks = usedBlocks.load();
        usedBlocks = nextUsedBlock;
      }

      for (size_t i=0; i<MAX_THREAD_USED_BLOCK_SLOTS; i++) 
      {
        threadUsedBlocks[i] = nullptr;
        threadBlocks[i] = nullptr;
      }
      
      /* reset all thread local allocators */
      thread_local_allocators2.apply([] (ThreadLocal2* alloc) { alloc->reset(); });
    }

    /*! frees all allocated memory */
    __forceinline void clear()
    {
      cleanup();
      bytesUsed = 0;
      bytesWasted = 0;
      if (usedBlocks.load() != nullptr) usedBlocks.load()->clear_list(device); usedBlocks = nullptr;
      if (freeBlocks.load() != nullptr) freeBlocks.load()->clear_list(device); freeBlocks = nullptr;
      for (size_t i=0; i<MAX_THREAD_USED_BLOCK_SLOTS; i++) {
        threadUsedBlocks[i] = nullptr;
        threadBlocks[i] = nullptr;
      }
    }

    __forceinline size_t incGrowSizeScale()
    {
      size_t scale = log2_grow_size_scale.fetch_add(1)+1;
      return size_t(1) << min(size_t(16),scale);
    }

    /*! thread safe allocation of memory */
    void* malloc(size_t& bytes, size_t align, bool partial) 
    {
      assert(align <= maxAlignment);

      while (true) 
      {
        /* allocate using current block */
        size_t threadIndex = TaskScheduler::threadIndex();
        size_t slot = threadIndex & slotMask;
	Block* myUsedBlocks = threadUsedBlocks[slot];
        if (myUsedBlocks) {
          void* ptr = myUsedBlocks->malloc(device,bytes,align,partial); 
          if (ptr) return ptr;
        }
        
        /* throw error if allocation is too large */
        if (bytes > maxAllocationSize)
          throw_RTCError(RTC_UNKNOWN_ERROR,"allocation is too large");

        /* parallel block creation in case of no freeBlocks, avoids single global mutex */
        if (likely(freeBlocks.load() == nullptr)) 
        {
          Lock<SpinLock> lock(slotMutex[slot]);
          if (myUsedBlocks == threadUsedBlocks[slot]) {
            const size_t allocSize = min(max(growSize,bytes),size_t(maxAllocationSize));
            assert(allocSize >= bytes);
            threadBlocks[slot] = threadUsedBlocks[slot] = Block::create(device,allocSize,allocSize,threadBlocks[slot],atype);
          }
          continue;
        }        

        /* if this fails allocate new block */
        {
          Lock<SpinLock> lock(mutex);
	  if (myUsedBlocks == threadUsedBlocks[slot])
	  {
            if (freeBlocks.load() != nullptr) {
	      Block* nextFreeBlock = freeBlocks.load()->next;
	      freeBlocks.load()->next = usedBlocks;
	      __memory_barrier();
	      usedBlocks = freeBlocks.load();
              threadUsedBlocks[slot] = freeBlocks.load();
	      freeBlocks = nextFreeBlock;
	    } else {
	      //growSize = min(2*growSize,size_t(maxAllocationSize+maxAlignment));
              const size_t allocSize = min(growSize * incGrowSizeScale(),size_t(maxAllocationSize+maxAlignment))-maxAlignment;
	      usedBlocks = threadUsedBlocks[slot] = Block::create(device,allocSize,allocSize,usedBlocks,atype);
	    }
	  }
        }
      }
    }

    /*! add new block */
    void addBlock(void* ptr, ssize_t bytes)
    {
      Lock<SpinLock> lock(mutex);
      const size_t sizeof_Header = offsetof(Block,data[0]);
      void* aptr = (void*) ((((size_t)ptr)+maxAlignment-1) & ~(maxAlignment-1));
      size_t ofs = (size_t) aptr - (size_t) ptr;
      bytes -= ofs;
      if (bytes < 4096) return; // ignore empty or very small blocks
      freeBlocks = new (aptr) Block(SHARED,bytes-sizeof_Header,bytes-sizeof_Header,freeBlocks,ofs);
    }

    /* special allocation only used from morton builder only a single time for each build */
    void* specialAlloc(size_t bytes) 
    {
      assert(freeBlocks.load() != nullptr && freeBlocks.load()->getBlockAllocatedBytes() >= bytes);
      return freeBlocks.load()->ptr();
    }

    size_t getAllocatedBytes() const 
    {
      size_t bytesAllocated = 0;
      if (freeBlocks.load()) bytesAllocated += freeBlocks.load()->getAllocatedBytes();
      if (usedBlocks.load()) bytesAllocated += usedBlocks.load()->getAllocatedBytes();
      return bytesAllocated;
    }

    size_t getReservedBytes() const 
    {
      size_t bytesReserved = 0;
      if (freeBlocks.load()) bytesReserved += freeBlocks.load()->getReservedBytes();
      if (usedBlocks.load()) bytesReserved += usedBlocks.load()->getReservedBytes();
      return bytesReserved;
    }

    size_t getUsedBytes() const 
    {
      size_t bytes = bytesUsed;

      for (size_t t=0; t<thread_local_allocators2.threads.size(); t++)
	bytes += thread_local_allocators2.threads[t]->getUsedBytes();

      return bytes;
    }

    size_t getFreeBytes() const 
    {
      size_t bytesFree = 0;
      if (freeBlocks.load()) bytesFree += freeBlocks.load()->getAllocatedBytes();
      return bytesFree;
    }

    size_t getWastedBytes() const 
    {
      size_t bytes = bytesWasted;
      if (usedBlocks.load()) bytes += usedBlocks.load()->getFreeBytes();

      for (size_t t=0; t<thread_local_allocators2.threads.size(); t++)
	bytes += thread_local_allocators2.threads[t]->getWastedBytes();
      
      return bytes;
    }

    void print_statistics(bool verbose = false)
    {
      size_t bytesFree = getFreeBytes();
      size_t bytesAllocated = getAllocatedBytes();
      size_t bytesReserved = getReservedBytes();
      size_t bytesUsed = getUsedBytes();
      size_t bytesWasted = getWastedBytes();
      printf("  allocated = %3.3fMB, reserved = %3.3fMB, used = %3.3fMB (%3.2f%%), wasted = %3.3fMB (%3.2f%%), free = %3.3fMB (%3.2f%%)\n",
	     1E-6f*bytesAllocated, 1E-6f*bytesReserved,
	     1E-6f*bytesUsed, 100.0f*bytesUsed/bytesAllocated,
	     1E-6f*bytesWasted, 100.0f*bytesWasted/bytesAllocated,
	     1E-6f*bytesFree, 100.0f*bytesFree/bytesAllocated);
      
      if (verbose) 
      {
        std::cout << "  slotMask = " << slotMask << std::endl;
        std::cout << "  use_single_mode = " << use_single_mode << std::endl;
        std::cout << "  defaultBlockSize = " << defaultBlockSize << std::endl;
        std::cout << "  used blocks = ";
        if (usedBlocks.load() != nullptr) usedBlocks.load()->print_list();
        std::cout << "[END]" << std::endl;
        
        std::cout << "  free blocks = ";
        if (freeBlocks.load() != nullptr) freeBlocks.load()->print_list();
        std::cout << "[END]" << std::endl;
      }
    }

  private:

    struct Block 
    {
      static Block* create(MemoryMonitorInterface* device, size_t bytesAllocate, size_t bytesReserve, Block* next, AllocationType atype)
      {
        const size_t sizeof_Header = offsetof(Block,data[0]);
        bytesAllocate = ((sizeof_Header+bytesAllocate+PAGE_SIZE-1) & ~(PAGE_SIZE-1)); // always consume full pages
        bytesReserve  = ((sizeof_Header+bytesReserve +PAGE_SIZE-1) & ~(PAGE_SIZE-1)); // always consume full pages
       
        /* either use alignedMalloc or os_reserve/os_commit */
        void *ptr = nullptr;
        if (atype == ALIGNED_MALLOC) 
        {
          if (bytesReserve == (2*PAGE_SIZE_2M))
          {
            /* full 2M alignment for very first block */
            const size_t alignment = (next == NULL) ? PAGE_SIZE_2M : PAGE_SIZE;
            if (device) device->memoryMonitor(bytesAllocate+alignment,false);
            ptr = alignedMalloc(bytesAllocate,alignment);           
 
            const size_t ptr_aligned_begin = ((size_t)ptr) & ~(PAGE_SIZE_2M-1);
            /* first os_advise could fail as speculative */
            os_advise((void*)(ptr_aligned_begin +            0),PAGE_SIZE_2M);
            /* second os_advise should succeed as with 4M block */
            os_advise((void*)(ptr_aligned_begin + PAGE_SIZE_2M),PAGE_SIZE_2M);
            
            return new (ptr) Block(atype,bytesAllocate-sizeof_Header,bytesAllocate-sizeof_Header,next,alignment);
          }
          else 
          {
            const size_t alignment = CACHELINE_SIZE;
            if (device) device->memoryMonitor(bytesAllocate+alignment,false);
            ptr = alignedMalloc(bytesAllocate,alignment);
            return new (ptr) Block(atype,bytesAllocate-sizeof_Header,bytesAllocate-sizeof_Header,next,alignment);
          }
        } 
        else if (atype == OS_MALLOC)
        {
          if (device) device->memoryMonitor(bytesAllocate,false);
          ptr = os_reserve(bytesReserve);
          os_commit(ptr,bytesAllocate);
          return new (ptr) Block(atype,bytesAllocate-sizeof_Header,bytesReserve-sizeof_Header,next,0);
        }
        else
          assert(false);
        return NULL;
      }

      Block (AllocationType atype, size_t bytesAllocate, size_t bytesReserve, Block* next, size_t wasted) 
      : cur(0), allocEnd(bytesAllocate), reserveEnd(bytesReserve), next(next), wasted(wasted), atype(atype)
      {
        assert((((size_t)&data[0]) & (maxAlignment-1)) == 0);
        //for (size_t i=0; i<allocEnd; i+=defaultBlockSize) data[i] = 0;
      }

      void clear_list(MemoryMonitorInterface* device) 
      {
        Block* block = this;
        while (block) {
          Block* next = block->next;
          block->clear_block(device);
          block = next;
        }
      }

      void clear_block (MemoryMonitorInterface* device) 
      {
        const size_t sizeof_Header = offsetof(Block,data[0]);
        const ssize_t sizeof_Alloced = wasted+sizeof_Header+getBlockAllocatedBytes();

        if (atype == ALIGNED_MALLOC) {
          alignedFree(this);
          if (device) device->memoryMonitor(-sizeof_Alloced,true);
        } 

        else if (atype == OS_MALLOC) {
         size_t sizeof_This = sizeof_Header+reserveEnd;
         os_free(this,sizeof_This);
         if (device) device->memoryMonitor(-sizeof_Alloced,true);
        } 

        else /* if (atype == SHARED) */ {
        }
      }
      
      void* malloc(MemoryMonitorInterface* device, size_t& bytes_in, size_t align, bool partial) 
      {
        size_t bytes = bytes_in;
        assert(align <= maxAlignment);
        bytes = (bytes+(align-1)) & ~(align-1);
	if (unlikely(cur+bytes > reserveEnd && !partial)) return nullptr;
	const size_t i = cur.fetch_add(bytes);
	if (unlikely(i+bytes > reserveEnd && !partial)) return nullptr;
        if (unlikely(i > reserveEnd)) return nullptr;
        bytes_in = bytes = min(bytes,reserveEnd-i);
        
	if (i+bytes > allocEnd) {
          if (device) device->memoryMonitor(i+bytes-max(i,allocEnd),true);
          if (atype == OS_MALLOC)
            os_commit(&data[i],bytes); // FIXME: optimize, may get called frequently
        }
	return &data[i];
      }
      
      void* ptr() {
        return &data[cur];
      }

      void reset_list ()
      {
        for (Block* block = this; block; block = block->next)
          block->reset_block();
      }

      void reset_block () 
      {
        allocEnd = max(allocEnd,(size_t)cur);
        cur = 0;
      }

      void shrink_list (MemoryMonitorInterface* device) 
      {
        for (Block* block = this; block; block = block->next)
          block->shrink_block(device);
      }
   
      void shrink_block (MemoryMonitorInterface* device) 
      {
        if (atype == OS_MALLOC)
        {
          const size_t sizeof_Header = offsetof(Block,data[0]);
          size_t newSize = os_shrink(this,sizeof_Header+getBlockUsedBytes(),reserveEnd+sizeof_Header);
          if (device) device->memoryMonitor(newSize-sizeof_Header-allocEnd,true);
          reserveEnd = allocEnd = newSize-sizeof_Header;
        }
      }

      size_t getBlockUsedBytes() const {
        return min(size_t(cur),reserveEnd);
      }

      size_t getBlockAllocatedBytes() const {
        return min(max(allocEnd,size_t(cur)),reserveEnd);
      }

      size_t getBlockReservedBytes() const {
        return reserveEnd;
      }

      size_t getBlockFreeBytes() const {
	return max(allocEnd,size_t(cur))-cur;
      }

      size_t getUsedBytes() const {
        size_t bytes = 0;
        for (const Block* block = this; block; block = block->next)
          bytes += block->getBlockUsedBytes();
        return bytes;
      }

      size_t getAllocatedBytes() const {
        size_t bytes = 0;
        for (const Block* block = this; block; block = block->next)
          bytes += block->getBlockAllocatedBytes();
        return bytes;
      }

      size_t getReservedBytes() const {
        size_t bytes = 0;
        for (const Block* block = this; block; block = block->next)
          bytes += block->getBlockReservedBytes();
        return bytes;
      }

      size_t getFreeBytes() const {
        size_t bytes = 0;
        for (const Block* block = this; block; block = block->next)
          bytes += block->getBlockFreeBytes();
        return bytes;
      }

      void print_list () 
      {
        for (const Block* block = this; block; block = block->next)
          block->print_block();
      }

      void print_block() const 
      {
        if (atype == ALIGNED_MALLOC) std::cout << "A";
        else if (atype == OS_MALLOC) std::cout << "O";
        else if (atype == SHARED) std::cout << "S";
        std::cout << "[" << getBlockUsedBytes() << ", " << getBlockAllocatedBytes() << ", " << getBlockReservedBytes() << "] ";
      }

    public:
      std::atomic<size_t> cur;        //!< current location of the allocator
      std::atomic<size_t> allocEnd;   //!< end of the allocated memory region
      std::atomic<size_t> reserveEnd; //!< end of the reserved memory region
      Block* next;               //!< pointer to next block in list
      size_t wasted;             //!< amount of memory wasted through block alignment
      AllocationType atype;      //!< allocation mode of the block
      char align[maxAlignment-5*sizeof(size_t)-sizeof(AllocationType)]; //!< align data to maxAlignment
      char data[1];              //!< here starts memory to use for allocations
    };

  private:
    Device* device;
    SpinLock mutex;
    size_t slotMask;
    std::atomic<Block*> threadUsedBlocks[MAX_THREAD_USED_BLOCK_SLOTS];
    std::atomic<Block*> usedBlocks;
    std::atomic<Block*> freeBlocks;

    std::atomic<Block*> threadBlocks[MAX_THREAD_USED_BLOCK_SLOTS];
    SpinLock slotMutex[MAX_THREAD_USED_BLOCK_SLOTS];
    
    bool use_single_mode;
    size_t defaultBlockSize;
    size_t growSize;
    std::atomic<size_t> log2_grow_size_scale; //!< log2 of scaling factor for grow size
    size_t bytesUsed;            //!< number of total bytes used
    size_t bytesWasted;          //!< number of total wasted bytes
    ThreadLocalData<ThreadLocal2,FastAllocator*> thread_local_allocators2; //!< thread local allocators
    AllocationType atype;
  };
}